"Formation and elasticity of membranes of the class II hydrophobin Cera" by Xujun Zhang, Stephanie M. Kirby et al.

Faculty Publications

Title

Formation and elasticity of membranes of the class II hydrophobin Cerato-ulmin at oil-water interfaces

Authors

Xujun Zhang, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, United States; Georgia Tech Polymer Network, GTPN, Georgia Institute of Technology, Atlanta, GA 30332, United States.
Stephanie M. Kirby, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States.
Yuwu Chen, Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803-1804, United States.
Shelley L. Anna, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States.
Lynn M. Walker, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States.
Francisco R. Hung, Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803-1804, United States; Department of Chemical Engineering, Northeastern University, Boston, MA 02115, United States.
Paul S. Russo, School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, United States; Georgia Tech Polymer Network, GTPN, Georgia Institute of Technology, Atlanta, GA 30332, United States; School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, United States. Electronic address: paul.russo@mse.gatech.edu.

Document Type

Article

Publication Date

4-1-2018

Abstract

Protein surfactants show great potential to stabilize foams, bubbles, and emulsions. An important family of surface active proteins, the hydrophobins, is secreted by filamentous fungi. Two hydrophobin classes have been recognized, with Class II exhibiting slightly better solubility than Class I, although neither is very soluble in water. Hydrophobins are small proteins (8-14 kDa), but they are larger and more rigid than typical surfactants such as sodium dodecyl sulfate. This rigidity seems to be manifested in the strength of adsorbed hydrophobin layers on oil droplets or air bubbles. A particular Class II hydrophobin, Cerato-ulmin, was characterized at the oil-water interface (the oil was squalane). The results are compared to measurements at the air-water interface, newly extended to lower Cerato-ulmin concentrations. For both oil-water and air-water interfaces, static and dynamic properties were measured during the evolution of the membrane structure. The static measurements reveal that dilute Cerato-ulmin solution efficiently decreases the interfacial tension, whether at oil-water or air-water interfaces. The reduction in surface tension requires several hours. Interfacial mechanics were characterized too, and the dilatational modulus was found to reach large values at both types of interfaces: 339 ± 19 mN/m at the squalane-water interface and at least 764 ± 45 mN/m at the air-water interface. Both values well exceed those typical of small-molecule surfactants, but come closer to those expected of particulate-loaded interfaces. Circular dichroism provides some insight to adsorption-induced molecular rearrangements, which seem to be more prevalent at the oil-water interface than at the air-water interface.

Publication Source (Journal or Book title)

Colloids and surfaces. B, Biointerfaces

First Page

Last Page

106

Recommended Citation

Zhang, X., Kirby, S. M., Chen, Y., Anna, S. L., Walker, L. M., Hung, F. R., & Russo, P. S. (2018). Formation and elasticity of membranes of the class II hydrophobin Cerato-ulmin at oil-water interfaces. Colloids and surfaces. B, Biointerfaces, 164, 98-106. https://doi.org/10.1016/j.colsurfb.2018.01.017

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