GROUND-STATE VIBRATIONAL-SPECTRA OF CYSTEINE AND SERINE ZWITTERION - A THEORETICAL PREDICTION

Transferability of scale factors from smaller constituents to a larger one is successfully attempted for two important amino acids cysteine (Cys) and serine (Ser) in zwitterionic form. A complete set of scale f actors are generated for alanine (Ala) by fitting the ab initio (HF/6- 31++G) solvated model force field to the experimental frrequencies of five different isotopomers. These scale factors are then used to scal e the ab initio force field of both the molecules. Scale factors of th e side chain residues of both cysteine and serine are obtained by fitt ing the ab initio solvated model force field of ethanethiol and ethano l to their respective experimental frequencies at the same level of th eory. In both the cases the predicted frequencies and their normal mod e descriptions are excellent compared to the size and complexity of th e molecules. (C) 1998 Elsevier Science B.V.