Molecular dynamics study of infinitely dilute aqueous solutions of small biological molecules. Calculation of the static and dynamic properties of formaldehyde

A molecular dynamics calculation of a dilute aqueous solution of formaldehyde was carried out using the MCY potential for the water-water interaction and an ab initio potential, a fit by a 12-6-1 type potential function, for the formaldehyde-water interaction. Several static and dynamic properties (thermodynamic functions, radial distribution functions, coordination numbers, velocity and dipole autocorrelation functions, mean square displacements, diffusion coefficients and reorientational correlation times) were calculated for this system. The results show the hydrophobic nature of the CH, group, and a strong interaction between the solute and solvent molecules that hydrate the carbonyl group, which hinders the translational and rotational movement of formaldehyde in this medium. The comparison of dynamical properties for pure water and in solution show how the presence of this solute leads to a smooth stabilization of the system, an enhancement of the ''cage'' effect in the structure of the solvent, a decrease of the translational diffusion coefficient and an increase of the reorientation time.