An alternative view of phospholipid phase behavior at the air-water interface. Microscope and film balance studies

摘要: Pure-lipid films at the water interface have surface-pressures vs. area isotherms that are often interpreted as involving first-order phase transitions from a condensed region to liquid-expanded region. Two phases presumed coexist in intermediate part of isotherm. We constructed film balance could be placed on stage an epifluorescence microscope. A dipalmitoyl phosphatidylcholine containing low concentration fluorescent lipid probe showed inhomogeneous fluorescence distribution so-called Only and regions prepared so optically homogeneous below 25 degrees C. investigated membrane flow lateral diffusion trough. The isochores were measured. results require, least, modified description monolayer structure various isotherms. solid-condensed corresponds gel lipids where there is no membrane, low, compressibility homogeneous. "liquid-condensed/liquid-expanded" appears both rapid. This high compressibility. "liquid-expanded" not seen under microscope, surface layer can very fast.