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United States Department of Agriculture

Agricultural Research Service

Title: Molecular Modeling Studies of the Molecular Components of Starch. I. An Atomistic Model of the Double Helical Structure of Amylose and Amylopectin

item Momany, Frank
item Willett, Julious

Submitted to: Society of Plastics Engineers Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 2, 1999
Publication Date: N/A

Interpretive Summary: Starch is one of the most important biological molecules known, in addition to being one of the largest renewable crops on the planet. For these reasons, scientific investigations into the nature of its main components, amylose and amylopectin, have been carried out for many years and have utilized a variety of scientific techniques. In spite of these efforts, a detailed understanding of both amylose and amylopectin is still lacking. In this paper we present results on this subject using new computer simulation methods developed in our laboratory. With these computational tools, we can relate previous information obtained by other researchers to details on the basic structure of the components of starch. This work has allowed us to better understand the size and organization of said components, as well as to more accurately define the role of water in the starch granule. This work will lead to the design of new chemical modifications of starch that will result in properties useful for commercial applications such as new polymeric blends.

Technical Abstract: This work is an attempt to improve our detailed understanding of the molecular structure of starch and its components. Computational studies, using a newly derived molecular force field, were made on fragments of amylose and amylopectin. The double helical structure of two 12-unit chains of amylose was found to be unstable at room temperature with water molecules surrounding the complex, but was energetically stable to dynamics simulation when the amylopectin type of one-six bridge was attached. A new double helical form was discovered when water molecules were located in the core of the double helix and the structure was found to be energetically stable without distortion. Both calculated double helical structures reproduced helix repeat distances found from experimental X-ray diffraction results on the A and B forms of crystalline amylose and amylopectin. The computational studies reported here are important in advancing our understanding of complex starch structures and will provide data useful for chemical modification studies designed to change and enhance specific physical properties of starch.

Last Modified: 4/22/2015
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