title: Liquid crystalline/gel state phase separation in docosahexaenoic acid-containing bilayers and monolayers.
abstract: The phase behavior of lipid mixtures containing 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (18:0, 22:6 PC) with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was studied with bilayers using differential scanning calorimetry (DSC), and with monolayers monitoring pressure/area isotherms and surface elasticity, and lipid domain formation followed by epifluorescence microscopy. From DSC studies it is concluded that DPPC/18:0, 22:6 PC phase separates into DPPC-rich and 18:0, 22:6 PC-rich phases. In monolayers, phase separation is indicated by changes in pressure-area isotherms implying phase separation where 18:0, 22:6 PC is 'squeezed out' of the remaining DPPC monolayer. Phase separation into lipid domains in the mixed PC monolayer is quantified by epifluorescence microscopy using the fluorescently labeled phospholipid membrane probe, 1, 2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl). These results further describe the ability of docosahexaenoic acid to participate in lipid phase separations in membranes.
authors.affiliation: Department of Biology, Indiana University-Purdue University at Indianapolis, 723 W. Michigan Street, Indianapolis, IN 46202-5132, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Dumaual
authors.forename: L J
authors.initials: LJ
authors.lastname: Jenski
authors.forename: W
authors.initials: W
authors.lastname: Stillwell
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D005456:Fluorescent Dyes; D005782:Gels; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D010713:Phosphatidylcholines / Q000737:chemistry*; D010714:Phosphatidylethanolamines / Q000737:chemistry; D011312:Pressure; D012235:Rhodamines / Q000737:chemistry
chemical_list: C409542:1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine; D005456:Fluorescent Dyes; D005782:Gels; D008051:Lipid Bilayers; D008081:Liposomes; C053685:N-(lissamine rhodamine B sulfonyl)-1,2-dioleoylphosphatidylethanolamine; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D012235:Rhodamines; D015060:1,2-Dipalmitoylphosphatidylcholine