Evaluation of Denaturation Property of Surfactants onto Protein as Measured by Circular Dichroism

Abstract

The well known property of surfactants to denature proteins was systematically reexamined to elucidate the molecular aspects of denaturation associated with the chemical structure of surfactants. Bovine Serum Albumin (abbreviated as BSA) was used for specimen. The degree of denaturation of protein was estimated as the change of molar ellipticity of BSA as obtained from CD spectra at 220nm in 50mM sodium phosphate buffer at pH 7.0. The denaturation power of the commercially available surfactants were found to be in the order
LAS>SDS>DTMAC>AOS>AES>>Noionics≅Ampholytic
The ampholytic and nonionic surfactants hardly denatured BSA compared with those ionic surfactants. The effect of intramolecular electrical shielding is expected for ampholytic surfactant. The longer the oxyethylene chain of AES was, the less the BSA denaturation was. The AES with more than 6 oxyethylene chains does not cause any change in the CD spectrum of BSA. A remarkable effects was observed in inhibiting denaturation of BSA caused by anionic surfactants with the addition of cationic surfactant or amine oxide.