Fourier Phase Codec Combined With Broadband Inversion Toward J-edited Spectra

Homonuclear coupling is a double-edged sword.On the one hand,it is a well-established source of valuable information on molecular structure,reflecting torsion or bond angles in the case of scalar couplings,and internuclear vectors in the case of residual dipolar couplings(RDCs).On the other hand,when,as is almost always the case,multiple couplings are present,the complexity of the resulting multiplets and the narrow range of 1H chemical shifts conspire to cause spectral overlap.This complicates spectral analysis and often prevents measurement of individual 1H-1H couplings.In recent years,much effort has been invested in generating broadband homonuclear decoupled,or "pure shift" spectra,collapsing multiplets to singlets and yielding a limiting resolution close to the natural linewidth.Unfortunately,the gain in resolution comes at the cost of losing direct access to valuable coupling information.The G-SERF method can measure the coupling constants of independent nuclear spin pairs,but the sensitivity is low.PSYCHEDELIC can obtain a high sensitivity spectrum,which takes quite a long sampling time.We propose a method to overcome the influence of the selective nuclear spin by the indirect coupling of multiple nuclear spin,and directly detect the independent indirect coupling relationship between the selected nuclear spin and all the coupling nuclei,and in the same time,the signal to noise ratio can be improved compared to the Clean-G-SERF method.The main work is summarized as follows:First,the basic principles of nuclear magnetic resonance(NMR)are described in detail.Then,the development history of pure shift spectrum in recent ten years is introduced,especially the PSYCHE technology.Second,two key technologies to implement the new J-resolved spectrum are introduced.First,the principle of Fourier phase encoding and decoding is introduced based on the 1D NMR spectrum based on Fourier phase encoding and decoding.Then we expound the principle of clean gradient encoding homonuclear selective refocusing(Clean-G-SERF).Third,we present a method termed as time-optimized Fourier encoding(TOFEE)-J-edited for accurate measuring scalar coupling networks for specific spins,which is based on imparting a discrete phase modulation of the targeted cross peaks,and combine it with a pure shift experiments(PSYCHE)based J-modulated scheme,providing simple 2D J-edited spectra for accurate measurement of scalar coupling networks.Chemical shifts and J coupling constants of protons coupled to the specific protons are demonstrated along the F2 and F1 dimensions,respectively.Polychromatic pulses by Fourier phase encoding were performed to simultaneously detect several coupling networks.Proton-proton scalar couplings are chosen by a polychromatic pulse and a PSYCHE element.Axis peaks and unwanted couplings are complete eradicated by incorporating a selective COSY block as a preparation period.The theoretical principles and the signal processing procedure are laid out,and experimental observations are rationalized on the basis of theoretical analyses.Finally,we present a novel pulse sequence based on TOFEE-J edited spectroscopy termed as improved TOFEE-J edited spectroscopy,in which a new indirect dimension is introduced.The final spectra can be decoupled in the F2 dimension,which can be used to further enhance the resolution and SNRs of the NMR spectrum.