Native E. coli inner membrane incorporation in solid-supported lipid bilayer membranes

Solid-supported bilayer lipid membranes (SBLMs) containing membrane protein have been generated through a simple lipid dilution technique. SBLM formation from mixtures of native Escherichia coli bacterial inner membrane (IM) vesicles diluted with egg phosphatidylcholine (egg PC) vesicles has been explored with dissipation enhanced quartz crystal microbalance (QCM-D), atomic force microscopy (AFM), attenuated total internal-reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and fluorescence recovery after photobleaching (FRAP). QCM-D studies reveal that SBLM formation from vesicle mixtures ranging between 0% and 100% IM can be divided into two regimes. Samples with ≤40% IM form SBLMs, while samples of greater IM fractions are dominated by vesicle adsorption. FRAP experiments showed that the bilayers formed from mixed vesicles with ≤40% IM were fluid, and comprised a mixture of both egg PC and IM. ATR-FTIR measurements on SBLMs membranes formed with 30% IM confirm that protein is present. SBLM formation was also explored as a function of temperature by QCM-D and FRAP. For samples of 30% IM, QCM-D data show a decreased mass and viscoelasticity at elevated temperatures, and an increased fluidity is observed by FRAP measurements. These results suggest improved biomimetic characteristics can be obtained by forming and maintaining the system at, or close to, 37 °C.