MOLECULAR-WEIGHTS, LENGTHS, AND DISTRIBUTION OF SIDE-CHAINS IN ALPHA-D-POLYGLUCANES

Freshly prepared starch (from potatoes P, from maize M) was separated quantitavely into amyloses and amylopectins under mild conditions. Furthermore, glycogen (G) was extracted from livers of rabbits under observation of physiological provisoes (feeding, rapid removal of the organ under anaesthetic and freezing‐stop). The molecular weights, determined by analytical ultracentrifuge. The side‐chain parts of the amylopectins and of the liver glycogen which were checked by partial enzymatic break‐down into β‐dextrin by β‐amylase (EC 3.2.1.2) and into the basic structure by pullulanase (EC 3.2.1.41) is 64% for P, 62.7% for M, and 65.4% for G. The lengths of the side‐chains, expressed in glucoside residues, are calculated at 12.0 for P and M, and 8.0 for G; the intervals between the side‐chains are 7.0 for P and M, and 4.0 for G. Sources of error with respect to the lengths of and to the intervals between the side‐chains are, firstly, free‐ending, undecomposed side‐chains inside the big molecules which cannot be reached by the two enzymes because fo steric obstruction, and, secondly, the degree of ramification of the basic structures and, consequently, the number of α‐1,4 and α‐1,6‐bound glucoside residues which cannot be split off by pullulanase. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim