Glucose-Based Fluorinated Surfactants As Additives for the Crystallization of Membrane Proteins: Synthesis and Preliminary Physical-Chemical and Biochemical Characterization

We report herein the synthesis of a series of fluorinated surfactants with a glucose moiety as a polar head group and whose alkyl chain was varied in length and in fluorine/hydrogen ratio. They were synthesized in two or four steps in 20 to 50% overall yields allowing gram-scale synthesis. Their solubility in water is between 0.2 and 13.8 g/L, which indicates low water solubility. Two derivatives of the series were found to form micelles in water at ∼11 mM. Their hydrophilic-lipophilic balance was determined both by Griffin's and Davies' methods; they may exhibit a "harsh" character toward membrane proteins. This, combined with their low water solubility, suggest that they could advantageously be used in detergent mixtures containing a "mild" detergent. Finally, the potency of one of the derivatives, FH-β-Glu, to act as an additive for the crystallization of AcrB was evaluated in detergent mixtures with -dodecyl-β-d-maltopyranoside (DDM). Among the six crystallization conditions investigated, adding FH-β-Glu improved the crystallization for three of them, as compared to control drops without additives. Moreover, preliminary tests with other compounds of the series showed that none of them hampered crystallization and suggested improvement for three of them. These novel glucose-based fluorinated detergents should be regarded as potential additives that could be included in screening kits used in crystallization.