The effect of the presence of Sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) on the interactions between Sodium dodecyl sulfate (SDS) and protein papain

Abstract

Interactions between mixed anionic surfactants: Sodium dodecyl sulfate (SDS) and Sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) and papain were investigated over the entire mole fraction range of SDS i.e. αSDS. The UV–visible and fluorescence behavior revealed the binding of papain to mixed surfactants at lower concentrations and increase in hydrophobic interactions with decrease in αSDS. The critical aggregation concentration (cac) values estimated from conductivity were found to decrease with decrease in αSDS indicating a decrease in binding affinity of anionic surfactants to polypeptide chain. The critical micellization concentration (cmc) of mixed micelles increased linearly with papain concentration. From Clint equation, it was evaluated that mixed micelles behave nonideally in pure water as well as at different concentrations of papain. The Kraft temperature (TK) of the studied systems was also observed. Ultrasonic velocity and density measurements at varying αSDS were also carried out.