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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Plant Polymer Research » Research » Publications at this Location » Publication #211480
Title: DFT STUDIES OF ALPHA-MALTOSE: ISO-ENERGETIC AND ISO-GEOMETRIC GLYCOSIDIC BONDS CONTOUR MAPS, AND DFT+COSMO MOLECULAR DYNAMICS

Author
item Momany, Frank
item Willett, Julious
item BOSMA, WAYNE - BRADLEY UNIV/CHEM DEPT
item Schnupf, Udo

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2007
Publication Date: 8/20/2007
Citation: Momany, F.A., Willett, J.L., Bosma, W., Schnupf, U. 2007. DFT STUDIES OF ALPHA-MALTOSE: ISO-ENERGETIC AND ISO-GEOMETRIC GLYCOSIDIC BONDS CONTOUR MAPS, AND DFT+COSMO MOLECULAR DYNAMICS. Meeting Abstract. xx.

Interpretive Summary:

Technical Abstract: We recently published DFT (B3LYPD/6-311++G**) optimization studies on 67 conformations of alpha-maltose including clockwise(c), and counter clockwise(r) hydroxyl groups, 'kink' structures, and band-flip conformers. The optimization studies presented a picture of the low energy states of the rigid molecule. To examine the flexibility of alpha-maltose, iso-energetic difference maps were calculated using a smaller basis set (B3LYP/6-31+G*) at 5 deg C intervals around the glycosidic (psi, phi) = (0,0) position, for a number of gg/gt/tg-r/c combinations. The results of the maps as well as the geometry optimization studies show that the low energy conformations depend strongly on the direction taken by the hydroxyl groups bridging across the glycosidic bond. Optimization with COSMO, a solvation method, showed significant reordering of conformational energies. It was found that the energy landscape is very flat near the minimum on the iso-energetic contour maps. Deviations in selected internal coordinates as well as deviations in dipole moments are shown as psi-phi difference maps. The global energy minimum for alpha-maltose is a tg-gg-c conformer, with other conformations also of low energy. Further, to examine the dynamic aspects of the maltose molecule, short DFT molecular dynamics simulations at constant energy were carried out for selected conformers. These studies are enhancing our understanding of the structural and conformational properties of complex carbohydrates.