We describe a novel method for forming macroscopically aligned lipid bilayers of various composition using anodic aluminum oxide (AAO) nanoporous membranes. It is shown that such nanotubular bilayers retain many properties of unsupported lipid bilayers that model biological membranes. Further, lipid nanotube arrays are suitable for aligning membrane proteins for biophysical studies including high resolution solid state NMR and EPR. Lipid nanotube arrays offer two principal advantages for such membrane proteins studies: 1) the structures retain high hydration level and macroscopic alignment under a broad range of pH and salt concentrations and 2) both leaflets of lipid nanotubes could be made accessible to small water soluble molecules. This opens new opportunities for structure-function protein studies using physically the same sample. Here we describe recent progress in reconstructing both small pore-forming peptides and large membrane protein complexes, such as bacterial reaction center (RC) protein from Rhodobacter sphaeroides, into substrate-supported lipid nanotubes. It is proposed that a large number of membrane proteins and their complexes could be incorporated into AAO-supported lipid nanotubes. The macroscopic lipid and protein alignment in such structures combined with solvent accessibility would assist structure-function studies with variety of spectroscopic techniques such as NMR, EPR, and optical spectroscopy without protein crystallization.
Professor Vladimir Ladizhansky