The principal goals of this project are the development of algorithms that allow one to make the best use of NMR data to determine solution structures of biomolecules, to assess in a systematic fashion their accuracy and precision, and to explore the extent to which dynamical information can be extracted from NMR data. This will involve the following components: Studies of conformation-dependent chemical shifts and anisotropies. Earlier empirical treatments of shifts in proteins will be extended to the non-exchangeable protons in nucleic acids; ab initio quantum chemistry and empirical calculations will be used to explore patterns of shift anisotropies in peptide and nucleic acid fragments. Updated refinement methods. Refinement models will be developed that incorporate conformational disorder through the """"""""locally enhanced sampling"""""""" model that uses multiple copies of portions of the macromolecule. Studies on protein and nucleic acid dynamics. Models for calculating rates of both homonuclear and heteronuclear relaxation, with increased attention to anisotropic tumbling and to conformational disorder, will be studied, along with contributions from internal motions to chemical shift anisotropy (CSA) relaxation and to CSA-dipolar cross-correlated relaxation. Applications to important biological macromolecules. In collaborative experimental/theoretical efforts, these ideas will be applied to systems of significant interest to biochemistry, including: (a) studies of conformational heterogeneity and disorder in thioredoxin and zinc- finger/DNA complexes; (b) studies of the binding of duocarmycin analogues to DNA; (c) work on LFA1 integrin-ligand domains and on the interactions of zinc fingers with 5S RNA; (d) use of direct dipolar couplings and chemical shift analysis for structure elucidation in small RNA and RNA/protein interactions.
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