Thermotropic and barotropic phase transitions on diacylphosphatidylethanolamine bilayer membranes

• Published in: Biochimica et biophysica acta. Biomembranes Vol. 1859; no. 7; pp. 1222 - 1232
• Main Authors: Matsuki, Hitoshi, Endo, Shigeru, Sueyoshi, Ryosuke, Goto, Masaki, Tamai, Nobutake, Kaneshina, Shoji
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2017
• Subjects: Calorimetry, Differential Scanning; Differential scanning calorimetry; Lipid bilayer membrane; Lipid Bilayers - chemistry; Phase stability; Phase transition; Phosphatidylethanolamine; Phosphatidylethanolamines - chemistry; Pressure; Thermodynamics; Differential scanning calorimetry; Phosphatidylethanolamine; Phase stability; Lipid bilayer membrane; Pressure; Phase transition
• ISSN: 0005-2736; 1879-2642
• DOI: 10.1016/j.bbamem.2017.03.020

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 Lc phase, 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 Lα phase 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/HII transition 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. [Display omitted] •Bilayer phase transitions of six diacylphosphatidylethanolamines (PEs) were studied.•Temperature-pressure phase diagrams were constructed for these PE bilayer membranes.•Applying pressure changed the gel-phase stability of saturated PE bilayer membranes.•Thermodynamic quantities were compared to those of diacylphosphatidylcholines (PCs).•Thermotropic and barotropic bilayer transitions of PEs were systematically discussed.