title: Protein-surfactant interactions at hydrophobic interfaces studied with total internal reflection fluorescence correlation spectroscopy (TIR-FCS).
abstract: The aim of this work was to study the dynamics of proteins near solid surfaces in the presence or absence of competing surfactants by means of total internal reflection fluorescence correlation spectroscopy (TIR-FCS). Two different proteins were studied, bovine serum albumin (BSA) and Thermomyces lanuginosus lipase (TLL). A nonionic/anionic (C12E6/LAS) surfactant composition was used to mimic a detergent formulation and the surfaces used were C18 terminated glass. It was found that with increasing surfactant concentrations the term in the autocorrelation function (ACF) representing surface binding decreased. This suggested that the proteins were competed off the hydrophobic surface by the surfactant. When fitting the measured ACF to a model for surface kinetics, it was seen that with raised C12E6/LAS concentration, the surface interaction rate increased for both proteins. Under these experimental conditions this meant that the time the protein was bound to the surface decreased. At 10 microM C12E6/LAS the surface interaction was not visible for BSA, whereas it was still distinguishable in the ACF for TLL. This indicated that TLL had a higher affinity than BSA for the C18 surface. The study showed that TIR-FCS provides a useful tool to quantify the surfactant effect on proteins adsorption.
authors.affiliation: YKI, Institute for Surface Chemistry, Stockholm, Sweden.
authors.forename: Andreas W
authors.initials: AW
authors.lastname: Sonesson
authors.forename: Hans
authors.initials: H
authors.lastname: Blom
authors.forename: Kai
authors.initials: K
authors.lastname: Hassler
authors.forename: Ulla M
authors.initials: UM
authors.lastname: Elofsson
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Callisen
authors.forename: Jerker
authors.initials: J
authors.lastname: Widengren
authors.forename: Hjalmar
authors.initials: H
authors.lastname: Brismar
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000201:enzymology; D001665:Binding Sites; D002417:Cattle; D005456:Fluorescent Dyes; D057927:Hydrophobic and Hydrophilic Interactions; D007834:Lasers; D008049:Lipase / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D011506:Proteins; D013501:Surface-Active Agents; D012710:Serum Albumin, Bovine; D008049:Lipase