Formation of Supported Lipid Bilayer Membranes on SiO2 from Proteoliposomes Containing Transmembrane Proteins

We report the preparation of protein-containing supported phospholipid bilayers (SPBs) on silica (SiO2). The bilayers are formed from small proteoliposomes, which convert to an SPB when the liposomes adsorb on the surface. The kinetics of this conversion process was followed in real time, using the quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR) techniques. The proteoliposomes were prepared by reconstitution of two different proteins into small unilamellar liposomes (diameter ∼ 26 nm), creating proteoliposomes with diameters ranging from ca. 50 to 85 nm, depending on protein concentration. The two proteins were proton translocating nicotinamide nucleotide transhydrogenase (TH) from Escherichia coli and gramicidin A (GrA) from Bacillus brevis. The SPB formation process was measured and compared for different protein situations in the liposomes:  (i) with the intact TH in the proteoliposomes, (ii) after removal of the water-exposed, hydrophilic domains of ...