Molecular dynamics simulation of the hydration of the alanine dipeptide

Molecular dynamics computer simulations of an alanine dipeptide molecule in aqueous solutions have been carried out. Three different molecular conform ations (alpha, beta, and C-7(ax)) have been considered. Structural and dyna mical properties of the hydration water molecules have been calculated sepa rately for solvent molecules surrounding different atoms or atomic groups o f such dipeptide, i.e., two carbonyl oxygens, three methyls, and two amide hydrogens. The results for the three conformations have been compared for p ossible differences. The study includes molecule sites--water radial distri bution functions and coordination numbers as well as residence times, hydro gen bonding, and reorientational times of water molecules in the hydration shells. The little differences between the properties of water around the p olar and nonpolar atomic groups have been carefully analyzed. The discrepan cies between the hydration water properties on the different conformations are not significant.