PHONONS AND THEIR DISPERSION IN ALPHA-POLY(BETA-BENZYL-L-ASPARTATE)

Poly(beta-benzyl-L-aspartate) (PBLA) is an unusual polypeptide which i s capable of going into four different conformations; namely, left-han ded alpha-helix, right-handed alpha-helix, omega-helix and beta pleate d sheet. The present work is a complete study of normal modes and thei r dispersion in the unusual left-handed alpha form. A special feature of some dispersion curves is their tendency to bunch in the neighbourh ood of helix angle. It has been attributed to the presence of strong i ntramolecular interactions. Crossing and repulsion between the dispers ion curves is also observed. The N-deuterated analogue of PBLA has bee n studied to check the validity of assignments and force field (Urey B radley). Specific heat has been obtained from dispersion curves via de nsity-of-states. A comparative study of left-handed and right-handed f orms is presented.