MOLECULAR-SIZE CORRECTIONS TO THE STRENGTH OF THE HYDROPHOBIC EFFECT - A CRITICAL-REVIEW

Large increases in the strength of the hydrophobic effect and, consequ ently, in the estimates of the hydrophobic contribution to the thermod ynamics of protein folding (and other biologically-relevant processes) , have been recently advocated on the basis of the application, to mod el transfer thermodynamic data, of corrections for the solute/solvent size disparity. In this work we first examine the effect of molecular- size corrections on the values calculated from several types of model transfer data. For the transfer of a solute from an organic solvent to water, the above increase is exclusively associated with the applicat ion of a solute/water molecular-size correction. Secondly, we critical ly review and assess the several theoretical arguments that lead to th ese corrections. In particular, we eu show that, contrary to previous claims in the literature, the analysis of dissolution processes in ter ms of ideal-gas, intermediate states does not lead to the molecular-si ze correction term, but only to expressions equivalent (although not s trictly identical) to those derived from the well-known Ben-Naim's sta tistical-mechanical approach. In general, the several analyses offered or discussed in this work disfavor the application of the solute/wate r molecular-size corrections.