Calculation of the aqueous solvation energy and entropy, as well as free energy, of simple polar solutes

With the advent of more powerful computers, the question of calcg. thermodn. quantities, such as the energy and the entropy, in solute-solvent systems is revisited.  The calcn. of these thermodn. quantities was limited in the past by their slow convergence relative to the free energy.  Using mol. dynamics simulations, the energy, entropy, and free energy of solvation of N-Me acetamide and CH3NH2, as well as their relative values, have been detd.  Three different methods (the thermodn. perturbation method, the thermodn. integration method, and a finite-difference method) are compared.  The finite difference method gives the best results and accurate values for the entropy and energy which were obtained using a reasonable amt. to computer time.  The results suggest that a meaningful thermodn. description of biomol. processes can be realized with present methods and the available computer time.