SA - negatively charged solvent-accessible atomic surface area
qA - atomic partial charge
D.T. Stanton, P.C. Jurs, Anal. Chem., 1990 62, 2323; D.T. Stanton, L.M. Egolf, P.C. Jurs, M.G. Hicks, J. Chem. Inf. Comput. Sci., 1992 32, 306.