界面活性剤の逆ミセル中におけるタンパク質の構造: 逆ミセルに可溶化した水（water poor）の異常性

Abstract

The secondary structural change and the tertiary structural change of bovine serum albumin (BSA) in the reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) have been examined mainly by the measurements of circular dichroism, time-resolved fluorescence, tryptophan fluorescence, and dynamic light scattering. The diameter of the reverse micelle increases with an increase of water content (W(0)=[H2O]/[AOT]). The diameter of the reverse micelle, containing BSA, is larger than the empty reverse micelle at each W(0). Upon the incorporation of BSA into the reverse micelles, the helical structures are disrupted, the fluorescence lifetime of N-iodoacetyl-N'-(5-sulfo-l-naphthyl) ethylenediamine bound to Cys34 shortens, and the maximal wavelength of tryptophan fluorescence shifts from 340 to 330 nm. These changes substantially agree with those observed in the aqueous AOT solution, indicating that the interaction between the hydrophilic groups of AOT and the oppositely charged amino acid residues of BSA plays an important role in the reverse micelle as well as the abnormality of water.