The peculiar thermo-structural behavior of the anionic lipid DMPG

• Published in: Chemistry and physics of lipids 2003, Vol.122 (1), p.19-32
• Main Authors: Lamy-Freund, M.Teresa, Riske, Karin A
• Format: Article
• Language: English
• Subjects: Calorimetry, Differential Scanning; Dimyristoylphosphatidylcholine - chemistry; DMPG; DSC; Electron Spin Resonance Spectroscopy; ESR; Fluorescence; Gel–fluid transition; Light and X-ray scattering; Molecular Structure; Osmolar Concentration; Temperature
• ISSN: 0009-3084; 1873-2941
• DOI: 10.1016/S0009-3084(02)00175-5

Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 °C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel–fluid transition region, ranging from 18 to 35 °C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel–fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.