Influence of Mn(III)porphyrins with different polarities on dimyristoylphosphatidic acid monolayers

The behavior of three Mn(III)porphyrins with different polarities at air/water interfaces and their interaction with the phospholipid dimyristoylphosphatidic acid (DMPA) were studied through surface potential and pressure–area isotherms. Multilayer films of Mn(III)porphyrin have been formed at air/liquid interfaces. Some DMPA–Mn(III)porphyrin mixed monolayers have provided a second transition of phases around 20 mN/m absent in pure DMPA monolayers. This transition has been explained on basis of the re-arrangement of DMPA molecules within free spaces existent among Mn(III)porphyrin molecules and also by the interaction of metallic center of the complex with the negatively charged phosphate groups of DMPA. Changes on the geometry of Mn(III)porphyrin has been considered as an important factor that drives DMPA reorganization at air/water interfaces.