A statistical model for amylopectin and glycogen. The condensation of A-R-Bf1 units

Starch Biosynthesis. I. The Size Distributions of Amylose and Amylopectin and Their Relationships to the Biosynthesis of Starch

“…In 1956 and 1958 [14,15] and later [16,17] it was shown that the linear chains of amylopectin do not correspond to the broad size distribution of A-R-B 2 condensation polymerizations but rather have a much narrower size distribution. Evidence will be presented here which verifies this conclusion since in order for the theoretical data to fit the polymodal experimental size distribution curves for debranched amylopectin, then the linear chains of debranched amylopectin must correspond to a mixture of individual polymers, each having the much narrower Poisson size distribution of a "monomer addition without termination".…”

Starch Biosynthesis. II. The Statistical Model for Amylopectin and Its Precursor Plant Glycogen

“…1 and 3). Nevertheless, many structures are present as seen previously from the large ratio of Mw/Mn [9,10] for both aggregated and disaggregated amylopectins and also as seen from the diverse structures observed for clusters [30]. Thus it is the statistical model, modified as in the Meyer model with hidden inner A-chains, that best represents amylopectin.…”

“…In the examination of the properties of amylopectin, it was previously concluded [9,10] that although the branching structure of amylopectin appeared to be random as in a statistical model, the size distribution of the linear chains of amylopectin did not follow the broad size distribution expected for an A-R-B 2 type condensation polymer. Hence, better agreement was obtained with experimental results when the size distribution of the linear chains of amylopectin were restricted by assuming rods of ten or so glucose units in length to represent the chains between branch points.…”

“…This much narrower size distribution was supported in the previous paper [11] by the examination of the polymodal behavior of debranched amylopectin chains, where it was shown that these linear chains can be correlated with several distinct polymers, each of which correlates with the very narrow Poisson size distribution. Thus the previously used [9,10] rod structures were actually a rough representation of the very narrow Poisson size distribution for a statistically branched polymer. In this paper an examination of the properties of the precursor glycogen and its amylopectin and amylose will be made in order to determine how starch is made in various plant tissues, how the statistical model can explain the relationship between the number of removed branches and yield of amylose in the conversion of glycogen to amylopectin, and how genetic variations can alter this mechanism of starch synthesis.…”

Fine Structure of Amylopectin

“…The number-average value (M n ) is considerably smaller than M w (McIntyre et al 2013). The polydispersity index (M w /M n ) is therefore large (Erlander and French 1956;Stacy and Foster 1957).…”