(57e) Hydrophobic Association with Amphiphilic and Superhydrophilic Cosolutes

Hydrophobic association in aqueous solution plays an important role in biological and chemical processes such as protein folding, protein-protein aggregation and enzyme-substrate association. This critical association can be affected by the environmental factors such as temperature, pressure and co-solutes. A recent experiment (Keefe A. and Jiang S., Nature Chemistry, 2012, 4, 59-63) showed that the poly-betaine and poly-(ethylene glycol) conjugated proteins have different substrate affinities. This observation implicates differing influences of carboxybetaine (CB) and ethylene glycol (EG) on hydrophobic association. Zwitterionic CB is superhydrophilic and EG is amphiphilic. In this work, we explored the effects of CB and EG to the hydrophobic association. We selected the association of two methane molecules as a model and the potential of mean force of this association with CB and EG of various concentrations were investigated. The structure and dynamics of the aqueous solution were also investigated to explore the relation between the variation of hydrophobic association and the change of aqueous environment. The simulation results offer fundamental information at the molecular level for the rational design of related biomaterials.