Conformation of Novel Cycloamylose: Topological Aspects and Simulations

Abstract

It has recently been discovered that cycloamylose, cyclic α-1,4-glucan with a degree of polymerization ranging from 17 to several hundred, can be produced by the action of potato d-enzyme (EC 2.4.1.25) on amylose. To obtain structural insights into this new series of cycloamylose, the topological aspects of its circular structure were discussed in terms of a ribbon model properly introduced. A simple analysis of the chain-length dependence of the product population was performed on the basis of an elastic wire model. If the amylose chain is rather stiff, a double-helical structure with foldbacks is more reasonable than a circularized single-helical structure. This is because theoretical calculations for the latter predict a periodic population oscillation, which is caused by the need for the helix ends to meet, whereas such an oscillation was not experimentally observed. However, due to the unknown chain stiffness, it is difficult to draw a definite conclusion. To answer some questions that arose in the a...