Several peptides and peptide-like model compounds will be studied in order to obtain a better understanding of the influence of sequence, end groups and solvent on the conformational preferences of peptides and their resulting spectroscopic properties. These studies will be based on a concerted approach involving applications of recent developments in the areas of (a) peptide synthesis, (b) IR and NMR spectroscopy and (c) computer simulation techniques. Basically, the research will proceed along three major areas of activity. First, investigations on the conformations of linear homo- and co-oligopeptides will be carried out primarily by high resolution NMR spectroscopy. Second, several peptide-like model compounds will be synthesized and assignment of their vibrational frequencies will be made from an analysis of the IR spectra. These model compounds will include: N-methylacetamide, N-acetyl-alanine-N'-methylamide and other amino acid derivatives, L,L-alanine diketopiperazine, bicyclolactams and N-adamantyl-adamantoic acid amides. In addition, bridged peptide structures will be studied as model systems for folded conformations (Beta-turns, Delta-turn and ten-membered hydrogen bonded ring). Third, the vibrational frequency data on he model compounds will be used to derive an empirical force field. IR spectroscopic data and force field calculations will be combined in an iterative fashion to yield more accurate force fields, from which a reliable potential energy surface for peptides will be obtained. This, in turn, will e an invaluable tool for making more accurate conformational assignments from IR and NMR spectoscopic data. A major long-term goal of this research is to achieve the ability to assess the presence and significance of the structures studied in model compounds in biologically interesting molecules (e.g. peptide hormones).
