Macroscopic and Nanoscopic Heterogeneous Structures in a Three-Component Lipid Bilayer Mixtures Determined by Atomic Force Microscopy.
Much of lipid raft properties can be inferred from phase behavior of multicomponent lipid membranes. We use liquid compatible atomic force microscopy (AFM) to study a three-component system composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), egg sphingomyelin (eSM), and cholesterol. Specifically, we obtain macroscopic and nanoscopic heterogeneous structures in a broad compositional space of DOPC/eSM/cholesterol (23 °C). In the macroscopic liquid coexisting region, we quantify area fraction of the coexisting phases and determine a set of thermodynamic tie-lines. When lipid compositions are near the critical point, we obtain fluctuation-like nanoscopic structures. We also use AFM height images to explore the hypothetical three-phase coexisting region. Finally, we use fluorescence microscopy to compare the phase behavior from our AFM measurements to that in free-floating giant unilamellar vesicles (GUVs). Our results highlight the role of lipid composition in mediating lipid domain formation and stability.
Department of Physics, University of South Florida , Tampa, Florida 33620, United States.
Nawal K
NK
Khadka
Department of Physics, University of South Florida , Tampa, Florida 33620, United States.
Chian Sing
CS
Ho
Department of Physics, University of South Florida , Tampa, Florida 33620, United States.
Jianjun
J
Pan
D002784:Cholesterol / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry; D018625:Microscopy, Atomic Force; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry*; D013109:Sphingomyelins / Q000737:chemistry*; D013816:Thermodynamics; D053835:Unilamellar Liposomes / Q000737:chemistry*
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D053835:Unilamellar Liposomes; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine