Conformation of Poly-L-alanine and Poly-DL-alanine in the Solid State

Abstract

Proton magnetic resonance, dielectric, mechanical and thermal properties of poly-L-alanine, poly-DL-alanine and poly-DL-alanine, in which deuterium was substituted for α-hydrogen, in the solid state were investigated in the temperature range -196°C+100°C.
NMR spectra below -20°C can be explained only by the rotational motion of methyl group. However, at near and above the room temperature, another motional process was examined in the NMR spectra and the same process was found in the dielectric studies at the temperature range -50-0°C.
On the other hand, mechanical loss peak for poly-L-alanine, in which small quantities of water are included, was obtained at +45°C and 33 c/s.
Differential thermal analysis curve for the same poly-L-alanine showed anomalous behavior at 50°C.
The relation between these phenomena and denatura: ion of the native protein in the aqueous solutions was considered.