Miscibility of binary phospholipid mixtures under hydrated and non-hydrated conditions. III. Reinvestigation of phosphatidic acids with different acyl chain length

✍ Scribed by Tohru Inoue; Yoshinori Nibu

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 640 KB
• Volume: 76
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(95)02441-k

✦ Synopsis

Our previous study on the miscibility property of phosphatidic acids with different acyl chain length under hydrated and non-hydrated conditions Chem. Phys. Lipids 63, 203-212) was reinvestigated using an improved procedure to prepare the lipid samples for differential scanning calorimetric (DSC) measurements. The phospholipid species examined were dimyristoyl-, dipalmitoyl-, and distearoylphosphatidic acids (DMPA, DPPA and DSPA, respectively). Phase diagrams of binary mixtures among these phospholipids were constructed based on the DSC thermograms. The phase diagrams obtained for hydrated mixtures revealed that DMPA and DPPA are mutually miscible in both liquid-crystalline and gel bilayers, whereas DMPA and DSPA exhibit a partial phase separation in the gel phase although they are miscible in the liquid-crystalline bilayer. These mixing behaviors are quite different from those reported in the previous paper, where the occurrence of partial and complete demixing was concluded in liquid-crystalline and gel bilayers, respectively. A thermodynamic model was applied to analyze the phase diagrams obtained in the present reinvestigation for hydrated PA mixtures, and discussed on the basis of the non-ideality parameter of mixing derived by this approach.