Enhanced selectivity in aqueous micellar two-phases distribution for extraction of hydrophobic membrane proteins

水溶性聚合物，如聚乙二醇（PEG）或二乙胺乙基右旋糖酐（DEAE-Dx），可以诱导辛基- β - d -硫代葡萄糖苷（OTG）的胶束水溶液在0℃下相分离。这样形成的一种相是水溶性聚合物的无表面活性剂水溶液（水相），另一种是浓缩的OTG溶液（表面活性剂相）。OTG与PEG结合后，细胞色素P450 （P450）和细胞色素b_5 （b_5）被很好地提取到表面活性剂相中，没有发生明显的变性。P450的提取率略高于b_5。与PEG和Dx相比，DEAE-Dx使b_5的提取量明显减少，而P450的提取量基本保持不变。DEAE-Dx具有诱导相分离和减少b_5进入表面活性剂相的双重功能，从而实现P450与b_5的高选择性分离。这些结果将为在生理上可接受的温和条件下分离P450和b_5提供一条更快、更有效的途径，以防止这两种膜蛋白变性。

A water-soluble polymer such as polyethylene glycol (PEG) or diethylaminoethyl-Dextran (DEAE-Dx) could induce aqueous micellar solutions of octyl-beta-D-thioglucoside (OTG) to phase separate at 0 ﾟC.One of the phases thus formed wasa surfactant-depleted aqueous solution (aqueous phase) of a water-soluble polymer and the other a concentrated OTG solution (surfactant phase). In combination of OTG with PEG,cytochrome P450 (P450) and cytochrome b_5 (b_5) were well extracted into the surfactant phase without significant denaturation. The extraction yield of P450 was slightly higher than that of b_5. In contrast to PEG and Dx, DEAE-Dx yields a marked decrease in the extraction of b_5, while that of P450 remained almost unchanged. DEAE-Dx could serve the dual functions of inducing the phase separation and of reducing theentry of b_5 into the surfactant phase, thus resulting in the highly selective separation of P450 and b_5. These results would provide a faster and more effective route for isolation of P450 and b_5 under mild condition taht would be physioligically acceptableso as to prevent denaturation of the two membrane proteins.