Papers by Keyword: Lipid Bilayer

Abstract: Lipids and proteins can influence each other in so many different ways. Lipids may affect the structure of membrane proteins by influencing their backbone conformation, the tilt, rotation angles of their transmembrane (TM) segments, and the orientation of their side chains. The membrane-spanning parts in integral membrane proteins are predominantly hydrophobic, and most often helical. At the lipid-protein interface, the TM part of the protein and the hydrocarbon chains of the lipid molecules have to coexist to maintain the integrity of the membrane. Lipids are important components of lipid membrane are used in various experiments reported in this thesis and can act as model lipid bilayers. Once they support on solid substrate like silicon wafers, their structural properties can investigate by X-ray and neutron reflectivity and by other useful techniques. Reflectivity technique can provide detailed information such as their thickness and interaction between lipids and peptides. The thesis reports a detailed investigation of these lipids and peptides by X-ray and neutron reflection techniques

Abstract: Bacterial photosynthetic antenna complexes are composed of α-helical hydrophobic polypeptides and pigments (e.g., bacteriochlorophyll a). We report here self-assembling properties of an engineered hydrophobic polypeptide with zinc-substituted bacteriochlorophyll a ([Zn]-BChl a) in various lipid bilayer to investigate the effect of lipid species on the self-assembling properties. When the polypeptide and [Zn]-BChl a were mixed in surfactant solution (n-octyl β-D-glucopyranoside: OG) at 25°C, the absorption band [Zn]-BChl a was red-shifted from 770 to 812 nm, that is assignable to quasi-dimeric “subunit-type” complex. By subsequent dilution and cooling of the solution, the absorption band further red-shifted to 836 nm indicative for progressed assembly, ‘LH1-type’ complex. When the subunit-type complex was assembled in lipid bilayer, e.g., phosphatidylcholines (PC’s) and phosphatidylglycerol (PG’s), the assembling property to form LH1-type complex prominently depended on the character of their fatty acid chains in the phospholipids. The subunit complex remained in the fluidic bilayers, but further assembled to form LH1-type complex in solid-like phospholipid bilayers, suggesting that intermolecular force of phospholipid governs the assembling of the polypeptide/[Zn]-BChl a complex.