A one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering
By employing selective dual quantum filtering and the Dixon signal separation method, the problem of insufficient signal selectivity in complex spectra is solved, achieving efficient and accurate molecular structure analysis, which is applicable to the field of nuclear magnetic resonance spectroscopy detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAMEN UNIV
- Filing Date
- 2023-11-13
- Publication Date
- 2026-07-17
AI Technical Summary
Existing one-dimensional nuclear magnetic resonance correlation spectroscopy techniques lack selectivity when faced with complex and crowded spectra, making it difficult to accurately select signals. In particular, the chemical shift distribution range is narrow and the spectra are crowded and overlapping in the proton spectrum, which limits the ability to resolve molecular structures.
A selective dual quantum filtering method is employed to filter out signals within the chemical shift region using multicolor pulses and gradient fields. Combined with Dixon signal separation and correlation spectroscopy modules, coupling network information is acquired using different waiting times to generate a one-dimensional nuclear magnetic resonance correlation spectrum.
It achieves efficient and accurate extraction of coupling network information, with results obtained in a single scan, low time cost, wide applicability, and the ability to resolve molecular structures in complex systems. It is suitable for various nuclear magnetic resonance spectrometers.
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Figure CN117554874B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nuclear magnetic resonance spectroscopy detection, and specifically to a method for generating one-dimensional nuclear magnetic resonance correlation spectra based on selective dual quantum filtering. Background Technology
[0002] Nuclear magnetic resonance (NMR) spectroscopy is a crucial component of the NMR field. One-dimensional selected proton co-nuclear correlation spectroscopy (one-dimensional COSY) can obtain the direct coupling relationships of selected nuclei within three chemical bonds in a single scan, greatly aiding in molecular structure analysis. However, current one-dimensional NMR correlation spectroscopy heavily relies on the selectivity of the selective pulse. When faced with complex and crowded spectra, the selective pulse cannot accurately select the desired signal. This problem is particularly severe in proton NMR spectroscopy because the chemical shift distribution range (0-15 ppm) of the 1H nucleus is narrow and exhibits extensive scalar coupling splitting, resulting in significant spectral crowding and overlap. The insufficient selectivity of traditional one-dimensional correlation spectroscopy greatly limits its ability to resolve molecular structures in complex chemical and biological samples.
[0003] To address this problem, numerous techniques have been proposed, including various selective pulse optimization techniques and chemical shift selection techniques. However, these techniques all have significant drawbacks. For instance, chemical shift selection techniques require the accumulation of spectra from dozens of experiments, resulting in high time costs; selective pulse optimization techniques have stringent requirements for pulse design and still cannot achieve precise signal selection even in crowded spectral peaks.
[0004] Therefore, a universal, highly selective, concise, efficient, and easy-to-operate one-dimensional correlation spectrum signal extraction method for nuclear magnetic resonance is proposed to obtain the direct coupling network correlation spectrum of specific signals. This method is of great significance for the analysis of molecular structures in complex chemical and biological environments and can further broaden the application scope of nuclear magnetic resonance technology. Summary of the Invention
[0005] In view of the aforementioned technical problems, the purpose of the embodiments of this application is to propose a one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering, so as to solve the technical problems mentioned in the background section above.
[0006] This invention provides a method for generating one-dimensional nuclear magnetic resonance correlation spectra based on selective dual quantum filtering, comprising the following steps:
[0007] S1. Obtain the one-dimensional proton spectrum of the sample to be tested, determine the two chemical shifts of the target signal, the target signal includes a first signal and a second signal with a coupling relationship, and measure the time width of the 90° pulse required for the excitation of the target signal.
[0008] S2, a 90° hard pulse is applied to the sample to be tested to excite the full spectrum signal. Based on the chemical shift information and time width, a multicolor pulse required to excite the target signal is generated. The multicolor pulse is applied to the sample to be tested in conjunction with a gradient field. The signal in the chemical shift region is filtered out from the full spectrum signal. The first and second signals that are coupled to each other are filtered out from the signals in the chemical shift region by a selective dual quantum filter module. Another identical multicolor pulse is applied to the sample to be tested, and the phases of the first and second signals that are coupled to each other are adjusted to obtain the first and second signals that are re-coupled.
[0009] S3, the Dixon signal separation method is used to separate the first and second signals of the re-coupling to obtain the first and second signals;
[0010] S4, The first signal and the second signal are extended through J-coupling evolution using the correlation spectrum module to obtain the coupling network information of the target signal;
[0011] S5, in step S3, set two different waiting times and repeat steps S2-S4 to obtain the coupling network information of the target signal corresponding to the two different waiting times;
[0012] S6. Generate a first spectrum and a second spectrum based on the coupling network information of the target signal obtained from two different waiting times. Process the first spectrum and the second spectrum to obtain the one-dimensional nuclear magnetic resonance correlation spectrum of the first signal and the one-dimensional nuclear magnetic resonance correlation spectrum of the second signal.
[0013] Preferably, a first spectrum and a second spectrum are generated based on the coupling network information of the target signal obtained from two different waiting times, specifically including:
[0014] After deriving the density operator, the simplified signal model at Dixon is:
[0015]
[0016] Where, ω I With ω S These represent the chemical shifts of the selected target signals;
[0017] By setting different waiting times, the following expression is obtained:
[0018]
[0019] When the waiting time τ1 = 0, the first positive phase signal +I is obtained. + The coupling network information and the positive phase second signal +S + The first spectrum of the superimposed coupled network information;
[0020] When waiting time At that time, the first positive phase signal +I is obtained. + The coupling network information and the negative phase second signal -S + The second spectrum is a superposition of coupled network information.
[0021] Preferably, a 180° hard pulse is applied to the sample to be tested, and a first evolution time and a second evolution time, determined based on the waiting time and constant evolution time, are set before and after the 180° hard pulse is applied to the sample to be tested.
[0022] As a preferred option, the first evolution time is... The second evolutionary time is
[0023] Where Δ is the constant evolution time and τ1 is the waiting time.
[0024] Preferably, the multicolor pulse required to excite the target signal is generated based on the chemical shift information and time width, specifically including:
[0025] Based on the chemical shift information and the reference time width, at least two single-frequency excitation pulses corresponding to at least two frequency points are generated. The main parameters are amplitude and phase. The amplitude and phase form a vector in the polar coordinate system. The vectors formed by the parameters of the at least two single-frequency excitation pulses are vector-added to obtain a multicolor pulse that can excite at least two frequency points simultaneously.
[0026] Preferably, the selective dual quantum filter module uses two sets of 90° hard pulses and subsequent gradient fields to act on the sample under test. The ratio of the intensity of the gradient field after the first set of 90° hard pulses to the intensity of the gradient field after the second set of 90° hard pulses is -1:2.
[0027] As a preferred option, the correlation spectrum module uses a 90° hard pulse in conjunction with two gradient fields of the same area applied to the sample to be tested.
[0028] Preferably, the multicolor pulse is a 180° multicolor pulse.
[0029] Preferably, the one-dimensional NMR correlation spectrum of the first signal and the one-dimensional NMR correlation spectrum of the second signal are obtained by processing the first spectrum and the second spectrum, specifically including:
[0030] Adding the first spectrum to the second spectrum yields the one-dimensional nuclear magnetic resonance correlation spectrum of the first signal;
[0031] Subtracting the first spectrum from the second spectrum yields the one-dimensional nuclear magnetic resonance correlation spectrum of the second signal.
[0032] As a preferred method, a single pulse consisting of a 90° radio frequency hard pulse and a signal sampling period is used during the one-dimensional hydrogen spectrum acquisition process.
[0033] Compared with the prior art, the present invention has the following beneficial effects:
[0034] (1) The one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering proposed in this invention has good selectivity through the selective dual quantum filtering module designed for chemical shift frequency points. It can be used to cleanly select a pair of coupled nuclei. Then, through the improved Dixon signal separation method and correlation spectrum module, the coupling network information of the corresponding selected atomic nuclei signal can be obtained through two experiments. This method is a one-dimensional spectrum method with high filtering efficiency. The result can be obtained in a single scan. The minimum experimental time is less than 10 seconds, which has low time cost and high experimental efficiency.
[0035] (2) The one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering proposed in this invention uses a pulse sequence structure that is simple, has a high signal-to-noise ratio, a wide range of applications, strong robustness, and excellent selectivity. It can accurately resolve the molecular structure of specific substances in systems with complex compositions without causing damage to organisms. It can achieve structural resolution of specific molecules in complex chemical and biological samples on various commercial nuclear magnetic resonance spectrometers. It can be used for signal filtering in any coupled system. During use, any pair of coupled signals from any molecule can be selected for signal extraction. It can be used multiple times, selecting different atomic nuclei for excitation, thereby mutually verifying and resolving the network relationships of the entire molecule.
[0036] (3) The one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering proposed in this invention has the advantages of high experimental efficiency, accuracy and universality. It can accurately extract the coupling network information of the selected signal in a system with complex composition (when the spectral peaks are crowded), suppress other related interference signals, and finally obtain the one-dimensional nuclear magnetic resonance correlation spectrum of the target atomic nucleus. It has important application significance for the structural analysis of chemical and biological complex samples in the field of nuclear magnetic resonance spectroscopy detection. Attached Figure Description
[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0038] Figure 1 This is a schematic flowchart illustrating a method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering, as exemplified by an embodiment of this application.
[0039] Figure 2 This is a schematic diagram of the pulse sequence used in the one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering, as an embodiment of this application.
[0040] Figure 3 This diagram illustrates the detailed processing steps of the Dixon signal separation method for separating the coupling network information of the two extracted signals using a one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective double quantum filtering, as described in an embodiment of this application. The sample used is a γ-aminobutyric acid (GABA) solution sample. Figure (a) shows a traditional one-dimensional proton spectrum, and Figure (b) shows the two phase-sensitive signals obtained after selective double quantum filtering. Figure (c) shows the spectra obtained from two experiments using the Dixon method by setting different τ1 values. Figure (d) shows the absolute value spectrum of the direct coupling network signal of nucleus 1 in GABA obtained by adding the two scan signals. Figure (e) shows the absolute value spectrum of the direct coupling network signal of nucleus 2 in GABA obtained by subtracting the two scan signals.
[0041] Figure 4 Figure 1 shows the experimental results of testing amikacin using the one-dimensional nuclear magnetic resonance correlation spectrum generation method based on selective dual quantum filtering according to an embodiment of this application. Figure 2 shows the molecular structure and one-dimensional proton nuclear magnetic resonance spectrum of amikacin. The amikacin molecule contains three ring structures with multiple atomic nuclei with similar chemical shifts. Therefore, there is severe signal congestion and overlap in the chemical shifts of 3-4.2 ppm and around 2 ppm. Figures 3b-1i show the one-dimensional filtered correlation spectra obtained by sampling using the method proposed in this invention. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0043] Figure 1 An embodiment of this application illustrates a method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering, comprising the following steps:
[0044] S1, acquire the one-dimensional proton spectrum of the sample to be tested, determine the two chemical shifts of the target signal, the target signal includes a first signal and a second signal with a coupling relationship, and measure the time width of the 90° pulse required for the excitation of the target signal.
[0045] In a specific embodiment, a single pulse consisting of a 90° radio frequency hard pulse and a signal sampling period is used in the one-dimensional hydrogen spectrum acquisition process.
[0046] Specifically, the sample to be tested and the target signal to be extracted are selected. The chemical shift information of the target signal to be extracted is determined by literature search or one-dimensional proton spectrum of pure solution. The sample to be tested is placed, the one-dimensional proton spectrum of the sample is acquired, and the time width pw of the 90° pulse required for the excitation of the target signal is measured. The chemical shift information of the sample to be tested is calibrated according to the calibration material. Calibration can fix the chemical shift and prevent inconsistencies in the chemical shift of the same substance in multiple experiments due to instrument instability or other reasons.
[0047] S2, a 90° hard pulse is applied to the sample to be tested to excite a full-spectrum signal. Based on the chemical shift information and time width, a multicolor pulse required to excite the target signal is generated. The multicolor pulse is applied to the sample to be tested in conjunction with a gradient field. The signal in the chemical shift region is filtered out from the full-spectrum signal. The first and second signals that are coupled to each other are filtered out from the signals in the chemical shift region by a selective dual quantum filter module. Another identical multicolor pulse is applied to the sample to be tested, and the phases of the first and second signals that are coupled to each other are adjusted to obtain the first and second signals that are re-coupled.
[0048] In a specific embodiment, the multicolor pulse is a 180° multicolor pulse.
[0049] For details, please refer to Figure 2 First, a full-spectrum signal is obtained by excitation with a 90° hard pulse. Based on the chemical shift information of the target signal to be extracted and the measured time width pw of the 90° pulse, a 180° multicolor pulse required for excitation is generated. The first 180° multicolor pulse, in conjunction with a gradient field, is applied to the sample to filter signals in two chemical shift regions. A selective dual-quantum filter module further filters out the mutually coupled first and second signals from the signals in the two chemical shift regions. A second 180° multicolor pulse is applied to adjust the phase of the extracted signal. This second multicolor pulse is the same as the first, thus achieving re-coupling coupling and obtaining the re-coupled first and second signals.
[0050] In a specific embodiment, generating the multicolor pulse required to excite the target signal based on chemical shift information and time width specifically includes:
[0051] Based on the chemical shift information and time width, at least two single-frequency excitation pulses corresponding to at least two frequency points are generated. The main parameters are amplitude and phase. The amplitude and phase form a vector in the polar coordinate system. The vectors formed by the parameters of the at least two single-frequency excitation pulses are vector-added to obtain a multicolor pulse that can excite at least two frequency points simultaneously.
[0052] Specifically, the 180° multicolor pulse, after inputting the chemical shift information of the target signal to be excited, and referring to the time width pw of the 90° pulse, calculates and generates a multicolor pulse capable of simultaneously exciting two frequency points through the vector addition principle. Let the two frequency points to be excited be (f1, f2). First, two single-frequency excitation pulses with frequencies f1 and f2 are generated respectively. The parameters of this pulse after generation are mainly amplitude (Amp1 and Amp2) and phase (Pha1 and Pha2). Through amplitude and phase, a vector can be formed in the polar coordinate system. By vector-adding the vectors formed by the parameters of the two single-frequency excitation pulses, the desired multicolor pulse for simultaneous dual-frequency excitation can be obtained. More excitation frequencies can be obtained in the same way. When this multicolor pulse acts on a specific frequency point, it can excite signals at multiple specific chemical shift positions. The first 180° multicolor pulse is used to select signals in two specific chemical shift regions, and the second 180° multicolor pulse is used for re-coupling evolution to realize the phase-sensitive mode of the extracted two signals. The second 180° multicolor pulse is exactly the same as the first, and is used to cancel the J coupling evolution during the action of the first 180° multicolor pulse, so that the signal becomes an absorption line shape and a phase-sensitive spectrum is achieved.
[0053] In a specific embodiment, the selective dual quantum filter module applies two sets of 90° hard pulses and subsequent gradient fields to the sample under test. Specifically, the ratio of the intensity of the gradient field after the first set of 90° hard pulses to the intensity of the gradient field after the second set of 90° hard pulses is -1:2.
[0054] Specifically, the selective dual quantum filter module can further filter the signals in the chemical shift region excited by multicolor pulses and extract the signals that are coupled, namely the first and second signals that are coupled with each other.
[0055] S3. The first and second signals of repolymerization coupling are separated using the Dixon signal separation method to obtain the first and second signals. The first and second evolution times before and after the 180° hard pulse is applied to the sample are determined based on the waiting time and constant evolution time.
[0056] In a specific embodiment, a 180° hard pulse is applied to the sample to be tested, and a first evolution time and a second evolution time, determined based on the waiting time and constant evolution time, are set before and after the 180° hard pulse is applied to the sample to be tested.
[0057] In a specific embodiment, the first evolution time is The second evolutionary time is
[0058] Where Δ is the constant evolution time and τ1 is the waiting time.
[0059] For details, please refer to Figure 3 The Dixon signal separation method is mainly achieved by setting different τ1 values in two experimental samplings, so that the first and second re-coupling signals extracted after the selective dual quantum filter module have different positive and negative phases. In the first experiment, τ1 is set to 0, and the constant evolution time Δ is set according to the actual situation, generally about 30 milliseconds. By setting different τ1 values in the two experiments, the extracted signals have different positive and negative phases, so that addition and subtraction between them can yield one signal separately. The traditional Dixon signal separation method achieves signal separation in imaging experiments through different chemical shifts of water and lipids. In this experiment, by adding a constant evolution time Δ and a 180° hard pulse, it is improved and further applied to the first and second re-coupling signals extracted after the selective dual quantum filter module. After the derivation of the density operator, the simplified signal model at Dixon is: Where, ω I With ω S These are the chemical shifts of the two target signals, respectively, when the receiver frequency is aligned with ω. I At that time, by setting different values of τ1, the following expression can be obtained: This expression shows that in the two experiments, τ1 is set to 0 and 1 / 2Δω respectively, where Δω is ω I -ω S When τ1 is 0, the experimentally obtained signal is the first signal with positive phase.
[0060] +I + The second signal with positive phase +S + When τ1 is 1 / 2Δω, since the receiver frequency is aligned with the I nucleus, the I nucleus is unaffected by chemical shift evolution and its phase remains unchanged. The S nucleus, however, undergoes chemical shift evolution, resulting in a negative phase and the positive-phase first signal.
[0061] I + The second signal with negative phase -S + .
[0062] S4, using the correlation spectrum module, the first signal and the second signal are extended through J coupling evolution to obtain the coupling network information of the target signal.
[0063] In a specific embodiment, the correlation spectrum module uses a 90° hard pulse in conjunction with two gradient fields of the same area before and after it to act on the sample to be tested.
[0064] Specifically, the final step involves the correlation spectrum module. During the constant evolution time Δ, the target signal undergoes direct intramolecular J-coupling, transmitting its signal along the direct coupling network. The coupling network information of the target signal is obtained by being excited by the last 90° pulse in the correlation spectrum module.
[0065] S5, in step S3, set two different waiting times and repeat steps S2-S4 to obtain the coupling network information of the target signal corresponding to the two different waiting times.
[0066] Specifically, in the first experiment, the positive-phase first signal +I was... + The second signal with positive phase +S + J-coupling evolution was performed using the correlation spectrum module to obtain the first positive-phase signal +I. + The coupling network information and the positive phase second signal +S + The coupling network information. In the second experiment, the positive-phase first signal +I... + The second signal with negative phase -S + J-coupling evolution was performed using the correlation spectrum module to obtain the first positive-phase signal +I. + The coupling network information and the negative phase second signal -S + Coupled network information.
[0067] S6. Generate a first spectrum and a second spectrum based on the coupling network information of the target signal obtained from two different waiting times. Process the first spectrum and the second spectrum to obtain the one-dimensional nuclear magnetic resonance correlation spectrum of the first signal and the one-dimensional nuclear magnetic resonance correlation spectrum of the second signal.
[0068] In a specific embodiment, a first spectrum and a second spectrum are generated based on the coupling network information of the target signal obtained from two different waiting times, specifically including:
[0069] After deriving the density operator, the simplified signal model at Dixon is:
[0070]
[0071] Where, ω I With ω S These represent the chemical shifts of the selected target signals;
[0072] By setting different waiting times, the following expression is obtained:
[0073]
[0074] When the waiting time τ1 = 0, the first positive phase signal +I is obtained. +The coupling network information and the positive phase second signal +S + The first spectrum of the superimposed coupled network information;
[0075] When waiting time At that time, the first positive phase signal +I is obtained. + The coupling network information and the negative phase second signal -S + The second spectrum is a superposition of coupled network information.
[0076] In a specific embodiment, the one-dimensional nuclear magnetic resonance correlation spectrum of the first signal and the one-dimensional nuclear magnetic resonance correlation spectrum of the second signal are obtained by processing the first spectrum and the second spectrum, specifically including:
[0077] Adding the first spectrum to the second spectrum yields the one-dimensional nuclear magnetic resonance correlation spectrum of the first signal;
[0078] Subtracting the first spectrum from the second spectrum yields the one-dimensional nuclear magnetic resonance correlation spectrum of the second signal.
[0079] Specifically, in the first experiment, the signal was acquired to obtain the first spectrum. Steps S2-S4 were repeated for the second experiment. In the second experiment, the following settings were made: ω I With ω S The first and second spectra are obtained by acquiring the chemical shifts of the selected signals. The coupling network information of the first and second signals is separated by adding and subtracting the first and second spectra respectively. The spectral data is then saved, yielding the one-dimensional NMR correlation spectrum of the first and second signals.
[0080] The above method will be verified by specific experiments.
[0081] Example 1
[0082] Amikacin is an antibiotic used to treat bacterial infections. Its efficacy usually depends on its unique molecular structure, but overlapping peaks exist in the nuclear magnetic resonance spectrum of amikacin. Figure 3 The concentration of amikacin (3.0ppm-4.2ppm) makes structural analysis difficult. Therefore, by exciting different coupling pairs in amikacin, the coupling relationship of the amikacin molecule was clearly demonstrated, and its molecular structure was resolved. The instrument used in Example 1 of this application was a Varian 500MHz nuclear magnetic resonance spectrometer.
[0083] Step 1: Dissolve amikacin in D2O to prepare a 200 mM amikacin aqueous solution as the test sample. Place the test sample into the NMR cavity. After performing tuning, field locking, and shimming operations in the NMR spectrometer software interface, apply a 90° hard pulse to obtain... Figure 4(a) shows the one-dimensional proton spectrum of amikacin. Based on prior knowledge, we can understand the coupling relationships of some signals in amikacin and their chemical shift positions in the proton spectrum. Here, coupling pairs of signals are selected from each of the three carbon rings in the amikacin molecular structure—A2 and A3, B1 and B2, C1 and C2, C3 and C4; as shown... Figure 4 The arrow annotation in the text.
[0084] Step 2: Reference Figure 4 (a) In a one-dimensional proton spectrum, the center of the multicolor pulse is aligned with the chemical shift position of one of the two signals to be extracted. Based on the 90° hard pulse pw and the chemical shift information of the two signals to be extracted, the parameters of the multicolor pulse are designed. After optimizing the parameters τ1 and Δ in the Dixon module according to the chemical shift difference between the two signals, the pulse is directly applied. Figure 2 The pulse sequence shown can be used to obtain the one-dimensional correlation spectrum of the selected pair of coupled signals. To obtain the coupling relationship spectrum of each signal separately, two scans are required, with different τ1 values set, and the scan results are added or subtracted.
[0085] In this embodiment, the pulse sequence used ( Figure 2 The specific parameters are as follows: the duration of the 90° hard pulse is 12.25 μs; the multicolor pulse used is of type rsnob with a bandwidth of 40 Hz; the constant evolution times Δ for the A2 and A3 coupling signals of Amika star are 57 ms and 20 ms, respectively, with τ1 being 750 μs. The constant evolution times Δ for the B1 and B2 coupling signals of Amika star are 20 ms and 30 ms, respectively, with τ1 being 517 μs. The constant evolution times Δ for the C1 and C2 coupling signals of Amika star are 30 ms and 30 ms, respectively, with τ1 being 725 μs. The constant evolution times Δ for the A2 and A3 coupling signals of Amika star are 30 ms and 20 ms, respectively, with τ1 being 2.58 ms.
[0086] pass Figure 4 As shown in the experimental results (b)-4(i), the embodiments of this application can successfully extract the coupling network information of selected specific atomic nuclei from complex and overlapping NMR spectra. The arrows in the spectrum represent the selected hydrogen nucleus signals, and the other labeled signals are their coupling network information. This experimental result is consistent with previous literature reports and also conforms to the molecular structure of amikacin. This demonstrates that the method proposed in the embodiments of this application has the ability to efficiently extract the coupling network information of specific hydrogen nuclei from complex chemical and biological samples.
[0087] In summary, the sample used in Example 1 is a representative sample selected by the present invention. One-dimensional nuclear magnetic resonance correlation spectra can also be obtained by using other samples and the method proposed in the embodiments of this application.
[0088] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.
Claims
1. A method for generating one-dimensional nuclear magnetic resonance correlation spectra based on selective dual quantum filtering, characterized in that, Includes the following steps: S1, acquire the one-dimensional proton spectrum of the sample to be tested, determine the two chemical shifts of the target signal, the target signal including a first signal and a second signal with a coupling relationship, and measure the time width of the 90° pulse required for the excitation of the target signal; S2, apply a 90° hard pulse to the sample to be tested to excite a full-spectrum signal. Generate a multicolor pulse required to excite the target signal based on the chemical shift information and time width. Apply the multicolor pulse to the sample to be tested in conjunction with a gradient field. Filter out the signal within the chemical shift region from the full-spectrum signal. Filter out the mutually coupled first and second signals from the signals within the chemical shift region using a selective dual-quantum filter module. Apply another identical multicolor pulse to the sample to be tested and adjust the phase of the mutually coupled first and second signals to obtain re-coupled first and second signals. S3, the first and second signals of the re-coupling coupling are separated using the Dixon signal separation method to obtain the first and second signals; S4, The first signal and the second signal are extended through J-coupling evolution using the correlation spectrum module to obtain the coupling network information of the target signal; S5, in step S3, two different waiting times are set respectively and steps S2-S4 are repeated to obtain the coupling network information of the target signal corresponding to the two different waiting times; S6, generating a first spectrum and a second spectrum based on the coupling network information of the target signal obtained from two different waiting times, specifically including: After deriving the density operator, the simplified signal model at Dixon is: ； in, and These represent the chemical shifts of the selected target signals; By setting different waiting times, the following expression is obtained: ； When waiting time At that time, the first signal with positive phase is obtained. The coupling network information and the positive phase second signal The first spectrum of the superimposed coupled network information; When waiting time At that time, the first signal with positive phase is obtained. The coupling network information and the second signal with negative phase The second spectrum, formed by superimposing the coupling network information, is used to process the first and second spectra to obtain the one-dimensional NMR correlation spectrum of the first signal and the one-dimensional NMR correlation spectrum of the second signal. Specifically, this includes: Add the first spectrum to the second spectrum to obtain the one-dimensional nuclear magnetic resonance correlation spectrum of the first signal; Subtracting the first spectrum from the second spectrum yields the one-dimensional nuclear magnetic resonance correlation spectrum of the second signal.
2. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 1, characterized in that, A 180° hard pulse is applied to the sample to be tested, and a first evolution time and a second evolution time, determined based on a waiting time and a constant evolution time, are set before and after the 180° hard pulse is applied to the sample to be tested.
3. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 2, characterized in that, The first evolution time is The second evolution time is ; in, For constant evolution time, For waiting time.
4. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 1, characterized in that, The step of generating the multicolor pulse required to excite the target signal based on the chemical shift information and time width specifically includes: Based on the chemical shift information and the reference time width, at least two single-frequency excitation pulses corresponding to at least two frequency points are generated. The parameters are mainly amplitude and phase. The amplitude and phase are used to form a vector in the polar coordinate system. The vectors formed by the parameters of the at least two single-frequency excitation pulses are vector-added to obtain a multicolor pulse that can excite at least two frequency points simultaneously.
5. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 1, characterized in that, The selective dual quantum filter module applies two sets of 90° hard pulses and subsequent gradient fields to the sample under test. The ratio of the intensity of the gradient field after the first set of 90° hard pulses to the intensity of the gradient field after the second set of 90° hard pulses is -1:
2.
6. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 1, characterized in that, The correlation spectrum module uses a 90° hard pulse in conjunction with two gradient fields of the same area before and after it to act on the sample to be tested.
7. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 1, characterized in that, The multicolor pulse is a 180° multicolor pulse.
8. The method for generating a one-dimensional nuclear magnetic resonance correlation spectrum based on selective dual quantum filtering according to claim 1, characterized in that, The one-dimensional hydrogen spectrum acquisition process uses a single pulse consisting of a 90° radio frequency hard pulse and a signal sampling period.