Burial of Hydrocarbon Causes Cooperative Enhancement of Electrostatic Binding

摘要

The hydrophobia effect, involving the burial ef hydrocarbon formerly exposed to water, provides a major driving force in molecular recognition, and is fundamental to our understanding of the structure and function of biological systems. The desire torationalize the forces involved in molecular complexation and the stabilization of highly ordered molecular assemblies has led to attempts to correlate the magnitude of the hydropho-bic free energy with the nonpolar surface area no longer accessible to solvent. This approach potentially provides a useful numerical estimate for assessing binding contributions in molec ular recognition studies. However, data from protein engineering experiments and Hgand binding studies suggest that the hydrophobic effectpromotes binding in aqueous solution to a larger extent than is estimated from solvent transfer measurements. An explanation for this discrepancy has been sought, at least partially, in terms of changes in volume entropy in the two sets of experiments.In the present work we show that burial of hydrocarbon in a molecular recognition site can lead to the strengthening of adjacent electrostatic interactions.