Study On Ultrafast Two-Dimensional NMR Spectroscopy Based On Slice-selective Module

Nuclear magnetic resonance(NMR)spectroscopy serves as an important tool for both qualitative and quantitative analyses of various systems in chemistry,biology,and medicine.However,applications of one-dimensional 1H NMR are often restrained by the presence of severe overlap among different resonances.The advent of two-dimensional(2D)1H NMR constitutes a promising alternative by extending the crowded resonances into a plane and thereby alleviating the spectral congestions.Generally,two aspects arise to hinder the 2D NMR from broader applications.First,numerous transients with progressive evolution delays should be collected to construct the indirect dimension with decent resolution in conventional 2D NMR,resulting in expensive time cost to peril high throughout detections.Second,peak volumes in 2D NMR are influenced simultaneously by a series of factors including scalar couplings and pulse inaccuracies,certain calibration procedure will thus be necessary.Accelerations of 2D NMR have been an active subfield in NMR with fruitful achievements.Since long acquisition times originate from awaiting durations inserted between every adjacent scans to recover longitudinal magnetizations,small angle tilting is proposed to optimize awaiting delays and to further shorten experimental durations.The echo train acquisition is also demonstrated to be effective in compressing a J-resolved experiment into a single scan by repeatedly introducing mixing pulses during the acquisition period.The ultrafast spatiotemporal encoding technique arises as a totally different alternative by replacing conventional temporal evolutions with spatial encodings.An echo planar spectroscopic imaging(EPSI)module then ensues to repeatedly read out the encoded information as well as construct an additional Fourier-transformation based dimension,thus recording a complete 2D NMR in a single scan.More-over,Aforementioned methods accelerate 2D NMR experiments in way of exploring experimental techniques.The"Zangger-Sterk"(ZS)module is widely utilized for homo-nuclear decoupling and then supplying pure-shift information.Without complex splitting patterns,the pure-shift spectroscopy significantly reduces spectral congestions and simplifies resonance distributions to facilitate spectral assignments and structural elucidations.The principle of the ZS module in providing pure-shift information lies in its selective exciting in unison with a weak gradient to selectively retain different resonances within different sample layers.On the basis of the ZS module,in this study,we develop a selective excitation method to accelerate 2D correlation spectroscopy(COSY)and J-resolved spectroscopy with feasibility and effectiveness verified by experiments:First,the basic principle and development of nuclear magnetic resonance(NMR)are described,and the principles of spatial coding and ZS module are introduced.Second,we develop a selective coherence transfer(SECOT)method to accelerate 2D correlation spectroscopy(COSY)with feasibility and effectiveness verified by experiments.Moreover,we evaluate the quantitative property of the SECOT method under both homogeneous and inhomogeneous magnetic fields to demonstrate the potentiality of SECOT for quantitative applications.Finally,we develop a SGEN-J method to obtain 2D J-resolved spectroscopy method within single scan,combining selective excitation synchronized with gradient encoding module,with J-acquisition module stemming from echo planar spectroscopic imaging(EPSI)module.And the qualitative and quantitative performances of SGEN-J have been tested by a set of experiments both under homogeneous and inhomogeneous fields.