Refolding of protein unfolded by gemini surfactants using β-cyclodextrin and sodium dodecyl sulfate in aqueous medium: Study on role of spacer chain of surfactants

Abstract

Interactions between protein, BSA and gemini surfactants, 12-n-12 (n = 3, 6, 8, 12) and step-by-step refolding of protein present as protein-gemini surfactant complex using β-cyclodextrin (β-CD)/sodium dodecyl sulfate (SDS) as stripping agents have been demonstrated by means of UV absorption, steady-state and time-resolved intrinsic fluorescence of BSA, circular dichroism spectroscopy, dynamic light scattering and field emitting scanning electron microscopy. This method is in contrast with the refolding of protein via artificial chaperone protocol. Mechanisms of interactions between protein-gemini complex and β-CD/SDS have been described. Role of spacer chain of gemini surfactants on the refolding of BSA unfolded by the surfactants has been explained. It has been observed that initially a gemini surfactant molecule with a long flexible spacer chain can more easily be stripped off by β-CD molecules forming simple inclusion complexes or nanotubes/rods depending on the concentration of β-CD. After the protein-micelles aggregates are dissociated, refolding of protein occurs more easily in case of gemini surfactant molecules with a short spacer chain. Method of β-CD induced refolding of a denatured protein has been validated by demonstrating refolding process in case of another protein, lysozyme. Unfolded proteins are also get refolded by SDS through the formation of catanions (mixed micelles, vesicles etc.).