Dielectric and Nuclear Magnetic Resonance Studies of the Synthetic Polypeptides in the β-Form in the Solid State

Abstract

Dielectric measurement of poly-S-carbobenzoxy-L-cysteine (PSCBLC) and nuclear magnetic resonance measurements of PSCBLC, poly-S-carbobenzoxyethyl-L-cysteine (PSCBELC) and poly-S-carbomethoxyethyl-L-cysteine (PSCMELC) were made. The activation energy obtained for the dielectric dispersion in PSCBLC which has benzyl groups in side chains was 50 kcal./mole, which is the same as is obtained for helical synthetic polypeptides with benzyl groups in side chains. In a temperature range from 77 to 370°K., rotation of the side chains was suggested as the mechanism of molecular motion in these β-forming polypeptides. The molecular motion for β-forming polypeptides may have no specific characteristics. Infrared spectrum analysis disclosed that PSCMELC existed in the antiparallel β-form.