The binding profiles of sodium dodecyl sulfate to domain sized fragments of bovine serum albumin

Abstract

The binding of sodium dodecyl sulfate (SDS) to the three fragments of bovine serum albumin, corresponding to sequences 1–306, 193–368, and 383–511 in the parent protein, was studied in a phosphate buffer of ionic strength 0.014 using gel chromatography. The cooperative binding of SDS to each fragment proceeded stepwise in a manner similar to the binding to the intact protein. The saturated quantities of the SDS binding were approximately 100, 65, and 50 mol/mol for 1–306, 193–368, and 383–511, respectively. The Scatchard equation was applied to the binding isotherms at low concentrations of SDS. The intrinsic binding constants of SDS to the fragments were 2–5 × 10 3 M −1 at 25°C. The numbers of stoichiometric binding sites were 9, 4, and 3 for 1–306, 193–368, and 383–511, respectively, indicating the appearance of new binding sites through the fragmentation.