A COMPREHENSIVE STUDY OF THE ROTATIONAL ENERGY PROFILES OF ORGANIC-SYSTEMS BY AB-INITIO MO THEORY, FORMING A BASIS FOR PEPTIDE TORSIONAL PARAMETERS

Ab initio molecular orbital calculations have been carried out on over 50 model organic molecules and ions to provide the data necessary in the determination of torsional parameters for a force field involving polypeptides. The rotational energy profiles were obtained at the HF/6 -31G//HF/6-31G* level. The results were supported, in many cases, by full geometry optimizations and with consideration of correlation corr ections at the MP2 level. With the exception of the dihedral angle bei ng studied, all of the molecules were fully optimized with C-1 symmetr y. (C) 1995 by John Wiley & Sons, Inc.