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United States Department of Agriculture

Agricultural Research Service

Research Project: ADVANCED STARCH-BASED MATERIALS FOR NON-FOOD APPLICATIONS

Location: Plant Polymer Research

Title: Constant energy DFT molecular dynamics simulations of solvated carbohydrates at the B3LYP/6-31+G* level of theory

Authors
item Momany, Frank
item Schnupf, Udo
item Willett, Julious

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 8, 2008
Publication Date: June 14, 2008
Citation: Momany, F.A., Schnupf, U., Willett, J.L. 2008. Constant energy DFT molecular dynamics simulations of solvated carbohydrates at the B3LYP/6-31+G* level of theory. Meeting Abstract. xx.

Technical Abstract: The disaccharide, alpha/beta-maltose, has been studied using constant energy ab initio molecular dynamics at the B3LYP/6-31+G* COSMO (solvent) level of theory. Maltose is of particular interest as the variation in glycosidic dihedral angles is dependent upon the starting hydroxyl conformation. That is, when the simulation is started from the clockwise, gg-gg-c, or counterclockwise, gg-gg-r, form, convergence toward an intermediate 'r-like' form occurs as the molecules become equilibrated. It is noted that 'r' conformations with COSMO have lower starting energies (~1 kcal/mol) than the 'c' forms, in contrast to the vacuum optimized structures where similar relative energies are found. The H1---H4' distance is ~2.15A for both the 'c' and 'r' forms, in excellent agreement with recent NMR studies. The conformer, gt-gt-r, undergoes a transition to a 'kink' conformation during dynamics, however, when a simulation is started from a 'kink' gt-gt-r conformation, the structure moves back to the normal or syn form. Results of ab initio molecular dynamics simulations on different alpha/beta-maltose conformers are described. Recent DFT optimization results on DP-3 and DP-4 alpha-linked amylose fragments suggest that maltose should be considered as two end groups rather than a model for amylose.

Last Modified: 4/23/2014
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