The conformation of amylose in neutral, aqueous salt solution

Abstract

Linear amylose has been subfractionated, and the hydrodynamic properties of the fractions examined. From measurements of the limiting-viscosity number, [ n], in 0.33m potassium chloride, and of the weight-average molecular weight, M w , by light scattering on the acetate, the relation ▪ was found. The significance of the exponent in this relation and others in the literature is discussed. Estimations of the “stiffness” of the amylose molecule in aqueous solution have been obtained for various model systems, i.e., the Kuhn statistical length, the Kratky-Porod persistence length, and Nagai's theory for a mixture of helical and randomly coiled segments. The results of each individual theory are ambiguous. It is shown, on the basis of Nagai's theory, that there is definite evidence for the absence of rigid helical segments in amylose in aqueous solution. The temperature coefficient of [ n] for amylose in aqueous solution is also discussed.