On the non-random nature of amylopectin branching

The cluster model of amylopectin (AP) provides a useful conceptual basis for understanding of the structure of the molecule, and this model guides current thinking related to AP biosynthesis and physical behavior. The chain length profile of constituent linear regions of the molecule is commonly determined, and the cluster model guides the interpretation of results with an emphasis on the clustering of the linear regions of these chains. Less attention has been given to the related but distinct question of the clustering of the branch points in AP, perhaps because this work is methodologically more difficult than for determination of the chain length profile and interpretation of the results is less straightforward. However, the unique aspect of AP is that its branching is non-random, and the physical properties of AP may be considered to result from this unique structure. This review addresses the available information on the distribution of branch points in AP. Emphasis on this aspect of the cluster model has ramifications for future research on AP biosynthesis and AP physical behavior.