Water structuring around complex solutes: theoretical modeling of α-d-glucopyranose Original Research Article

The structuring of solvent water by sugar solutes is studied using a molecular dynamics (MD) simulation of α-d-glucopyranose in aqueous (SPC) solution. The distribution of water positions actually observed in the MD simulation is compared to the solvent positions expected from a locally-tetrahedral distribution of hydrogen-bonded water molecules around the oxygen atoms. A reasonable correspondence between the observed and predicted hydration sites was found, but with certain deviations resulting from the incommensurate solvation requirements of adjacent functional groups. No evidence was found to support previous theories about sugar hydration which are based upon a supposed coincidence of the sugar structure with an assumed lattice-like model of liquid water. Solvent pair distribution functions were also used to characterize the observed water structuring, and methods of eliminating artificial minima in these distributions resulting from spherical averaging were examined.