title: Supramolecular organization of lysophosphatidylcholine-packaged Gramicidin A.
abstract: Heat derived gramicidin A'/L-alpha-lysophosphatidylcholine complexes were separated on a sucrose gradient to form two fractions: Fraction A which had an approximately constant Gramicidin A' to phospholipid ratio of 8 to 10 lipid molecules per Gramicidin A' molecule and Fraction B which had a larger but variable ratio. Fluorescence and circular dichroism studies confirmed Fraction A to be a lipid-incorporated channel state. Electron microscopic studies, using uranyl acetate negative staining, showed fraction A to be a membranous state with the formation of bilayer vesicles, that is, the interaction of peptide and phospholipid micelles causes the lipid to reorganize into a bilayer structure. Freeze-fracture replicas of the channel incorporated state demonstrated the presence of a supramolecular organization of particles exhibiting a tendency to form rows with a 50-60 A periodicity along the row and with 70-80 A distance between rows. An idealized working model for the incorporated state is presented.
mesh_terms: D001692:Biological Transport; D002942:Circular Dichroism; D006096:Gramicidin; D008081:Liposomes; D008244:Lysophosphatidylcholines; D008854:Microscopy, Electron; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008081:Liposomes; D008244:Lysophosphatidylcholines; D006096:Gramicidin