STABILIZATION OF INTEGRAL MEMBRANE-PROTEINS IN AQUEOUS-SOLUTION USINGFLUORINATED SURFACTANTS

Surfactants carrying either a hydrocarbon or a fluorocarbon alkyl chai n have been synthesized. The polar head was either tris(hydroxymethyl) acrylamidomethane (THAM), telomerized THAM, or a glycosylated THAM moi ety. The aqueous solubility of some of these molecules was increased b y oxidizing to a sulfoxide the thioether function that associates thei r hydrophobic and hydrophilic moieties. In all cases, the critical mic ellar concentration was principally determined by the length and chemi cal nature of the alkyl chain. The usefulness of these surfactants in handling integral membrane proteins in solution has been examined usin g as test materials chloroplast thylakoid membranes and the photosynth etic complex cytochrome b(6)f. In keeping with earlier observations in other systems, none of the fluorinated surfactants was able to solubi lize thylakoid membranes. Transfer to a solution of fluorinated surfac tant of b(6)f complexes that had been solubilized and purified in the presence of a classical detergent usually resulted in aggregation and precipitation of the protein, while most homologous molecules with hyd rocarbon chains did keep the b(6)f complex soluble. Two of the fluorin ated surfactants, however, proved able to maintain the b(6)f complex w ater-soluble, intact, and enzymatically active. Because of their limit ed affinity for lipid alkyl chains and other hydrocarbon surfaces,fluo rinated surfactants appear as potentially interesting tools for the st udy of membrane proteins that do not stand well exposure to classical detergents ((C) Societe francaise de biochimie et biologie moleculaire / Elsevier, Paris).