Conformational Changes of Bovine Serum Albumin in an Aqueous Solution of Sodium Bis(2-ethylhexyl) Sulfosuccinate and in the Reverse Micelle of the Same Surfactant
✍ Scribed by Kunio Takeda; Kazumasa Harada; Kouji Yamaguchi; Yoshiko Moriyama
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 284 KB
- Volume
- 164
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
The helicity of bovine serum albumin (BSA) decreased both in the reverse micelle of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and in the aqueous solution of the same surfactant (the saturated binding amount to the protein was (70 \mathrm{~mol} / \mathrm{mol}) ). In both cases, the final helicity was approximately identical to that attained in the aqueous solution of sodium dodecyl sulfate. The fluorescence lifetime of (N)-iodoacetyl- (N^{\prime})-(5-sulfo-1-naphthyl) ethylenediamine bound to BSA shortened upon incorporation into the reverse micelle. Although the helicity remained unchanged regardless of the change in water content (\left(R_{w}\right)) in the reverse micelle, the lifetime further shortened with an increase in (R_{w}) and then flattened out beyond (R_{w} 22). A similar shortening of the lifetime was observed in the aqueous (\Lambda O T) solution. In the present study, it appeared likely that secondary structural changes of proteins in reverse micelles of ionic surfactants generally resemble those observed in aqueous solutions of the identically charged ionic surfactants. This is probably because an electrostatic interaction between the protein and the surfactant is of considerable importance to the protein structure. In the present system, the essentially same interaction of BSA with AOT might be expected to occur between the protein and the inner-charged double-layer of the reverse micelle, as occurs in the aqueous solution. However, the interaction was not very dependent on (\boldsymbol{R}_{w}) in the case of BSA. 1994 Academic Press, Inc.