title: Label-free quantification of membrane-ligand interactions using backscattering interferometry.
abstract: Although membrane proteins are ubiquitous within all living organisms and represent the majority of drug targets, a general method for direct, label-free measurement of ligand binding to native membranes has not been reported. Here we show that backscattering interferometry (BSI) can accurately quantify ligand-receptor binding affinities in a variety of membrane environments. By detecting minute changes in the refractive index of a solution, BSI allows binding interactions of proteins with their ligands to be measured at picomolar concentrations. Equilibrium binding constants in the micromolar to picomolar range were obtained for small- and large-molecule interactions in both synthetic and cell-derived membranes without the use of labels or supporting substrates. The simple and low-cost hardware, high sensitivity and label-free nature of BSI should make it readily applicable to the study of many membrane-associated proteins of biochemical and pharmacological interest.
authors.affiliation: Department of Chemistry, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Baksh
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Kussrow
authors.forename: Mauro
authors.initials: M
authors.lastname: Mileni
authors.forename: M G
authors.initials: MG
authors.lastname: Finn
authors.forename: Darryl J
authors.initials: DJ
authors.lastname: Bornhop
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D002772:Cholera Toxin / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000378:metabolism; D006801:Humans; D007368:Interferometry / Q000379:methods*; D007700:Kinetics; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D019718:Receptors, CXCR4 / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism; D012031:Refractometry / Q000379:methods; D000099252:Fatty Acid Amide Hydrolases
chemical_list: D000581:Amidohydrolases; D002772:Cholera Toxin; D005677:G(M1) Ganglioside; D008024:Ligands; D008565:Membrane Proteins; D019718:Receptors, CXCR4; D018080:Receptors, GABA-B; D000099252:Fatty Acid Amide Hydrolases