JPH0516741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a nuclear magnetic resonance (NMR) measurement method, particularly a two-dimensional (2D) NMR method. [Prior Art] Recently, the 2DNMR method has been attracting attention as a new NMR measurement method. This 2DNMR method has the advantage of displaying the NMR signal as a two-dimensional spectrum, which improves the resolution compared to conventional methods, making it easier to analyze the spectrum, and elucidating the interaction between nuclear spins. ing. Figure 7 shows the steps required to perform such a 2DNMR method.
An example of an NMR device is shown. In the figure, a sample coil 2 is placed within a static magnetic field generated by a magnet 1, and a measurement sample is inserted into the space inside the sample coil 2. A high frequency signal having the resonant frequency of the observation nucleus generated from the high frequency oscillator 3 is given a predetermined phase by the variable phase shift circuit 4 which can select any phase from 0° to 360°, and then sent to the amplifier 5 and the gate. 6 to the coil 2 as a high-frequency pulse, and irradiates the sample. After the high-frequency pulse irradiation, the resonance signal induced in the coil 2 is sent to the demodulation circuits 9 and 10 via the gate 7 and the reception circuit 8. A 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 via the 90° phase shift circuit 11, so the two demodulation circuits constitute a two-channel detection system CHa, CHb with a 90° phase difference.
The free induction attenuation signal obtained from this two-channel detection system is converted into a digital signal by A-D converters 12 and 13, sent to a computer 14, and stored in an attached memory 15. 16 is
Phase shift circuit 4, gates 6, 7 and A-D converter 1
2 and 13, the order of the pulse train irradiated to the sample, the pulse width, the phase of the high frequency included in each pulse, and the A-D converters 12 and 13.
The timing of sampling is preprogrammed, and a series of measurements are performed according to the program. Conventional 2DNMR measurement using such a device is
For example, 90°x−t ₁ −90°x−t ₂ as shown in Figure 8a.
This will be explained using the following pulse sequence. The general measurement process in the 2DNMR method is
As shown in Figure a, there are three stages: a preparation period before the first 90° pulse, a development period (t ₁ ), and a detection period (t ₂ ).
It consists of two time domains. The preparation period is necessary to maintain the magnetization of the nucleus in a suitable initial state; the preparation pulse (first 90° pulse) brings the magnetization into a non-equilibrium state, and this state is developed during the development period _t1 . , its magnetization behavior at t ₁ is passed as phase and amplitude information to the free induction damped signal (FID signal) detected during the detection period t ₂ after the application of the detection pulse (second 90° pulse). Therefore, by changing _t1 as a variable stepwise, for example, in n steps, m FIDs obtained from two detection systems whose reference signal phases differ by 90 degrees from each other are measured at each step.
If we obtain complex set data S ₁ (t ₁ , t ₂ ) in which one of the signals (FIDa1 to FIDam and FIDb1 to FIDbm) is combined with the real part and the other as the imaginary part, this data contains the magnetization at t ₂ . In addition to the behavior of , information on the behavior of magnetization at t ₁ is also included. Next, using the pulse sequence shown in Fig. 8b in which only the phase of the detection pulse is different by 90°, measurements are made for the same plurality of t ₁ as above, and thereby multiple set data S ₂ (t ₁ , t ₂ ) get. By adding or subtracting these two complex set data S ₁ (t ₁ , t ₂ ), S ₂ (t ₁ , t ₂ ), P type data P (t ₁ , t ₂ ), N
Type data N(t ₁ , t ₂ ) is obtained, and this is t ₁ ,
P-type by double Fourier transform for t ₂
2DNMR spectrum data P (ω ₁ , ω ₂ ) or N
Type 2 DNMR spectrum data N(ω ₁ , ω ₂ ) is obtained. Here, ω ₁ and ω ₂ are Fourier components of t ₁ and t ₂ , respectively. When the 2DNMR spectrum data obtained in this way is expressed on a plane, diagonal peaks and cross peaks appear symmetrically, and both the diagonal and cross peaks have a shape that is a mixture of absorption waveform and dispersion waveform. This makes the spectrum difficult to analyze. As a countermeasure, the conventional method is to obtain the absolute value of the two-dimensional spectrum and display it as a so-called power spectrum (K. Nagayama et al, Journal of
Magnetic Resonance, 31 , 133 (1978)), a pure absorption mode spectral display method that displays absorption spectra in both ω ₁ and ω ₂ frequency directions of a two-dimensional spectrum (DJ States et al, Journal of Magnetic
Resonance, 48 , 286 (1982), D.Marion and K.
Wu¨thrich, Biochem, Biophys.Res.Commun,
113, 967 (1983)) has been adopted. [Problems to be solved by the invention] However, although the method of displaying the absolute value of a two-dimensional spectrum does not require phase correction and the spectrum calculation is simple and automatic, the line width of each peak is wide. In addition, the pure absorption mode spectrum display method has a narrow line width and a sharp tail, so the resolution is high, but it requires phase correction and is complicated. . The present invention is intended to solve the above problems,
It is an object of the present invention to provide a two-dimensional nuclear magnetic resonance measurement method that can improve separation ability and automate and simplify spectrum calculation. [Means for Solving the Problems] To this end, the present invention provides: (a) a post-irradiation development period t ₁ of the preparation pulse or pulse train;
Using a sequence in which a detection pulse or a pulse train is irradiated at _a time of Complex set data S ₁ consisting of multiple FID signals measured for the value of t ₁
(t ₁ , t ₂ ); (b) the sequence is the same as the sequence in (a) above, and the phase between the preparation pulse or pulse train and the detection pulse or pulse train is the same as in the sequence in (b) above; Using 90° different sequences,
Complex set data S ₂ (t ₁ , t ₂ ) consisting of multiple FID signals measured for the same multiple t ₁ as in (a) above
(c) sum data P (t ₁ , t ₂ ) of the set data S ₁ (t 1 , t 2 ), S ₂ (t ₁ , _{t 2} ) and difference data N (t ₁ , t ₂ ); ₂ ) Only one of them is time-reversed with respect to t ₁ ,
Either perform complex Fourier transform on the data S (t ₁ , t ₂ ) obtained by taking the sum or difference with the other, or
Or P (t ₁ , t ₂ ) obtained by complex Fourier transform
(ω ₁ , ω ₂ ) and N(ω ₁ , ω ₂ ) obtained by complex Fourier transform of N(t ₁ , t ₂ ), only one of which is inverted about the ω ₁ axis and the sum or difference with the other is calculated. A two-dimensional nuclear magnetic resonance measurement method consisting of: creating absolute value spectrum data of S( _{ω 1 , ω 2 )} obtained by The present invention is characterized by a two-dimensional nuclear magnetic resonance measurement method that consists of creating spectral data that has been subjected to chromatographic processing. [Operation] The two-dimensional nuclear magnetic resonance measurement method according to the present invention
Two-dimensional FID data P (t ₁ , t ₂ ) of type and N type
and N(t ₁ , t ₂ ), only one of them is time-reversed with respect to t ₁ and the data S(t ₁ , t ₂ ) obtained by calculating the sum with the other is subjected to a complex Fourier transform, or Alternatively, either P(ω ₁ , ω ₂ ) obtained by complex Fourier transform of P(t ₁ , t ₂ ) or N(ω ₁ , ω ₂ ) obtained by complex Fourier transform of N(t ₁ , t ₂ ) By taking the absolute value of S(ω ₁ , ω ₂ ) obtained by inverting only ω about _{the 1} axis and summing it with the other, we can create an absolute value-absorption mixed mode two-dimensional spectrum that does not require phase correction. Obtain data and further |S(ω ₁ , ω ₂ ) |
By performing symmetrization processing, it is possible to obtain pure absorption two-dimensional spectrum data with good resolution and no tails in both directions of the ω ₁ and ω ₂ axes. [Example] Hereinafter, an example will be described with reference to the drawings. Acquisition of data through 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 shown in FIG. 8a, and complex set data S ₂ (t ₁ , t ₂ ) is obtained by measurement using the sequence shown in FIG. 8 b. is obtained. The obtained complex set data S ₁ (t ₁ , t ₂ ) and S ₂ (t ₁ , t ₂ ), if relaxation is ignored, are respectively 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 ), and by adding and subtracting these two complex set data, the sum data P( _t1 , _t2 )
and difference data N(t ₁ , t ₂ ) are 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, P(t ₁ , t ₂ ) and N(t ₁ , t ₂ ) are first subjected to complex Fourier transform with respect to t ₂ , and P(t ₁ , ω ₂ ) and N(t ₁ , ω ₂ ). P (t ₁ , ω ₂ ) = exp (iω ₁ t ₁ ) × {a ₂ (ω ₂ ) + id ₂ (ω ₂ )} N (t ₁ , ω ₂ ) = exp (−iω ₁ t ₁ ) × { a ₂ (ω ₂ ) + id ₂ (ω ₂ )} Here, a ₂ (ω ₂ ) is where T ₂ ^* is the transverse relaxation time about the ω ₂ axis, and ω ₀ is the reference angle corresponding to the observed frequency on the ω ₂ axis. It is an even function that gives an absorption waveform as a ₂ (ω ₂ )=T ₂ ^* /{1+T ₂ ^*2 (ω ₂ +ω ₀ ) ² }. Also, d ₂ (ω ₂ ) is expressed by the following formula, and the dispersion waveform is d ₂ (ω ₂ )=T ₂ ^*2 (ω ₂ +ω ₀ ) /{1+T ₂ ^*2 (ω ₂ +ω ₀ ) ² } It is an odd function that gives P(t ₁ , ω ₂ ) and N(t ₁ , ω ₂ ) are further subjected to complex Fourier transform with respect to t ₁ , and 2D spectral data P(ω ₁ , ω ₂ ) and N(ω ₁ , ω ₂ ) are obtained. It will be done. P(ω ₁ , ω ₂ )= {a ₁ (ω ₁ )+id ₁ (ω ₁ )}× {a ₂ (ω ₂ )+id ₂ (ω ₂ )} N(ω ₁ , ω ₂ )= {a ₁ (−ω ₁ )+id ₁ (−ω ₁ )}× {a ₂ (ω ₂ )+id ₂ (ω ₂ )} Here, a ₁ (ω ₁ ) is T ₂ as the transverse relaxation time about the ω ₁ axis, ω It is expressed by a temporal equation where ₀ is the reference angular frequency corresponding to the observation frequency of the ω ₁ axis, and the absorption waveform is a ₁ (ω ₁ ) = T ₂ / {1 + T ₂ ² (ω ₂ + ω ₀ ) ² } is an even function that gives Also, d ₁ (ω ₁ ) is expressed by the following formula, and a dispersive 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. The process up to this point is the same as the conventional method explained earlier, and conventionally, based on the two-dimensional spectral data P (ω ₁ , ω ₂ ) and N (ω ₁ , ω ₂ ) obtained in this way, It was displaying a dimensional NMR spectrum. For example, a ₁ (ω ₁ )a ₂ of the real part of P(ω ₁ , ω ₂ )
The spectrum based on (ω ₂ )−d ₁ (ω ₁ )d ₂ (ω ₂ ) is 2
It appears as a dimensional peak. The same applies to the spectrum based on N(ω ₁ , ω ₂ ). By the way, both of these peaks are a(ω)
and d(ω), the waveform becomes a mixture of an absorption waveform and a dispersion waveform. Therefore, the frequency of one spectrum data is inverted with respect to _ω1 . For example, spectral data N
If (ω ₁ , ω ₂ ) is found by frequency inverting (ω ₁ , ω ₂ ) with respect to ω ₁ , a ₁ (ω ₁ ) is an even function, d ₁
Since (ω ₁ ) is an odd function, (ω ₁ , ω ₂ )= {a ₁ (ω ₁ )−id ₁ (ω ₁ )}× {a ₂ (ω ₂ )+id ₂ (ω ₂ )} becomes. Next, the obtained inverted data (ω ₁ , ω ₂ )
is added to the other data P (ω ₁ , ω ₂ ) to obtain the combined data S (ω ₁ , ω ₂ ). S (ω ₁ , ω ₂ )=2a ₁ (ω ₁ ) {a ₂ (ω _{2 )} )+id ₂ (ω ₂ )}, and the real part of S(ω ₁ , ω ₂ ) is 2a ₁ (ω ₁ )a ₂ (ω ₂
)
As can be seen from the expression, the spectrum peak displayed based on the real part of this data is a pure absorption waveform. Note that by performing exactly the same calculation process on the difference with P, a two-dimensional peak expressed as 2d ₁ (ω ₁ )d ₂ (ω ₂ ) appears symmetrically. However, in reality, S(ω ₁ , ω ₂ ) becomes S(ω ₁ , ω ₂ )=2a ₁ (ω ₁ ){a ₂ (ω ₂ )+id ₂ (ω ₂ )}e ⁱ 〓, and unless this phase correction is performed, dispersion and absorption will be mixed. Therefore, in the present invention, the absolute value of S(ω ₁ , ω ₂ ) is taken, and |S(ω ₁ , ω ₂ )|= 2a ₁ (ω ₁ ){a ₂ ² (ω ₂ )+d ₂ ² (ω ₂ )} ^1/2 is obtained. As can be seen from the above equation, the phase factor e ⁱ 〓 can be removed from this spectrum data. FIG. 1 shows a flowchart for obtaining such spectral data. The general form of the absolute value mode is |S'(ω ₁ , ω ₂ )|= {a ₁ ² (ω ₁ )+d ₁ ² (ω ₁ )} ^1/2 {a ₂ ² (ω ₂ )+d ₂ ² (ω
₂ )} The general form of ^{the 1/2} pure absorption mode is S″(ω ₁ , ω ₂ )=a ₁ (ω ₁ )a ₂ (ω ₂ ), so the spectral data of the present invention is in the ω ₁ direction. is a pure absorption type, and in the ω ₂ direction is an absolute value type, and the display method is an absolute value-absorption mode that is intermediate between the absolute value mode and the pure absorption mode. Figure 5a shows the absolute value of the present invention. Figure 5b shows the conventional absolute value mode spectrum, and Figure 5c shows the conventional pure absorption mode spectrum.The absolute value absorption mode spectrum of the present invention does not require complicated phase correction. It can be seen that the sharpness of the hem has become better.In the above explanation, an example was shown in which the frequency of N(ω ₁ , ω ₂ ) was inverted, but when P(ω ₁ , ω ₂ ) Exactly the same result can be obtained by inverting the frequency of P(t ₁ , t ₂ ) and adding or subtracting it from N(ω 1 , ω 2 ).Also, as shown in Figure 2, P(t ₁ , t ₂ ) and N
(t ₁ , t ₂ ) is inverted in the t ₁ direction and (t ₁ , t ₂ ) is added to obtain S(t ₁ , t ₂ ), which is then subjected to two-dimensional complex Fourier transform to S(ω ₁ , ω ₂ ), only one Fourier transform is required. In this case as well, it goes without saying that P(t ₁ , t ₂ ) may be time-reversed with respect to t ₁ . Also, as shown in Figure 3, the real and imaginary parts of N(t ₁ , t ₂ ) are exchanged, time-reversed about t ₂ , complex Fourier transform is performed, and the real and imaginary parts are exchanged ( ω ₁ , ω ₂ ) may be obtained. In this case as well, the above processing may be performed on P(t ₁ , t ₂ ) instead of the above processing on N(t ₁ , t ₂ ). FIG. 4 is a diagram showing another embodiment according to the present invention,
For example, |S obtained with the flow shown in Figure 1
This is an example in which (ω ₁ , ω ₂ )| is further symmetrically processed. The symmetrization operation here is min{S(ω ₁ , ω ₂ ), S(ω ₂ , ω ₁ )} → S(ω ₁ , ω ₂ )=S(ω ₂ , ω ₁ ). That is, the sizes of data at positions symmetrical to the diagonal are compared and the smaller one is adopted as the data at both positions. Figure 6a shows the spectrum display when such symmetrization processing is performed, and Figure 6c shows the spectrum displayed in Figures 1 to 3.
The absolute value-absorption mode spectrum obtained by the example shown in the figure is shown, and Fig. 6e shows the P type of the conventional method.
FIG. 6 is a diagram showing an absolute value spectrum without phase correction obtained from FID, and FIGS. 6b, d, and f show spectra in the ω ₂ direction and ω ₁ direction, respectively. The symmetrization operation in this embodiment is performed at a position symmetrical to the diagonal, as shown in FIG.
Compare the values of S _A and S _A ′, and S _B and S _B ′, and in this case
The values of S _A ′ and S _B ′ are respectively adopted. By applying this to each point, we get ω ₁ ,
A two-dimensional spectrum with good resolution can be obtained in both ω ₂ directions. FIG. 4 is a diagram showing a flowchart when the flow for determining the absolute value-absorption mode of FIG. 2 is used and further symmetrization processing is performed. Note that this embodiment is not limited to the method of deriving the absolute value of S(ω ₁ , ω ₂ ), so it goes without saying that it may be combined with the method shown in FIGS. 2 and 3. As described above, in the present invention, in two-dimensional NMR, P
It is applicable to all possible methods of outputting type and N type data, but if there is an initial delay at time _t1 , the dispersion component will mix in the _ω1 direction, so it will not become a pure absorption mode. Furthermore, it cannot be applied to the J decomposition method and the SECSY method, which cannot separate P and N. The following are concretely applicable two-dimensional methods: Homogeneous nuclei: COSY, RELAY, MQT filfered
COSY NOESY，MQT coherence，FOCSY，
TOCSY etc. Hetero COSY, hetero RELAY, etc.
hetero MQT coherence (2DINADEQUATE
etc.) etc. [Effects of the Invention] As described above, according to the present invention, there is no need for phase correction, and it is possible to automate calculations.
Furthermore, a spectrum with a narrow line width and well-defined peak tails can be obtained, and the separation between peaks is improved. In addition, since absolute values are basically calculated, all peaks take positive values, which makes it easier to see, allows accurate extraction of peak intensities, and improves measurement sensitivity (S/N ratio).
is √2 compared to the conventional absolute value mode spectrum.
Improved twice.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the flow of one embodiment for determining an absolute value-absorption mode spectrum according to the present invention, and FIGS. 2 and 3 are diagrams showing other embodiments for determining an absolute value-absorption mode spectrum according to the present invention. Figure 4 is a diagram showing the flow of an example for obtaining a pure absorption mode spectrum according to the present invention. Figure 5 is a diagram showing the spectrum of absolute value-absorption mode, absolute value mode, and pure absorption mode. Figure 6 showing
The figure shows a two-dimensional spectrum, and Fig. 7 shows a two-dimensional spectrum.
A diagram showing an example of an NMR apparatus for performing the 2DNMR method, and FIG. 8 is a diagram showing a pulse sequence used in the 2DNMR measurement. 1... Magnet, 2... Sample coil, 3... High frequency oscillator, 4... Variable phase shift circuit, 6, 7... Gate, 9, 1
0... Demodulation circuit, 11... 90° phase shift circuit, 12, 13
...A-D conversion circuit, 14...computer, 15...
Memory, 16...Pulse programmer.

Claims (1)

[Claims] 1 (a) A detection pulse or pulse train is irradiated after a development period t ₁ after the irradiation of the preparation pulse or pulse train, and the FID from the sample is detected over the detection period t ₂ after the irradiation of the detection pulse or pulse train. Complex set data consisting of multiple FID signals measured at different values of t ₁ using a sequence in which the signals are detected by two detection channels with a 90° phase difference.
S ₁ (t ₁ , t ₂ ); (b) the sequence is the same as the sequence in (a) above, and the phase between the preparation pulse or pulse train and the detection pulse or pulse train is the same as that in the sequence in (b) above; Using a sequence 90° different from the case,
Complex set data S ₂ (t ₁ , t ₂ ) consisting of multiple FID signals measured for the same multiple t ₁ as in (a) above
(c) sum data P (t ₁ , t ₂ ) of the set data S ₁ (t 1 , t 2 ), S ₂ ( _{t 1} , t ₂ ) and difference data N (t ₁ , t ₂ ); ₂ ) Only one of them is time-reversed with respect to t ₁ ,
Either perform a complex Fourier transform on the data S (t ₁ , t ₂ ) obtained by taking the sum or difference with the other, or
Or P (t ₁ , t ₂ ) obtained by complex Fourier transform
(ω ₁ , ω ₂ ) or N(ω ₁ , ω ₂ ) obtained by complex Fourier transformation of N(t ₁ , t ₂ ), only one of which is inverted about the ω ₁ axis and the sum or difference with the other is calculated. A two-dimensional nuclear magnetic resonance measurement method comprising: creating absolute value spectrum data of S(ω ₁ , ω ₂ ) obtained by taking the data. 2 Spectral data inverted about the ω ₁ axis of P(ω ₁ , ω ₂ ) or N(ω ₁ , ω ₂ ) is P(t ₁ , t ₂ )
Or, it is characterized by exchanging the real and imaginary parts of N(t ₁ , t ₂ ), time-reversing with respect to t ₂ , and exchanging the real and imaginary parts of the spectrum data obtained by complex Fourier transform. A two-dimensional nuclear magnetic resonance measurement method according to claim 1. 3 (a) After a development period t ₁ after irradiation of the preparation pulse or pulse train, irradiate the detection pulse or pulse train, and over the detection period t ₂ after irradiation of the detection pulse or pulse train, change the FID signal from the sample at a 90° phase. Complex set data consisting of multiple FID signals measured at different values of t ₁ using detection sequences with two different detection channels.
S ₁ (t ₁ , t ₂ ); (b) the sequence is the same as the sequence in (a) above, and the phase between the preparation pulse or pulse train and the detection pulse or pulse train is the same as that in the sequence in (b) above; Using a sequence 90° different from the case,
Complex set data S ₂ (t ₁ , t ₂ ) consisting of multiple FID signals measured for the same multiple t ₁ as in (a) above
(c) sum data P (t ₁ , t ₂ ) of the set data S ₁ (t 1 , t 2 ), S ₂ ( _{t 1} , t ₂ ) and difference data N (t ₁ , t ₂ ); ₂ ) Only one of them is time-reversed with respect to t ₁ ,
Either perform a complex Fourier transform on the data S (t ₁ , t ₂ ) obtained by taking the sum or difference with the other, or
Or P (t ₁ , t ₂ ) obtained by complex Fourier transform
(ω ₁ , ω ₂ ) or N(ω ₁ , ω ₂ ) obtained by complex Fourier transformation of N(t ₁ , t ₂ ), only one of which is inverted about the ω ₁ axis and the sum or difference with the other is calculated. (d) Creating spectral data by symmetrizing |S( _{ω 1 ,} ω _{2 )} | Nuclear magnetic resonance measurement method. 4 Spectral data inverted about the ω ₁ axis of P(ω ₁ , ω ₂ ) or N(ω ₁ , ω ₂ ) is P(t ₁ , t ₂ )
Or, it is characterized by exchanging the real and imaginary parts of N(t ₁ , t ₂ ), time-reversing with respect to t ₂ , and exchanging the real and imaginary parts of the spectrum data obtained by complex Fourier transform. A two-dimensional nuclear magnetic resonance measurement method according to claim 3.