JPS58176536A - Method for measuring nuclear magnetic resonance - Google Patents

Abstract

PURPOSE:To enable indirect measurement, by utilizing the information on an intended nucleus and the other nucleus which is spin to spin coupled to said nucleus in measuring the relaxation time for the intended nucleus. CONSTITUTION:The 180 deg.x pulse of a <13>C nucleus is irradiated simultaneously with inrradiation of the first 180 deg.x pulse of a <1>H nucleus (the high frequency pulse applied with the time width for rotating the magnetization 180 deg. around the x axis) to eliminate the energy level of the <13>C nucleus, whereby the relaxation time of the <1>H nucleus can be measured. A 90 deg. pulse and 90 deg. pulse are irradiated at an interval of every tau second in this order to the non-observed nucleus after the irradiation (t) second of said 180 deg. pulse. A 180 deg. pulse and 90 deg. pulse are irradiated to the observation nucleus in synchronization respectively with said 180 deg. pulse and the 90 deg. pulse in succession to the same. The free induction attenuation signal of the observation nucleus after said pulse irradiation is obtained. The relaxation time is determined in accordance with plural pieces of the free induction attenuation signals F obtained by irradiating the above- mentioned pulses plural times by changing the (t).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a nuclear magnetic resonance method characterized in that the relaxation time of a target nucleus is indirectly determined based on information from other nuclei that are spin-spin coupled to the target nucleus. (Regarding NMR>measurement method.

Measurement of relaxation time occupies a large part of NMR measurement and is widely performed. Figure 1 shows longitudinal relaxation time (T1)
In the pulse sequence used for the measurement of The value M(t) after t seconds of magnetization returning to is observed by applying a 90''X pulse (observation pulse), and T1 is determined from the following formula.

M(t)=Mo(1-28-t/T+) (1) where Mo is magnetization in an equilibrium state.

However, for example, in the case of hydrogen nuclei IH, the chemical shift is as narrow as 110 PP or less, and the spectra overlap in a complicated manner due to spin-spin coupling between hydrogen nuclei, and there are many cases where the peaks cannot be separated sufficiently. It was impossible to measure the relaxation time.

On the other hand, recently 130 or 15N has been combined with 111.
As a method to observe nuclides with poor sensitivity such as
native Nuclei Enhanced by
Po1arization Transfer method ('I
N E P T method) has been proposed.

This INEPT method transfers a large polarization (magnetization) of 1 to 1 to a nucleus such as 13C or 15N through coupling.
It is used to observe nuclei such as G or N, and has the great effect of greatly improving the sensitivity of these nuclei. Second
The figure shows the pulse sequence that is the basis of the INEPT method.
900× pulses, 180° at intervals of τ seconds on the nucleus
× pulse, 90' V pulse (magnetization 90' around the Y axis
180'x pulse and 90'x pulse of the 13c nucleus are irradiated to the 13G nucleus in synchronization with the iso'x pulse and 90'y pulse, From this, the large magnetization of the IH nucleus is transferred to the 13G nucleus, and the free induction decay signal (F rD times signal F) of the 130 nucleus after the 90°X pulse is observed. Considering that the magnetization of the nucleus is directly transferred to the 13G nucleus and measured, in the measurement method explained earlier using Fig. 1, the magnetization after 180° x pulse irradiation is measured using a 90'' x pulse (observation pulse). ), but instead of this observation pulse, I
If we apply the pulse sequence of the NEPT method and observe the magnetization of H after seconds of 180°
We thought it would be possible to measure the relaxation time of an IH nucleus indirectly through the nucleus, and conducted repeated experiments. As a result, the pulse sequence of the INEPT method shown in FIG. 2 was used instead of the 90°X pulse in FIG. 1, and as shown in FIG. It was discovered that the relaxation time of an IH nucleus can be measured by irradiating the nucleus with a 180°X pulse and eliminating one unit of energy of the 13c nucleus.

That is, if the relaxation time determined based on this pulse sequence is T l (l N E P T ), then T1 (I
NEPT) can be analyzed as follows by considering only the dipole interaction. ')] is bonded to both 12C and 13c as shown in Figure 4, but what we are observing is IH (130 satellite) that is bonded to 13C, and the obtained T+ (INEPT) 'H1' of this 13G satellite! It can be regarded as the sum time Tt (Sat). Therefore, T+ (Sat,)=Tt, (INEPT)...
・(2) can be assumed.

T+ (Saj) is 13 of IH's 130 satellites.
The H relaxation time T 1 (1-I C) associated with the interaction with G (a in Figure 4) and the daily relaxation time T associated with the interaction between adjacent Hs (A in Figure 4)
It is expressed by the following formula as a synthesis of I(1-I H).

1,,/T+ (Sat) -1/T+ (HC)
+1/T+(Ht1) ・ ・ ・ (3)
Here 1/T+ (tlc), 1/Tt (HH)
are each represented by ten equations, of which T+ (HH) is the relaxation time of H, which is usually used.

Also, if the relaxation time of C is T+ (CH), then T
1 (CH) is represented by the following formula.

In equations (4), (5), and (6), γ is a constant expressed as h/2π, where h is a blank constant. , IH are the gyromagnetic ratio of 13C and IH, roH, respectively.

r, H are the distances between 1-0 and H-H, T0 is the autocorrelation time, ωC9ωH are the resonance angular frequencies of C and H, respectively, n
is the number of H's connected to /JC.

lz For liquids, ωdτ. ,ωCr(,,(ωH−ωo
)2τ0', (ωH+ωo)2τt are all sufficiently smaller than 1, and n 11-1s are bound to 13C@, but only one 130 is bound to the IH nucleus. It is considered that the above equation holds true between equations (4) and (6).

1 /1- I (CH) -Sato n /T 1
(T1 C) ・ ・ ・ (7) Therefore, equation (3) is 1, /T+ (Saj)”1/ (n −TI (
CH))+1/T+(HH)...(8) Substituting equation (2) into this and rearranging it, we get 1/T
+ (HH)=1/T+ (INEPT)-17'
(n −T 1 (Ct 1) ) ・
・ ・(9) is obtained.

TI(CH) in equation (9), that is, the relaxation time of C is
It is easily determined by the conventional T1 measurement method using the pulse sequence of FIG. 1, and can also be easily determined by other methods.

Therefore, TI (I
NEPT), the above T> (CH), and n, the relaxation time of T1(HH), that is, Fl can be measured according to equation (9).

Fig. 5 shows an example of a device for measuring TI (INEPT) by irradiating the pulse sequence shown in Fig. 3 to 'H nucleus and 130 nucleus, in which 1 is formed between the magnetic poles 2 and 2'. An NMR probe placed in a static magnetic field. An IH nuclear irradiation coil 4 is installed around the sample tube 3 inserted into the probe.
．． A transmitting coil 5 for '3C nucleus and a receiving coil 6 for T nucleus are arranged. Irradiation] Illumination 4. The transmitting coil 5 has 'H
Nuclear oscillator 7゜13c The high frequency having the resonance frequency of each nucleus generated by the nuclear oscillator 8 is transmitted through four-phase circuits 9, 10,
The pulses are supplied as high-frequency pulses via selection circuits 11.12 and gate circuits 13.14, respectively, and are irradiated onto the sample. If the pulse width is set appropriately by gate circuit 13.14, 90° pulse of IH nucleus, 180° Hals, or 13
CM (7) 90° pulse and 180' pulse can be created respectively. The four-phase circuits 9 and 10 and the selection circuits 11 and 12 are for setting the phase of the high frequency wave in the 90° pulse or the 180° pulse to 0", 90°, 180", or 270°, If 0° is selected, pulses 90°x and 180°X with the subscript x can be created, and if 90° is selected, the pulse 90°y with the subscript y can be created. In addition, if the phase is selected to 1806, a pulse with a subscript of -X can be created, and if the phase is also selected to 270°, a pulse with a subscript of -V can be created.

15 is a pulse programmer that controls the selection circuits 11, 12 and gate circuits 13 and 14 to generate the pulse sequence shown in FIG. A detection signal generated in the receiving coil 6 due to the irradiation of the pulse sequence is sent to the demodulation circuit 18 via the amplifier 17, and the FID signal is extracted by demodulation. The computer 16 determines the relaxation time based on the F I l) signal.

In the above configuration, the above-mentioned TI (INEPT) is obtained according to the following procedure. That is, the pulse programmer 15 sets the pulse sequence of FIG. 3 at sufficient time intervals,
Create and irradiate twice by changing t.

Then, the computer 16 extracts the first data value (signal intensity M(t) at point D in FIG. 6) for the FID signals obtained by k irradiations, and extracts (1 ) is used to calculate T1. This is T.
(INEPT).

In addition, TI (CH) in equation (9) can be determined by the conventional method of irradiating the C nucleus with the pulse sequence shown in Figure 1, and therefore, as mentioned earlier, TI (CH) can be calculated from equation (9).
(HH) can be obtained.

The present inventor confirmed that the formula (9) holds true by using 1-phenylpropertool as a sample and using the apparatus shown in FIG.

That is, 1-phenylpropertool has a structure as shown in Figure 7, and its spectrum is relatively simple, so it can be measured using the conventional measurement method using the pulse sequence shown in Figure 1 (TI (HH).
) can be measured.

Table 1 shows TI (HH>, TI(
The value of TI (CH) and its TI (HH), TI (CH
) calculated by substituting equation (9) into TI (INFPT
), and Table 2 shows the actual values of TI (INEPT) measured by irradiating the pulse train of FIG. 3 according to the present invention. The three carbon atoms attached to the phenyl group are distinguished from those closest to the phenyl group as C1, C2, and C3, and TI (HH) is measured for each carbon atom, and TI (CH) is measured for each carbon atom. The measurements were taken for

Comparing the Tl ("INEPT) values in Table 1 and Table 2, the difference between them is 1, which is usually recognized in NMR measurements.
This is within the error range of approximately 0%, confirming that it is safe to assume that equation (9) holds true. Therefore, for a sample such as cholesterol, for which it is difficult to measure TI (HH) using conventional methods, if TI (INEPT) is measured using the pulse sequence shown in Figure 3,
TI (HH) can be determined indirectly.

Incidentally, in the INEPT method, it has been proposed to use the pulse sequence shown in FIG. 2 as a basis and add some pulses after that, and it goes without saying that these pulse sequences may be used.

Further, in the above explanation, the 1 day nucleus and the 130 nucleus were taken as an example, but the combination is not limited to these two nuclei, but any combination of nuclei may be used as long as they are in a bonding relationship.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a pulse sequence for conventional relaxation time measurement, Fig. 2 is a diagram showing a basic pulse sequence of the INEPT method,
Figure 3 is a diagram showing the pulse sequence of the present invention, Figure 4 is %3C
Figure 5 is a diagram for explaining the satellite, Figure 5 is a diagram showing an example of an apparatus for carrying out the method according to the present invention, Figure 6 is a diagram for explaining the data to be extracted, and Figure 7 is a diagram for explaining the 1-phenylprop. FIG. 3 is a diagram showing the structure of the tool. ': NMR probe, 4.5, 6: coil, 7°8: oscillator, 9, 10: 4-phase circuit, 11.12: selection circuit,
13.14: Gate circuit, 15: Pulse programmer, 1
6: Computer, 18: Demodulation circuit. Patent applicant JEOL Ltd. Representative Tadao Kase

Claims (1)

[Claims] (a) Simultaneously irradiating an observation line and the observed nucleus connected to the observation line with a 180° pulse of each nucleus; (b) Irradiating the 180° pulse a second later; τ in the unobserved nucleus
90° pulse at intervals of seconds, 1806 pulses,
irradiating the 90° pulse in this order; (C) irradiating the observation line with the 180° pulse and the 90' pulse in synchronization with the 180° pulse and the subsequent 90° pulse in (b) above; (d) ) Above (C
) to obtain a free induction attenuation signal of the observation line after pulse irradiation, (e) to obtain a plurality of free induction decay signals obtained by performing the pulse irradiation of (a), (b), and (c) above multiple times with different 1. Determining the relaxation time based on the induced decay signal.