Miscibility Phase Behavior Of GUV Membranes Containing Ternary Mixtures Of PS Lipids, PC Lipids, And Cholesterol

Abstract

Vesicles containing ternary mixtures of phospholipids and cholesterol produce coexisting liquid phases over a range of compositions and temperatures. To date, most studies of membrane phase behavior have used uncharged lipids, which readily produce giant unilamellar vesicles through electroformation. My goal is to study the phase behavior of membranes containing charged lipids such as phosphatidylserine, which is found in the inner leaflet of cell plasma membranes. I present experimental protocols to prepare giant unilamellar vesicles containing ternary mixtures of phosphatidylserine (PS) lipids, phosphatidylcholine (PC) lipids, and cholesterol, based on earlier protocols by Akashi et al [1], Rodriguez et al [2], and Claessens et al [3]. I also detail the phase behavior of membranes of several compositions that incorporate PS lipids. [1] Akashi et al., “Formation of Giant Liposomes Promoted by Divalent Cations: Critical Role of Electrostatic Repulsion.” 74 (1998) 2973-2982. [2] Rodriguez et al., “Giant vesicles formed by gentle hydration and electroformation: A comparison by fluorescence microscopy.” Colloids and Surfaces B: Biointerfaces 42 (2005) 125-130. [3] Claessens et al., “Charged Lipid Vesicles: Effects of Salts on Bending Rigidity, Stability, and Size.” Biophysical Journal 87(6) (2004) 3882-3893.