Phonons and their dispersion in Poly(S-benzyl-L-cysteine)

Poly(S-benzyl-L-cysteine) (PBLC) is a S-benzyl derivative of the natural am ino acid poly(L-cysteine). Its normal modes and their dispersion in antipar allel beta-sheet conformation have been obtained within the first Brillouin zone using Wilson's G.F. matrix method, as modified by Higgs for an infini te polymeric chain. The zone center frequencies and the Urey Bradley force field have been obtained by "best fitting" the observed Fourier transform I R (FTIR) absorption bands. The characteristic features of dispersion curves such as crossing, repulsion, and exchange of character are discussed. Pred ictive values of heat capacity in the temperature range of 50-500 K are rep orted. (C) 1999 John Wiley & Sons, Inc.