A molecular dynamics study of the dielectric properties of aqueous solutions of alanine and alanine dipeptide

The frequency-dependent dielectric susceptibility of aqueous solutions of alanine and alanine dipeptide was computed using molecular dynamics simulations. Four alanine solutions, ranging in concentration from 0.13-0.55 mol/liter, and two solutions of alanine dipeptide, were studied. The strong dielectric increment for both solutes, whose molecular origin is shown to be the zwitterionic nature of the solutes, was found. The results show that the interaction between waters surrounding the solute(s) and bulk water molecules leads to a relaxation process occurring on an intermediate time scale.