One might anticipate that relative solvation energies (comparing different isomers of the same protein) are likely to be more accurate than absolute solvation energies, and indeed we find that difference in ∆G elst are more consistent, comparing HetPCM with ε nonp = 4 versus ε nonp = 10 (Table ). These results are consistent in trend (but not necessarily magnitude) with those presented by Su and Li. In general, our calculations afford larger values of |∆G elst | as compared to those reported in Ref. 107, consistent with the use of smaller atomic radii in the present work. Results obtained with unitedatom radii (Table ) are more consistent with those in Ref. 107.