COMPARISON OF A GB SOLVATION MODEL WITH EXPLICIT SOLVENT SIMULATIONS - POTENTIALS OF MEAN FORCE AND CONFORMATIONAL PREFERENCES OF ALANINE DIPEPTIDE AND 1,2-DICHLOROETHANE

The potential of mean force in aqueous solution for rotation around th e two backbone dihedrals phi and psi of the alanine dipeptide is compu ted in explicit water and in th-continuum approximation by numerical i ntegration of the self-energies and the generalized Born (GE) equation . The two models show good agreement. The experimentally observed incr ease in the gauche/trans population ratio for dichloroethane in going from the gas phase to the pure liquid is reproduced by the GB solvatio n model with a solvent dielectric constant of 10.5. This test case sho ws that the GR model gives accurate predictions also for solvents with much lower polarizability than water. For both test systems additiona l calculations with a finite difference Poisson equation solver yield somewhat more accurate results at a much higher computational cost tha n the GB solvation model.