PHONON-DISPERSION IN OMEGA-HELICAL POLY N-EPSILON (P-BRONAOBENZOYL-L-ORNITHINE)

Poly Ne(p-bromo benzoyl-L-ornithine) is one of the few biopolymers exi sting in rare omega helical (four-fold) conformation which can be obta ined from or form through an irreversible heat treatment. A study of i ts normal modes and dispersive behaviour shows several interesting fea tures such as 'crossing over', 'repulsion with character exchange' and Von Hove type 'singularities' which lead to a fuller interpretation o f infrared (i.r.) spectra. The existence of alternately different side chain conformations which makes the phonon problem too large has been taken into account by considering the vibrations of the PBrBO chains with two independent conformations. Detailed study of skeletal, amide and side chain modes has been reported.