Study On NMR Methods For Simultaneously Measuring All H-H Coupling Constants In A Molecule

Since Nuclear Magnetic Resonance(NMR)was discovered,NMR technique has experienced a fast development,and is widely applied in physics,chemistry,biology,medicine and many other areas.The NMR realm has witnessed five Nobel prizes,exhibiting its important academic value and wide application prospect.NMR technique serves as a powerful tool in the molecular structure analysis.The scalar coupling,an essential feature in NMR spectra,serves as an important role in molecular structure elucidation.Many NMR methods for measuring H-H coupling constants have been proposed in recent years.These methods can reveal coupling networks and accurately measure J coupling constants,thus greatly facilitating molecular structure elucidation.This paper mainly proposes methods for simultaneously measuring H-H coupling constants in a molecule,and the main work is listed as below:1.We briefly introduce the history and development of NMR,demonstrate mechanisms of NMR multi-dimensional spectroscopy and spin-spin coupling,as well as the mechanism and application of homonuclear broadband decoupling.We also introduce methods for measuring coupling constants.2.We design a SMS-SEJRES method which combines decoupling technique and spatially-encoded selective reversing,for revealing all scalar coupling networks and coupling constants within one experiment.In this method,we employ the echo planar spectroscopic imaging(EPSI)detection module.After data rearrangements,we obtain a 3D dataset.Then we can extract several 2D spectra corresponding to coupling networks of different protons,from different layers in the spatial dimension.This method can increase the experimental efficiency,and will facilitate applications of NMR spectroscopy in the molecular structure analysis.We elaborate on the principle of the SMS-SEJRES pulse sequence,and demonstrate its feasibility and accuracy in simple and complex solution samples.3.We design a SMS-SECTJRES pulse sequence which combines selective constant-time evolution and spatially-encoded gradient,as well as the EPSI detection module,for revealing all scalar coupling networks and coupling constants within one experiment.After data rearrangements,a 3D dataset can be obtained.Then we can extract several 2D spectra corresponding to coupling networks of different protons,from different layers in the spatial dimension.Simple solution samples are used to investigate the feasibility of the SMS-SECTJRES pulse sequence,offering the possibility for applications in more complex samples.