Micellar and biochemical properties of a propyl-ended fluorinated surfactant designed for membrane-protein study

Our goal is to design optimised fluorinated surfactants for handling membrane proteins in solution. We report herein the self-assembling and biochemical properties of a new hemifluorinated surfactant (H3F6H3DigluM) with a branched diglucosylated polar head group and an apolar tail consisting of a perfluorohexane core decorated with a hydrogenated propyl tip. For the sake of comparison, its fluorinated analogue without propyl tip (F6H3DigluM) was also studied. Isothermal titration calorimetry and surface tension showed that the addition of a propyl tip has a significant effect on the overall hydrophobicity of the surfactant, in contrast to the behaviour described when adding an ethyl tip to a fluorinated surfactant. From dynamic light scattering, analytical ultracentrifugation and small-angle X-ray scattering, both H3F6H3DigluM and F6H3DigluM self-assemble into small globular micelles of 5-7 nm in diameter and have aggregation numbers of 62±8 and 46±2, respectively. Finally, H3F6H3DigluM was found to be the best fluorinated surfactant developed in our group to stabilise the model membrane protein bacteriorhodopsin (bR) in aqueous solution. This study demonstrates the suitability of this new propyl-ended fluorinated surfactant for biochemical and structural applications and confirms the superiority of hemifluorinated chains over fluorinated ones.