All statistics presented use their standard definitions with the exception of the mean unsigned error (MUE). It is well known that MMPBSA results have a significant offset from experimental values (typically of the order of 15 to 25 kcal mol -1 ) due to a range of factors, in particularly the neglect of entropic contributions . Consequently we present values corrected for the systematic (mean signed) error and designate them cMUE.