Studies on the Cooperativie Transformation of Hydrogen-Bonds During the Intramolecular First-Order Transitions of Polypeptides-An Application of ^2H NMR Analysis in the Liquid Crystalline State

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1.Screw-sense inversion behaviors (left- to right-handed or vice versa) of α-helical polyaspartates differ substantially depending on the chemical structure (X) of the ester group at the side-chain terminals. The cause of such phenomenological differences among polymers (X=benzyl, chlorobenzyl, and phenethyl) have been investigated by constructing the phase diagram as a function of solvent composition (TCE/TFA) and temperature.2.The helix-coil transition of polyaspartates (X=benzyl and X=phenethyl) in m-cresol at elevated temperature (a normal-type transition) has been studied by NMR methods. The observed ^1H-^1H vicinal coupling constant around the _χ1 bond rotation suggests that the g^- conformation decreases from 〜50% to 〜30% with increasing temperature in the transition region from the left-handed to random-coil state.3.The nematic conformation of main-chain liquid crystals has been studied to examine the possible incorporation of the intramolecular hydrogen-bond. The spectroscopic as well as thermodynamic (PVT) analyses led to a conclusion that a group of partially oriented conformation persists over the entire range of the nematic state. This is an encouraging evidence for the molecular design of a new class of chemical structures.