Comparative study of 3D-RISM theory and molecular dynamics calculations for the free-energy landscape of a hydrated dipeptide

In the present study, the free-energy landscape of a hydrated alanine dipeptide has been studied by the 3D-RISM theory. We calculate the hydration free energy as a function of dihedral angles and using both the 3D-RISM theory and the umbrella sampling method. The 3D-RISM results are found to be in good agreement with those by the umbrella sampling calculations, demonstrating the reliability of the integral equation theory applied to bimolecular systems.