(303a) Molecular Dynamics Simulations of Hydrophobins Encapsulating Organic Molecules

Hydrophobins are nature’s most surface-active proteins abundantly produced by filamentous fungi in soil and decaying vegetation. Preliminary experiments suggest that these proteins can efficiently encapsulate oil in cylindrical ‘blobs’, or gases in cylindrical bubbles, which implies a striking surface activity. These properties, as well as the abundance and ease of biosynthetic manufacture of hydrophobins, suggest that they could be used as ‘natural’ oil spill dispersants. Here we first report molecular dynamics (MD) simulations for a class I hydrophobin, EAS, near gas/water and oil/water interfaces. Interfacial properties (free energies, density profiles, radius of gyration of the hydrophobins) that are relevant for the possible use of hydrophobins as ‘natural’ oil dispersants were probed in our simulations using both all-atom and coarse-grained models. The EAS molecules prefer to remain at the interfaces, with the adsorption behavior being strong and irreversible. Significant changes in the radius of gyration of the hydrophobins were observed upon binding to the gas/water and oil/water interfaces. We also performed MD simulations using coarse-grained models where we probed the stability of benzene blobs encapsulated by hydrophobins, with sizes comparable to those realized experimentally by the Russo group. The structures observed in our simulations are not spherical but rather elongated, as indicated by simulation snapshots and measurements of the characteristic dimensions (moments of inertia and asymmetry parameter) of the structures. The stability of the bubbles, as indicated by measurements of the root mean squared deviations (RMSDs) from the initial sizes, is assessed and discussed.