title: Critical pressures in multicomponent lipid monolayers.
abstract: Epifluorescence microscopy has been used previously to study coexisting liquid phases in lipid monolayers of dihydrocholesterol and dimyristoylphosphatidylcholine at the air/water interface. This binary mixture has a critical point at room temperature (22 degrees C), a monolayer pressure of approx. 10 mN/m, and a composition in the vicinity of 20-30 mol% dihydrocholesterol. It is reported here that this critical pressure can be lowered, raised, or maintained constant by systematically replacing molecules of this phosphatidylcholine with molecules of a phosphatidylethanolamine, or an unsaturated phosphatidylcholine, or mixtures of the two, while maintaining the dihydrocholesterol concentration at 20 mol%. Thus, even complex mixtures of lipids may be characterized by a single, well-defined second-order phase transition. In principle, such transitions might be found in biological membranes.
authors.affiliation: Stauffer Laboratory of Physical Chemistry, Department of Chemistry, Stanford University CA 94305-5080, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Hagen
authors.forename: H M
authors.initials: HM
authors.lastname: McConnell
mesh_terms: D004083:Cholestanol / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D008956:Models, Chemical; D010743:Phospholipids / Q000737:chemistry*
chemical_list: D010743:Phospholipids; D004083:Cholestanol