Electrochemical properties of honeycomb-like structured HFBI self-organized membranes on HOPG electrodes

Hydrophobins: multifunctional biosurfactants for interface engineering

Hydrophobins are highly surface-active proteins that have versatile potential as agents for interface engineering. Due to the large and growing number of unique hydrophobin sequences identified, there is growing potential to engineer variants for particular applications using protein engineering and other approaches. Recent applications and advancements in hydrophobin technologies and production strategies are reviewed. The application space of hydrophobins is large and growing, including hydrophobic drug solubilization and delivery, protein purification tags, tools for protein and cell immobilization, antimicrobial coatings, biosensors, biomineralization templates and emulsifying agents. While there is significant promise for their use in a wide range of applications, developing new production strategies is a key need to improve on low recombinant yields to enable their use in broader applications; further optimization of expression systems and yields remains a challenge in order to use designed hydrophobin in commercial applications.

Flattened-Top Domical Water Drops Formed through Self-Organization of Hydrophobin Membranes: A Structural and Mechanistic Study Using Atomic Force Microscopy

The Trichoderma reesei hydrophobin, HFBI, is a unique structural protein. This protein forms membranes by self-organization at air/water or water/solid interfaces. When HFBI forms a membrane at an air/water interface, the top of the water droplet is flattened. The mechanism underlying this phenomenon has not been explored. In this study, this unique phenomenon has been investigated. Self-organized HFBI membranes form a hexagonal structured membrane on the surface of water droplets; the structure was confirmed by atomic force microscopy (AFM) measurement. Assembled hexagons can form a planar sheet or a tube. Self-organized HFBI membranes on water droplets form a sheet with an array of hexagonal structures or a honeycomb structure. This membrane, with its arrayed hexagonal structures, has very high buckling strength. We hypothesized that the high buckling strength is the reason that water droplets containing HFBI form flattened domes. To test this hypothesis, the strength of the self-organized HFBI membranes was analyzed using AFM. The buckling strength of HFBI membranes was measured to be 66.9 mN/m. In contrast, the surface tension of water droplets containing dissolved HFBI is 42 mN/m. Thus, the buckling strength of a self-organized HFBI membrane is higher than the surface tension of water containing dissolved HFBI. This mechanistic study clarifies why the water droplets formed by self-organized HFBI membranes have a flattened top.