Development of Partially Fluorinated Phospholipids for Biochemical and Biophysical Studies of Membrane Proteins

Abstract

As possible materials for structural and functional characterization of membrane proteins in vitro, we have developed novel partially fluorinated phospholipids that are modified with the substitution of the terminal alkyl group in the myristoyl chains of dimyristoylphosphatidylcholine (DMPC) by the perfluoroalkyl (C_nF_2n+1 ) group at different lengths. Differential scanning calorimetric (DSC) measurements were performed for the novel partially fluorinated phospholipids Fn-DMPC (n=2,4,6,8). DSC curves of Fn-DMPC suspension demonstrated that Fn-DMPC suspension has significant Rf chain length-dependent gel-to-liquid crystalline phase transition temperature (Tm): Fn-DMPC with the short Rf groups (n=2,4,6) has lower Tm than unfluorinated DMPC, while Tm dramatically elevated to ~66°C upon elongation of the Rf group to n=8. We have also investigated structural and functional properties of a photoreceptor membrane protein bacteriorhodopsin (bR) incorporated into F4-DMPC liposome. As the result, bR in F4-DMPC liposome adopts native-like higher order structure and photocycle both in the gel and the liquid crystalline phase, which is in stark contrast with phase transition-induced structural changes for bR in DMPC liposome. These experimental results suggest that partially fluorinated phospholipid is promising for biochemical and biophysical studies of membrane proteins.