title: Thermotropic and barotropic phase transitions on diacylphosphatidylethanolamine bilayer membranes.
abstract: The bilayer phase transitions of four diacylphosphatidylethanolamines (PEs) with matched saturated acyl chains (Cn=12, 14, 16 and 18) and two PEs with matched unsaturated acyl chains containing a different kind of double bonds were observed by differential scanning calorimetry under atmospheric pressure and light-transmittance measurements under high pressure. The temperature-pressure phase diagrams for these PE bilayer membranes were constructed from the obtained phase-transition data. The saturated PE bilayer membranes underwent two different phase transitions related to the liquid crystalline (Lα) phase, the transition from the hydrated crystalline (Lc) phase and the chain melting (gel (Lβ) to Lα) transition, depending on the thermal history. Pressure altered the gel-phase stability of the bilayer membranes of PEs with longer chains at a low pressure. Comparing the thermodynamic quantities of the saturated PE bilayer membranes with those of diacylphosphatidylcholine (PC) bilayer membranes, the PE bilayer membranes showed higher phase-transition temperatures and formed more stable Lcphase, which originates from the strong interaction between polar head groups of PE molecules. On the other hand, the unsaturated PE bilayer membranes underwent the transition from the Lαphase to the inverted hexagonal (HII) phase at a high temperature and this transition showed a small transition enthalpy but high pressure-responsivity. It turned out that the kind of double bonds markedly affects both bilayer-bilayer and bilayer-nonbilayer transitions and the Lα/HIItransition is a volume driven transition for the reconstruction of molecular packing. Further, the phase-transition behavior was explained by chemical potential curves of bilayer phases.
authors.affiliation: Graduate School of Bioscience and Bioindustry, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8513, Japan. Electronic address: matsuki@tokushima-u.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Matsuki
authors.affiliation: Department of Biological Science and Technology, Faculty of Engineering, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Endo
authors.affiliation: Department of Biological Science and Technology, Faculty of Engineering, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Sueyoshi
authors.affiliation: Graduate School of Bioscience and Bioindustry, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8513, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Goto
authors.affiliation: Graduate School of Bioscience and Bioindustry, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8513, Japan.
authors.forename: Nobutake
authors.initials: N
authors.lastname: Tamai
authors.affiliation: Department of Biological Science and Technology, Faculty of Engineering, Tokushima University, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Kaneshina
mesh_terms: D002152:Calorimetry, Differential Scanning; D008051:Lipid Bilayers / Q000737:chemistry*; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D010714:Phosphatidylethanolamines; C483858:phosphatidylethanolamine
keywords: Differential scanning calorimetry; Lipid bilayer membrane; Phase stability; Phase transition; Phosphatidylethanolamine; Pressure