title: Effect of ions on the organization of phosphatidylcholine/phosphatidic acid bilayers.
abstract: Lipid bilayers are two-dimensional fluids. Here, the effect of monovalent ion concentration on the mixing, and consequently the organization, of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dioleoyl-sn-glycero-3-phosphate (DOPA) bilayers has been examined. Epifluorescence microscopy was used to visualize the organization. Fluorescence recovery after photobleaching and attenuated total reflection-Fourier transform infrared spectroscopy were used to assess the fluidity of the lipids. At high ionic strength the DOPC and DOPA lipids appear uniformly mixed. Upon lowering the ionic strength, rapid separation is observed. The DOPA-rich regions appear fractal-like and exhibit hysteresis in their properties. The lipids freely exchange between the two regions. These experiments clearly demonstrate the significant effect that electrostatics can have on membrane organization.
authors.affiliation: Department of Chemistry and Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Lee R
authors.initials: LR
authors.lastname: Cambrea
authors.forename: Farzin
authors.initials: F
authors.lastname: Haque
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Schieler
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Rochet
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Hovis
mesh_terms: D004295:Dihydroxyphenylalanine / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D007477:Ions; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D008856:Microscopy, Fluorescence; D010712:Phosphatidic Acids / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013997:Time Factors; D051844:alpha-Synuclein / Q000737:chemistry
chemical_list: D007477:Ions; D008051:Lipid Bilayers; D008055:Lipids; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D051844:alpha-Synuclein; D004295:Dihydroxyphenylalanine; C017251:1,2-oleoylphosphatidylcholine