(593i) Molecular Dynamics Simulations of Nanostructures Formed By Hydrophobins and Oil in Seawater
AIChE Annual Meeting
2021
2021 Annual Meeting
Engineering Sciences and Fundamentals
Thermodynamics at the Nanoscale
Thursday, November 11, 2021 - 10:16am to 10:30am
Classical molecular dynamics simulations using the Martini coarse-grained force field were performed to study oil nanodroplets surrounded by fungal hydrophobin (HP) proteins in seawater. The class I EAS and the class II HFBII HPs were studied along with two model oils, benzene and n-decane. Both HPs exhibit free energy minima at the oil-seawater interface, which are much deeper in benzene systems than in interfaces with n-decane. Smaller surface tensions are observed at benzene-seawater interfaces coated with HPs compared to their n-decane counterparts, in which the surface tension remains unchanged upon increases in the surface concentration of HPs, which in contrast lead to surface tension reductions at the benzene-seawater interface. EAS has a larger tendency to cluster together in the interface compared to HFBII, with both HPs having larger coordination numbers when surrounding benzene droplets compared to when they are around n-decane nanoblobs. The HP/oil nanostructures in seawater examined have radii of gyration ranging between 2-12 nm, where the n-decane structures are larger and have more irregular shapes (as quantified through different shape measures) compared to the benzene blobs. The n-decane molecules within the nanostructures form a compact spherical core, with the HPs partially covering its surface and clustering together, conferring irregular shapes to the nanostructures. The EAS/n-decane structures are larger and have more irregular shapes compared to their HFBII/n-decane counterparts. In contrast, in the HP/benzene structures both HPs tend to penetrate into the benzene part of the droplet. The HFBII/benzene structures having the larger benzene/HP ratios examined tend to be more compact and spherical compared to their EAS/benzene counterparts; however, some of the HFBII/benzene systems that have smaller benzene/HP ratios have a more elongated structure compared to their EAS counterparts. This simulation study provides insights into HP/oil nanostructures that are smaller than the oil droplets and gas bubbles recently studied in experiments, and thus might be challenging to examine with experimental techniques.