(295e) Context-Dependent Hydrophobic Interactions in Water

The structuring of water near non-polar molecular fragments or surfaces mediates cohesive interactions (so-called hydrophobic interactions) that underlie a broad range of biophysical, colloidal and materials-related phenomena. Substantial progress has been made during the past decade towards understanding hydrophobic interactions in simple model systems, but in most biological and technological contexts, non-polar domains are found in close proximity to polar and charged functional groups. We are using conformationally-stable beta-amino acid oligomers and single-molecule force measurements to elucidate hydrophobic interactions encoded by specific chemical nanopatterns. These measurements reveal, for example, that ions immobilized adjacent to non-polar domains can substantially increase or decrease the strength of hydrophobic interactions between molecules in water, with the effect strongly dependent on the specific ion type. This understanding is providing a fresh starting point for understanding molecular thermodynamics in aqueous environments in a broad range of contexts.