High-resolution NMR Spectroscopy And Its Applications Via Intermolecular Multiple-quantum Coherence And Diagonal-peak Suppression

High-resolution nuclear magnetic resonance(NMR)spectroscopyprovides a powerful tool in many fields,such as biology,chemistry,physics,medicine and life science,due to its high-throughputinformation related to component analyses and its non-invasive property without altering detected samples.However,it is difficult to obtain high-resolutionliquidNMRspectra in inhomogeneous fieldeither resulting from the external field inhomogeneity or the internal susceptibility variations,because the inhomogeneity could lead to broadened line peaks and overlapped peaks.Moreover,in solid-state magic angle spin(MAS)NMR,high-resolution chemical shift correlation spectra of proteins are also hard to acquire since the intense diagonal peaks would generally hide the close-lying cross peaks,which might contain important structural information.By using the immune property of intermolecular multiple-quantum coherences(iMQCs)to inhomogeneous field,we applied this technique to obtain high-resolution spectra in biological components and tissues,even and in vivo samples.On the other hand,we also designed pulses sequence for diagonal peak suppression.The main achievements are as follows:1.The principles and theories of iMQCs and ultrafast acquisition are summarized.The accompanied MATLAB data processing procedures for methods based on those two techniques based are organized,making MATLAB programs more convenient and clear for the pulse sequence designers.2.The NMR techniquewas used in studying fish and its products(fish oils and fish eggs).Fish and its products,which are closely relatedto human daily life,capture extensive attentions with therapid development of the aquaculture.We proposed an NMR approach combining intermoleculardouble-quantum coherences(iDQCs)and spatialencoding technique to fast recover high-resolution 2D J-resolved spectra in inhomogeneous fields.The proposed method can resist thefield inhomogeneity in biological foods without superfluouspretreatments and time-consuming shimming procedures,andyield satisfactory 2D J-resolved information for analyseswithin minutes.Herein,theproposed method may constitute an effective technique inanalyzing fish and its products.3.A single-scan method is proposed to obtainhigh-resolution 2D J-resolved NMR spectra in inhomogeneous magnetic fields by utilizing iDQCsand the spatial encoding forNMRobservables.Chemical shifts,J coupling constants,andmultiplet patterns were recovered even when fieldinhomogeneities were severe enough to completely obscureconventional NMR spectra.Ourresults of ethyl 3-bromoproprionate in acetone,a complex mixture of organic compounds and pig bone marrowshowed that the new method was a fast and effective toolfor studying complex chemical mixtures and biological tissues.The method could potentially be usefulfor real-time in vivo NMR studies.4.TheiDQCs technique was applied into the study of in vivoearthworms.Earthworms,especially in vivoearthworms,could reveal significant environment pollution information as a marker for ecotoxicological studies.In vivoearthworms were subjected to internal susceptibility variations,and they kept moving during the experiments,which posedchallenge to direct analysis by NMR.However,with enhanced NMR sensitivity in high magnetic field,we monitored the complete corrupting process of earthworm from alive to dead by employing the IDEAL-?method proposed by Zhong Chen et al to obtain high-resolution spectra,finding that the iDQCs application could provide important earthworm metabolite variation information during the corraption processing from alive to dead.5.The feasibility of using the spin-echo based diagonal peak suppression method in solid-state MAS NMRhomonuclear chemical shift correlation experiments is demonstrated.A complete phase cycling wasdesigned in such a way that in the indirect dimension only the spin diffused signals were evolved,whileall signals not involved in the polarization transfer were refocused for cancellation.A data processing procedurewas further introduced to reconstruct this acquired spectrum into a conventional two-dimensionalhomonuclear chemical shift correlation spectrum.A uniformly 13C,15N labeled Fmoc-valine sampleand the transmembrane domain of a human protein,LR11(sorLA),in native Escherichia coli membraneshad been used to illustrate the capability of the proposed method in comparison with standard 13C-13Cchemical shift correlation experiments.