JP2517592B2 - t ▲ lower 2 ▼ -two-dimensional nuclear magnetic resonance measurement method by inversion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a nuclear magnetic resonance (NMR) measurement method, and more particularly to a two-dimensional (2D) method.
D) It relates to the NMR method.

[Prior Art] The 2DNMR method is excellent in that it displays the NMR signal as a two-dimensional spectrum, so that the resolution is improved and the spectrum can be easily analyzed, and the interaction between nuclear spins can be elucidated. I have a point.

FIG. 4 shows an example of an NMR apparatus for performing such 2D NMR method. In the figure, a sample coil 2 is arranged in a static magnetic field generated by a magnet 1, and a measurement sample is inserted into a space inside the sample coil 2. The high frequency signal having the resonance frequency of the observation nucleus generated from the high frequency oscillator 3 is given a predetermined phase by the variable phase shift circuit 4 capable of selecting an arbitrary phase from 0 ° to 360 °, and then the amplifier 5 and the gate 6 are supplied. A high frequency pulse is supplied to the coil 2 via the high frequency pulse and irradiates the sample. The resonance signal induced in the coil 2 after the frequency pulse irradiation is sent to the demodulation circuits 9 and 10 via the gate 7 and the receiving circuit 8. The high frequency signal from the high frequency oscillator is sent to the demodulation circuits 9 and 10 as a reference signal.
One of them is sent through the 90 ° phase shift circuit 11,
The two demodulation circuits form two channels of detection systems CHa and CHb having different 90 ° phases. The free induction decay signal obtained from this two-channel detection system is the AD converter 12, 13
Is converted into a digital signal, sent to the computer 14, and stored in the attached memory 15. 16 is a phase shift circuit
4, a pulse programmer for controlling the gates 6 and 7 and the A / D converters 12 and 13, and the sequence of the pulse train for irradiating the sample, the pulse width, the phase of the high frequency contained in each pulse, the A-D converters 12 and 1
The timing of sampling by 3 is programmed in advance, and a series of measurements are performed according to the program.

A conventional 2D NMR measurement by such an apparatus will be described using a pulse sequence of 90 ° x-t ₁ -90 ° x-t ₂ as shown in FIG. 5 (a), for example.

The general measurement process in the 2D NMR method is shown in Fig. 5 (a).
As shown in (3), it consists of three time regions: a preparation period before the first 90 ° pulse, a development period (t ₁ ) and a detection period (t ₂ ). The preparatory period is necessary to keep the magnetization of the nucleus in a suitable initial state, and the preparatory pulse (first 90 ° pulse) brings the magnetization to a non-equilibrium state, which is developed during the expansion period t ₁ , The magnetization behavior at t ₁ is handed as phase and amplitude information to the free induction decay signal (FID signal) detected during the detection period t ₂ after the detection pulse (second 90 ° pulse) is applied. Accordingly, stepwise for example changing the n stage t ₁ as a variable, FID signals (FIDa1～FIDam and each m pieces obtained from two detection systems having different phases by 90 ° from one another of the reference signal measured at each stage FIDb1 ~ FI
Dbm) If one obtains complex set data S ₁ (t ₁ , t ₂ ) that combines one of them as the real part and the other as the imaginary part, not only the magnetization behavior at t ₂ but also t ₁ Information on the behavior of the magnetization in will be included.

Next, using the pulse sequence of FIG. 5 (b) in which only the phase of the detection pulse is different by 90 °
A measurement is performed on t ₁ , which results in the multi-set data S
_{Get 2} (t ₁ , t ₂ ). These two complex set data S ₁ (t ₁ , t
₂ ), S ₂ (t ₁ , t ₂ ) is added or subtracted to obtain P type data P (t ₁ , t ₂ ), N type data N (t ₁ , t ₂ ).
Is obtained, and P-type 2D NMR spectrum data P (ω ₁ , ω ₂ ) is obtained by subjecting t ₁ and t ₂ to double Fourier transform.
Alternatively, N-type 2D NMR spectrum data N (ω ₁ , ω ₂ ) can be obtained. Here, ω ₁ and ω ₂ are Fourier components of t ₁ and t ₂ , respectively.

When the 2D NMR spectrum data thus obtained is shown on a plane, diagonal peaks and cross peaks appear symmetrically.

[Problems to be solved by the invention]

By the way, such a 2D NMR spectrum has a shape in which the absorption waveform and the dispersion waveform are mixed at both the diagonal and crossing peaks, which makes the spectrum difficult to analyze. Has been proposed, and a pure phase mode display method has been proposed in which a so-called power spectrum is displayed and a two-dimensional spectrum of absorption spectra in both ω ₁ and ω ₂ frequencies is displayed.

Although the absolute value mode display method is easy to process data, it has a problem that the peaks are tailed and the resolution is poor because the dispersion modes are mixed, and that spin-spin coupling and NOE peak code cannot be discriminated. There are also drawbacks. On the other hand, in the pure phase mode display, the peak tail is good, the resolution is superior to the absolute value mode display, and the peak code can be discriminated. However, the absolute value mode display method does not require phase correction, whereas the pure phase mode display method requires phase correction, and thus has a drawback in that the process as a whole is troublesome. Generally, in the NMR apparatus, the phase detection is performed by the QD method, but the sign of the signal in the t ₁ direction cannot be discriminated from the two-dimensional data measured by the QD method, so that it is difficult to display the pure phase mode. It was
However, the following three algorithms have been reported as methods for solving this problem and enabling pure phase mode display.

States et al. (1982, TPPI: Time Proposal Phasse
Increment ¹⁾ ), Marion et al. (1983, TPPI: Time Proposal Phasse)
Increment ²⁾ ), Nagayama's method (1986, ω ₁ -inversion or t ₁ -inversion method)
³⁾ ), 1) DJStates, RAHaberHorn and DJRuben, Journal
of Magnetic Resonance, 48 , 286 (1982). 2) D. Marion and K. Wuthrich, Biochem, Biophys.Res.Co
mmun, 113, 967 (1983). 3) K. Nagayama et al, Journal of Magnetic Resonanc
The method of e, 66 , 240 (1986) uses the radio wave phase in the x and y directions for the read pulse, holds the data files respectively, and uses both of them to make the signal in the t ₁ direction complex and calculate. And is the Redfield for the signal component in the t ₁ direction.
This is a method that uses a trick. Method holds two files from the measurement in which the phase of the read pulse is shifted by 90 °, uses them to create P-type and N-type spectra, and then inverts the N-type spectrum in the t ₁ direction, and this and P A pure phase spectrum is obtained by taking the sum (or difference) with the type spectrum, but inversion can be performed in the time domain or the frequency domain. However, both methods use inversion in the t ₁ direction, and inversion in the t ₂ direction has not been considered.

The present invention has been made in view of the above circumstances, and utilizes inversion in the t ₂ direction, has high resolution, has a well-cut peak, and is capable of discriminating the sign of a peak. It is an object of the present invention to provide a two-dimensional nuclear magnetic resonance measurement method by t ₂ -inversion for obtaining NMR spectrum data.

[Means for solving problems]

Therefore, the two-dimensional nuclear magnetic resonance measurement method by t ₂ -reversal of the present invention is (a) irradiating a detection pulse or pulse train with a development period t ₁ after irradiation of the preparation pulse or pulse train, and irradiating this detection pulse or pulse train A sequence in which the FID signal from the sample is detected by two detection channels with 90 ° different phases over the post-detection period t ₂ is used, and a plurality of different t ₁
To obtain complex set data S ₁ (t ₁ , t ₂ ) consisting of a plurality of FID signals measured for the value of, (b) the same sequence as the sequence in (a) and the preparation pulse or pulse train and the detection pulse or A complex set data S ₂ (t) composed of a plurality of FID signals measured for a plurality of t _{1 which} are the same as that of the above (a) is used by using a sequence whose phase from the pulse train is different by 90 ° from the case of the sequence in (a) _1, t ₂₎ to obtain, and (c) the aggregate data _{S 1 (t 1, t 2} ), the sum data P _{S 2 (t 1, t 2} ) (t 1, t 2), the difference data N Create (t ₁ , t ₂ ), (d) Either P (t ₁ , t ₂ ) or N (t ₁ , t ₂ )
For t ₂ and complex Fourier exchanged for the other, taking the complex conjugate is performed to invert the t ₂ period, and for t ₂ to complex Fourier exchanged in any order,
Data S obtained by taking the sum or difference of these
It is characterized in that S (ω ₁ , ω ₂ ) is created by performing a complex Fourier transform of (t ₁ , ω ₂ ).

[Action]

The present invention according t ₂ - 2-dimensional nuclear magnetic resonance measuring method according inversion time inversion, the order of the complex Fourier transform any of only one of the complex conjugate, t ₂ of the two-dimensional FID data P type and N type Then, the other is subjected to complex Fourier transform with respect to t ₂ to obtain the sum or difference of both, and the obtained data S (t ₁ , ω ₂ ) is subjected to complex Fourier transform to S (ω ₁ , ω 2
By creating ₂ ), the resolution is increased, the tail of the peak is cut off, and the sign of the peak can be discriminated.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram for explaining a two-dimensional nuclear magnetic resonance measurement method by t ₂ -inversion according to the present invention.

Acquisition of data by measurement is the same as in the conventional case described above. Complex set data S ₁ (t ₁ , t ₂ ) is obtained by measurement using the sequence of FIG. 5 (a), and complex set data S ₁ (t ₁ , t ₂ ) is obtained by measurement using the sequence of FIG. 5 (b).
S ₂ (t ₁ , t ₂ ) is obtained. Obtained complex set data S ₁ (t
₁ , t ₂ ), S ₂ (t ₁ , t ₂ ) are S ₁ (t ₁ , t ₂ ) ＝ cosω ₁ t ₁ exp (iω ₂ t ₂ ) S ₂ (t ₁ , t ₂ ) = isinω ₁ t ₁ exp (iω ₂ t ₂ ). By adding and subtracting these data, the sum data P (t ₁ , t ₂ ) and the difference data N (t ₁ , t ₂ )
Is obtained as follows.

P (t ₁ , t ₂ ) = cos (ω ₂ t ₂ ＋ ω ₁ t ₁ ) + isin (ω ₂ t ₂ ＋ ω ₁ t ₁ ) N (t ₁ , t ₂ ) ＝ cos (ω ₂ t ₂ −ω ₁ t ₁ ) + isin (ω ₂ t ₂ −ω ₁ t ₁ ) Next, when P (t ₁ , t ₂ ) is subjected to complex Fourier transform with respect to t ₂ , P (t ₁ , ω ₁ ) = exp (iω ₁ t ₁ ) × {a ₂ (ω ₂ ) + id ₂ (ω ₂ )} where a ₂ (ω ₂ ) is T ₂ ^* which is the lateral relaxation time with respect to the ω ₂ axis, and ω ₀ is a reference corresponding to the observation frequency of the ω ₂ axis. Is an even function that gives an absorption waveform by a ₂ (ω ₂ ) = T ₂ ^* / {1 + T ₂ ^{* 2} (ω ₂ + ω ₀ ) ² }.

Further, d ₂ (ω ₂ ) is represented by the following equation, and d ₂ (ω ₂ ) = T ₂ ^{* 2} (ω ₂ + ω ₀ ) / {1 + T ₂ ^{* 2} (ω ₂ + ω ₀ ).
² } is an odd function that gives a dispersed waveform.

In addition, the complex conjugate ^N of _{N (t 1, t 2)} * _{^{is, N * (t 1, t}} 2) = cos (ω 2 t 2 -ω 1 t 1) -isin (ω 2 t 2 -ω 1 t ₁ ) If N ^* is inverted with respect to t ₂ , then N ^{* t2} = cos (ω ₂ t ₂ + ω ₁ t ₁ ) + isin (ω ₂ t ₂ + ω ₁ t ₁ ) If this is complex Fourier-exchanged with respect to t ₂ , then ^{* t 2} (t ₁ , ω ₂ ) = exp (iω ₁ t ₁ ) × {a ₂ (ω ₂ ) −id ₂ (ω ₂ )} Therefore, the sum of P (t ₁ , ω ₂ ) and ^{* t} ₂ (t ₁ , ω ₂ ). S
(T ₁ , ω ₂ ) becomes S (t ₁ , ω ₂ ) = a ₂ (ω ₂ ) exp (iω ₁ t ₁ ), and when this is subjected to complex Fourier exchange with respect to t ₁ , S (ω ₁ , ω _2). ) = A ₂ (ω ₂ ) {a ₁ (ω ₁ ) + id ₁ (ω ₁ )} = a ₁ (ω ₁ ) a ₁ (ω ₂ ) + id ₁ (ω ₁ ) a ₂ (ω ₂ ).

Where a _{1 (ω 1)} is expressed by the following equation when the transverse relaxation time for omega ₁ axis T _2, and the angular frequency of the reference corresponding to omega ₀ to observation frequency of omega ₁ axis, a ₁ ( ω ₁ ) = T ₂ / {1 + T ₂ ² (ω ₂ + ω ₀ ) ² } is an even function giving an absorption form.

Also, d ₁ (ω ₁ ) is expressed by the following formula, and a distributed waveform is given by d ₁ (ω ₁ ) = T ₂ ² (ω ₁ + ω ₀ ) / {1 + T ₂ ² (ω ₁ + ω ₀ ) ² ) It is an odd function.

Therefore, it can be seen that a pure absorption spectrum can be obtained from the real part.

Note that if the difference between P (t ₁ , ω ₂ ) and ^{* t} ₂ (t ₁ , ω ₂ ) is taken, then S ′ (t ₁ , ω ₂ ) = id ₂ (ω ₂ ) exp (ω ₁ t ₁ ) When the complex Fourier exchange is performed on t ₁ , S ′ (ω ₁ , ω ₂ ) == id ₂ (ω ₂ ) {a ₁ (ω ₁ ) + id ₁ (ω ₁ )} = −d ₁ (ω ₁ ) d ₂ (Ω ₂ ) + ia ₁ (ω ₁ ) d ₂ (ω ₂ ), and the dispersed waveform is obtained from the real part.

Thus, taking the complex conjugate of an N type file (N
^* ), This is inverted in the t ₂ direction ( ^* t ₂ ), and the result of addition and subtraction of the obtained P and ^{* t 2} gives a pure phase spectrum. Freeer transformation (t ₂ −FT) in the t ₂ direction needs to be performed separately for P and ^{* t2} , but to obtain the complex conjugate, t ₂
This is because the sign of the phase correction parameter is different between P and ^{* t2} .

It should be noted that in the above embodiment, the complex conjugate of the N type output, t ₂ −
Although it is inverted, it does not depend on the order because it is a linear operation including FT. Therefore, similar results can be obtained by the following five modifications other than FIG. The arrow indicates the process of making ^{* t2} from N.

(1) N → t ₂ − inversion → FT → complex conjugate → (2) N → t ₂ − inversion → complex conjugate → FT → (3) N → FT → t ₂ − inversion → complex conjugate → (4) N → FT → complex conjugate → t ₂ − inversion → (5) N → complex conjugate → FT → t ₂ − inversion → When the final spectrum is output in N type, complex conjugate, t ₂ − inversion, FT, etc. The calculation is applied to P (t ₁ , t ₂ ).

FIG. 2 is a diagram showing an experimental result according to the present invention, and FIG. 3 is a diagram showing an experimental result obtained by the ω ₁ -inversion or t ₁ -inversion method. Similarly, a pure phase spectrum can be obtained. I understand.

The present invention can be applied to all two-dimensional NMR methods capable of P-type and N-type output.

The two-dimensional method that can be applied concretely is as follows: homogeneous nuclei: COSY, RELAY, MQT filtered COSY NOESY, MQT coh
erence, FOCSY, TOCSY etc Heterogeneous nuclei: hetero COSY, hetero RELAY, hetero MQT cohe
rence (2DINADEQUATE, etc.) and so on.

〔The invention's effect〕

As described above, according to the present invention, two two-dimensional NMR data measured by shifting the phase of the final read pulse by 90 ° are stored in separate data files (memory), and P type is added and subtracted by both files. , N type spectrum complex conjugate is taken and the spectrum is inverted in the t ₂ direction and P
Since the type spectrum is added (subtracted), the resolution is good, the tail of the peak is well cut, and the two-dimensional spectrum of the pure phase mode display capable of distinguishing the sign of the peak can be obtained. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of an embodiment of a two-dimensional nuclear magnetic resonance measurement method by t ₂ -inversion according to the present invention, FIG. 2 is a diagram showing experimental results according to the present invention, and FIG. 3 is ω ₁ -inversion. Or t ₁
-A diagram showing the experimental results obtained by the inversion method, Fig. 4 is 2D
A diagram showing an example of an NMR apparatus for performing the NMR method, FIG. 5 is a 2D
It is a figure which shows the pulse sequence used for NMR measurement. 1 ... Magnet, 2 ... Sample coil, 3 ... High-frequency oscillator,
4 ... Variable phase shift circuit, 6, 7 ... Gate, 9, 10 ... Demodulation circuit, 11 ... 90 ° phase shift circuit, 12, 13 ... AD conversion circuit, 14 ... Computer, 15 ... … Memory, 16… Pulse programmer

Claims (1)

(57) [Claims] (A) A detection pulse or pulse train is irradiated with a development period t ₁ after irradiation of a preparation pulse or pulse train, and the FID signal from the sample is 90 ° over a detection period t ₂ after irradiation of this detection pulse or pulse train. Multiple t _{1 with} different sequences are used by using the sequence to detect with two detection channels with different phases.
To obtain complex set data S ₁ (t ₁ , t ₂ ) consisting of a plurality of FID signals measured for the value of, (b) the same sequence as the sequence in (a) and the preparation pulse or pulse train and the detection pulse or A complex set data S ₂ (t) composed of a plurality of FID signals measured for a plurality of t _{1 which} are the same as that of the above (a) is used by using a sequence whose phase from the pulse train is different by 90 ° from the case of the sequence in (a) _1, t ₂₎ to obtain, and (c) the aggregate data _{S 1 (t 1, t 2} ), the sum data P _{S 2 (t 1, t 2} ) (t 1, t 2), the difference data N Create (t ₁ , t ₂ ), (d) Either P (t ₁ , t ₂ ) or N (t ₁ , t ₂ )
For t ₂ and complex Fourier exchanged for the other, taking the complex conjugate is performed to invert the t ₂ period, and for t ₂ to complex Fourier exchanged in any order,
Data S obtained by taking the sum or difference of these
(T _1, ω ₂₎ and S (ω _1, ω ₂₎ and the complex Fourier transform to create a, t ₂ consist - 2-dimensional nuclear magnetic resonance measuring method according to inversion.