Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 15, 2006
Publication Date: March 1, 2006
Citation: French, A.D. 2006. An ancient modeling method for amylose. American Chemical Society Abstracts. CELL:90. Technical Abstract: Structures of polysaccharides can be predicted based on crystal structures of disaccharides that contain the relevant monosaccharide residues and linkages. Simple geometric extrapolation of the atomic coordinates of the individual monomer residues, the linkage torsion angles and the glycosidic bond angle allows the construction of helices that have proven features. Early workers using similar methods had only a few crystal structures to work with, but new data continue to become available. Extrapolation of all of the new structures provides a nearly continuous range of helical structures having as few as 3.6 residues per turn to more than 9. Such models may be self-intersecting, suitable for modeling the cyclodextrins, or may be completely extended, with a rise per residue along the helix axis exceeding the length of the shortest observed glucose residues. This flexibility gives a different picture of molecular shape than is developed in textbooks, which state that amylose and the branch chains of amylopectin are composed of six-fold helices. It is in agreement, however, with the numerous molecular shapes reported by fiber x-ray diffraction studies over the years.