Synthesis of nickel-chelating fluorinated lipids for protein monolayer crystallizations

Nickel-chelating lipids have been synthesized for use as functionalized templates for 2-D crystallization of membrane proteins. These monolayer-forming lipids have been designed with three distinct components: (i) a branched hydrocarbon tail to confer fluidity of the monolayer, (ii) a perfluorinated central core for detergent resistance, and (iii) a nickel-chelating hydrophilic headgroup to facilitate binding of recombinant, polyhistidine-tagged fusion proteins. Alkylations of fluorinated alcohols used in these syntheses proceed in good yields only with the application of prolonged sonication and, in some cases, in the presence of phase-transfer catalysts. Formation of 2-D crystals of the His-tagged membrane protein BmrA from Bacillus subtilis is reported.