Much of the proposed research represents a novel application of solid-state 67Zn NMR applied to proteins and their model systems. Many of the proposed experiments will be directed towards understanding the structural basis for 67Zn NMR parameters (quadrupole couplings, shielding tensors and their relative orientation). Low temperature 67Zn experiments will be performed as a means of obtaining the spectroscopic data. These data, in turn, will provide a critical test to the surrogate probe strategy of replacing Zn+2 with Cd+2 to investigate metal binding sites in metalloproteins, while providing invaluable structural information about this important class of proteins. Specific systems to be examined include the inhibitory Zn+2 site in carboxypetidase-A, characterization of intermediates in carbonic anhydrase and the unique chemistry afforded some Zn sites in DNA binding proteins. Further, the PI will prepare new model systems where the coordination environment about Zn and Cd can be carefully controlled, contrasted and investigated by single crystal and powder 67Zn and 113Cd NMR methods. Further, we will continue to develop the ab initio MO calculations of metal ion quadrupole and shielding tensors. These calculations have proven to be helpful in developing structural models for metal binding sites of biological complexes, e.g., the early stages of mineralization.
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