Fluorinated diglucose detergents for membrane-protein extraction.

ABSTRACT

Fluorinated surfactants have scarcely been explored for the direct extraction of proteins from membranes because fluorination is believed to abrogate detergency. However, we have recently shown that a commercially available fluorinated surfactant readily solubilizes lipid membranes, thereby suggesting that fluorination per se does not interfere with detergent activity. In this work, we developed new fluorinated surfactants that exhibit detergency in terms of both lipid-vesicle solubilization and membrane-protein extraction. The compounds made and tested contain two glucose moieties as polar headgroup, a hydrogenated thioether linker, and a perfluorinated alkyl tail with either 4, 6, or 8 carbon atoms. The physicochemical properties of the micelles formed by the three fluorinated surfactants were evaluated by NMR spectroscopy, surface tensiometry, isothermal titration calorimetry, dynamic light scattering, small-angle X-ray scattering, and analytical ultracentrifugation. At 25 °C, micellization was mainly entropy-driven, and the CMC values were found to decrease with chain length of the fluorinated tail, whereas the aggregation number increased with chain length. Remarkably, all three surfactants were found to solubilize lipid vesicles and extract a broad range of proteins from Escherichia coli membranes. These findings demonstrate, for the first time, that nonionic fluorinated surfactants could be further exploited for the direct extraction and solubilization of membrane proteins.