AM-1 molecular orbital calculations of silica-alanine-nitrogen interaction.
Chemical binding of proteins with bioactive surfaces is modeled using a semi-empirical molecular orbital theory (AM-1). The model calculates the optimized molecular structures of an amino acid (L-alanine) interacting with a cyclotetrasiloxane silica cluster (a four-membered hydrated silica ring). The calculated heats of formation for various orientations of alanine show +5 kcal/mol difference for binding via the -NH2 group following a condensation reaction with a pentacoordinate Si intermediate. Hydrogen bonding of the alanine via the -COOH group occurs with +13 to +15 kcal/mole differences in heats of formation and imposes a highly specific geometric orientation on the amino acid. Association of a diatomic N2 molecule with the silica cluster before interaction with alanine inhibits formation of an intermolecular bond, as is observed experimentally in studies of silica-alanine epitaxy.
West
J K
JK
Department of Materials Science and Engineering, University of Florida, Gainesville 32611.
Hench
L L
LL
D000409:Alanine / Q000737:chemistry*; D008422:Materials Testing; D008954:Models, Biological; D009584:Nitrogen / Q000737:chemistry*; D011485:Protein Binding; D012822:Silicon Dioxide / Q000737:chemistry*
D012822:Silicon Dioxide; D009584:Nitrogen; D000409:Alanine