US20070128608A1 - Novel mixtures for assaying nucleic acid, novel method of assaying nucleic acid with the use of the same and nucleic acid probe to be used therefor - Google Patents

Novel mixtures for assaying nucleic acid, novel method of assaying nucleic acid with the use of the same and nucleic acid probe to be used therefor Download PDF

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US20070128608A1
US20070128608A1 US10/583,457 US58345704A US2007128608A1 US 20070128608 A1 US20070128608 A1 US 20070128608A1 US 58345704 A US58345704 A US 58345704A US 2007128608 A1 US2007128608 A1 US 2007128608A1
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nucleic acid
probe
internal standard
labeled
target nucleic
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Inventor
Kazunori Nakamura
Takahiro Kanagawa
Naohiro Noda
Satoshi Tsuneda
Hidenori Tani
Shinya Kurata
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NATIONAL INSTITUTE OF ADV INDUSTRIAL SCI and Technology
National Institute of Advanced Industrial Science and Technology AIST
Kankyo Engineering Co Ltd
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NATIONAL INSTITUTE OF ADV INDUSTRIAL SCI and Technology
Kankyo Engineering Co Ltd
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Assigned to NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY, KANKYO ENGINEERING CO., LTD. reassignment NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KANAGAWA, TAKAHIRO, KURATA, SHINYA, NAKAMURA, KAZUNORI, NODA, NAOHIRO, TANI, HIDENORI, TSUNEDA, SATOSHI
Publication of US20070128608A1 publication Critical patent/US20070128608A1/en
Priority to US12/540,390 priority Critical patent/US7951604B2/en
Priority to US13/089,420 priority patent/US20110224417A1/en
Priority to US13/665,566 priority patent/US9587271B2/en
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
    • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
    • C12Q1/6813—Hybridisation assays
    • C12Q1/6816—Hybridisation assays characterised by the detection means
    • C12Q1/6818—Hybridisation assays characterised by the detection means involving interaction of two or more labels, e.g. resonant energy transfer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T436/00—Chemistry: analytical and immunological testing
    • Y10T436/14—Heterocyclic carbon compound [i.e., O, S, N, Se, Te, as only ring hetero atom]
    • Y10T436/142222—Hetero-O [e.g., ascorbic acid, etc.]
    • Y10T436/143333—Saccharide [e.g., DNA, etc.]

Definitions

  • This invention relates to a novel mixture for assaying a nucleic acid, and specifically to a novel mixture for assaying accurately, conveniently and non-expensively one or plural nucleic acids, and a method for assaying a nucleic acid using the same, and nucleic acid probes to be used for the assaying method and a nucleic acid-assaying kit.
  • methods for assaying a target nucleic acid are methods for assaying a nucleic acid in a homogenous solution by using a fluorescent dye-labeled target nucleic acid probe having properties changing in fluorescence on hybridizing with a target nucleic acid (called a nucleic acid probe for a homogenous solution system or a target nucleic acid probe, having the same meaning).
  • the method does not require, by this characteristics, 1) any step immobilizing a target nucleic acid (or any step washing a probe) indispensable for common hybridizing method and 2) any step washing out non-reacting probes (or any step immobilizing non-reacting genes); the method, therefore, is a method for assaying easily, rapidly and accurately a target nucleic acid. With such reasons, the method for assaying quantitatively a target nucleic acid has been in a wide used for various methods for analyzing genes (see non-patent reference 1).
  • an object could be achieved by using the following procedures.
  • the conventional methods need any of the means, 1) diluting a target nucleic acid sample, and 2) preparing in advance plural assaying systems with a probe having various concentrations.
  • the above 1) requires a diluting processing step; the operation become complicated.
  • the above 2) has such problems that (1) long assaying time is needed; (2) diluting errors occur; and (3) on automation of the assaying, an for dilution is needed.
  • the reaction time and reaction temperature suitable for hybridization vary with response to the concentrations of an added probe (if a target nucleic acid and a target nucleic acid probe are higher in concentrations, the time for completed hybridization becomes shorter; if contrary to the former, the reaction time becomes longer. If a target nucleic acid and a probe are higher in concentrations, a Tm value is higher; if contrary to the former, it becomes lower); as a result, there is such problems that (1) an assaying system needs to be optimized in every concentration of a probe, and (2) a calculating curve needs to be prepared in every concentration of an added probe.
  • Non-patent reference 1 Protein, Nucleic Acid and Enzyme; vol. 35, No. 17, Kyoritu Shuppan Co., Ltd.; Experimental Medical; vol. 15, No. 7, 1997, Yodosha Co., Ltd.
  • the present invention has as an object to provide a novel mixture for assaying a target nucleic acid, characterized by enabling a nucleic acid assaying method to assay a target nucleic acid without requiring any processing step of diluting of a target nucleic acid and any procedures of changing a probe concentration, a novel method for assaying a nucleic acid using the same, and a novel nucleic acid probe to be used for these.
  • a target nucleic acid is added to a reaction solution (a hybridizing reaction system) comprising a known concentration of a specific internal standard nucleic acid, a specific target nucleic acid probe labeled with a fluorescent dye for a homogenous solution system and/or a specific internal standard nucleic acid probe labeled with a fluorescent dye and making it possible to hybridize the above internal standard nucleic acid, and then, is allowed to make a hybridizing reaction; while an occurred change of an optical character is measured. Further a measured-value ratio of the internal standard nucleic acid and the target nucleic acid is determined; these steps enabled the present invention to be completed.
  • a reaction solution a hybridizing reaction system
  • the present invention provides:
  • Novel mixture or novel reaction solution for assaying one or two or more target nucleic acids, which comprises one or two or more below nucleic acid probes for a homogenous solution system and one or two or more below internal standard nucleic acid, or further one or two or more below internal standard nucleic acid probe:
  • Target nucleic acid probe for homogenous solution system
  • said target nucleic acid probe is formed of one stranded oligonucleotide
  • said target nucleic acid probe is labeled with one or two or more molecule of fluorescent dyes of one or two or more kinds at least one of both end portions and/or at least one of base portions in the chain, at least one of sugar moieties and/or at least one of phosphate moieties of the oligonucleotide;
  • said target nucleic acid probe enables a fluorescent character to change on hybridizing with a target nucleic acid and/or an internal standard nucleic acid
  • said target nucleic acid probe is capable of hybridizing without discriminating with a target nucleic acid or an internal standard nucleic acid
  • said target nucleic acid probe is capable of producing a difference between the amount of a change in a fluorescent character on hybridizing with an internal standard nucleic acid and that on hybridizing with a target nucleic acid;
  • Internal standard nucleic acid (called an “internal gene” or an “internal standard gene” in a case): wherein said internal standard nucleic acid has a structure different in at least a portion from the structure of a target nucleic acid of a region corresponding to the above target nucleic acid probe, and is capable of producing a difference between the amount of a change in a fluorescent character produced on hybridizing with the above target nucleic acid probe and one on the hybridization of a target nucleic acid with the above target nucleic acid probe;
  • said internal standard nucleic acid probe has the above characteristics a) to e) of the above target nucleic acid probe, wherein a fluorescent labeling portion and a fluorescent character of a labeled fluorescent dye each are different from those of the above target nucleic acid probe;
  • target nucleic acid probe is a probe having a base sequence not complementary to a target nucleic acid in a partial region
  • the amount of a change in an optical character is the increased amount (for example, a probe labeled with dyes each causing an FRET phenomena) or the decreased amount (for example, a Q probe);
  • said target nucleic acid probe and/or said internal standard nucleic acid probe are/is a probe labeled at least two portions (end portions, base portions in an chain, sugar moieties, phosphate moieties) with fluorescent dyes with different fluorescent character occurred on hybridization of a target nucleic acid probe and/or an internal standard nucleic acid probe with a target nucleic acid and/or an internal standard nucleic acid (hereinafter, these probes are called simply “a doubly-labeled nucleic acid probe”);
  • said doubly-labeled nucleic acid probe is a doubly-labeled nucleic acid probe making at one portion of the labeled portions a difference between the amount of a change in a fluorescent character on hybridization with a target nucleic acid and that on hybridization with an internal standard nucleic acid, but not making such a difference at the other portion;
  • the dissociating temperature of the hybrid complex of a target nucleic acid probe or a doubly-labeled nucleic acid probe and a fluorescent quenching substance-labeled probe is lower than the dissociating temperature of the hybrid complex of a target nucleic acid probe or a doubly-labeled nucleic acid probe and a nucleic acid or an internal standard nucleic acid.
  • a fluorescent quenching substance-labeled probe After the hybridization of a target nucleic acid probe or a doubly-labeled nucleic acid probe with a target nucleic acid, or after the hybridization of a target nucleic acid probe or a doubly-labeled nucleic acid probe with a target nucleic acid, a fluorescent quenching substance-labeled probe can hybridize with a probe for a homogenous solution system or a doubly-labeled nucleic acid probe due to the characteristics of the above (1).
  • novel mixture according the above 1), wherein said novel mixture comprises a) an internal standard nucleic acid, b) a target nucleic acid probe and/or c) an internal standard nucleic acid probe according to the above 1), and d) exonuclease under the below conditions or exonuclease attached to the novel mixture as a kit;
  • a target nucleic acid probe and/or an internal standard nucleic acid probe are not complementary to at least one of a target nucleic acid and an internal standard nucleic acid at a fluorescent-labeled portion region (the region: 1 (one) to 3 base in length, preferably 1 (one) base);
  • exonuclease is 3′ ⁇ 5′exonuclease, 5′ ⁇ 3′ exonuclease, S1 nuclease or Mung Bean Nuclease;
  • novel mixture according to the above 1), wherein said novel mixture comprises one or two or more pairs of internal standard probes and target nucleic acid probes;
  • target nucleic acid is a nucleic acid amplified by a gene amplification method (until any phase of an initial phase, a middle phase and a stationary phase);
  • novel method for assaying one or two or more target nucleic acids according to the above wherein said novel mixture according to any one of the above 1) to 23) comprises the following target nucleic acid probe or doubly-labeled nucleic acid probe and a known concentration of an internal standard nucleic acid according to any one of the above 1) to 20);
  • Target nucleic acid probe (hereinafter, this kind of a probe will be called a “recognizable nucleic acid probe”): a target nucleic acid probe according to any one of the above 1) to 23) is not complementary to any one of a target nucleic acid and an internal standard nucleic acid at least any one or two or more ones of portions labeled with a fluorescent dye(s).
  • Doubly-labeled nucleic acid probe (hereinafter, this sort of a probe will be called a “recognizable doubly-labeled nucleic acid”): a doubly-labeled nucleic acid probe according to any one of the above
  • 5) to 23) is not complementary to any one of a target nucleic acid and an internal standard nucleic acid at any one of portions labeled with any one of two sorts of fluorescent dyes.
  • x ( ⁇ a′ ⁇ B+Ba′+b′+A ⁇ Ab ′)/( b′ ⁇ b ⁇ Ab′+Ab ⁇ a′+a+Ba′ ⁇ Ba ) wherein said equation is valid under the below conditions; and said signs have the below meanings:
  • the conditions are as follows: in the novel method, the doubly-labeled nucleic acid probe is used, wherein said nucleic acid probe is labeled with dyes A and B.
  • y a proportion of a hybridized probe
  • x a proportion of a target gene
  • A a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on no hybridization in use of a practical sample to the fluorescent intensity of dye A of the doubly-labeled nucleic probe on no hybridization;
  • a a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target nucleic acid to the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on no hybridization;
  • a′ a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with an internal standard nucleic acid to the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on no hybridization;
  • b a ratio of the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target gene to the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on no hybridization;
  • b′ a ratio of the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with an internal standard nucleic acid to the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on no hybridization.
  • x ( b ⁇ B ⁇ Ab+A+a′B ⁇ a ′)/( a′B ⁇ a′ ⁇ aB+a ) wherein said equation is valid under the below conditions; and said signs have the below meanings:
  • the conditions are as follows: in the novel method, the doubly-labeled nucleic acid probe is used, wherein said nucleic acid probe is labeled with dyes A and B.
  • y a proportion of a hybridized probe
  • x a proportion of a target gene
  • A a ratio of the fluorescent intensity for dye A of the doubly-labeled nucleic acid probe on use of a practical sample to the fluorescent intensity for dye A of non-hybridizing doubly-labeled nucleic probe;
  • a a ratio of the fluorescent intensity for dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target nucleic acid to the fluorescent intensity for dye A of non-hybridizing doubly-labeled nucleic acid probe;
  • a′ a ratio of the fluorescent intensity for dye A of the doubly-labeled nucleic acid probe on the 100%-hybridization of the doubly-labeled nucleic acid probe with an internal standard nucleic acid to the fluorescent intensity for dye A of the doubly-labeled probe on 100%-hybridization of the doubly-labeled nucleic acid probe with the quenching substance-labeled probe;
  • b a ratio of the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target gene and an internal standard gene to the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with a quenching substance-labeled nucleic acid probe.
  • a kit for assaying a nucleic acid comprising a novel mixture according to the above 1) or 5);
  • a novel method for assaying a nucleic acid which comprises: amplifying one or plural target nucleic acids and an internal standard nucleic acid in a reaction system comprising one or plural internal standard nucleic acids until an optional phase of from a beginning phase to a stationary phase by a gene-amplification method; and determining starting concentrations prior to the amplification of one or plural target nucleic acids by using the resultant reaction or the amplified product as a sample;
  • said gene-amplification method is a method for amplifying a target nucleic acid and an internal standard nucleic acid by using a primer set common to the amplification of the target nucleic acid and to that of an internal standard nucleic acid;
  • a novel mixture for assaying one or plural target nucleic acids based on measurement of a Tm value which comprises a pair of a below nucleic acid and a below internal standard nucleic acid;
  • the target nucleic acid probe which is one-strand oligonucleotide labeled with one or two or more fluorescent dyes, wherein said oligonucleotide is capable of hybridizing with a target nucleic acid and an internal standard nucleic acid, and enables a change of a fluorescent character of the labeled fluorescent dyes on hybridization with the nucleic acid and internal standard nucleic acid, wherein in plural nucleic acid probes the fluorescent dyes of the probes each are different.
  • the internal standard nucleic acid in which the base sequence of a portion of said internal standard nucleic acid hybridizing with said nucleic acid probe is different in part from the base-sequence of a portion of a target nucleic acid hybridizing with said nucleic acid probe.
  • nucleic acid probe is a single stranded oligonucleotide labeled with a fluorescent dye at a cytosine portion of the oligonucleotide
  • a novel method for assaying a target nucleic acid which comprises measuring fluorescent intensity using said novel mixture according to the above 39) with changing temperature under the presence of plural target nucleic acids; and determining a target nucleic acid by the following procedures:
  • kits for assaying a nucleic acid which comprises a novel mixture according to the above 1) or 39);
  • a target nucleic acid probe or a doubly-labeled nucleic acid probe in which said target nucleic acid probe or doubly-labeled nucleic acid probe is described above and has at least any one of the below structures:
  • said structure has a portion not complementary to a target nucleic acid and/or an internal standard nucleic acid at a end portion or both end portions;
  • said nucleic acid probe is labeled with a fluorescent dye at one portion not complementary to the target nucleic acid and/or an internal standard nucleic acid, having a cytosine (a C) or a guanine (a G) in a range of 1 to 3 bases from the labeled base in a fluorescent dye-labeled portion (the labeled base is numbered as 1 (one));
  • the one other portion not complementary to a target nucleic acid and/or an internal standard nucleic acid is a portion opposite the one end portion labeled with a fluorescent dye
  • one other portion not complementary to a target nucleic acid and/or an internal standard nucleic acid is in a range of 1 (one) to 4 bases as the number of bases;
  • portions labeled with fluorescent dyes were at least two bases
  • the base sequence according to the above (6) are complementary to a target nucleic acid or an internal standard nucleic acid excluding both end portion (at least from the 1 st base to the 3 rd base, the end base being counted as the 1 st base);
  • the doubly-labeled nucleic acid probe according to the above (6) or (9) is a doubly-labeled nucleic acid probe making at one portion a difference between the amount of change in a fluorescent character on hybridization with a target nucleic acid and that on hybridization with an internal standard nucleic acid, but not making such a difference at the other portion;
  • a base sequence of a target nucleic acid probe or a doubly-labeled nucleic acid is at least complementary to a target nucleic acid or an internal standard nucleic acid excluding to both end base portions (a base sequence of at least from the 1 st base to the 3 rd base; the end base being counted as the 1 st base);
  • a target nucleic acid probe or a doubly-labeled nucleic acid probe has a base sequence completely complementary to a target nucleic acid and an internal standard nucleic acid;
  • the number of G of the corresponding target nucleic acid and internal standard nucleic acid in a end base sequence of from the 1 st base to the 3 rd base is larger in a target nucleic acid than in an internal standard nucleic acid in one end region, and in other end region smaller in a target nucleic acid than or equal in an internal standard nucleic acid in other end rejoin; or in one end region smaller in a target nucleic acid than in an internal standard nucleic acid and in other end region larger in a target nucleic acid than or equal in an internal standard nucleic acid;
  • the base of a target nucleic acid corresponding to both end base of a target nucleic acid probe or a doubly-labeled nucleic acid probe is taken as the 1 st base
  • the corresponding base sequence of a target nucleic acid and internal standard nucleic acid in a end base sequence of from the 1 st base to the 3 rd base is different in the one end region, but the same in the other end region.
  • a novel method having the following characteristics is completed by using the above novel mixture according to the present invention. That is, in the method for assaying a nucleic acid, 1) processing steps for diluting a target nucleic acid are not required; 2) a change of the concentration of a nucleic acid for use with response to the concentration of a target nucleic acid are not required; 3) plural target nucleic acids can be assayed in a like assaying system; 4) an assaying sensitivity is enhanced; and 5) the combination of a method for assaying a nucleic acid according to the present invention and a method for amplifying a nucleic acid provides the following merits:
  • the combined method makes it possible to assay in a rapid and convenient way a nucleic acid without opening a reaction tube for the gene amplifying reaction; therefore, it does not require a PCR post processing step and can simply, easily and rapidly assay a nucleic acid; (2) to open a gene-amplifying reaction tube is not needed; the combined method does not have any risk of contamination with amplified products; (3) the assay is hard to be affected by inhibitors because the combined method is a competitive method; (4) since a gene-amplifying processing-step and a detecting processing step of a amplified product can be completely divided, a large quantity-sample becomes to be treated; and a sample-treating power can be conveniently and non-expensively improved (for example, subsequent to the gene-amplification by using plural non-expensive PCR-apparatuses not having any fluorescence-measuring function, by analyzing obtained data in order using a fluorescence-measuring apparatus,
  • FIG. 1 illustrates an outline of a method for detecting a target gene and an internal standard gene by using a Qprobe.
  • FIG. 2 illustrates an outline of a method for assaying quantitatively a gene by a dissociation curve(Tm) analysis using a Qprobe.
  • FIG. 3 illustrates an outline of a method for assaying quantitatively a gene by using a doubly-labeled Qprobe (a switching probe).
  • FIG. 4 illustrates an outline of the principle for a competitive PCR method.
  • FIG. 5 illustrates an outline of the relation of a fluorescence-quenching ratio and a constituent ratio of genes.
  • FIG. 6 illustrates the relation of a fluorescence-quenching ratio and a constituent ratio of genes (in using a switching probe).
  • FIG. 7 illustrates the relation of a fluorescence quenching ratio and a constituent ratio of genes prior to a nucleic acid-amplification reaction (PCR) (in using an end-point gene-quantitatively-assaying method through a gene-amplification method using a switching probe).
  • PCR nucleic acid-amplification reaction
  • FIG. 8 illustrates the experimental procedures in Example 2.
  • FIG. 9 illustrates an outline of the method for assaying quantitatively a constituent ratio of genes by using a target nucleic acid probe.
  • FIG. 10 illustrates the relation of a constituent ratio of genes and a fluorescence-quenching ratio in the use of a probe for a homogenous solution system.
  • FIG. 11 illustrates a outline of the method for detecting a gene using a doubly-labeled nucleic acid probe (its part 2)
  • FIG. 12 illustrates the relation between a ratio of a fluorescence-quenching ratio in BODIPY FL dye to a fluorescence-quenching ratio in TAMURA dye and a constituent ratio of genes of a target gene/an internal standard gene.
  • ⁇ gene amount 200 nM; ⁇ gene amount: 400 nM; ⁇ total gene amount: 800 nM
  • FIG. 13 illustrates an outline of a method for detecting a gene by using a doubly-labeled nucleic acid probe (its part 3).
  • FIG. 14 illustrates a difference between a calculating curve with correction in TAMURA dye and a calculating curve with no correction in TAMURA dye.
  • FIG. 15 is an illustrative figure concerning conditions of a probe and a fluorescent change.
  • FIG. 16 illustrates an relative equation as to a proportion of a target gene and a fluorescence-quenching ratio
  • FIG. 17 illustrates the detection of a target gene and an internal standard gene under the no presence of a quenching substance-labeled nucleic acid probe or under the presence of it.
  • FIG. 18 illustrates an outline of a method for using an enzyme having a 3′ ⁇ 5′exonuclease activity.
  • FIG. 19 illustrates a relation of a fluorescence-measuring-value ratio and a constituent ratio of genes.
  • FIG. 20 illustrates an outline of a method for assaying quantitatively a gene by using a combination of a doubly-labeled nucleic acid probe and a quenching substance-labeled nucleic acid probe.
  • target nucleic acid as used herein means a nucleic acid the detection or quantitatively assaying of which is intended.
  • a gene should be compassed in the terms “nucleic acid”, “target nucleic acid” and “internal standard nucleic acid”.
  • a target nucleic acid an internal standard nucleic acid”, or simply “nucleic acid” are used; as specifical terms, “target gene”, “internal standard gene”, or simply “gene” are used.
  • a nucleic acid contained in a sample may be also called simply a target nucleic acid or an objective nucleic acid.
  • to assay a nucleic acid or “to measure the concentration of a nucleic acid” as use herein means to perform a quantitative detection of the nucleic acid, to perform a qualitative detection of the nucleic acid, to simply measure or simply monitor the intensity of fluorescence from a nucleic acid polymerization system, or to measure a change or the amount of a change in an optical character of target nucleic acid(s) in an assaying reaction system by using a plural wavelength and then to calculate a ratio between the measuring values, followed by to determine the concentration of the target nucleic acid with the ratio.
  • the above expression should also be interpreted to encompass an operation or the like that the data obtained as described above is studied by the known method of Kurata et al. (EP 1 046 717 A9) to determine the concentration (the number of copies or the like) of a nucleic acid existing in a single system.
  • a nucleic acid contained in a sample should be not only limited to any specific nucleic acid(s) to be assayed, but also should be interpreted to include an unspecified nucleic acid capable of be detected by the method according to the present invention with no intention. Needless say, it encompasses genes and the like. These nucleic acids may exist together. In addition, no limitation is imposed on the concentration or size of those. These nucleic acids should be interpreted to encompass further a DNA, an RNA and the modified nucleic acids thereof.
  • optical character means one of various absorption spectra and fluorescence emission spectrum of a fluorescent dye, quencher or the like, with which a nucleotide is labeled, or its optical characteristic or the like such as absorption intensity, polarization, fluorescence emission, fluorescence intensity, fluorescence lifetime, fluorescence polarization or fluorescence anisotropy (these optical characteristics will be collectively called “fluorescence intensity”). It may also mean a characteristic determined by totally analyzing one or more measurement values of at least one fluorescent dye or the like, with which a labeled nucleotide or the like is labeled, as measured at least one measurement wavelength. For example, a fluorescence intensity curve or the like of a modification reaction of a nucleic acid can be used as an optical character.
  • optical character is used; as a specific term, a “fluorescent intensity”, or simply “fluorescence” is used.
  • the expression “from a change or the amount of a change in fluorescence intensity” shall embrace not only a change in fluorescence intensity on the basis of a nucleic acid polymer synthesized in the present invention, but also a change or the amount of a change in fluorescence intensity when a nucleic acid probe for a homogeneous solution system, said nucleic acid probe having been labeled with a fluorescent dye and/or quencher, is hybridized with the amplified nucleic acid.
  • hybridization complex between a primer probe and a corresponding nucleic acid is called a “hybrid” or a “hybrid complex”, or simply a “nucleic acid-primer complex” or a “primer-nucleic acid complex”.
  • nucleic acid probe “complements” or “is complementary to”, or in addition “does not complement” or “is not complementary to” a target nucleic acid at a partial region of the probe.
  • complements or “is complementary to” means that when two kinds of oligonucleotides exist in a single system, the nucleic acids can bind each other's at corresponding bases by hydrogen bonding. In addition, it means that one of the nucleic acids can hybridize with the other.
  • a partial region of a nucleic acid probe “corresponds with” a partial region of a target nucleic acid the term “correspond with” in this instance has no concept of the hydrogen bonding between corresponding bases; and it means that simply the nucleic acids have a relation of one to one. Accordingly, the term “correspond” means both of “complement” or “be complementary to” and “do not complement” or “be not complementary to”.
  • a “change ratio in an optical character” as used the present invention means a ratio of an optical measuring-value of a fluorescent dye or the like in a reaction system or an assaying system on no hybridization of a nucleic acid probe (a target nucleic acid probe, an internal standard nucleic acid probe) with a target nucleic acid and/or an internal standard nucleic acid to that on hybridization.
  • an calculating equation such as (a measuring value on hybridization)/(a measuring value on no hybridization) ⁇ 100 may be illustrated. If the change is a quenching in fluorescence, it is called a “fluorescence-quenching ratio”; while if an emission in fluorescence, a “fluorescent emission ratio” or the like.
  • the hybridization occurs preferably at 10° C. to 90° C.; the no hybridization occurs at 90° C. or more. There is an intermediate hybridization; accordingly, it is preferable to measure accurately every each experiment.
  • a portion at which a nucleic acid probe according to the present invention is labeled with a fluorescent dye according to the present invention is called a “fluorescent dye-labeled portion” or “fluorescence-labeled portion”; these terms have, however, the same meanings.
  • fluorescent dye which may also be called ‘fluorescent substance’
  • fluorescent dye generally means a fluorescent dye which is generally used to label a nucleic acid probe to assay or detect the nucleic acid.
  • Illustrative are fluorescein and its derivatives [for example, fluorescein isothiocyanate (FITC) and its derivatives], Alexa 488, Alexa 532, cy3, cy5, 6-joe, EDANS, rhodamine 6G (R6G) and its derivatives [for example, tetramethylrhodamine (TMR), tetramethylrhodamine isothiocynate (TMRITC), and x-rhodamine], Texas red, “BODIPY FL” (“BODIPY” is a trademark, “FL” is a tradename; product of Molecular Probes Corporation, U.S.A.; this will hereinafter apply equally), “BODIPY FL/C3”, “BODIPY
  • TAMRA fluorescent dyes
  • FITC fluorescent dyes
  • EDANS Texas Red, 6-joe
  • TMR Alexa 488, Alexa 532
  • BODIPY FL/C3 BODIPY R6G
  • BODIPY FL BODIPY FL/C6
  • BODIPY TMR 5-FAM
  • BODIPY 493/503 BODIPY 564
  • BODIPY 581 Cy3, Cy5, x-Rhodamine, Pacific Blue and the like
  • quencher means a substance, which acts on the above-described fluorescent dye and reduces or quenches the emission of fluorescence from the fluorescent dye.
  • Illustrative are Dabcyl, “QSY7” (product of Molecular Probes Corporation), “QSY33” (product of Molecular Probes Corporation), Ferrocene and its derivatives, methyl viologen, and N,N′-dimethyl-2,9-diazopyrenium, BHQ, Eclipse, with Dabcyl being preferred.
  • the fluorescent emission of the fluorescent substance is susceptible to a quenching effect of a quencher.
  • a method for amplifying a nucleic acid as used in the present invention is a method for amplifying in vitro a nucleic acid. It may be a known one or a unknown one. It should encompass, for example, a PCR method, an LCR method (ligase chain reaction), a TAS method, an ICAN method (Isothermal and Chimeric primer-initiated Amplification of Nucleic acids), an LAMP method, an NASRA method, an RCA method, a TAMA method, a UCAN method and the like.
  • a PCR method using primer probes or a simple probe is preferable.
  • the above PCR method can preferably have any system.
  • a quantitative PCR method a real-time quantitative PCR method, an RT-PCR method, an RNA-primed PCR method, an Stretch PCR method, a reverse PCR method, an Alu-sequence-using PCR method, a multiple PCR method, a mixed-primer probe-using PCR method, a PNA-using PCR method, and also a method for examining or analyzing a dissociating curve in regard to a nucleic acid amplified by a PCR method.
  • a “Q probe” or Qprobe” is a probe proposed by KURATA et al. (Kurata et al., Nucleic Acids Research, 2001, Vol. 29, No. 6, e34).
  • This probe is a nucleic acid probe for a homogeneous solution system, in which a single-stranded oligonucleotide is labeled with a fluorescent dye.
  • the base labeled with the fluorescent dye is a G or a C, or there is a G or a C at a position 1 to 3 bases apart from a base in a target nucleic acid, said base corresponding to a labeled base and being counted as the 1 st base.
  • a labeling portion of an oligonucleotide to be labeled with a fluorescent dye can be an end portion or in its chain.
  • a labeling position thereof can be a sugar moiety, a phosphate moiety or a base moiety.
  • the labeling can be labeled on the 3′-OH group or 2′-OH group of the sugar moiety at the 3′-end, or the 5′-OH group of the sugar moiety obtained by dephosphorylation at the 5′-end.
  • the phosphate portion can be replaced with a sulfonate group, or sulfinyl group.
  • the labeling portion is preferably a portion containing a C or a G or their selves, with a portion containing a C being the most preferable.
  • the present invention comprises four invention, with each comprising further sub-invention.
  • a novel mixture according to the present invention can be in a liquid, a powder, a tablet, or a capsule; any can be preferably used; and the form is in particular not limited. In the following description, no form of the novel mixture is, therefore, mentioned.
  • target nucleic acid or an internal standard nucleic acid should encompass an amplified product until an optional amplification phase (including a stationary phase).
  • a target nucleic acid should contain a product amplified concurrently in a reaction system from together a target nucleic acid and an internal standard nucleic acid corresponding thereto, its resultant reaction solution, or an one isolated therefrom together with the target nucleic acid and internal standard nucleic acid.
  • a same probe can be used, or not be used.
  • a nucleic acid-amplification method can be a conventional one as described below.
  • the nucleic acid probe (a target nucleic acid and/or an internal standard nucleic acid) as used in the present invention is a nucleic acid probe changing its optical character; a nucleic acid probe decreasing or increasing in a fluorescent intensity can be exemplified.
  • exemplified can be the above mentioned Qprobe as one decreasing in a fluorescent intensity, a nucleic acid probe labeled with two dyes related to FRET phenomena as one increasing (Proc. Natl. Acad. Sci. USA, Vol. pp 8790-8794, 1988; U.S. Pat. No. 4,996,143; JP H05-50152A; JP H08-313529A; JP H10-215897A; JP Application H11-292861) and the like.
  • the present invention is related to a novel mixture or novel reaction solution (hereinafter, the both together are collectively called simply a “novel mixture”.) for assaying one or two or more target nucleic acids, which comprises one or two or more below nucleic acid probes for a homogenous solution system and one or two or more below internal standard nucleic acid or further below internal standard nucleic acid probes:
  • a nucleic acid probe for a homogenous solution system (hereinafter, called “the target nucleic acid probe”) having below characteristics:
  • oligonucleotide It is formed of a single strand oligonucleotide. It has a length of 10 to 100 bases, preferably 15 to 60 bases, more preferably 20 to 40 bases. It can be oligodeoxynucleotide or an oligoribonucleotide. It can also be a chimeric oligonucleotide.
  • one molecule of it is labeled with one or two or more molecules of fluorescent dyes and with one or two or more kinds of fluorescent dyes at an end portion and/or a base portion in the chain of the oligonucleotide, and at a sugar moiety and/or a phosphate moiety;
  • the labeling fluorescent dye it can cause the labeling fluorescent dye to change in an fluorescent character on hybridizing with any one of a target nucleic acid and an internal standard nucleic acid;
  • g) its chain length is preferably the same as that of an internal standard nucleic acid or similar to;
  • h its chain length is preferably the same as that of an internal standard nucleic acid probe or similar to.
  • oligonucleotide a single strand oligonucleotide. Its chain length is 40 to 2000 bases, preferably 60 to 500 bases, more preferably 80 to 150 bases.
  • the oligonucleotide can be an oligodeoxynucleotide or an oligoribonucleotide. Those can be a chimeric oligonucleotide; and
  • the present invention relates to a novel mixture, wherein the above target nucleic acid probe, internal standard nucleic acid, and an internal standard nucleic acid as included therein each can have preferably at least any one of the following structures, and each those can preferably have the following relationship.
  • the structures of the labeled portions are at least different from each others';
  • the above base sequence is at least 2 or 3 or more bases as the integral number of a base
  • a fluorescent dye-labeled portion of the above target nucleic acid is a guanine (a G) base portion and/or a cytosine (a C) portion, or a portion wherein a G and/or a C exists in a range near a base of a labeled portion (in a range from the 1st base to the 3rd base to a 3′-end or 5′-end (the labeled base being counted as the 1 st base)
  • the portion labeled with a fluorescent dye as mentioned above is a 3′- or 5′-end portion
  • the end portion as described above is an end base moiety, a sugar moiety (any one of a 2′- or 3′-OH group of the 3′-end, and a 5′-OH group (being obtainable by dephosphorylation)), and a phosphate moiety (or the phosphate moiety should encompass a sulfonate group or a sulfite group).
  • the nucleic acid probe as described above is labeled at least two portions (end portions, base moieties in the chain, sugar moieties, phosphate moieties) with fluorescent dyes having characters different from each other's (hereinafter, called “a doubly-labeled nucleic acid probe”); (13-2) the fluorescent dyes with fluorescent characters different from each other's are fluorescent dyes not producing FRET (fluorescence resonance energy transfer) at two portions; (13-3) the fluorescent dyes with fluorescent characters different from each other's are fluorescent dyes producing FRET at two portions;
  • the at least two portions as described in the above (12) are at least two bases; the length as the number of a base between two bases is 1 (one) to 100 bases, preferably 10 to 60 bases, more preferably 20 to 40 bases;
  • the base as described in the above (12) is cytosine (hereinafter abbreviated “C”);
  • the base sequence of the target nucleic acid probe as described above is complementary to a target nucleic acid and an internal standard nucleic acid excluding both base end portions (two portions comprising from the 1st base to the 3rd base in length; the end base is counted as the 1 st base);
  • the doubly-labeled nucleic acid as described above is a doubly-labeled nucleic acid probe making at one portion a difference between the amount of a change in a fluorescent character on hybridization with a target nucleic acid and that on hybridization with an internal standard nucleic acid, but not making such a difference at the other portion;
  • the base sequence of said target nucleic acid probe or said doubly-labeled nucleic acid as described above is at least complementary to a target nucleic acid or an internal standard nucleic acid excluding both end base portions (a base sequence of at least from the 1st to the 3rd base in length; the end base is counted as the 1 st base);
  • the base sequence of the target nucleic acid probe or said doubly-labeled nucleic acid probe as described above has a base sequence complementary to a target nucleic acid and/or an internal standard nucleic acid;
  • the number of a G of the corresponding target nucleic acid and internal standard nucleic acid in a base sequence of the end portion in a range of from the 1 st base to the 3 rd base is larger in a target nucleic acid than in an internal standard nucleic acid in one end region, and in the other end region smaller in a target nucleic acid than or equal in an internal standard nucleic acid in the other end region; or in one end region smaller in a target nucleic acid than in an internal standard nucleic acid; and in the other end region larger in a target nucleic acid than or equal in an internal standard nucleic acid;
  • the base of a target nucleic acid corresponding to one end base of a target nucleic acid probe or a doubly-labeled nucleic acid probe is a base other than G and the base corresponding to the other end base is a G;
  • (25) a novel mixture according to the above 1) or 5), wherein, if the base of a target nucleic acid corresponding to both end bases of a target nucleic acid probe or a doubly-labeled nucleic acid probe is assumed as 1 (one), the corresponding base sequence of a target nucleic acid and internal standard nucleic acid in a end base sequence of from the 1st base to the 3rd base is different in one end region, but the same in the other end region;
  • nucleic acid probe and doubly-labeled nucleic acid probe as described above are a fluorescence-quenching probe (for example, a Qprobe);
  • nucleic acid probe and doubly-labeled nucleic acid probe as described above are a fluorescence-emitting probe
  • the doubly-labeled nucleic acid probe as described above is labeled with a quenching dye and a fluorescence-emitting dye;
  • the above target nucleic acid probe has a base sequence designed so that at least one G is present in a range of from the 1 st base to 3 rd base to the 3′end- or 5′end-direction from the labeled base (the labeled base is counted as the 1 st base);
  • the end portion opposite the fluorescent dye-labeling portion as described above is not complementary to a target nucleic acid and/or an internal standard nucleic acid (an optional base sequence of from the 1st base to the 5th base, with a preferable base sequence being of from the 1st base to the 3rd base, wherein an end base is counted in the above number of the base sequence.);
  • At least one of the both ends as described above can be any of a oligonucleotide, trinucleotide and mononucleotide, wherein these nucleotides may be formed of a deoxynucleotide or riboxynucleotide.
  • the position of the fluorescent dye-labeling as described above in the end sugar moiety is any one of the OH group of the 5° C. of the 5′-end sugar (the OH group being formed by dephosphorylation) and the OH group of the 3° C. or 2° C. of the 3′-end sugar (the 2′-OH group is in the case of a ribonucleotide);
  • the target nucleic acid probe or doubly-labeled nucleic acid probe as described above is a probe having a base sequence(s) designed so that the base sequence(s) is corresponding to one or two of these regions including a G or a C (corresponding to the above regions), wherein the base sequence is labeled with a fluorescent dye.
  • a novel mixture according to the present invention comprising, in addition, one or two or more fluorescence-quenching substances capable of quenching the fluorescence of a target nucleic acid probe or a doubly-labeled nucleic acid probe not hybridizing with a target nucleic acid or an internal standard nucleic acid, or one or two or more oligonucleotides labeled with the above substance (hereinafter, called a “quenching substance-labeled probe) in addition to the components of the mixture as described above.
  • the dissociating temperature of the hybrid complex of a target nucleic acid probe or a doubly-labeled nucleic acid probe and a fluorescent quenching substance-labeled probe is lower than the dissociating temperature of the hybrid complex of a target nucleic acid probe or a doubly-labeled nucleic acid probe and a nucleic acid or an internal standard nucleic acid.
  • a fluorescent quenching substance-labeled probe After the hybridization of a target nucleic acid probe or a doubly-labeled nucleic acid probe with a target nucleic acid, and after the hybridization of a target nucleic acid probe or a doubly-labeled nucleic acid probe with a target nucleic acid, a fluorescent quenching substance-labeled probe can hybridize with a probe for a homogenous solution system or a doubly-labeled nucleic acid probe due to the above characteristics (1).
  • An internal standard nucleic acid is not complementary to a target nucleic acid in one or two or more regions.
  • An internal standard nucleic acid is not complementary to a target nucleic acid in one or two or more regions.
  • a target nucleic acid probe is complementary to a target nucleic acid at the fluorescent dye-labeled region of the target nucleic acid probe, the target nucleic acid probe is not complementary to an internal standard nucleic acid at the region.
  • a target nucleic acid probe is complementary to an internal standard nucleic acid at the fluorescent dye-labeled region of the target nucleic acid probe, the target nucleic acid probe is not complementary to a target nucleic acid at the region.
  • the internal standard nucleic acid probe has at least the same characteristics as that of the above target nucleic acid probe and the same structure, but its fluorescent dye-labeled portion has a structural portion different from that of the above target nucleic acid probe.
  • the fluorescent dye-labeled portion of the above target nucleic acid probe is the 3′end; while that of the internal standard nucleic acid is the 5′end. In contrary to the former, further its relation become contrary in response to this.
  • a target nucleic acid is an optional nucleic acid and in particular not limited.
  • the method can have various modes by the combination of the above probe for a homogenous solution system and the internal standard nucleic acid, and further by the combination of those and the internal standard nucleic acid probe.
  • reaction product amplified by a gene-amplifying method (a product amplified until an optional phase reaching to a stationary phase (any phase of an initial phase, a middle phase and a stationary phase)).
  • the method can have various modes by the combination of the above probe for a homogenous solution system and the internal standard nucleic acid, and further by the combination of those and the internal standard nucleic acid probe.
  • the second invention according to the present invention is divided largely to the following modes.
  • a specific method for assaying a nucleic acid comprises, any instance, conducting a hybridization in the presence of a target nucleic acid and/or an internal standard nucleic acid; measuring a change in an optical character of a reaction system, with the change being derived from a fluorescent dye of a target nucleic acid probe and/or an internal standard nucleic acid probe; calculating a ratio of the obtained measuring values or a ratio of measured changing ratios of the optical character; and determining a concentration of the target nucleic acid based on the calculated ratios.
  • the method comprises conducting a hybridization in the presence of one or two or more target nucleic acids and/or internal standard nucleic acids, and determining concentrations of one or plural target nucleic acids.
  • the method comprises assaying a target nucleic acid by using a nucleic acid probe capable of discriminating a target nucleic acid and an internal standard nucleic acid according to the present invention (a nucleic acid capable of discriminating).
  • this method comprises assaying a target nucleic acid by quenching the fluorescence from a target nucleic acid probe or internal standard nucleic acid probe not hybridizing with an internal standard nucleic acid and a target nucleic acid.
  • this method comprises adding, subsequent to the hybridization, an exonuclease into an assaying system, and measuring a change in an optical character of an assaying system.
  • the assaying method A will first described.
  • This method is divided by combining a probe for a homogenous solution system with an internal standard probe, and further divided by combining the combined method with an internal standard nucleic acid probe in the following way.
  • This method can be divided by a method for measuring an assaying system to the following two methods.
  • this method is a method using a doubly-labeled nucleic acid in stead of the above probe for a homogenous solution system.
  • this method is a method using a mixture comprising an internal standard nucleic acid probe.
  • FIG. 9 illustrates a method for assaying a nucleic acid according the present invention, in which the simplest labeled nucleic acid and internal standard nucleic acid are used.
  • the illustrated method adopts a Q probe (called a “Qprobe”) as a target nucleic acid probe.
  • a Q probe (called a “Qprobe”) as a target nucleic acid probe.
  • Any of the above probes is preferably usable as a target nucleic acid probe in the present invention.
  • the most preferable target nucleic acid probe is a probe in which an end portion opposite a fluorescent dye-labeled portion is not complementary to a target nucleic acid and/or an internal standard nucleic acid (an optional base sequence comprising a range of from the 1st base to the 5th base, preferably of 1 to 3 bases; in this counting an end base is counted as the 1st base).
  • FIG. 1 The simplest target nucleic acid and internal standard nucleic acid are illustrated in FIG. 1 , in which a singly-labeled nucleic acid is illustrated as a Qprobe.
  • the target nucleic acid probe the singly-labeled probe, is designed so that a change (decreasing (quenching)) in an optical character (fluorescent emission) of a labeling fluorescent dye occurs on its hybridization with a target nucleic acid.
  • a probe as a singly-labeled nucleic acid probe, is arranged such that, as a base sequence of the portion of the target nucleic acid capable of hybridizing with the singly-labeled nucleic acid probe, the base corresponding to the fluorescence-labeled end base of this singly-labeled nucleic acid probe is a G or a C; and a base corresponding to non-fluorescence-labeled end base is a base other than a G.
  • a base sequence is chosen as a base sequence of the portion of an internal standard nucleic acid capable of hybridizing with the singly-labeled nucleic acid probe such that the base corresponding to the fluorescence-labeled end base of this singly-labeled nucleic acid probe is a base other than a G; and a base corresponding to non-fluorescence-labeled end base is a G or a C.
  • the base sequence of the singly-labeled nucleic acid probe should be a base sequence complementary to a target nucleic acid and an internal standard nucleic acid except for bases of both ends.
  • the base of a fluorescence-labeled end of the singly-labeled nucleic acid probe should be complementary to the target nucleic acid, but not to the internal standard nucleic acid; the base of a non-fluorescence-labeled end should be contrary to the fluorescence-labeled end.
  • the singly-labeled nucleic acid probe is possible to design so that, when it hybridizes with an internal standard nucleic acid, a change (decreasing (quenching) in an optical character of a fluorescent dye used for the singly-labeled nucleic acid probe occurs).
  • a base sequence in the region of the internal standard nucleic acid hybridizing with the singly-labeled nucleic acid probe should be arranged so that a base of the internal standard nucleic acid corresponding to a fluorescence-labeled end base of the singly-labeled nucleic acid probe is a G or a C and a base corresponding to a fluorescence-unlabeled end base is a base other than a G.
  • the base sequence in the region of the target nucleic acid hybridizing with the singly-labeled nucleic acid probe should be chosen so that a base of the internal standard nucleic acid corresponding to the fluorescence-labeled end base of the singly-labeled nucleic acid probe is a base other than a G, and a base corresponding to a non-fluorescence-labeled end base is a G or a C.
  • a base sequence of the singly-labeled nucleic acid probe should be a base sequence complementary to the internal standard nucleic acid and the target nucleic acid with excluding both end bases; the fluorescence-labeled end base of the singly-labeled nucleic acid probe should be complementary to the internal standard nucleic acid, but not complementary to the target nucleic acid.
  • the above matters should be contrary.
  • FIG. 9B demonstrates the above description.
  • a base sequence of the internal standard nucleic acid should preferably be identical to the target nucleic acid except both end bases.
  • a preferable internal standard nucleic acid is described.
  • the base of the internal standard nucleic acid corresponding to the base of a fluorescent dye-labeled portion of the above probe should be designed so as to be complementary to the base of a fluorescent dye-labeled portion of the above probe. That is, when the base of a fluorescent dye-labeled portion of the above probe is a C, the base of the internal standard nucleic acid corresponding to that of the above probe should be a G; or, when the base of a fluorescent dye-labeled portion of the above probe is a G, the base of the internal standard nucleic acid corresponding to that of the probe should be a C.
  • the base of the internal standard nucleic acid corresponding to the base of a fluorescent dye-unlabeled portion of the probe should be designed so as to be not complementary to the base of the probe. Its base is preferably an adenine (an A) or a thymine (a T).
  • the base sequence region of a target nucleic acid should be chosen such that, when the base of a fluorescent dye-labeled portion of the probe is a C, the base of a target nucleic acid corresponding to that base is a G; or when the base of a fluorescent dye-unlabeled portion of the probe is a G, the base of the target nucleic acid corresponding to that base is a C; and the base of the target nucleic acid corresponding to the base of a fluorescent dye-labeled portion of the probe is not complementary to the base of the fluorescent dye-labeled portion of the probe.
  • the number of base-pairs formed between the target nucleic acid probe and a target nucleic acid and GC contents of the probe or the nucleic acid become equivalent to that between the target nucleic acid probe and the internal standard nucleic acid and GC contents of the nucleic acid or the internal standard nucleic acid.
  • the both probes is considered to hybridize equally with the target nucleic acid and the internal standard nucleic acid.
  • the above described pattern is related to a pattern such that fluorescence increases on the hybridization of a singly-labeled nucleic acid probe with an internal standard nucleic acid; while the method having a pattern contrary to the above pattern (namely, a pattern showing decreasing fluorescence upon the hybridization of the singly-labeled nucleic acid with the target nucleic acid) is practicable in the present invention.
  • the base sequence of the internal standard nucleic acid should be designed such that, when the base of a fluorescent dye-labeled portion of the singly-labeled nucleic acid probe is a C, the base of the internal standard nucleic acid corresponding to that of the probe is a G; or when the base of a fluorescent dye-unlabeled portion of the probe is a G, the base of the internal standard nucleic acid corresponding to that of the fluorescent dye-unlabeled portion of the probe is a C; and the base of the internal standard nucleic acid corresponding to the base of a fluorescent dye-labeled portion of the probe is not complementary to that of the probe.
  • the pattern is suitably shown in FIG. 8A .
  • a Qprobe receives a markedly fluorescence-quenching effect (decreased intensity of fluorescence; hereinafter having the same concept) on hybridization with a target nucleic acid; such effect produces from the presence of a G in a position complementary to fluorescence-labeled (fluorescent dye-labeled) a C.
  • the base sequence of an internal standard gene should be designed so that an adenine (an A) of the gene presents in a position complementary to a C of the 5′-end of a Qprobe; and a G of the gene presents in a position complementary to a C of the 3′-end of a Qprobe.
  • a G When a Qprobe has hybridized with the internal standard gene, a G does not present in a position complementary to the fluorescence-labeled 5′-end of a Qprobe; as a result, it does not receive any fluorescence-quenching effect. On the contrary, when a Qprobe has hybridized with the target nucleic acid, it receives a markedly fluorescence-quenching effect owing to the presence of a G.
  • a Qprobe can, therefore, specifically detect a target nucleic acid based on a difference of fluorescence-quenching rates.
  • a Qprobe receives a markedly fluorescence effect on hybridizing with an internal standard nucleic acid, which effect is caused by the presence of a G of the internal standard nucleic acid in a position corresponding to a C of the fluorescence-labeled 5′-end of the probe; on hybridization with the target gene, a Qprobe is not found to receive any markedly fluorescence-quenching effect because an A is present in a position of the target gene complementary to a C of the fluorescence-labeled 5′-end.
  • a Qprobe can, therefore, specifically detect an amplifying product from the internal standard gene.
  • FIG. 2 illustrates specifically the method.
  • It comprises one or two or more pairs of one or two or more types of the below target nucleic acid probes and one or two or more types of the below internal standard nucleic acids.
  • the target nucleic acid probe Any target nucleic acid probe as described above can be used, insofar as it is caused a fluorescent character to change on the hybridization with the internal standard nucleic acid. In particular, it preferably has a portion (including a portion of one base) not complementary to the internal standard nucleic acid in one or two or more portions of the probe other than a fluorescence-labeled portion.
  • the internal standard nucleic acid in particular, it is a preferable one having a portion (including a portion of one base) not complementary to the target nucleic acid in one or two or more portions of the internal standard nucleic acid. Further, it is a preferable one having a base-sequence structure (including a structure of one base) such that a region other than a region corresponding to a fluorescence-labeled portion of the target nucleic acid probe is different in one or two or more portion in a region of the internal standard nucleic acid corresponding to the hybridization region of the target nucleic acid probe with the target nucleic acid.
  • a fluorescent dye-labeled portion of the target nucleic acid is a portion including a C or a G, or these bases (within a portion of from the 1st base to the 3rd base, the labeled is counted as the 1st base).
  • the target nucleic acid probe is a Q probe.
  • This method is an illustrative method applicable when it is a method for assaying a target nucleic acid by determining a Tm value using the above novel mixture.
  • the method as described in the below 2) is preferable.
  • the method is a method comprising adding one or plural target nucleic acids into the above-described novel mixture; conducting a hybridization; measuring a fluorescent intensity of the hybridizing solution with increasing temperature; and determining the target nucleic acids by the below procedures.
  • kits comprising the above-described nucleic acid probe and internal standard nucleic acid.
  • a dissociation curve can be rapidly and easily determined by monitoring fluorescence in continuation with changing temperature; a dissociation peak can be obtained by differentiating the resulted dissociating curve.
  • a peak area ratio of the dissociation peaks varies depending upon a constituent ratio of genes (a existing ratio of target nucleic acids). This method is related to a method for determining a gene-constituent ratio based on the dissociation peaks.
  • This method comprises a processing step adding an internal standard nucleic acid; the usable internal standard nucleic acid is an internal standard nucleic acid having mutation incorporated into the region hybridizing with a QProbe.
  • the dissociation between the internal standard nucleic acid and a QProbe occurs in lower temperature than that between the target gene and a QProbe.
  • the dissociation curve becomes such a curve that two curves have been fused.
  • the dissociation curve can be completely separated into two ( FIG. 2 should be referred).
  • a height ratio of the peaks is highly co-relative to a gene-constituent ratio; a gene-constituent ratio among genes in a system can be determined based on a height ratio of peaks obtained from a dissociation curve.
  • a target gene is, thereby, quantitatively assayed.
  • this method is an illustrative method applicable when an internal standard gene meets the above requirement.
  • This method like the method for assaying a gene using the below-described two QProbes (a target nucleic acid probe and an internal standard nucleic acid probe), a method for assaying quantitatively a target gene by determining a gene constituent ratio.
  • a concentration of a probe is lower than a total sum concentration of a target gene and an internal standard gene, it is possible to quantitatively determine correctly a concentration of the target gene insofar as the concentration of an internal standard gene is suitable for determining a gene constituent ratio.
  • this method has following features: 1) no requirement for a processing step for diluting a target gene; 2) no requirement for changing a concentration of a probe; it is possible to solve conventional problems.
  • Two probes for a homogenous solution are used for a method for assaying a gene using two QProbes, which method is the above-described novel method for assaying a gene.
  • Each probe causes a fluorescence-quenching effect on hybridization with any one of the target gene and the internal standard gene.
  • a QP probe using in this method can hybridize with a target gene and an internal standard gene without differentiating both genes, on other wards, half portions of the probe hybridizing with a target gene or an internal standard gene causes no fluorescence-quenching effect.
  • the resulting fluorescence-quenching rate is not great as an expected rate; in particular when a target gene is little in the amount, there are problems such that analyzing errors become greater.
  • the problems can be solved by the above described method according to the present invention. That is, the problems have been expected to be capable of being solved by each of the both ends of a QProbe being labeled with one sort of fluorescent dye being different from the other dyes (see FIG. 3 ).
  • a switching probe one sort of doubly-labeled probe (called a “Switching probe”) obtainable by doubly-labeling both ends of a QProbe with two sorts of dye different from each other, when the probe hybridizes with any of a target gene and an internal standard gene, a fluorescence-quenching effect is caused, namely, any of the hybridized probes causes a fluorescence-quenching effect.
  • a fluorescence-quenching rate is theoretically enhanced two times or more as compared with that using two sorts of QProbes; as a result, a detecting sensitivity is possible to improve two times or more (see FIGS. 3, 11 , and 13 ).
  • This method is specifically not limited insofar as it is a method using a novel mixture comprising the above described doubly-labeled nucleic acid probe and internal standard nucleic acid. Further, it can be a method using the doubly-labeled nucleic acid probe and internal standard nucleic acid described above.
  • the doubly-labeled nucleic acid probe Any doubly-labeled nucleic acid probe as described above is usable without any specified limitation. If changes in optical characters of two sorts of fluorescent dyes labeled to the doubly-labeled nucleic acid probe fall within, as one example, the following instances, the probe is preferable.
  • the base sequence of a probe corresponding to this instance can have optional bases as bases of both of the dye-labeled portions, but on other hand, the base sequence of a target nucleic acid is designed such that a portion of the target nucleic acid corresponding to a portion labeled with any one of both dyes used in the probe includes a G, and that corresponding to a portion labeled with the other dye does not include a G, but includes only an A and/or a T.
  • the base sequence of the internal standard nucleic acid is designed such that it is contrary to that of the target nucleic acid.
  • a base of a dye-labeled portion of the probe can be optional; a base sequence in a target nucleic acid side should be designed so that both regions of the target nucleic acid corresponding to both portions labeled with two dyes in the probe include a G, or does not a G. On other hand, a base sequence in the internal standard nucleic acid should be designed so that any one of both of the regions includes a G.
  • a base of a dye-labeled portion of the probe can be optional; a base sequence in a target nucleic acid side should be designed so that any one of both regions of the target nucleic acid corresponding to both portions labeled with two dyes in the probe include a G. On other hand, a base sequence in the internal standard nucleic acid should be designed so that both of the regions include a G, or does not a G. See FIG. 13 .
  • such a probe as described above is preferably usable.
  • a doubly-labeled nucleic acid is a Qprobe preferable.
  • a characterizing form of the above nucleic acid probe is preferably similar to that in the first invention except the above-described characteristics.
  • It comprises: adding one or plural target nucleic acid into the above-described mixture and conducting hybridizing reaction; measuring a change in an optical character from both dyes in the reaction system; calculating a ratio of the resulting measuring values, or a rate of an changed optical character (one example: a fluorescence-quenching rate); and determining a concentration of the target nucleic acid.
  • An illustrative method will be described in examples 6 and 7.
  • the method is a method using a novel mixture containing an internal standard nucleic acid probe in addition to the ingredient in the mixture as described above, any method can be applicable; the following method is preferable.
  • the method is characterized, in that the method comprises: adding one or plural target nucleic acid into the above-described mixture and conducting hybridizing reaction; measuring a change in an optical character from each dye in the reaction system; calculating a ratio of the resulting measuring values, or a rate of changing in an optical character (a decreasing rate or a emitting rate); and determining concentrations of one or plural target nucleic acids.
  • FIG. 1 The method for assaying a target nucleic acid according to the present invention is shown in FIG. 1 , in which it uses a reaction solution prior to a reaction, including the simplest target nucleic acid probe, internal standard nucleic acid probe and internal standard nucleic acid.
  • the present invention can not be limited by an illustrative method of FIG. 1 .
  • a QProbe is used as a target nucleic acid probe or internal standard nucleic acid probe for simplifying.
  • the method will be described hereinafter with reference to FIG. 1 by using the simplest target nucleic acid probe, internal standard nucleic acid probe and internal standard nucleic acid.
  • QProbe A is used as a target nucleic acid probe and QProbe B as an internal standard nucleic acid probe.
  • target nucleic acid a target gene
  • internal standard nucleic acid an internal standard gene
  • That the number of non-complementary bases of the target nucleic acid probe is caused to be equal to that of bases of the internal standard nucleic acid probe, which bases are complementary to the target nucleic acid in a fluorescence-labeled portion of the internal standard nucleic acid is preferable because the thermo-stability of the hybridizing complex between a target nucleic acid probe and a target nucleic acid comes to be identical to that between an internal standard nucleic acid probe and an internal standard nucleic acid.
  • an fluorescent dye-labeled end portion of the probe is caused to be complementary to a region of the target nucleic acid corresponding to the fluorescent dye-labeled end portion of the probe and is caused to be not complementary to the region of the internal standard nucleic acid corresponding to that of the probe.
  • the end portion opposite the fluorescence-labeled portion is caused to be not complementary in the target nucleic acid and to be complementary in the internal standard nucleic acid.
  • a fluorescence-labeled portion of the probe is caused to be a portion containing a G or a C, or to be a G or C self.
  • a base sequence of the region of the target nucleic acid corresponding to the labeled portion of the probe is designed such that the corresponding region is caused to contain a C or a G, to be a C or G self.
  • the base of the target nucleic acid corresponding to the labeled base of the probe is not necessarily a C or a G; and at least one base of a C or a G is included within a region (in a range of one base to three bases in a direction of the 5′- or 3′-end apart from the base corresponding to a labeled base of the probe, wherein the corresponding base is counted as the 1 st base) of the target nucleic acid containing the base corresponding to a labeled base of the probe.
  • a base sequence of the other end region of the probe should be designed such that the base sequence is caused to be not complementary to a target nucleic acid, but to be complementary to an internal standard nucleic acid. Since this region of the internal standard nucleic acid corresponding to the other end region of the probe has been designed so as to be complementary to a fluorescence-labeled portion of an internal standard nucleic acid probe, the region includes at least one base of a C or a G. Accordingly, the other end region of the target nucleic acid probe includes at least one base of a C or a G, or is a portion of self thereof.
  • the correspondence should be that the region of the internal standard nucleic acid corresponding to the other end region of the probe includes a G or a C, or is a portion of self thereof; that of a target nucleic acid includes a C, or is a portion of C self.
  • a corresponding region of an internal standard nucleic acid includes a C, or is a portion of self thereof
  • that of a target nucleic acid should include a G, or should be a portion of G self.
  • Its base sequence should be the same as that of a target nucleic aid probe, wherein a fluorescence-labeled portion should be contrary to that of the target nucleic acid probe as shown in FIG. 1 .
  • a fluorescent dye to be labeled should be different from that of the target nucleic acid. It is designed such that it hybridizes indiscriminately a target gene and an internal standard gene; and only on hybridization with a target nucleic acid, changes (for example, the figure shows decreasing (quenching)) in optical characters (fluorescence-emission) of dyes used for labeling the probe can occur.
  • the probe is, in this instance, preferably designed such that the end region opposite a labeled portion of the probe is not complementary a target nucleic acid. That the number of non-complementary bases of the target nucleic acid probe is caused to be equal to that of bases of the internal standard nucleic acid.
  • any internal standard nucleic acid with any structure is preferably applicable.
  • the base sequence of the internal standard nucleic acid is preferable to make identical to that of the target nucleic acid except both end bases.
  • the base of the internal standard nucleic acid corresponding to the base of a fluorescent dye-labeled portion of an internal standard nucleic acid probe is complementary to the base of the internal standard nucleic acid probe.
  • the labeled region of the internal standard nucleic acid probe contains a C, or is a portion of C self
  • the corresponding region of the internal standard nucleic acid contains a or is a portion of G self
  • the labeled region of the internal standard nucleic acid probe includes a G, or is a portion of G self
  • the corresponding region of the internal standard nucleic acid contains a C, or is a portion of C self.
  • the region of the internal standard nucleic acid corresponding to the base of a fluorescent dye-unlabeled portion of an internal standard nucleic acid probe is not complementary to the base of the internal standard nucleic acid probe. That is, when the unlabeled region of the internal standard nucleic acid probe includes a G, or is a portion of G self, the corresponding region of the internal standard nucleic acid is caused not to contain a C, and is caused to be a portion containing only a G, an A or a T, or to be a portion of each self thereof, preferably being caused to be a portion including only an adenine (a A) and/or a thymine (a T), or to be a portion of each self thereof.
  • a corresponding region of an internal standard nucleic acid probe contains a C, or is a portion of C self
  • a corresponding region of an internal standard nucleic acid is caused not to contain a G, and is caused to be a portion containing only a C, an A, a T, or a portion of each self thereof.
  • thermo-stability of the hybridizing complex between a target nucleic acid probe and a target nucleic acid comes to be identical to that between an internal standard nucleic acid probe and an internal standard nucleic acid; both probes are expected to be capable of hybridizing with a target nucleic acid and an internal standard nucleic acid indiscriminately.
  • this assaying method will be illustrated with reference to FIG. 1 .
  • a G of the target nucleic acid comes at a position complementary to a fluorescence-labeled C (labeled with a fluorescent dye); the fluorescence emission of QProbe A is markedly quenched (a fluorescent intensity is reduced) (hereinafter, meaning the same).
  • a base sequence of an internal standard nucleic acid is arranged such that an adenine (a A) of the internal standard nucleic acid comes at a position complementary to the 5′-end base C of QProbe A; as a result, on hybridization of QProbe A with the internal standard nucleic acid, the fluorescence-emission of Qprobe A is not quenched because G is not present in a position complementary to the fluorescence-labeled 5′-end. On hybridization with the target nucleic acid, the fluorescence-emission of QProbe A is markedly quenched, because G comes at the complementary position: In this way, a QProbe can detect specifically a target nucleic acid based on the difference of quenching rates.
  • a A adenine
  • the fluorescence-emission of QProbe B is markedly quenched, because G of the target nucleic acid comes at a position complementary to a fluorescence-labeled 3′-end C; on hybridization of QProbe B with the target nucleic acid, the fluorescence-emission of Qprobe B is not found to be quenched because an A comes at a position complementary to the fluorescence-labeled 3′-end C of the QProbe B. In this way, QProbe B can detect, on the contrary to QProbe A, specifically a PCR-amplified product from the internal standard nucleic acid.
  • the assaying method comprises: adding one or plural target nucleic acid into the mixture and conducting hybridizing reaction; measuring a change in an optical character from the target nucleic acid probe and a change in an optical character from the internal standard nucleic acid probe; calculating a ratio of the resulting measuring values, and determining a concentration of the target nucleic acid by multiplying a used concentration of the internal standard by an obtained calculating value.
  • each of the above-described QProbe A and QProbe B can hybridize with the target gene and the internal standard gene indiscriminately. Thereby, the hybridization of any of the probes with any of genes relies completely on an existing ratio of genes. On this reason, a ratio between measuring values obtained by measuring changes in optical characters from QProbe A and that from QProbe B becomes to be a constituent ratio between the target nucleic acid and the internal standard nucleic acid.
  • the novel method for assaying a target nucleic acid is, as described above, a method for determining a gene constituent ratio.
  • a method for determining a gene constituent ratio even when the total sum concentration of a target nucleic acid and an internal standard nucleic acid is higher than a total sum concentration of a target nucleic acid probe and an internal standard nucleic acid probe (such case as that a nucleic acid concentration is higher than a probe concentration), it is possible to determine a constituent ratio of a target nucleic acid and an internal standard nucleic acid insofar as the concentration of an internal standard nucleic acid is suitable for determining a nucleic acid constituent ratio (insofar as a concentration of an internal standard nucleic acid is enough close to a concentration of a target nucleic acid).
  • this method can accurately determine quantitatively a concentration of a target nucleic acid.
  • nucleic acids comprising the above-described target nucleic acid probes and internal standard nucleic acid probes.
  • Kits for assaying a target nucleic acid comprising one or plural pairs of nucleic acids comprising the above-described target nucleic acid probes and internal standard nucleic acid probes; and one or plural internal standard nucleic acids corresponding to pairs of the nucleic acid probe as described in above 1).
  • the method has the following two ways.
  • the method is based on hybridization without discriminating a target gene and an internal standard gene; that any of the probes hybridizes with any of genes relies completely on an existing ratio of genes. Owing to this, for example, it is expected that a constituent ratio of genes can be determined, based on hybridizing ratio between the hybridization of QProbe A with a nucleic acid and the hybridization of QProbe B with a nucleic acid. Fluorescence-quenching is excitingly caused on hybridization of QProbe A with a nucleic acid or on hybridization of QProbe B with an internal standard nucleic acid.
  • a ratio between a fluorescence-quenching rate from QProbe A and that from QProbe B is positively proportional to a constituent ratio between the target nucleic acid and the internal standard nucleic acid; as a result, a constituent ratio of genes can be determined based on the ratio of fluorescence-quenching rates.
  • novel mixture in this method comprises one or two or more nucleic acids as described below.
  • novel mixture comprising two or more nucleic acids, sorts of dyes, with which each probe is labeled, are different from each others; and the dyes have different optical characters from each others, as described above.
  • nucleic acids comprised one or two or more nucleic acids and internal standard nucleic acids as described below.
  • the target nucleic acid probe of the present invention is not complementary to a target nucleic acid and an internal standard nucleic acid at one or two or more portions of a fluorescent dye-labeled region.
  • the doubly-labeled nucleic acid probe according to the present invention is not complementary to any one of a target nucleic acid and an internal standard nucleic acid at a labeled portion with any of two dyes used for labeling the doubly-nucleic acid.
  • the method according to the present invention can, subsequent to determination of an existing ratio of a target nucleic acid and an internal standard nucleic acid, determine correctly a concentration or amount of the target nucleic acid based on the obtained existing ratio.
  • An A a C or a G containing portion (preferably C) of region one (1) to region n of a single stranded oligonucleotide (including an end portion, a base moiety, a sugar moiety, or a phosphate moiety of a portion in its chain; n stands 10, preferably 5, more preferably 3.) is labeled with each of dye 1 to dye n, respectively, which each dye can cause a change in an optical character on its hybridization with a target nucleic acid. Sorts of dye 1 to dye n each independently are different fluorescent dyes. In addition, region 1 to region n independently are different regions.
  • the structure of a labeled portion in the probe and the structure of a target nucleic acid corresponding to the probe are like those as described above.
  • a preferable example of the multiply-labeled nucleic acid probe is a QProbe; further, its preferable labeled portion is a portion of C self or a region containing the portion.
  • nucleic acid like the internal standard nucleic acid used in the assaying method using a doubly-labeled nucleic acid probe.
  • the structure of its portion corresponding to each of the fluorescent dye-labeled portions of the multiply-labeled nucleic acid probe should be different from that of a nucleic acid.
  • the “different structure” herein means whether or not a structure is complementary to a fluorescent dye-labeled portion of the probe. These structures each have a structure applied correspondingly to the above both structures.
  • two or more internal standard nucleic acids become to be needed correspondingly; the above-described novel mixture of the present invention should comprise two or more internal standard nucleic acids.
  • Its method comprises: adding one or two or more target nucleic acids into the novel mixture in this method; conducting hybridization; measuring a change or changing rate (for example, a quenching rate) in an optical character of each fluorescent dye labeled to each probe in the hybridizing system using one or two or more measuring wave length, in that the change is caused by the hybridization of a target nucleic acid or internal standard nucleic acid and a corresponding probe; calculating a ratio between a measuring value in regard to the target nucleic acid and that in regard to the internal standard nucleic acid; and determining one or two or more target nucleic acids on the basis of the obtained ratio because the concentrations of the internal standard nucleic acids have been predetermined.
  • a change or changing rate for example, a quenching rate
  • a usable novel mixture may be an one like the mixture as described above.
  • the method is a method comprising adding one or plural target nucleic acids into the above-described novel mixture; conducting a hybridization; measuring a fluorescent intensity of the hybridizing solution with increasing temperature; and determining a existing ratio of the target nucleic acids by the below procedures.
  • a dissociation curve can be rapidly and easily determined by monitoring fluorescence in continuation with changing temperature; a dissociation peak can be obtained by differentiating the resulted dissociating curve.
  • a peak area ratio of the dissociation peaks varies depending upon a constituent ratio of genes (a presence ratio of target nucleic acids). This method is related to a method for determining a gene-constituent ratio based on the dissociation peaks.
  • This method is a method for determining a existing ratio of genes. Thereby, even when the total sum concentration of a target gene and an internal standard gene is higher than a total sum concentration of QProbe A and QProbe B (such case as that a gene concentration is higher than a probe concentration), it is possible to determine a constituent ratio of a target gene and an internal standard gene insofar as the concentration of an internal standard gene is suitable for determining a gene constituent ratio (insofar as a concentration of an internal standard gene is enough close to a concentration of a target gene). As a result, this method can determine accurately and quantitatively a concentration of a target gene.
  • this method has following features: 1) no requirement for a processing step for diluting a target gene; and 2) no requirement for changing a concentration of a probe; it is possible to solve conventional problems.
  • this method comprises assaying a target nucleic acid by quenching the fluorescence from a target nucleic acid probe or internal standard nucleic acid probe not hybridizing with either an internal standard nucleic acid or a target nucleic acid.
  • An object of the present invention is capable of being achieved by using illustrative quenching substances or quenching substance-labeled probes as described below. These are mere examples; these cannot impose any limitation on the present invention. See Example 9.
  • Quenching substance Illustrative are the above quenchers. Any one of the illustrative substances can be preferably used. Preferably illustrative are Dabcyl, BH, Eclipse, Elle Quencher.
  • Quenching substance-labeled probe Preferably usable is a probe labeled with any one of the above quenchers at a portion of an oligonucleotide (any of a deoxynucleotide body and ribonucleotide body can be usable). Specifically see Example 9.
  • a labeling portion or position can be preferably usable any portion or position insofar as those can cause a change in an optical character (for example, a fluorescence emission or quenching) of a target nucleic acid probe and/or internal standard nucleic acid probe not hybridizing with a target nucleic acid and/or an internal standard nucleic acid.
  • an optical character for example, a fluorescence emission or quenching
  • the hybridization with equilibrium induces a change (for example, fluorescence emission or quenching) in the optical character(s) of a target nucleic acid probe and/or an internal standard nucleic acid.
  • the action of the exonulease to the probe (s) under such conditions can make a mononucleotide labeled with a fluorescent dye free from the nucleic acid probe(s).
  • the free mononucleotide labeled with a fluorescent dye does not any longer express any specific optical characteristics manifested on hybridization of a nucleic acid probe with a nucleic acid. This method measures that change.
  • the specific method for assaying a nucleic acid will be described in Examples.
  • the labeled target nucleic acid probe and/or internal standard nucleic acid probe are (is) not complementary to at least one of the nucleic acid and internal standard nucleic acid in a region containing a fluorescence-labeled portion (the region: a sequence of one base to three bases, preferably of one base).
  • a novel mixture according to the present invention contains an enzyme; the mixture containing the enzyme is not in a form such that the enzyme is mixed with a mixture comprising a target nucleic acid probe and/or an internal standard nucleic acid probe and an internal standard nucleic acid, but the enzyme is preferably in a form attached at a set to the novel mixture.
  • Exonuclease I (Armersham Biosciene Corp.), Vent DNA polymerase (New England Biolabs), T7 DNA polymerase (New England Biolabs), Klenow Fragment DNA polymerase (New England Biolabs), Phi29 DNA polymerase (New England Biolabs), Exonuclease III (Fermendas).
  • a product amplified by the nucleic acid-amplifying method is assayed by using the above method for assaying for assaying a nucleic acid.
  • This method is applicable to any product amplified by a gene-amplifying method.
  • This method comprises, in particular, amplifying one or plural target nucleic acids in a reaction system of the above invention containing one or plural internal standard nucleic acids by a gene-amplifying method; assaying a nucleic acid in the obtained reaction solution or amplified product as a sample by using the above-described nucleic acid-assaying method.
  • the invention comprises inventions A, B, C and D.
  • This method comprises, in particular, amplifying one or plural target nucleic acids in a reaction system comprising one or plural internal standard nucleic acids until a stationary phase (including an initial phase, middle phase and stationary phase) by a gene-amplifying method; and assaying a nucleic acid in the obtained reaction solution or amplified product as a sample by a conventionally-known nucleic acid-assaying method.
  • the method comprises; assaying a nucleic acid in the amplified product as described in the above 1) as a sample by a novel nucleic acid-assaying method of the present invention.
  • This method comprises amplifying one or two or more nucleic acids in a reaction system comprising an internal standard nucleic acid of the present invention by a gene-amplifying method; and assaying one or two or more nucleic acids prior to the amplification.
  • the gene-amplifying method is a nucleic acid-amplifying method using the same primer as a primer of a target nucleic acid and a primer of an internal standard nucleic acid; and the method for assaying a nucleic acid is a method for assaying one or two more nucleic acids prior to an amplification.
  • the gene-amplifying method is a method using a Qprobe as a primer; and the method for assaying a nucleic acid is a method for assaying one or two more nucleic acids prior to an amplification.
  • the gene-amplifying method is a method using a primer which is caused an optical character of the primer to increase upon hybridization of the primer with a target nucleic acid and/or internal standard nucleic acid; and the method for assaying a nucleic acid is a method for assaying one or two more nucleic acids prior to an amplification.
  • This invention is applicable to any product obtained by a gene-amplifying method.
  • it is preferably applicable to amplified product of a gene, which makes it impossible to assay, that is, the amplified product of a gene amplified until a stationary phase (including a stationary phase).
  • This invention is applicable to any product obtained by a gene-amplifying method.
  • it is preferably applicable to amplified product of a gene, which makes it impossible to assay, that is, the amplified product of a gene amplified until a stationary phase (including a stationary phase).
  • It is a novel method for assaying a target nucleic acid wherein said method comprise amplifying one or plural target nucleic acids in a reaction system comprising the internal standard nucleic acids as described in invention 2 of the 2 nd invention until a stationary phase (including a stationary phase); assaying using the novel mixture according to any one of the above 1) to 3) of invention 2 of the 2 nd invention one or two or more target nucleic acids prior to the amplification of the nucleic acids using the obtained reaction solution or amplified product as a sample, or
  • This invention is applicable to any product obtained by a gene-amplifying method.
  • it is preferably applicable to amplified product of a gene, which makes it impossible to assay.
  • the gene-assaying method through an gene-amplifying method is a method comprising amplifying a gene and determining the amplified gene; it is highly sensitive and can assay even a mere-existing gene. Thereby, the method is one of a gene-assaying methods used at present the most popularly.
  • various methods are known; and those have problems such as described subsequently. These detailed contents will be mentioned below.
  • a PCR method that is a gene-amplifying method used the most widely at present, the reaction is known to proceed in a exponential function until the amplified product accumulates to a certain level. With increasing an amplified product, however, its amplification efficiency is lowered and reaches to a fixed level (reaching to a plateau); this indicates that the obtained amplified product is constant regardless the initial amount of a gene on enough amplifying reaction. Thereby, the initial amount of a gene is incapable of being assayed based on the amount of the amplified gene product after completed amplification (at an endpoint). This problem is common to a known gene-amplifying method, a PCR method being not restricted.
  • a gene-amplification efficiency of a common gene-amplifying method is constant at an initial phase of the reaction regardless the initial amount of a gene. Therefore, a cycle number of the reaction, in that the amplified product reaches to a threshold, varies on initial amounts of a gene insofar as an amplified product is increased in an exponential function; for example, upon amplification of a predetermined gene diluted in some diluting rates, the cycle number (a CT value) on an amplified product reaching to a threshold is in reverse correlation to an initial concentration of the gene.
  • a relative equation obtained in thus way is usable as a calculation curve for assaying the unknown amount of a target nucleic acid in an unknown sample.
  • an amplification efficiency of a target gene in an unknown sample is expected to be constant; the initial concentration of the target gene can be determined quantitatively from the above calculating curve, following the determination of a Ct value obtained in a similar manner as above. Accordingly, an initial concentration of a gene can be assayed insofar as an amplified product can be monitored in real time.
  • the gene-assaying method based on this principal is a real time quantitative PCR method. This method does not requires (1) post-PCR processing steps and (2) to open a reaction tube, so that this method has excellent features such that the assaying is simple and rapid; and the content of the tube is not contaminated with a foreign matter.
  • a competitive PCR method comprises: adding a primer for amplifying a target gene and the target gene of the predetermined amount (called an internal standard gene) for being amplified by the same primer as in the target nucleic acid into a reaction system; amplifying at the same time together the target gene and internal standard nucleic acid; subsequent to completed amplification, isolating and quantitatively determining the amplified product from the target gene and the amplified product from the internal standard gene by using an electrophoresis and the like; calculating a ratio of the amplified products (the amplified product from the internal standard gene/that from the target gene); and determining a concentration of the target gene by multiplying the amount of the internal standard gene added at the start of amplification by the obtained ratio, because the amplification efficiency of the target gene and that of the internal gene is expected to be the same owing to the amplification using the same primer as a primer for the target gene
  • This method is difficult to be affected by an amplification inhibitor because a target gene and an internal standard gene are amplified in the coexistence thereof; the reliance on the obtained determining value is high (its cause: for example, even if the inhibitor is present in a assaying system, an amplification efficiency is at all lowered likely in regard to a target gene and a internal standard gene; the existing inhibitor does not affect a ratio of amplified products; as a result, an accurate determining value is obtainable in the competitive PCR.).
  • the characteristics can be mentioned such that the instrument for assaying is comparatively simple and non-expensive.
  • the real time competitive method is a method for assaying an initial concentration of a target gene prior to the amplification of the target gene, wherein it is an improved competitive PCR method and comprises: conducting an amplification of a target gene and an internal gene in the coexistence thereof using a TagMan probe, a QProbe or the like; monitoring at the same time in real time an amplified product from the target gene and an amplified product from the internal standard gene; and determining an initial concentration of a target gene prior to the amplification of the target gene based on the fluorescent signal amount from each the amplified products from the target gene and internal standard gene.
  • This method embraces excellent features such that it does not requires (1) post-PCR processing steps and (2) to open a reaction tube, and (3) further it is, however, difficult to be affected by an inhibitor because of a competitive method.
  • There are problems like the real time quantitative PCR method in this method such that (i) the apparatus usable for assaying is larger and expensive, and (ii) its sample-treating power is lower, because it is required in this method to monitor at the same time in real time an amplified product from an internal standard gene and that from a target gene.
  • the problems as described above are summarized in the following table.
  • the conventional gene-assaying method is recognized to have some problems.
  • the above described gene-assaying methods are applicable to any gene-assaying methods other than a PCR method such as an NASBA method, an LAMP method, an RCA method, an ICAN method; the methods are at present applied to many gene-determining method through various gene-amplifying method.
  • These methods embraces problems at all common to gene-amplifying methods; even in any gene-assaying method through any gene-amplifying method, the above-described problems are desired to be solved.
  • a conventional competitive PCR method makes it possible to determine a ratio of amplified products at an end point, but a reaction tube is necessary to open; so the ratio is capable of being rapidly determined.
  • a real time competitive PCR method being conventional like the above method and using a fluorescence-labeled probe, does not require to open a reaction tube and is capable of detecting rapidly an amplified product.
  • a ratio of fluorescent signals obtained using a conventional fluorescence-labeled probe in that method does not always reflect usually a quantitative ratio of amplified products; namely, a regional gene reflecting correctly it is limited.
  • each of amplified products requires to be detected in a regional gene where a fluorescent signal ratio is quantitatively proportional to an amplified product ratio. Thereby, a real time competitive PCR method has to be always monitored. As stated above, no method is present until now for determining an amplified product ratio at an endpoint and rapidly with closing a reaction tube.
  • This invention is related to a novel method for assaying a gene and a novel nucleic acid probe usable therefore. In the following description, those details will be described.
  • a Switching probe has features such that (1) the base of each of both ends of the probe is a C, and (2) the both ends are labeled with dyes having colors different in fluorescent emission.
  • the base sequence of a target nucleic acid is designed such that a G is present at a position complementary to a C of the 5′-end of the Switching probe, and an A is present at a position complementary to a C of the 3′-end; on the other hand, in the base sequence of an internal standard gene, the above G is replaced by an A, and the above A by G.
  • the absence of a G at a position of the amplified product corresponding to its 5′-end does not result in a markedly fluorescence-quenching effect in the dye labeled at its 5′-end; the presence of G complementary to its 3′-end does result in.
  • each of the amplified products comes to be capable of specifically being detected by the observation of fluorescence-quenching of any dye labeled at any the both ends.
  • the base sequence of the internal standard gene has features such that (1) the internal standard gene is capable of be amplified by using a primer common to that of a target gene, (2) a GC content of a target gene is the same as that of the internal standard gene, (3) a length of the base sequence of a portion of the internal standard gene completely complementary to the target gene on hybridization with an amplification product amplified from the target gene is the same as that of the target gene complementary to the internal standard gene on hybridization with an amplification product amplified from the internal standard gene, and (4) a base sequence of the target nucleic acid is the same as that of the internal standard gene except the bases complementary to both ends of a QProbe.
  • a Switching probe can hybridize at random with an amplification product from a target gene and that from an internal standard gene without differentiating those; a ratio between Switching probe binding to an amplification product from a target gene and Switching probe binding to that from an internal standard gene is completely identical to a ratio of an amplification product from the target gene and that from the internal standard gene. Thereby, Based on a ratio between fluorescence-quenching rates of the two dyes labeled to both ends of the Switching probe, a ratio of amplification products can be determined.
  • a gene-amplification rate is the same in a target gene and internal standard gene because (1) a primer of a target gene and internal standard gene is common, (2) a GC content of a target gene is completely the same as that of the internal standard gene, and (3) the base sequences of a target gene and a internal standard gene are the same except that two portions are different. Further, based on the above (2) and (3), no bias generated by re-bonding of amplification products could occur. Therefore, a constituent ratio of genes comes to be capable of keeping having a starting ratio.
  • an internal standard gene may or may not be required to have the above features.
  • an amplification product can be quantitatively determined based on fluorescence-quenching rates of two dyes labeled to the both ends of a Switching probe.
  • a ratio of amplification products can be quantitatively determined by using an internal standard gene and a Switching probe, wherein said determination can be rapidly and simply carried out at an end point without opening a reaction tube; many samples can be treated.
  • a method for assaying quantitatively a gene is a method comprising amplifying a target gene; then determining a ratio of amplification products from a target gene and an internal standard gene; and making quantification of the target gene.
  • a method for amplifying a gene is capable of amplifying together a target gene and internal standard gene with keeping a starting gene-constituent ratio
  • the method is applicable to any method for amplifying a gene regardless of its sort. Thereby, this method is applicable to an LAMP method, an RCA method, an ICAN method and the like, and further, a method for amplifying a gene other than a PCR method.
  • a gene-constituent ratio can be determined by analyzing a dissociation curve obtainable by a QProbe; this method is expected to be applicable to a competitive gene-assaying method through a gene-amplifying method.
  • An internal standard gene usable in this method should be a probe such that a mutation is inserted into a portion of said probe capable of hybridizing with a QProbe.
  • a dissociation curve is prepared of the obtained amplification products using the QProbe, followed by preparation of dissociation peaks based on the obtained dissociation curve.
  • a gene-constituent ratio can be determined based on a peak-height ratio of the dissociation peaks because the peak-height ratio is highly co-relative to a gene-constituent ratio.
  • requirements for an internal standard gene two requirements can be mentioned such that (1) a starting gene ratio prior to gene-amplification is kept in any phase of the amplification (an amplification efficiency of an internal standard gene is the same as that of a target gene.), and (2) a dissociation peak derived from a target gene are enough separated from a dissociation peak derived from an internal standard gene so that a gene-constituent ratio can be determined.
  • an internal standard gene is not always required to have the above features.
  • a method for amplifying a gene is capable of amplifying together a target gene and internal standard gene with keeping a starting gene-constituent ratio
  • the method is applicable to any method for amplifying a gene regardless of its sort.
  • this method is applicable to an NASBA method, an LAMP method, an RCA method, an ICAN method and the like, and further, a method for amplifying a gene other than a PCR method.
  • This invention is a method for determining accurately a target nucleic acid using a measuring value obtained by the methods of the present invention. The details will be described in Examples 8 and 11.
  • nucleic acid probes In this examples, various nucleic acid probes, internal standard nucleic acids, and target nucleic acids are used as an oligodeoxynucleotide, unless otherwise specifically indicated.
  • an fluorescence-labeled portion or position is the 5′-OH group of a sugar of the 5′-end in regard to the 5′-end (the group is obtainable by dephosphorylation); on the other hand, the 3′-OH group of a sugar of the 3′-end in regard to the 3′-end:
  • a novel mixture comprising two QProbes and a novel method for assaying a gene making use thereof.
  • the novel mixture having the following composition was prepared.
  • Target gene and internal standard gene oligonucleotides were used.
  • oligonucleotide by relying custom synthesis services (Espec oligoservices Inc.).
  • Base sequence of target gene 5′-AGTTC CGGAA AGGCC AGAGG AG-3′
  • Base sequence of internal standard gene 5′-GGTTC CGGAA AGGCC AGAGG AA-3′
  • the QProbe A (a Qprobe for detecting a target gene) was in fluorescence labeled with BODIPY FL (Molecular probes Inc., D-6140); the QProbe B (a QProbe for detecting an internal standard gene) was labeled with TAMRA (Molecular probes Inc., C-6123).
  • Buffer 10 mM Tris-HCl buffer (pH: 8.3), KCl: 50 mM, MgCl 2 : 1.5 mM.
  • fluorescence measurements were carried out by a fluorometer, LS50B (PerkinElmer Inc.) with an temperature-controlling instrument (Inc.); the measurements were conducted at 480 nm excitation wavelength and 520 nm fluorescence wavelength for the QProbe A, and at 550 nm excitation wavelength and 580 nm fluorescence wavelength for the QProbe B.
  • Fluorescence measurements on hybridization were conducted 60° C. A fluorescent intensity at the temperature (95° C.) as a reference, the temperature completely de-hybridizing from a probe; fluorescent quenching rates were determined based on the following equation.
  • a fluorescent quenching rate (%) (1 ⁇ (F60/F95)/(only F60 probe/only F95 probe)) ⁇ 100, wherein
  • F60 a fluorescent intensity value at 60° C. in presence of a target gene
  • F95 a fluorescent intensity value at 95° C. in presence of a target gene
  • F95 a fluorescent intensity value at 95° C. in absence of a target gene.
  • FIG. 5 illustrates the experimental results. On the basis of the graphs, it was cleared that a constituent ratio of a target gene/an internal standard gene was highly correlative to a ratio of QProbe A quenching rate/a QProbe B quenching rate. This method was, thereby, suggested to enable a target gene to be assayed.
  • this method is a method having features such that (1) a processing step for diluting a gene is not necessary; and (2) it is not necessary to make a concentration of a probe vary.
  • a probe was prepared in which said probe was labeled at a C of a sugar of the 3′-end with a dye to be screened.
  • a fluorescence-quenching rate was assayed by making the prepared probe hybridize with a corresponding chain in a solution.
  • Target gene an oligo DNA was used.
  • oligonucleotide by relying custom synthesis services (Espec oligoservices Inc.). Base sequence: 5′CCCCC CCCCC CCTTT TTT3′ Dye: PacificBlue (P-10163), TET (C-6166), TBSF (C-6166), HEX (T-20091), and R6G (C-6127) were tested.
  • Buffer 10 mM Tris-HCl buffer (pH: 8.3), KCl: 50 mM, MgCl 2 : 1.5 mM.
  • Fluorescent measurements were conducted by a fluorometer, LS50B (PerkinElmer Inc.) with a temperature-controlling instrument (PerkinElmer Inc.). Conditions for fluorescent measurements were determined by measuring maximum excitation wavelengths and maximum fluorescence wavelengths of each dyes using LS50B. In order to fluorescent quenching rates, measurements were conducted by using the obtained maximum excitation wavelength and maximum fluorescent wavelength. The maximum excitation wavelengths and maximum fluorescent wavelengths of each dyes were shown the description of the below result section. The slit width to measure was 5 nm in both excitation and fluorescent wavelengths.
  • FIG. 8 indicates the experimental procedures. The fluorescent measurement was conducted at 35° C.
  • Fluorescent quenching rate(%) (measuring value(i) ⁇ measuring value(ii)) ⁇ measuring value(i) ⁇ 100
  • fluorescent quenching was confirmed in all dyes tested. Specifically the fluorescent quenching was marked in PacificBlue and R6G; the fluorescent quenching rates were higher in those than in dyes known so far. Further, PacificBlue (its implement unknown), R6G (its implement unknown), BODIPY FL (its implement known) and TAMRA (its implement known) each were different in fluorescent character thereof; by using four probes labeled with the above dyes, four genes being present in the same could be detected concurrently.
  • the novel mixture having the following composition was prepared.
  • a target gene was assayed by adding the target gene in the above novel mixture. Further, the fluorescent quenching rates obtained by using the Switching probe and the fluorescent quenching rates obtained by using two QProbe were compared.
  • Target gene and internal standard gene oligonucleotides were used.
  • oligonucleotide by relying custom synthesis services (Espec oligoservices Inc.).
  • Base sequence of target gene 5′-TTTGG ATGAC TGACT GACTG ACTGA CGAGA TTT-3′.
  • Base sequence of internal standard gene TTTAG ATGAC TGACT GACTG ACTGA CGAGG TTT-3′.
  • Buffer 10 mM Tris-HCl buffer (pH: 8.3), KCl: 50 mM, MgCl 2 : 1.5 mM.
  • BODIPY FL was labeled on C of the 5′-end; the hybridization with a target gene resulted in a marked fluorescent quenching.
  • TAMRA was labeled on C of the 3′-end; the hybridization with an internal standard gene resulted in a marked fluorescent quenching.
  • a ratio between the quenching rate for BODIPY FL and the quenching rate for TAMRA was expected to be highly co-relative to a existing ratio of a target gene and an internal standard gene.
  • FIG. 6 illustrates the experimental results.
  • the fluorescent quenching rates obtained on making of the Switching probe and the fluorescent quenching rates obtained on making use of two QProbe were compared. Those results are shown in Table 3. As confirmed from this table also, the fluorescent quenching rates obtained on making use of Switching probe is about two-times higher than those obtained on making use of two QProbes. This fact indicates that the use of a Switching probe enables more accurate determination of a target gene than the use of two QProbes.
  • Target gene a PCR product of a soybean (round-up soybean) recombinant RRS gene; the base sequence of the target gene: 5′- A GTTC CGGAA AGGCC AGAGG A G -3′
  • the probe can hybridize with the described sequence.
  • the sequence other than those is common to that of the target gene or internal standard gene; thereby, it is not described.).
  • Internal standard gene a PCR product of a soybean (round-up soybean) recombinant RRS gene artificially incorporated with a mutation.
  • Base sequence of the internal standard gene 5′- G GTTC CGGAA AGGCC AGAGG A A -3′
  • the underlined portion is different from that of the target gene.
  • the probe was capable of hybridizing with the described sequence.
  • the sequence other than those was common to that of the target gene or internal standard gene; thereby, it is not described.).
  • Synthesis by relying custom synthesis services (Espec oligoservices Inc.).
  • An oligoDNA having a base sequence of a internal standard gene as targeted was prepared by relying custom synthesis services (Espec oligoservices Inc.).
  • the obtained oligoDNA was amplified, using itself as a temperate, by a PCR amplification method using the above primer for detecting; the amplification product was purified using Microcon PCR (Millipore Inc.). Following the purification, the amplification product was assayed quantitatively using PicoGreen (Molecular probes Inc.); the amplification product obtained in such a way is used as an internal standard gene.
  • Quantitative determination using PicoGreen was conducted at 480 nm as an excitation wavelength and 520 nm as a fluorescent wavelength. Used slit width was 5 nm in any wavelengths.
  • the PCR was conducted using a thermal cycler (iCycler, Biorad Inc.).
  • a QProbe was added in the DNA solution and then fluorescent measurements were conducted.
  • the fluorescent measurements were conducted at 60° C. and 95° C. (the measuring values at 60° C. were those on hybridization of the probe with a target gene; the measuring values at 95° C. were those on complete cleavage of the hybrid complex of the probe and the target gene).
  • the measuring values at 95° C. were taken as a reference so as to determine a fluorescence-quenching rate.
  • a relation of a ratio of the fluorescence-quenching rates of the each probes and a existing ratio of the target gene and the internal standard gene was examined; it was examined whether or not a gene existing ratio could be determined based this relative equation.
  • Target gene and internal standard gene oligonucleotides were used.
  • oligonucleotide by relying custom synthesis services (Espec oligoservices Inc.).
  • Base sequence of target gene 5′-AGTTC CGGAA AGGCC AGAGG AG-3′
  • Base sequence of internal standard gene 5′-GGTTC CGGAA AGGCC AGAGG AA-3′
  • Buffer 10 mM Tris-HCl buffer (pH: 8.3), KCl: 50 mM, MgCl 2 : 1.5 mM.
  • fluorescence measurements were carried out by a fluorometer, LS50B (PerkinElmer Inc.) with a temperature-controlling instrument (Inc.); the measurements were conducted at 480 nm excitation wavelength and 520 nm fluorescence wavelength.
  • a fluorescent quenching rate(%) (1-( F 60 /F 95)/(only F 60 probe/only F 95)) ⁇ 100, wherein
  • F60 a fluorescent intensity value at 60° C. in presence of a target gene
  • F95 a fluorescent intensity value at 95° C. in presence of a target gene
  • F95 a fluorescent intensity value at 95° C. in absence of a target gene.
  • FIG. 10 shows the experimental results.
  • the total sum amount of the target gene and the internal standard gene was equal to the additive amount of the probe (400 nM), and when more than the additive amount of the probe (800 nM), the calibration curves agreed with each other. This showed that, when the amount of the probe was not more than the total sum of the amount of a gene, the gene-constituent ratio obtained on determination of a fluorescent quenching rate for the BODIPY dye was equaled regardless of a total sum of the amount of a gene.
  • a gene-constituent ratio can be accurately determined quantitatively based on an obtained fluorescent quenching rate for a BODIPY dye.
  • a target nucleic acid is capable of being assayed accurately by making the amount of a probe vary variously
  • this method can preferably assay a target nucleic acid using a probe making its amount vary variously.
  • Target gene and internal standard gene oligonucleotides were used.
  • Base sequence of target gene (a sequence underlined is capable of hybridizing to the probe) 5′-TAA TG ATGAC TGACT GACTC ACTGA CGAT G CT-3′
  • Base sequence of internal standard gene (a sequence underlined is capable of hybridizing to the probe) 5′-TGG TA TGACT GACTG ACTGA CTGAC GAGT A AT-3′
  • Example 5 used fluorescent dyes and relying custom synthesis services and the like were like Example 5.
  • BODIPY FL of the doubly-labeled probe marked fluorescent quenching for was caused because of the presence of G in near proximity of a fluorescence-labeled end base on hybridization of the doubly-labeled probe to the internal standard nucleic acid. Therefore, a ratio between a fluorescent quenching rate for BODIDY FL and a fluorescent quenching rate for TAMRA was expected to be high co-relative to a ratio between a target gene and internal standard gene.
  • the experimental results are shown in FIG. 12 . From the graphs, a ratio between a fluorescent quenching rate for BODIDY FL and a fluorescent quenching rate for TAMRA is ascertained to be high co-relative to a ratio between a target gene and internal standard gene. It is suggested from these results that the method using the doubly-labeled nucleic acid probe of this model is capable of accurately assaying a target gene quantitatively in any case where the total amount of a gene was larger than that of a probe, or smaller.
  • Target gene and internal standard gene oligonucleotides were used.
  • Base sequence of target gene (a sequence underlined is capable of hybridizing to the probe) 5′-TAA GG ATGAC TGACT GACTG ACTGA CGAT G GT-3′
  • the proportion of a probe hybridized to a target nucleic acid (or an internal standard nucleic acid) to the total amount of the hybridized probe comes to be possible to determine. This will be explained based on the following examples. In the case that it was calculated that the quenching rate for a fluorescent dye having a difference in a fluorescent quenching level caused on hybridization between a target nucleic acid and an internal standard nucleic acid in a practical sample was 40%; and the half of the total amount of an added probe was hybridized, if on paying attention to only a hybridized probe, the 80% amount of the hybridized probe comes to cause a fluorescent quenching.
  • a probe used herein is taken to be a probe causing to quench completely a fluorescent emission of a BODIPY FL dye on hybridization of the probe to a target gene
  • the 80% amount of the hybridized probe is capable of being calculated based on the quenching rate (40%) in the practical sample.
  • Fluorescent quenching for TAMRA labeled at the 3′-end of the doubly-labeled probe was markedly caused in similar levels on hybridization to a target gene and on hybridization to an internal standard gene because of the presence of G in near proximity of a fluorescence-labeled end base in the both of the target gene and the internal standard gene on its hybridization to the target gene. Because of this, the quenching rate for a TAMRA dye came to indicate a proportion of a hybridized probe.
  • a target gene was capable of be determined quantitatively by correction of a quenching rate for a BODIPY FL dye with a quenching rate for a TAMRA dye irrespective of a magnitude of the total amount of a gene.
  • FIG. 14 shows experimental results.
  • FIG. 14A shows a correlation of a fluorescence-quenching rate for a BODIPY dye and an existing ratio of a target gene. From this figure, it was understood that calibration curves each other was different with depending on the total amount of a target gene. These results indicate that a fluorescence-quenching varies with changed amounts of genes even if existing ratios of target genes are the same. From this, it is apparently impossible to determine an existing ratio of target genes.
  • a value of a fluorescence-quenching rate for a BODIPY dye/a fluorescence-quenching rate for a TAMRA dye was confirmed to change with depending on only a existing ratio of target genes and without depending on the total amount of a target gene. It is suggested from the above results that the method using a doubly-labeled probe of the above type is capable of determining an existing ratio of target genes accurately and quantitatively irrespective of a magnitude of the total amount of a target gene.
  • a probe usable in the method can have features such as follows: (1) the fluorescence amount of a dye labeled at one portion of the probe on hybridization of the probe with a target gene is different from that on hybridization of probe with an internal standard gene, and (2) in a dye labeled at another portion, the fluorescence amount (it may be a fluorescence-quenching or a fluorescence-emission) is caused in similar levels on hybridization with either a target gene or an internal standard gene, namely insofar as the probe has such properties, this method is capable of assaying any gene based on the above principal.
  • any dye may be usable, namely insofar as a dye has such properties, specifically no limitation is imposed on a dye.
  • Probes used in the above Examples were probes such that fluorescence amounts for dyes with which the probes were labeled varied on hybridization of the probes with any one of a target gene and internal standard gene; on hybridization of the probes with the other gene, the fluorescence amounts were in similar levels as compared with that on no hybridization.
  • the existing forms of a probe were three forms wherein one of those is a target gene and probe hybridizing complex form, the other an internal standard gene and probe hybridizing complex form, and the further one a non-hybridizing form; but, upon the payment of attention to the fluorescence amount for every one molecule of a dye, the existing forms of a probe wherein the forms each were different in the fluorescence amount were only two forms (see FIG. 15 ).
  • a probe has been recognized to be present during the above achievement of the invention, which probe had three existing forms which each were different in the fluorescence amount, wherein the forms were three forms of a target gene and probe hybridizing complex form, an internal standard gene and probe hybridizing complex form, and a non-hybridizing form (see FIG. 15 ). Because there were a probe having three existing forms different in the fluorescence amount in a reaction system using a probe of such above type, it was thought to be difficult to determine a target nucleic acid by making use of a simple calculating-equation as described above.
  • a calculating method for determining a target gene quantitatively was invented, which method was designed on the premise of the use of a probe wherein the fluorescence amount for the probe was different independently in a target gene and probe hybridizing complex form, an internal standard gene and probe hybridizing complex form, and a non-hybridizing form; it will be illustrated in the following description.
  • a calculating equation is illustrated in the following description, which equation is usable in the case using a doubly-labeled probe designed such that the fluorescent intensity for a dye with which a probe is labeled at one portion thereof is reduced remarkably on hybridization with a target gene; that for a dye with which the probe was labeled at the other portion thereof was reduced remarkably on hybridization with an internal standard gene.
  • y a proportion of a hybridized probe
  • x a proportion of a target gene
  • A a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on no hybridization in use of a practical sample to the fluorescent intensity of dye A of the doubly-labeled nucleic probe on no hybridization;
  • a a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target nucleic acid to the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on no hybridization;
  • a′ a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with an internal standard nucleic acid to the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on no hybridization;
  • b a ratio of the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target gene to the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on no hybridization;
  • b′ a ratio of the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with an internal standard nucleic acid to the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on no hybridization.
  • a constituent ratio of target genes in samples prepared imitatively was determined by (1) a method comprising, subsequent to preparation of a calibration curve, determining quantitatively a constituent ratio of target genes by the prepared calibrating curve; or (2) a method comprising determining quantitatively a constituent ratio of target genes by the above calculating equation; and, based on the obtained results, the above two methods for determining quantitatively a constituent ratio of target genes were compared and evaluated.
  • Target gene and internal standard gene an oligonucleotide was used.
  • Base sequence of target gene (a sequence underlined is capable of hybridizing to the probe) 5′- AATTC GTACC AACTA TCCTC GTCGT CAGCT ATG -3′
  • Base sequence of internal standard gene (a sequence underlined is capable of hybridizing to the probe) 5′- GATTC GTACC AACTA TCCTC GTCGT CAGCT ATA -3′
  • Target gene 800 nM
  • the fluorescence-quenching rate—in a target gene and probe hybridizing complex form, an internal standard gene and probe hybridizing complex form, and a non-hybridizing form—of the probe used in this example were measured.
  • the fluorescent quenching rate for a TAMRA dye
  • the results are shown in the following table. As understood from the table, the fluorescent quenching rates of an experimental system with no addition of a gene (a gene-non-additive system) were not 0% for both dyes.
  • a constituent ratio of genes are capable of being appropriately determined in the case that the amount of a probe is smaller than the total sum amount of genes, and in the case that the determination was conducted using a probe designed such that the fluorescence amount for the probe used in the determination was different in no-hybridization with any gene, in hybridization with a target gene and in hybridization with an internal standard gene, respectively.
  • the additive amount of a probe in this example was 400 nM; in the case with the total sum amount of genes being 200 nM, the half of the additive amount of the probe does not hybridize to genes.
  • the fluorescence amount for a dye labeled at the probe was different in no hybridization with any genes, in hybridization with a target gene and in hybridization with an internal standard gene, respectively; in the case when the total sum amount of genes is smaller than the amount of a probe, the change amount in the fluorescence for each dye labeled at the probe comes to be derived from the both of the change amount in the fluorescence on hybridization with an internal standard gene and the change amount in the fluorescence on hybridization with a target gene (in the case when the change amount in the fluorescence on no hybridization with any genes was taken as a basal value).
  • the change amount in the fluorescence in regard to each dye came to be affected by the both of a target gene and an internal standard gene. Because of such a situation, it is understood that a ratio of change amounts in fluorescence did not reflect a ratio of a constituent ratio of genes; and appropriate determining values were not capable of being obtained.
  • a probe hybridized to any of a target gene and an internal standard a probe not hybridized was not present. Thereby, the change amount in fluorescence was derived from only one gene of the target gene and the internal standard gene. Accordingly, a ratio of the change amount in fluorescence came to reflect appropriately on a constituent ratio of genes; an appropriate determining value is thought to have been obtained.
  • Table 6 shows the results of determination of a constituent ratio of genes using the above described calculating equation.
  • the measuring values hose values were used for determining quantitatively by a calibrating curve—was divided by the fluorescence amount for a non-hybridized probe; the obtained values were incorporated in the calculating equation.
  • an accurate constituent ratio of genes (the amount of a target gene/the amount of an internal standard gene) had be capable of being determined even in the case when the total sum amount of genes was smaller than the total amount like in the case when larger. Therefore, a constituent ratio of genes is clearly capable of being quantitatively determined using the above-described relative equation nevertheless of the total sum amount of genes.
  • Example determining a target gene by using novel mixture according to present invention comprising quenching substance or probe labeled with quenching substance.
  • quenching substance-labeled probe a probe labeled with a fluorescence-quenching substance
  • the quenching substance-labeled probe can hybridize to a target nucleic acid probe
  • the quenching substance, with which the quenching substance-labeled probe is labeled can be located in close proximity to a dye, with which the target nucleic acid probe is labeled, on hybridization of the quenching substance-labeled probe with the target nucleic acid probe
  • the dissociation temperature of a hybrid complex between the target nucleic acid probe and the quenching substance-labeled probe can be lower than that of a hybrid complex between the target nucleic acid probe and a target nucleic acid or that of a hybrid complex between the target nucleic acid probe and an internal standard nucleic acid.
  • the quenching substance-labeled probe has the following features; (1) it has a base sequence complementary to that of a doubly-labeled probe; (2) on hybridization to the doubly-labeled probe, the base of the quenching substance-labeled probe complementary to a fluorescence-labeled base of the doubly-labeled probe is labeled with a quenching substance; and (3) it has two oligonucleotides shorter than that of a target nucleic acid probe; and each of the oligonucleotides can hybridize to a separate portion of the target nucleic acid probe without doubling.
  • the above features of (1), (2) and (3) can cause the fluorescence of a doubly-labeled nucleic acid probe to quench without inhibition of hybridization of the doubly-labeled nucleic acid probe to an internal standard nucleic acid and a target nucleic acid.
  • the experiment was conducted in a system with addition of the quenching substance-labeled nucleic acid probe and in a system without addition; the effect of the quenching substance-labeled nucleic acid probe was evaluated by comparison of determining values as to existing ratios of target genes in mimic samples.
  • the determination of a existing ratio of target genes was carried out by making use of the calculating equation as described in Example 8.
  • ranges of specific temperature were in advance determined; at one of the ranges the doubly-labeled nucleic acid probe was capable of hybridizing enough to only a target gene and an internal standard gene, but of not hybridizing to the quenching substance-labeled nucleic acid probe; at the other range the doubly-labeled nucleic acid probe was capable of hybridizing enough to a target gene, an internal standard gene and the quenching substance-labeled nucleic acid probe.
  • the temperature range was 55 to 60° C. in the former and not higher than 40° C. in the later. Based on the results, in ascertaining experiment, the temperature was changed to 95° C., 57° C., and 35° C. in this order and kept for one minute to an individual temperature.
  • the object of keeping the temperature to 57° C. was to make the doubly-labeled nucleic acid probe hybridize to only a target gene and an internal standard gene. Subsequent to that, the keeping of 35° C. made the doubly-labeled nucleic acid hybridize to the quenching substance-labeled nucleic acid probe to cause the fluorescence for the doubly-labeled nucleic acid to be quenched.
  • Quenching substance-labeled nucleic acid probe A 5′ CTCGT CGTCA GCTAT G G3′-DABCYL
  • Quenching substance-labeled nucleic acid probe B DABCYL-5′ G GATT CGTAC CAACT ATC
  • the following table shows the results of determination of a constituent ratio of genes in a system with no addition of a quenching substance-labeled nucleic acid probe.
  • the results show clearly that the amount of a change in fluorescence reduced with reducing amount of total genes because a ratio of fluorescent intensity (A and B) in the mimic samples came close to a ratio of fluorescent intensity of the non-hybridized probe.
  • the determining values of the gene constituent ratio in the mimic samples were consequently apart from the theoretical value with the reducing amount of a total sum of genes.
  • the following table shows the results of determination of a constituent ratio of genes in a system with addition of a quenching substance-labeled nucleic acid probe.
  • a ratio of fluorescent intensity (A and B) in the mimic samples was reduced with reducing amount of total genes.
  • the change in a fluorescent intensity was observed to be about 1.5 to 2.0 times greater as compared with that for a non-hybridized probe.
  • the obtained determining values of gene constituent ratios were the ones about close to the theoretical value.
  • the quenching substance-labeled probe enabled to measure exactly the fluorescence derived from a probe hybridized to a target gene or an internal standard gene by making the fluorescence for a non-hybridizing probe quench. On the basis of this reason, the quenching substance-labeled probe is in merit for all the target nucleic acid probes (including an internal standard nucleic acid probe and a doubly-labeled probe) as described in the present application, and for an assaying method making use thereof.
  • the quenching substance-labeled probe is usable based on the same reason as described above.
  • it is necessary to conduct such a treatment as phosphorylation of the 3′-end of a probe in the use of the quenching substance labeled probe, in which the 3′-end is not labeled, in order to inhibit to be used as a primer but, provided that the same shall not apply to the case when, subsequent to gene amplification, a constituent ratio of target genes is determined by adding a target nucleic acid probe (including an internal standard nucleic acid probe and a doubly-labeled nucleic acid probe) and a quenching substance-labeled probe in the reaction mixture of the gene amplification).
  • the example is below described, related to the additionally novel method making use of both of a target nucleic acid probe and internal standard nucleic acid probe.
  • This method makes use together of both of a target nucleic acid probe and internal standard nucleic acid probe and additionally an enzyme having exonuclease activity (hereinafter, called simply “exonuclease”). Its preferable example is described in FIG. 18 . This method is premised on making use of 3′ ⁇ 5′exonuclease.
  • a target nucleic acid probe and an internal standard probe which are labeled doubly with a fluorescent dye and a quenching substance are used.
  • Fluorescent dyes to be used for labeling the target nucleic acid probe and the internal standard probe are more preferable to be different each others.
  • fluorescence-labeling portion of the probes are preferably 3′-end portions; quenching substance-labeling portion of the probes are preferable to be different from the fluorescence-labeled portions.
  • the target nucleic acid probe is preferably a probe designed such that, on hybridization with one of the target gene and internal standard gene, the fluorescence-labeled 3′-end base of the probe is at least non-complementary to the one gene; and on hybridization with the other gene, the fluorescence-labeled 3′-end base of the probe is complementary to the other gene.
  • the target nucleic acid probe is designed so that, on its hybridization to a target gene, the fluorescence-labeled 3′-end base of the probe is at least non-complementary to the target gene; and on hybridization with the internal standard gene, the fluorescence-labeled 3′-end base of the probe is complementary to the internal standard gene.
  • the internal standard nucleic acid probe is designed so that, on its hybridization to an internal standard gene, the fluorescence-labeled 3′-end base of the probe is at least non-complementary to the internal standard gene; and on hybridization with the target gene, the fluorescence-labeled 3′-end base of the probe is complementary to the target gene.).
  • the fluorescence of the fluorescent dyes labeled at the probes is quenched with affection of the quenching substances labeled at a portion within the same molecules.
  • the 3′ ⁇ 5′exonuclease cleaves out the 3′-end base from the probes by recognizing the mismatch on hybridization of the target nucleic acid probe and internal standard nucleic acid probe with a target gene and internal standard gene in the presence of the enzyme having a characteristic such that the enzyme cleaves out the 3′-end base only in the case of a mismatch of the 3′-end. Accordingly, each probe comes to emit specifically fluorescence on hybridization to any one of a target gene and an internal standard gene (in FIG.
  • the target nucleic acid probe is cleaved and emits fluorescence only on hybridization to a target gene; the internal standard nucleic acid probe is cleaved and emits only on hybridization to an internal standard gene).
  • a difference between the number of base pairs between the target nucleic acid probe and the target gene and the number of base pairs between the target nucleic acid probe and the internal standard gene is only one base pair; that one base pair is the end base of the target nucleic acid; it can be understood that the target nucleic acid probe hybridizes to a target gene and an internal standard gene with indiscriminating those (the internal standard nucleic acid probe also is like this).
  • a ratio between fluorescence-determining values for each probes can appropriately reflect a gene-constituent ratio between a target gene and an internal standard gene existing a system. Accordingly, it is considered that the amount of a target gene can be determined quantitatively by this method also.
  • an existing ratio between a target gene and an internal standard gene existing in a system can be determined by using the above described target nucleic acid probe, internal standard nucleic acid probe and 3′ ⁇ 5′exonuclease.
  • a DNA solution was prepared, wherein the solution comprised a target gene and internal standard gene in various existing ratios between those; the target nucleic acid probe, internal standard nucleic acid probe and 3′ ⁇ 5′exonuclease was added in the solution; subsequent to the addition, the solution was incubated for a determined time; and then a fluorescence measurement was conducted. The fluorescence measurement was carried out 95° C.
  • a relation between a ratio of the amount of fluorescence derived from each probes and a gene-constituent ratio between a target gene and an internal standard gene was examined; and it was examined whether or not a gene-constituent ratio could be determined based on the obtained relative equation.
  • Target gene and internal standard gene oligonucleotides were used.
  • oligonucleotide by relying custom synthesis services (Espec oligoservices Inc.).
  • Base sequence of target gene 5′ TTGTC CGGAA AGGCC AGAGG AG-3′;
  • Base sequence of internal standard gene 5′-ATGTC CGGAA AGGCC AGAGG AG-3′;
  • BODIPY FL (like the dye used above), labeled portion: the 3′ end;
  • Quenching substance dye DABCYL (like the dye used above), labeled portion: the 5′ end;
  • TAMRA (like the dye used above), labeled portion: the 3′ end;
  • Corrosive sublimate dye DABCYL (like the dye used above), labeled portion: the 5′ end;
  • FIG. 19 indicates the relation between a ratio of fluorescence-determining values and a gene-constituent ratio of genes. Based on this figure, it is ascertained that there is a high co-relation between an amount ratio of changes in fluorescence and a gene-constituent ratio regardless of the total amount of genes. From these findings, it is clear that a gene-constituent ratio can be determined accurately, and, by utilizing this ratio, a target gene can be determined quantitatively. Many heat-resistant enzymes for a PCR method are known to have a 3′ ⁇ 5′exonuclease activity. Because of these findings, the application of this method to a PCR method makes it unnecessary to add an enzyme having a 3′ ⁇ 5′exonuclease activity into an assaying system; this method could be carried out practically.
  • a fluorescence-labeling portion of a target nucleic acid probe and internal standard nucleic acid probe should be preferably a 5′-end base portion; a quenching substance-labeling portion is preferably a 3′-end base portion.
  • the following description indicates an example making a doubly-labeled nucleic acid probe and a quenching substance-labeled probe in combination, wherein the doubly-labeled nucleic acid probe has the characteristics such that a difference between the fluorescent intensity in regard to a dye labeled at one portion of a doubly-labeled nucleic acid probe on hybridization of a doubly-labeled nucleic acid probe with a target gene and the fluorescent intensity on the hybridization of the above probe with an internal standard gene produces; and the fluorescent intensity in regard to a dye labeled at the other portion is in a similar degree on hybridization with any of the target gene and the internal standard gene.
  • FIG. 20 illustrates a preferable example applied with this method.
  • the one end of the doubly-labeled nucleic acid probe is labeled with a fluorescent dye (dye A) of such a type that the fluorescence for a fluorescent dye is capable of being quenched owing to an interaction of the dye with a G.
  • a fluorescent dye die A
  • the fluorescence-quenching can occur because G is present in close proximity of the dye A on hybridization of the probe to a target gene; on hybridization to an internal standard gene, the fluorescence-quenching can not occur because G is absent in close proximity of the dye A.
  • the other end should be labeled with a dye B, although any limitation should not be basically imposed on the dye, for which the fluorescent intensity becomes to be in the same level on hybridization of the probe with a target gene and on hybridization of the probe with an internal standard gene. Due to this labeling, the fluorescent intensity for dye B labeled on the other end portion of the probe is not affected by a sort of gene on hybridization of the probe with the gene to become like; the fluorescence for a non-hybridizing probe can be made to quench by a quenching substance-labeled probe; this make it possible to determine quantitatively the proportion of a hybridized probe.
  • a dye for labeling the other end a dye (dye B) which is difficult to be affected by a base sequence is preferable. Further, a dye difficult to be affected by a G is more preferable.
  • a dye for labeling a probe for which dye the fluorescent intensity is easy to be affected by a G
  • Cy dyes are Cy dyes, Alexa dyes, Texas Red and the like as dyes for which fluorescent intensity is difficult to subject to the affection of a base sequence
  • the effect of the quenching substance-labeled nucleic acid probe was evaluated by comparison of determining values of existing ratios of target genes in mimic samples.
  • the determination of a existing ratio of target genes was carried out by making use of the calculating equation as described below.
  • the doubly-labeled nucleic acid probe was capable of hybridizing enough to only a target gene and an internal standard gene, but of not hybridizing to the quenching substance-labeled nucleic acid probe.
  • the temperature range was 52 to 57° C. in the former, and in the later not higher than 35° C. Based on the results, in ascertaining experiment, the temperature was changed to 95° C., 52° C., and 30° C. in this order and kept for one minute to an individual temperature. The object of keeping the temperature to 52° C. was to make the doubly-labeled nucleic acid probe hybridize to only a target gene and an internal standard gene.
  • the keeping of 30° C. made the doubly-labeled nucleic acid hybridize to the quenching substance-labeled nucleic acid probe to cause the fluorescence for the doubly-labeled nucleic acid to be quenched.
  • This example illustrates a calculating method for determining a gene-constituent ratio quantitatively.
  • a dye is defined as dye A, which dye causes a difference between the fluorescent intensity for the doubly-labeled probe on its hybridization to a target gene and the fluorescent intensity for the doubly-labeled probe on its hybridization to an internal standard gene;
  • a dye is defined as dye B, which dye causes no difference.
  • y a proportion of a hybridized probe
  • x a proportion of a target gene
  • A a ratio of the fluorescent intensity for dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with the quenching substance-labeled probe in use of a practical sample to the fluorescent intensity of dye A of the doubly-labeled nucleic probe on its 100%-hybridization with a quenching substance-labeled probe;
  • a a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target nucleic acid to the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with a quenching substance-labeled probe;
  • a′ a ratio of the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its 100%-hybridization with an internal standard nucleic acid to the fluorescent intensity of dye A of the doubly-labeled nucleic acid probe on its hybridization with a quenching substance-labeled probe;
  • b a ratio of the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with a target gene and an internal standard gene to the fluorescent intensity of dye B of the doubly-labeled nucleic acid probe on its 100%-hybridization with a quenching substance-labeled probe;
  • the 3′-end was labeled with DABCYL.
  • Quenching substance-labeled probe B DABCYL-5′ G GGAG CAGTC AGTCA
  • the 5′-end was labeled with DABCYL.
  • Fluorescence for Cy5 was measured by an exciting wavelength: 600 nm and measuring wavelength: 670 nm.
  • the below table shows the results of quantitation of a constituent ratio of genes.
  • a ratio of fluorescent intensity (A and B) for BODIPY FL in the mimic samples was reduced with reducing amount of total genes.
  • the determining values of the gene constituent ratio in the mimic samples were almost close to the theoretical value. From the above results, it has become apparent that a gene-constituent ratio can be accurately determined quantitatively by addition of a quenching substance-labeled probe to reduce fluorescence for the non-hybridized probe, and, as a result, a target gene can be accurately determined quantitatively.
  • the calculation method as described in this Example also was apparently useful for determining a gene-constituent ratio quantitatively.
  • the quenching substance-labeled probe makes fluorescence for the non-hybridized probe reduce; thereby, the probe makes it possible to determine accurately fluorescence derived from the hybridization of the probe with a target gene and an internal standard gene.
  • the quenching substance-labeled probe is advantageous for all target nucleic acid probes (including an internal standard nucleic acid probe and a doubly-labeled nucleic acid probe) and all assaying methods making use thereof as described in this application.
  • a novel mixture according to the present invention is capable of provide a method for assaying a nucleic acid, the method producing advantageous effects as described in the above description.
  • the present invention therefore, can greatly contribute to genetic engineering, medicals, medical arts, agricultural techniques, development of various biological techniques, development of complex microbes usable in wastes-treatment plants and the like.

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US20130065237A1 (en) 2013-03-14
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DE602004026111D1 (de) 2010-04-29
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US7951604B2 (en) 2011-05-31
US20110224417A1 (en) 2011-09-15
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