Increasing protein stability by association with zwitterionic amphiphile cocamidopropyl betaine

Abstract

Stability of therapeutic proteins is one of the most important obstacles in their development. We studied the effects of the zwitterionic amphiphile cocamidopropyl betaine (CAPB) on protein stability against elevated temperatures and shear. Bovine serum albumin (BSA) was selected as a model protein to study the interaction with CAPB. Techniques such as gel electrophoresis, fluorimetry, and surface tensiometry were utilized to study protein aggregation and protein/CAPB complex formation. Our results indicate that CAPB effectively decreased the concentration of BSA at the air/water interface and subsequently prevented aggregation of the protein at the interface. Furthermore, complexes formed by the association of BSA and CAPB were more stable against both temperature and shear. The increased stability was achieved without loss of enzymatic activity of the protein. The effects of zwitterionic CAPB on protein enzymatic activity and conformational (tertiary structure) stability were also compared with polysorbate 20 and sodium dodecyl sulfate.