NORMAL-MODES 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 pleat ed sheet. The present work is a complete study of normal modes and the ir dispersion in the unusual left-handed alpha form. A special feature of some dispersion curves is their tendency to bunch in the neighborh 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).(dagger dagger) Specific heat has been obtained from dispersio n curves rin. density-of-states. A comparative study of left-handed an d right-handed forms is presented.