Layer Thickness of Hydrophobin Films Leads to Oscillation in Wettability

Abstract

In nanobiotechnology, the properties of surfaces are often key to sensor applications. If analytes possess a low tolerance or affinity regarding the sensory substrate (surface), then the setup of mediators may be indicated. Hydrophobins enable biocompatible surface functionalization without significant restrictions of the physicochemical substrate properties. Because of the imperfect formation of hydrophobin films, a high variation in surface properties is observed. In this study, we report on the relation between the film thickness of hydrophobin-coated solid surfaces and their wettability. We found that the wettability of protein-coated surfaces strictly depends on the amount of adsorbed protein, as reflected in an oscillation of the contact angles of hydrophobin-coated silicon wafers. Fusion proteins of Ccg2 and HFBI, representatives of class I and II hydrophobins, document the influence of fused peptide tags on the wettability. The orientation of the first crystal nuclei plays a decisive role in the formation of the growing hydrophobin layers. Here, a simple method of deducing the film thickness of hydrophobin assemblies on solid surfaces is presented. The determination of the static contact angle allows the prediction of which part of the protein is exposed to possible analytes.

Hydrophobin-Based Surface Engineering for Sensitive and Robust Quantification of Yeast Pheromones

“…This strain was selected because it ensures the cytoplasmic formation of disulfide bonds, which play a crucial role in stabilizing soluble hydrophobins by preventing premature self-assembly in the absence of an interface [ 46 , 47 ]. Both hydrophobins were found in the pellet fraction of E. coli lysates upon centrifugation, but could be solubilized by 8 M urea and subsequently purified using the (His) 6 -tag [ 37 , 38 , 39 ]. A sample of the purified proteins was separated by Tricine-SDS-PAGE and probed with antibodies specific for the (His) 6 -tag or the α-factor peptide ( Figure 1 b) to ensure the integrity of the proteins.…”

“…pET28b-EAS and pET28b-EAS-α, respectively, were transformed into E. coli SHuffle ® T7 Express lysY (New England Biolabs, Frankfurt, Germany). Expression and purification of the hydrophobins were carried out essentially as described previously [ 37 , 38 , 39 ]. Briefly, transformants were grown in LB medium (1.0% ( w / v ) peptone, 0.5% ( w / v ) yeast extract, 0.5% ( w / v ) sodium chloride, pH 7.4) at 30 °C to the early log phase and expression of the hydrophobins was induced by addition of 0.4 mM isopropyl-β- d -thiogalactoside (IPTG).…”

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

“…Hydrophobins are small proteins produced by filamentous fungi [9][10][11][12][13][14][15]. The most characteristic feature of hydrophobin is that they self-organize at air/water or water/solid interfaces [16][17][18].…”

PfaH2: A novel hydrophobin from the ascomycete Paecilomyces farinosus

“…A relation between the amount of adsorbed protein and the resulting film thickness and the wettability of hydrophobin‐coated solid surfaces was found . Imperfect formation of hydrophobin films may result in a high variability of surface properties.…”