Model dependence of the anisotropic structuring of solvent water around sugars in molecular dynamics simulations

Microcanonical ensemble molecular dynamics simulations have been used to examine the model dependence of the computed three-dimensional structuring which the typical sugar D-xylose imposes on surrounding solvent molecules in aqueous solution. The structuring imposed on water by biological solutes is quite complex, due to the complicated mix of chemical functionalities found in typical biopolymers, and has proven difficult to probe experimentally. Computer simulations have been the principal source of spatially resolved information about the solvent structuring about particular solutes, and previous simulations of this sugar have found configuration-dependent solvent structuring which appears to explain an important experimentally determined physical characteristic of the molecule, its anomeric ratio. Well-defined first and second solvation shells are observed around the sugar molecule with specific locations determined by the arrangement of functional groups in the solute. Here we examine the dependence of this calculated solvent structuring upon the Solvent model employed by comparing simulations using the TIP3P and SPC/E water force fields. The solvent structuring is found to be qualitatively the same in both simulations and is primarily determined by geometric constraints determined by the solute topology.