INFRARED ABSORBANCES OF PROTEIN SIDE-CHAINS

The spectral parameters of amino acid residue side chain and peptide b ond absorptions in the region 1800-1440 cm(-1) have been obtained by u sing an inverse matrix method applied to the infrared spectra of 42 am ino acids, dipeptides, and higher peptides in aqueous solution. In add ition the pH-dependent extinction coefficients of the amino acid and p eptide COO-/NH3+ end groups were derived. It is shown that the seconda ry structure prediction accuracy of proteins by multivariate data anal ysis methods increases slightly, if the side chain absorbances of the residues asparagine, glutamine, aspartic acid, glutamic acid, arginine , tyrosine, and lysine are subtracted from the amide I and amide II re gion. (C) 1998 Academic Press.