Proteins in a brave new surfactant world

This review discusses emerging topics within the field of protein-surfactant interactions over the last 4-5 years. The application of small-angle x-ray scattering has allowed us to construct ever more detailed models of the structures of different protein-surfactant complexes and has revealed common features shared between electrophoretic protein-SDS complexes and liprotides (complexes between lipids and partially denatured proteins), namely a generic core-shell structure which can also form beads on a string. SDS emerges as the best surfactant for gel electrophoresis from a series of studies comparing it with surfactants differing in chain length, degree of branching, and fluorination, as well as dodecyl sulfate with different counterions. Nevertheless, these surfactants possess useful properties for alternative applications. SDS also continues to serve as a useful tool for systematic folding/unfolding studies of membrane proteins together with the non-ionic surfactant dodecyl maltoside, as well as for studying hyperstable kinetically trapped proteins. Biosurfactants are coming to the fore as sustainable alternatives to chemical surfactants and show unique properties toward proteins that combine aspects of both ionic and non-ionic surfactants. (C) 2015 Elsevier Ltd. All rights reserved.