CONFORMATIONAL EFFECTS ON VIBRATIONAL FREQUENCIES OF CYSTEINE AND SERINE - AN AB-INITIO STUDY

The vibrational frequencies of three conformations of cysteine and ser ine in the non-ionized form have been evaluated using ab initio method s at the 4-31G level. The calculated frequencies along with the corre sponding potential energy distributions were used to assign the IR spe ctra of the methyl ester, hydrochloride and zwitterion of cysteine and serine. It was found that the nu(C(beta)X) frequency is dependent on the value of chi1[CC(alpha)C(beta)X] torsional angle. The conformation al dependence of some of the frequencies have been highlighted.