Self-Assembled Bilayers from the Protein HFBII Hydrophobin: Nature of the Adhesion Energy

Abstract

The hydrophobins are a class of amphiphilic proteins which spontaneously adsorb at the air/water interface and form elastic membranes of high mechanical strength as compared to other proteins. The mechanism of hydrophobin adhesion is of interest for fungal biology and for various applications in electronics, medicine, and food industry. We established that the drainage of free foam films formed from HFBII hydrophobin solutions ends with the appearance of a 6 nm thick film, which consists of two layers of protein molecules, that is, it is a self-assembled bilayer (S-bilayer), with hydrophilic domains pointing inward and hydrophobic domains pointing outward. Its formation is accompanied by a considerable energy gain, which is much greater than that typically observed with free liquid films. The experiments at different pH show that this attraction between the "hydrophilic" parts of the HFBII molecules is dominated by the short-range hydrophobic interaction rather than by the patch-charge electrostatic attraction.

Heterologous expression and characterization of the hydrophobin HFBI in Pichia pastoris and evaluation of its contribution to the food industry

“…The characteristic property of hydrophobins is that they self-assemble spontaneously at hydrophobic-hydrophilic interfaces (e.g., water/air and water/oil) into amphipathic membrane and convert the surface from hydrophilic to hydrophobic and vice versa Sunde et al 2008;Basheva et al 2011). Based on the remarkable surface activities and self-assembly abilities, hydrophobins are considered as interesting candidates for potential use in many applications, including biomaterials coatings (Qin et al 2007;Asakawa et al 2009;Hou et al 2009), separation technologies (Linder et al 2001;Lahtinen et al 2008), biosensors and electrodes (Wang et al 2010b), the proteinaceous glue and cosmetics productions (Misra et al 2006).…”

Pure Protein Bilayers and Vesicles from Native Fungal Hydrophobins

“…Yet, since in hydrophilic core bilayers, the finger medium is insulating, a thickness determination by capacitance measurements is not possible. The thickness can, however, be inferred from studies on the protein HFBII, which is in size and behavior very similar to HFBI: By interferometry, the authors report for foam films of HFBII a thickness of 6 nm, corresponding to two times the protein diameter. The contact angle of 51° ± 1° for that system is similar to ours under similar conditions, i.e., with air as surrounding medium (see Table S1, Supporting Information).…”

Recent Advances in Fungal Hydrophobin Towards Using in Industry

“…It deserves also mention Dr. Karin Scholtmeijer as a researcher from the same group with many publications Class II HFBI (10 mg/mL, purity of 68 %) Efficient purification of endoglucanase [80] Class I SC3 (300 lg/mL) Immobilization of glucose oxidase and horseradish peroxidase [81] Class I SC3 (30 lg/mL) Polymer surface modification [82] Class II HFBI (100 lg/mL) Glass surface modification [83] Class II HFBI (211 mg/mL, purity of 99 %) Potential fusion partner for one step purification of avidin from insect cells [84] Class II HFBII (1 mg/mL) Stabilization of bubbles and foams [53] Class I SC3 (40 lg/mL) Formulation of water insoluble drugs for oral administration [85] Class II HFBI (500 lg/mL) Coating of drug nanoparticle [78] Class II HFBI (20 lg/mL) Dispersion multi walled carbon nanotubes [86] about surface modification by hydrophobin [15,114,115] and other aspects [116]. [117,[120][121][122].…”