Author
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Momany, Frank |
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Schnupf, Udo |
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Willett, Julious |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 4/8/2008 Publication Date: 6/14/2008 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. Interpretive Summary: 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. |
