Journal Article level-set method Boltzmann theory Charged molecules Ligands Nonpolar molecules Poisson Proteins Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Solutions biomolecular modeling change of volume compact coupling interface method dielectric boundaries dielectric boundary force effective dielectric boundary force electrostatic energy ghost fluid method interface motion linear stability solute-solvent interface solvation free energy surface energy the Stokes equation traction boundary conditions variational implicit-solvent model