With this grant in the Theoretical and Computational Program of the Chemistry Division, Professor Dykstra will develop a comprehensive model suitable for the rapid evaluation of weak interaction potentials between large molecules and molecular clusters. These potentials will be employed within a molecular mechanics framework to calculate the effects of these weak interactions on intrinisic molecular properties, particularly nuclear magnetic resonance (NMR) parameters. The goal is to improve the value of certain NMR data and other spectroscopic data for structure elucidation in complex and extended molecular systems, including proteins and other biomolecules. The NMR parameters (e.g., shielding tensors, spin-spin coupling tensors, etc.) will be calculated analytically for representitive small molecules using ab-initio techniques developed by Professor Dykstra. High level electronic structure calculations will be employed to characterize local polarization response of molecules to external electrical properties, and then to evaluate the modeling of distributed electrical responses in spatially extended molecules. The treatment of polarization will be the key problem in achieving a realistic model of large systems. Ab-initio calculations will also be employed to benchmark cooperative effects, since these are important for any model applicable to large clusters. Nuclear magnetic resonance (NMR) spectroscopy is one of the most valuable tools available for the elucidation of the structures of molecules, particularly for molecules in solutions. The results of this project are expected to improve the utility of NMR and other spectroscopic data in the determination of structures of large biomolecules.
