Structure of water molecules in aqueous maltose and cellobiose solutions using molecular dynamics simulation. I. Statics

A molecular dynamics simulation, which includes all degrees of freedom of atomic motion, has been carried out for aqueous maltose and cellobiose solutions in order to investigate whether the solvent as a background of solutes changes its dynamic characteristics or not. Mean square displacement, velocity autocorrelation function, rotational correlation function, and newly defined hydrogen bond correlation function have been calculated for the whole solvent from which the first hydration shell of the solute was omitted. The first three functions concern motions of each water molecule, and the last one reveals relative motions of water molecules. Translational and rotational motions of water molecules are restricted more in the solution than in the bulk water, because the network defects, which weaken the power of a water molecule to retain others, exist less in the solution than in the bulk water. Between two solution systems, this tendency is stronger in the maltose solution than in the cellobiose one. The difference between two solution systems is clearly demonstrated in the present study dealing with the dynamic structure, although it was not clear in the static structure revealed in our previous paper.