MOLECULAR-DYNAMICS SIMULATIONS OF GLYCOSIDES IN AQUEOUS-SOLUTION

Molecular dynamics simulations for aq solutions of methyl-alpha- and - beta-D-glucopyranoside, galactopyranoside and talopyranoside have been carried out. A single molecule surrounded by 252 SPC water molecules was used under periodic boundary conditions. Preference for the gr and gg orientations for the hydroxymethyl groups in solution has been con firmed. Examination of the extent and pattern of hydrogen bonding betw een water and the sugar molecule hydroxyl groups showed that the galac tose and glucose derivatives were substantially better hydrogen-bond d onors at OH-2 and OH-4 than the respective ones of talose. Intramolecu lar hydrogen bonding involving OH-2 and OH-4 of the talosides persiste d for some 40% of the 100 ps simulation time in water. The remarkably long retention times (on reversed-phase HPLC in pure water) of the tal osides relative to the galactosides and glucosides were rationalised i n terms of differing extents of hydration, intramolecular hydrogen bon ding, and compatibility with the structure of water.