HEAT-CAPACITY AND PHONONS IN POLY(L-LEUCINE)

Poly(L-leucine) is one of the polyamino acids having a bulky hydrophob ic sidechain. For want of full phonon dispersion curves and density-of -states on this biopolymer Roles et al have interpreted their specific heat data in a limited way. In the present communication we report an analysis of the normal modes and their dispersion for poly(L-leucine) which leads to a very good agreement of the specific heat calculation s with experimental measurements. It is observed that the main contrib ution to specific heat comes from the coupling of the back-bone skelet al and side-chain modes. Several other assignments have been revised. A special feature of Same dispersion curves is their tendency to bunch in the neighbourhood of helix angle. It has been attributed to the pr esence of strong intramolecular interactions. Repulsion between the di spersion curves is also observed.