Protein—surfactant interactions. Spin label study of interactions between bovine serum albumin (BSA) and sodium dodecyl sulphate (SDS)

Abstract

Measurements have been made of changes in the mobility of spin-labelled stearic acid molecules bound at the high affinity sites of BSA as increasing numbers of SDS molecules become bound. Evidence is obtained for an increase in mobility with increasing SDS binding numbers (n) until n > 180 when all the stearic acid molecules are displaced from the protein. The results are explained in terms of (i) destruction of the high affinity binding sites when more than 10 SDS molecules become bound, and (ii) association of SDS molecules on the protein. On succinylation of BSA there is an increase in protein chain mobility resulting from unfolding of the protein molecule and this similarly leads to loss of the high affinity sites.