阅读说明：本技术 一种方便测量偶合常数的二维j分解谱的核磁共振方法 (Nuclear magnetic resonance method for conveniently measuring two-dimensional J-resolution spectrum of coupling constant ) 是由 林雁勤 曾庆 陈金永 陈忠 于 2019-09-19 设计创作，主要内容包括：本发明提供一种方便测量偶合常数的二维J分解谱的核磁共振方法,首先施加一个90度硬脉冲将磁化矢量从Z方向旋转到XY平面,再施加改进的自旋回波模块,即在常规的“t<Sub>1</Sub>/2-180°-t<Sub>1</Sub>/2”模块里插入选择性180°脉冲。再经过两维傅里叶变换后得到二维谱图,在常规二维J分解谱中沿45°排列的信号分离模式,变成了两条沿45°排列的分裂的信号。这两条信号之间的距离就是被选择性180°脉冲作用的核有关的J偶合。把二维谱做45°旋转,向直接维的投影得到纯化学位移一维谱,但是保留了与选择的核相关的J偶合。因此可以从直接维投影谱中方便地测量出与选择的核相关的J偶合常数。(The invention provides a nuclear magnetic resonance method for conveniently measuring two-dimensional J-resolution spectrum of coupling constant, which comprises the steps of firstly applying a 90-degree hard pulse to rotate a magnetization vector from a Z direction to an XY plane, and then applying an improved spin echo module, namely, in the conventional t 1 /2‑180°‑t 1 The/2 "module inserts selective 180 ° pulses. And obtaining a two-dimensional spectrogram after two-dimensional Fourier transform, wherein the two-dimensional spectrogram is changed into two split signals arranged along 45 degrees in a signal separation mode arranged along 45 degrees in a conventional two-dimensional J-split spectrum. The distance between these two signals is the J-coupling associated with the nucleus acted upon by the selective 180 ° pulse. The two-dimensional spectrum is rotated by 45 degrees and projected to the direct dimension to obtain a pure chemical shift one-dimensional spectrum, but the J coupling associated with the selected kernel is retained. The J-coupling constants associated with the selected kernel can thus be conveniently measured from the direct-dimensional projection spectra.)

1. A nuclear magnetic resonance method for conveniently measuring a two-dimensional J-split spectrum of a coupling constant is characterized by comprising the following steps:

1) collecting a nuclear magnetic resonance one-dimensional spectrum of a sample;

2) measuring the pulse width of a 90 degree hard pulse of the sample;

3) setting a coherent selection gradient G₁Intensity and duration;

4) setting the center position of hydrogen nuclei to be researched as the center frequency of the selective 180-degree pulse, determining the pulse width of the selective 180-degree pulse according to the signal distribution condition, and measuring the power of the selective pulse;

5) determining indirect dimension spectral width and indirect dimension sampling point number ni, i.e. evolution time t₁The number of increments of (a);

6) using the measured 90-degree hard pulse as the excitation pulse of the pulse sequence, at a time delay t₁After time/2, apply a first selective 180 degree pulse and 180 degree hard pulse, then delay a second t₁A second selective 180-degree pulse is applied in the time of/2, and then the nuclear magnetic resonance signal is collected;

7) and performing two-dimensional Fourier transform on the acquired nuclear magnetic resonance signal data, and then performing 45-degree rotation. Then, the projection in the direct dimension and the projection of the respective signals in the indirect dimension are performed.

2. A nmr method for facilitating the measurement of two-dimensional J-resolution spectra of coupling constants, according to claim 1, wherein: phase of useThe cycle is as follows: phi₁＝x,-x；Φ₂＝x，y,-x,-y；Φ₃＝Φ₄＝x；Φ_RX, -x, -x, x. Where x and y refer to the x and y directions, respectively.

Technical Field

The invention relates to a nuclear magnetic resonance method, in particular to a nuclear magnetic resonance method for conveniently measuring a two-dimensional J decomposition spectrum of a coupling constant.

Background

Nuclear magnetic resonance spectroscopy is a noninvasive and widely used analytical approach. J-coupling is an important parameter in nmr spectroscopy, which provides valuable information about molecular structure and conformation. The J-coupling constant can be measured from the signal splitting of a one-dimensional spectrum. However, due to the limited chemical shift range and signal splitting caused by scalar coupling, signal crowding is common even with overlapping nuclear magnetic resonance spectra. The two-dimensional J decomposition spectrum can separate chemical shift and J coupling into two dimensions, greatly reduces signal crowding and promotes measurement of J coupling constants. Subsequently, many methods have been proposed for J coupling constant measurement, such as high-resolution phase-sensitive J-resolution spectroscopy and selective J-resolution spectroscopy. Measurement of the J-coupling constant has been an important issue in nuclear magnetic resonance spectroscopy.

Disclosure of Invention

The invention aims to provide a nuclear magnetic resonance method for conveniently measuring a two-dimensional J decomposition spectrum of a coupling constant, which is used for promoting the measurement and analysis of the J coupling constant.

In order to solve the above technical problems, the present invention provides 1 a nuclear magnetic resonance method for conveniently measuring a two-dimensional J-split spectrum of a coupling constant, comprising the steps of:

1) collecting a nuclear magnetic resonance one-dimensional spectrum of a sample;

2) measuring the pulse width of a 90 degree hard pulse of the sample;

3) setting a coherent selection gradient G₁Intensity and duration;

4) setting the center position of hydrogen nuclei to be researched as the center frequency of the selective 180-degree pulse, determining the pulse width of the selective 180-degree pulse according to the signal distribution condition, and measuring the power of the selective pulse;

5) determining indirect dimension spectral width and indirect dimension sampling point number ni, i.e. evolution time t₁The number of increments of (a);

6) using the measured 90-degree hard pulse as the excitation pulse of the pulse sequence, at a time delay t₁After time/2, apply a first selective 180 degree pulse and a 180 degree hard pulse, then delaySecond t₁A second selective 180-degree pulse is applied in the time of/2, and then the nuclear magnetic resonance signal is collected;

7) and performing two-dimensional Fourier transform on the acquired nuclear magnetic resonance signal data, and then performing 45-degree rotation. Then, the projection in the direct dimension and the projection of the respective signals in the indirect dimension are performed.

In a preferred embodiment: the phase cycle employed was: phi₁＝x,-x；Φ₂＝x，y,-x,-y；Φ₃＝Φ₄＝x；Φ_RX, -x, -x, x. Where x and y refer to the x and y directions, respectively.

The invention provides a nuclear magnetic resonance method for conveniently measuring a two-dimensional J-resolution spectrum of a coupling constant, which comprises the steps of firstly applying a 90-degree hard pulse to rotate a magnetization vector from a Z direction to an XY plane. Followed by an improved spin echo module, i.e. at a conventional "t₁/2-180°-t₁The/2 "module inserts selective 180 ° pulses. The effect of this is to reunite the J-couplings associated with the nuclei acted upon by the selective 180 ° pulse in the indirect dimension, thus preserving the evolution of the other J-couplings in the indirect dimension. While in the direct dimension, the evolution time is normal, the chemical shift evolves with all J-couplings. Thus, a two-dimensional spectrogram is obtained after two-dimensional Fourier transform, and a signal separation mode arranged along 45 degrees in a conventional two-dimensional J decomposition spectrum becomes two split signals arranged along 45 degrees. The distance between these two signals is the J-coupling associated with the nucleus acted upon by the selective 180 ° pulse. The two-dimensional spectrum is rotated by 45 degrees and projected to the direct dimension to obtain a pure chemical shift one-dimensional spectrum, but the J coupling associated with the selected kernel is retained. The J-coupling constants associated with the selected kernel can thus be conveniently measured from the direct-dimensional projection spectra. Whereas in the projection of each signal in the indirect dimension the respective multiple peak splitting pattern is obtained. And the peak coupled to the selected nucleus, the multiplet splitting pattern is simplified by removing the coupling thereto. In the above-described method, the signal sensitivity is not affected. Therefore, the method can facilitate the measurement of J coupling constant by researchers.

Drawings

FIG. 1 is a pulse sequence diagram of a nuclear magnetic resonance method that facilitates the measurement of two-dimensional J-split spectra of coupling constants.

FIG. 2 is a conventional NMR one-dimensional spectrum of butyl methacrylate.

FIG. 3 shows the results of analysis of hydrogen nuclei H7 of butyl methacrylate by the above-mentioned method.

Detailed Description

The invention is further illustrated below with reference to the accompanying drawings and examples:

a nuclear magnetic resonance method for conveniently measuring a two-dimensional J-split spectrum of a coupling constant, comprising the steps of:

1) collecting a nuclear magnetic resonance one-dimensional spectrum of a sample;

2) measuring the pulse width of a 90 degree hard pulse of the sample;

3) setting a coherent selection gradient G₁Intensity and duration;

4) setting the center position of hydrogen nuclei to be researched as the center frequency of the selective 180-degree pulse, determining the pulse width of the selective 180-degree pulse according to the signal distribution condition, and measuring the power of the selective pulse;

5) determining indirect dimension spectral width and indirect dimension sampling point number ni, i.e. evolution time t₁The number of increments of (a);

6) using the measured 90-degree hard pulse as the excitation pulse of the pulse sequence, at a time delay t₁After time/2, apply a first selective 180 degree pulse and 180 degree hard pulse, then delay a second t₁A second selective 180-degree pulse is applied in the time of/2, and then the nuclear magnetic resonance signal is collected;

7) after the experiment is completed, two-dimensional Fourier transform is performed on the data, and then 45-degree rotation is performed. Then, the projection in the direct dimension and the projection of the respective signals in the indirect dimension are performed.

The phase cycles used for the experiments were: phi₁＝x,-x；Φ₂＝x，y,-x,-y；Φ₃＝Φ₄＝x；Φ_RX, -x, -x, x. Where x and y refer to the x and y directions, respectively.

The specific operations according to the above method are as follows:

this implementationFor example, using a Varian 500MHz NMR spectrometer, a sample of 0.12mol/L butyl methacrylate in deuterated dimethyl sulfoxide (DMSO-d)₆) The solution of (2) was used in a pulse sequence as shown in FIG. 1.

The method comprises the following steps: acquiring a nuclear magnetic resonance one-dimensional hydrogen spectrum of a sample, as shown in figure 2;

step two: the pulse width of the 90-degree hard pulse of the sample was measured to be 10.4. mu.s;

step three: setting a coherent selection gradient G₁Strength of G₁14.65G/cm for 1 ms;

step four: using RSnob-shaped selective pulses, the center position of the hydrogen nuclei H7 under investigation was set to the center frequency of the selective 180-degree pulse. Determining the pulse width of the selective 180-degree pulse to be 30 milliseconds according to the signal distribution condition, and measuring the power of the selective pulse to be 9 dB;

step five: determining that the indirect dimension spectral width is 50Hz and the number ni of indirect dimension sampling points is 64;

step six: using the measured 90-degree hard pulse as the excitation pulse of the pulse sequence, at a time delay t₁After time/2, apply a first selective 180 degree pulse and 180 degree hard pulse, then delay a second t₁A second selective 180-degree pulse is applied in the time of/2, and then the nuclear magnetic resonance signal is collected;

step seven: after the experiment is completed, two-dimensional Fourier transform is performed on the data, and then 45-degree rotation is performed. Then, the projection in the direct dimension and the projection of the respective signals in the indirect dimension are performed.

FIG. 3 shows the results of analysis of the hydrogen nuclei H7 of butyl methacrylate using the method described above. The two-dimensional spectrum has been rotated 45. The one-dimensional spectrum above the two-dimensional spectrum is a projection in the direct dimension and the insets give a partial magnification of the signal of H6 and H5 coupled to the hydrogen nuclei H7 studied and a partial magnification of the signal of H1 which has not been coupled to H7. It can be seen that the signals of H6 and H5 split into two doublets from which their coupling constants to H7 were measured, 2.0Hz and 1.8Hz, respectively. Whereas H1 did not couple with H7, showing a single peak. Indirect dimensional projection of H6, H5 and H1 signals is given below the two-dimensional spectrum, which facilitates multiple peak analysis.

In summary, the present invention provides a nuclear magnetic resonance method that facilitates two-dimensional J-resolution spectroscopy of coupling constants, facilitating measurement of J-coupling constants and multi-peak analysis.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.