Molecular Simulation of Hydrophobin Adsorption at an Oil–Water Interface

Abstract

Hydrophobins are small, amphiphilic proteins expressed by strains of filamentous fungi.They fulfil a number of biological functions, often related to adsorption at hydrophobic interfaces, and have been investigated for a number of applications in materials science and biotechnology. In order to understand the biological function and applications of these proteins a microscopic picture of the adsorption of these proteins at interfaces is needed. Using molecular dynamics simulations with a chemically detailed coarse-grained potential the behaviour of typical hydrophobins at the water-octane interface is studied. Calculation of the interfacial adsorption strengths indicates that the adsorption is essentially irreversible, with adsorption strengths of the order of 100 k B T (comparable to values determined for synthetic nanoparticles but significantly larger than small molecule surfactants and biomolecules). The protein structure at the interface is unchanged at the interface, which is consistent with the biological function of these proteins. Comparison of native proteins with pseudoproteins that consist of uniform particles shows that the surface structure of these proteins has a large effect on the interfacial adsorption strengths, as does the flexibility of the protein.

How stable are amphiphilic dendrimers at the liquid–liquid interface?

“…In both cases the dendrimers are strongly adsorbed to the liquid--liquid interface, with desorption free energies of 100 k B T and 75 k B T respectively, similar in magnitude to spherical nanoparticles (both from simulation 18 and experimental 29 studies and proteins 19 ).…”

“…Shown in Figure 5 are the free energy profiles for the uniform dendrimer (in poor solvent) and the Janus dendrimers (again due to the symmetry of the molecules these profiles are symmetric about z=0). In all cases, due to the amphiphilic nature of the molecules, the Janus dendrimers are more stable at the interface than the uniform dendrimer (similar to amphiphilic nanoparticles 20 and proteins 19 ). For the Janus dendrimers there are, however, significant differences between the different configurations investigated here.…”

Conformations of Myoglobin-Derived Peptides at the Air–Water Interface

“…Both atomistic [15][16][17][18] and coarse-grain models 19,20 have been used, the latter being more computationally e cient and due to their simpler parameterization capable of investigating the link between protein surface structure and interfacial behaviour. 20 Atomistic models by contrast are capable of modelling protein structural change at interfaces, giving some insight into protein function such as biomineralization 21 and catalysis 22 at interfaces. The combination of atomistic simulations and neutron reflectivity has proven to be increasingly common, 23,24 as the simulations can give direct insight into protein structure that can be used to rationalise the NR measurements.…”

Complex Molecules at Liquid Interfaces: Insights from Molecular Simulation

“…Using coarse-grain molecular dynamics simulations, I investigated the adsorption strength of two common type-II hydrophobins (HFBII and HFBI) at the water-octane interface [64]. Unlike class-I hydrophobins, which often undergo significant conformational change at interfaces, class-II hydrophobins have rigid globular structures that remain largely unchanged (Figure 6(a)).…”