Internal unit chain composition in amylopectins

Abstract

A series of 17 samples represented a diverse collection of different starch granules from different plants. The amylose content ranged from 0% to 28% and the crystallinity was established to represent A, B and C allomorphic types. The amylopectin components were isolated and their unit chain distributions analysed by anion-exchange chromatography. The internal unit chain profiles were obtained from the φ,β-limit dextrins. The internal profiles possessed two major fractions of short and long B-chains. The long B-chains were divided into two subgroups also found in the profiles of the whole amylopectins. The short, internal B-chains contained also two subgroups in all samples, of which one was a major group at DP 8–25, and the other was a minor group at DP 3–7. On the basis of the internal chain distribution profiles of (i) the long chains, reflecting the interconnection of clusters, and (ii) the short chains, reflecting the internal structure of the clusters, the samples were divided into four structural groups with typical characteristics. It was found that the unit chain profiles of the whole amylopectins could be divided into the same characteristic groups. The positions of the internal unit chains were theoretically traced into their original lengths in the profiles of the whole amylopectins. It was concluded that A-chains generally overlap with the shortest B-chains at DP 13–23, which coincided with fraction fb 1 of the periodic intervals described by Hanashiro et al. [Hanashiro, I., Abe, J.-i., & Hizukuri, S. (1996). Carbohydrate Research, 283, 151–159].