THE CRITICAL ONSET OF RADIATION INDUCED CONDUCTION IN HYDRATED BIOPOLYMERS AT ELEVATED WATER CONTENTS AND SUBZERO TEMPERATURES

Abstract
The nanosecond time-resolved microwave conductivity (TRMC) pulse radiolysis technique has been applied to the study of electronic conduction in hydrated biopolymers at temperatures ranging from -20 to -180°C. The polymers investigated were the nuclei acid DNA, the proteins collagen and gelatin and the polysaccharide kapa-carageenan. In no case was a conductivity transient found for the dry compounds. A certain weight fraction of water was required before a radiation induced transient conductivity was observable. The "critical" water fractions for the above compounds were 0.45, 0.30, 0.32 and 0.28 respectively. These water contents are thought to correspond to those required for formation of the first, strongly bound hydration layer of the biopolymer. Further addition results in a more ice-like hydration layer which displays a highly mobile electronic charge carrier similar to that found in bulk ice. The ice doped HF and NH₄F have marked effects on the conductivity transients.