Helical conformation of amylose in aqueous solution. II. Electron spin resonance, fluorescence depolarization, and sedimentation measurements

Abstract

AbstractIn the previous study [Elmgren, H. (1984) Biopolymers 23, 2525–2541] concerning the conformation of amylose in aqueous solution, it was stated that amylose in a neutral aqueous solution is a random coil consisting of helical segments. In terms of Kuhn statistics, each segment contains more than 100 monomers. The number of monomers per segment decreases by alkali addition. In an attempt to verify these statements, a combined electron spin resonance (esr) and ultracentrifugation (uc) study of a weakly hydroxyethylated amylose sample in water and alkaline solvents was performed. This combination of measuring techniques makes it possible to estimate the Brownian motion, and thus the mass of the polymer segments. As a control for the obtained esr data, fluorescence depolarization (fdp) measurements were performed on the polymer sample in a bicarbonate buffer at pH 10. The result of the study confirms that the amylose segments are very heavy in water. In strong alkaline solvents, the segment mass corresponds to that of a few monomers. Our findings thus support the statements made in the preceding article, and the data obtained by others. [Kitamura S., Yunokawa H., & Kuge T., (1982) Polym. J. 14, 85–91; Kitamura S., Yunokawa H., Mitsu'ie S., & Kuge T., (1982) Polym J. 14, 93–99].