Charge-induced pretransition in phosphatidylethanolamine multilayers. The occurrence of ripple structures.
The influence of pH and ionic strength on the phase transition behavior of 1,2-dihexadecylphosphatidylethanolamine was studied calorimetrically. In the range of ionic strength from 0.75 to 1.5 M NaCl at pH larger than 13, where the amino group of the phosphatidylethanolamine is in the deprotonated state, resulting in one negative charge per lipid molecule, the calorimetric scan shows a pretransition before the main transition. Accompanying freeze-fracture electron microscopic studies on these preparations in the temperature range between the pre- and main transitions show a regular suface, the so-called ripple structure. These are comparable with the structures seen in phosphatidylcholine-water systems at temperatures between the pre- and main transition.
D002151:Calorimetry; D005614:Freeze Fracturing; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D008968:Molecular Conformation; D009994:Osmolar Concentration; D010714:Phosphatidylethanolamines; D013816:Thermodynamics
D008567:Membranes, Artificial; D010714:Phosphatidylethanolamines