title: The effect of changes in gramicidin conformation on bilayer lipid properties.
abstract: The effects of two different gramicidin conformations on lipid phase behaviour and dynamics are compared. Samples of chain-perdeuterated dimyristoylphosphatidylcholine containing gramicidin were first prepared with gramicidin in a state having a circular dichroism spectrum generally identified as corresponding to the non-channel conformation. The effects, on bilayer lipid properties, of gramicidin in this conformation were then determined using deuterium nuclear magnetic resonance measurements of acyl chain orientational order and transverse relaxation times as a function of temperature. These samples were then incubated at 65 degrees C to convert the gramicidin to a state with a circular dichroism spectrum of the type generally identified with the channel conformation. The nuclear magnetic resonance measurements were then repeated. In the gel phase, it was found that transverse relaxation time and chain orientational order of the lipid were insensitive to gramicidin conformation. In the liquid crystalline phase, gramicidin in the channel conformation was found to have a slightly larger effect on transverse relaxation and orientational order than gramicidin in the non-channel conformation. The perturbation of the phase behavior by gramicidin was found to be relatively insensitive to gramicidin conformation.
authors.affiliation: Department of Physics, Memorial University of Newfoundland, St. John's, Canada.
authors.forename: M R
authors.initials: MR
authors.lastname: Morrow
authors.forename: G A
authors.initials: GA
authors.lastname: Simatos
authors.forename: R
authors.initials: R
authors.lastname: Srinivasan
authors.forename: N
authors.initials: N
authors.lastname: Grandal
authors.forename: L
authors.initials: L
authors.lastname: Taylor
authors.forename: K M
authors.initials: KM
authors.lastname: Keough
mesh_terms: D002942:Circular Dichroism; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D006096:Gramicidin / Q000737:chemistry*; D007473:Ion Channels / Q000737:chemistry; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D013696:Temperature
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D006096:Gramicidin; D004134:Dimyristoylphosphatidylcholine