Ultra-high modulus and strength films of high molecular weight polypropylene obtained by drawing of single crystal mats

Abstract

Conformation of Asp-containing dipeptides of the general formulae: Ac舑Asp舑X舑NHMe and A舑c舑X舑Asp舑NHMe (X = Ser, Lys, Asp, and Tyr) in solution were investigated using1H and13C NMR spectroscopy. The dominant formation of a ॆ-turn-like structure was confirmed in the dipeptides, Ac舑Ser舑Asp舑NHMe and Ac舑Lys舑Asp舑NHMe with the deprotonated Asp side chain, from the dependence of the amide proton chemical shifts on temperature, solvent composition, and peptide concentration, and from the backbone dihedral angle ०. The backbone conformations of these dipeptides changed with the deprotonation of Asp. In addition to the intramolecular hydrogen bond of the 4舑1 type constituting ॆ-turn structure, other kinds of intramolecular interaction between the carboxylate groups of Asp and side chains of neighboring residues were found in Ac舑Ser舑Asp舑NHMe, Ac舑Asp舑Ser舑NHMe, Ac舑Lys舑Asp舑NHMe by analysis of the side chain rotamer populations, spin-lattice relaxation times, and pKa values. These side chain interactions may possibly contribute to the stabilization of the ॆ-turn-like structure. © 1984 The Society of Polymer Science, Japan.