This research will be carried out primarily in San Luis-Argentina at the San Luis University in collaboration with Jorge A. Vila as an extension of NIH Grant Number: GM-14312. Protein and peptide conformational shifts, which are defined as the deviations of the 13Calpha and 13Cbeta chemical shifts from their corresponding statistical-coil values, can be used in many different ways in structural analysis. Possible applications include: (i) secondary structure mapping; (ii) generating structural constraints; (iii) three-dimensional structural refinement; and (iv) three-dimensional structural generation. Such a wide capability of NMR-derived data could play an important role in determination of protein structure in solution, and lead to a broad scope of possible theoretical applications. In particular, this proposal will focus on both the quantum-chemical computation of the Boltzmann-averaged values of the 13C( and 13C( chemical shifts for all the naturally occurring amino acids in water at neutral pH for a model peptide in both the canonical alpha-helical and beta-sheet conformations, respectively, and on the prediction of the tertiary structure of proteins with the help of 13C NMR chemical shift information. To accomplish these goals efficiently, a new protocol to explore the accessible conformational space more efficiently will be introduced. It is expected that the results derived from this investigation may be useful for both knowledge-based approaches and ab initio methods developed to predict the structures of globular proteins, as well as may contribute to our understanding of how statistical-coil states can be inter-related with the conformational preferences of more-structured states, such as alpha-helical and beta-sheet conformations. Although the conversion of chemical shift information into quantifiable structural information is a relatively new field, the results provided by this proposed research would provide additional assistance for an accurate tertiary protein structure prediction and, consequently, make a significant contribution to the solution of the, as yet unsolved, protein folding problem.
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