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Sheetal Kumar Jain

Development of Efficient and Robust Heteronuclear Cross-Polarization Techniques for Biological Solid-State Nuclear Magnetic Resonance Spectroscopy

Research output: Book/anthology/dissertation/reportPh.D. thesis

The work presented in this thesis is focused on development of experimental methods within solid-state NMR spectroscopy. The specific aim is to improve fundamental cross-polarization methods used for transfer of magnetization between heteronuclear spin species, with primary relevance for studies of biological macromolecules. A new method for polarization transfer called Rotor Echo Short Pulse IRradiATION mediated Cross-Polarization (RESPIRATIONCP) is introduced with a theoretical explanation of its polarization transfer efficiency. An analysis of robustness towards experimental imperfections such as radio frequency inhomogeneity and mismatch from the optimal conditions is given using numerical simulations as well as experiments on uniformly labeled alanine and model protein GB1. Furthermore, two modified versions of the RESPIRATIONCP have been suggested to address issues at ultrahigh magnetic fields such as the tolerance toward chemical shift offsets and transfer efficiency in the presence of large anisotropic interactions. Application to quadrupolar nuclei has been shown for two spin-1 nuclei (2H and 14N) using simulations and experiments at moderate spinning frequencies for the cases of 2H→13C and 1H→14N polarization transfers. The deuterium experiments were performed on deuterated glutamine and outer membrane protein G samples, while the nitrogen experiments were carried out on ammonium nitrate and alanine samples. Moreover, experiments with low power on the 2H channel are presented contemplating the feasibility of four channel (1H, 2H, 13C, 15N) probe experiments, where the power on the 2H channel is limited. A numerical analysis of the scope of the method in presence of larger quadrupolar couplings under high spinning conditions is given. Preliminary results of an on-going project on 14N→13C polarization transfer to facilitate 2-dimensional experiments detecting 14N in the indirect dimension are shown. Finally, to test the polarization transfer efficiency with very large chemical shift anisotropies, 19F→13C polarization transfer experiments for Poly Tetra Fluoro Ethylene (PTFE) and Silver Hepta Fluoro Butyrate (SHFB) are presented at high magnetic fields. It is demonstrated that important information about dynamics may be extracted from 19F→13C RESPIRATIONCP buildup curves, which are central to the dynamics studies of important biological and synthetic polymers.
Original languageEnglish
Publication statusPublished - Jul 2014

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