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

Transferability of scale factors from smaller constituents to a larger one is successfully attempted for two important amino acids cysteine and serine in acidic solution. The scale factors of, glycine in acidic solution from our earlier study were used to scale the ab initio forc e fields of both the molecules. Scale factors of the side chain residu es of both cysteine and serine are obtained by fitting the ab initio f orce fields of ethanethiol and ethanol to their respective experimenta l frequencies at the same level of theory. The present study is in sup port of our earlier observation that an isolated molecule ab initio mo del with a right choice of basis set can mimic the experimental spectr a of amino acids at acidic pH. In both the cases the predictions of th e frequencies and their normal mode descriptions are excellent. This f urther indicates that the scale factors of structurally related small organic molecules (ethanethiol and ethanol in the present case) can be used to mimic the right features of the amino acid side chain residue s. (C) 1998 Elsevier Science B.V.