title: Bovine serum albumin (BSA) plays a role in the size of SDS micelle-like aggregates at the saturation binding: the ionic strength effect.
abstract: The influence of ionic strength on the complexes formed by natural bovine serum albumin (BSA), pH 5.4 (near the isoelectric point), and sodium dodecyl sulfate (SDS) in aqueous buffered (sodium acetate) solution was investigated by using surface tension, fluorescence and small angle X-ray scattering (SAXS) techniques. Ionic strength was varied by changing sodium acetate buffer concentration from 0.020 to 0.5 M. Surface tension revealed that SDS:BSA saturation binding occurs at psp = 42 +/- 2 mM, independent of the solution ionic strength. Further, SAXS curves are consistent with the necklace and bead model, where micelle-like aggregates are randomly distributed along the partial unfolded protein. Micelle-like aggregates grow from small spheres at 10 mM SDS to small ellipsoids (upsilon = 1.3 , ratio between the largest and the shortest axes) near psp, in good agreement with micellar aggregation numbers obtained by fluorescence, independent of salt concentration. Protein-bound micelles stop growing above psp and further SDS addition induces free-micelle formation.
authors.affiliation: Departamento de Química da Universidade Federal de Santa Catarina, CEP 88040-900, Florianópolis, SC, Brazil.
authors.forename: Bianca
authors.initials: B
authors.lastname: Shweitzer
authors.forename: Dino
authors.initials: D
authors.lastname: Zanette
authors.forename: Rosangela
authors.initials: R
authors.lastname: Itri
mesh_terms: D000818:Animals; D002417:Cattle; D005453:Fluorescence; D008823:Micelles; D009994:Osmolar Concentration; D010316:Particle Size; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D008823:Micelles; D012710:Serum Albumin, Bovine; D012967:Sodium Dodecyl Sulfate