Evidence Supporting Enrichment of Dissolved Air Gases near Hydrophobic Macromolecules in Aqueous Solutions

In the present study, we deposited buffer solutions containing hydrophobic (GA)₁₅ fibrils onto highly oriented pyrolytic graphite (HOPG) and imaged the surfaces through atomic force microscopy (AFM). Within 3 h of applying ambient (nondegassed) buffers, we observed the formation of two-dimensional stripe-like domains on the HOPG surfaces surrounding the (GA)₁₅ fibrils. However, these stripe domains did not form under degassed buffers. Furthermore, the formation of stripe domains on HOPG occurred considerably faster in the presence of buffer solutions containing (GA)₁₅ fibrils than in the presence of pure buffer solutions. These stripe structures have recently been identified as nitrogen gas hydrate layers, which are formed through the self-assembly of nitrogen and water molecules on HOPG surfaces. Our findings suggest that gas enrichment occurs in the interfacial water surrounding hydrophobic macromolecules. The results have crucial implications for understanding hydrophobic interactions and the self-assembly of hydrophobic nano-objects in aqueous environments.