EFFECT OF COSOLVENT ON A TRIPEPTIDE SOLUTION USING MOLECULAR-DYNAMICSSIMULATIONS

We have performed molecular dynamics simulations on tricomponent solut ions containing tripeptide, cosolvent and water molecules to investiga te the structural and energetic effects of cosolvents on peptide and w ater molecules at 300 K. We use glycerol or urea molecules as cosolven ts and Gly-Ala-Phe (GAF) as the tripeptide in each simulation. The con centration of cosolvent is adjusted to about 6-7 vol% of water. We ana lyze the structural and dynamic change of the tripeptide by the torsio nal angle distribution and the root-mean-square (r.m.s.) fluctuation. The interactions between all constituent molecules are analyzed by the ir H-bonding characteristics. We examine the water structure through H -bonds, the distribution of energies and H-bonded circular networks, r ings. Cosolvent-induced conformational changes occur in the Ala residu e of the tripeptide in urea solution. The Ala residue interacts with u rea molecules substituted for water molecules through H-bonds. The wat er structure around the peptide is slightly more ordered in glycerol s olution where glycerol is excluded in the vicinity of the peptide.