Study On Methods For High-Resolution Homonuclear Pure Shift Correlation Spectroscopy

Nuclear Magnetic Resonance(NMR)technique has attracted the entensive attention and in-depth research of scientists since its introduction.After decades of vigorous development,it has been playing an important role in various fields.With the development of this technique,NMR spectra change from one-dimensional spectrum to multi-dimensional spectrum.With the increasement of dimension,the crowding of spectral lines is reduced.To a certain extent,the resolution of the spectrum is improved and the information of the relationship between nuclei is provided more clearly.Although the two-dimensional spectroscopy technique is continuously developed to obtain specific molecular information,the resolution of the two-dimensional spectroscopy is still difficult to satisfy the demand due to the complexity of the molecular structure and the effect of scalar coupling.Higher resolution is needed to improve the quality of the two-dimensional spectrum so that we can analyze it.The homonuclear correlation spectra COSY and TOCSY are classic two-dimensional spectra used to analyze coupling networks,and are also limited by the effect of scalar couplings.This paper mainly proposes two new methods for obtaining high-resolution COSY and TOCSY spectra.It is very convenient for us to analyze the coupling relationship between molecules.The main structure of this article is as follows:In this paper,we combine the pure shift technique and MFA(the acquisition of multiple free induction signal decays(FID)within the same scan)technique to design a pulse sequence.The pulse sequence allows us to obtain COSY and TOCSY spectra whose indirect dimensions are decoupled simultaneously,and through covariance processing,two-dimensional decoupled COSY and TOCSY spectra are obtained.This method improves the efficiency and resolution of homonuclear correlation spectra,facilitating the analysis of molecular coupling network.In the meanwhile,non-uniform sampling and compressed sensing algorithms can be used to reconstruct the spectrum to further improve efficiency.In this part,the pulse sequence will be explained and several samples were used to verify the feasibility of the pulse sequence.In this paper,different pure shift techniques are combined to design a pulse sequence to obtain two-dimensional pure shift TOCSY spectrum.The sequence can simultaneously remove the effect of scalar couplings in direct and indirect dimensions from the TOCSY spectrum,reducing the process of redundant data processing.Therefore,we can obtain a high-resolution two-dimensional pure shift TOCSY spectrum,which is conducive to improving the analysis of coupling network in molecular systems.This method can also use non-uniform sampling and compressed sensing algorithms to reconstruct the spectrum to further improve the sampling efficiency.In this part we will explain the pulse sequence and use several samples to verify the feasibility of the pulse sequence.