title: Effect of protein incorporation on the nanostructure of the bicontinuous microemulsion phase of Winsor-III systems: a small-angle neutron scattering study.
abstract: Small-angle neutron scattering (SANS) analysis using the Teubner-Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oil from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOT's sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. The results of this study demonstrate the importance of ionic strength to modulate protein-surfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.
authors.affiliation: Department of Biosystems Engineering and Soil Science, University of Tennessee , Knoxville, Tennessee 37996-4531, United States.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Hayes
authors.forename: Javier A
authors.initials: JA
authors.lastname: Gomez del Rio
authors.forename: Ran
authors.initials: R
authors.lastname: Ye
authors.forename: Volker S
authors.initials: VS
authors.lastname: Urban
authors.forename: Sai Venkatesh
authors.initials: SV
authors.lastname: Pingali
authors.forename: Hugh M
authors.initials: HM
authors.lastname: O'Neill
mesh_terms: D000336:Aerosols; D000818:Animals; D002417:Cattle; D004655:Emulsions; D006536:Heptanes / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D033363:Neutron Diffraction; D009821:Oils / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D053838:Scattering, Small Angle; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D004655:Emulsions; D006536:Heptanes; D009821:Oils; D011506:Proteins; D014867:Water