title: Direct visualization of asymmetric behavior in supported lipid bilayers at the gel-fluid phase transition.
abstract: We utilize in situ, temperature-dependent atomic force microscopy to examine the gel-fluid phase transition behavior in supported phospholipid bilayers constructed from 1,2-dimyristoyl-sn-glycero-3-phosphocholine, 1,2-dipentadecanoyl-sn-glycero-3-phosphocholine, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. The primary gel-fluid phase transition at T(m) occurs through development of anisotropic cracks in the gel phase, which develop into the fluid phase. At approximately 5 degrees C above T(m), atomic force microscopy studies reveal the presence of a secondary phase transition in all three bilayers studied. The secondary phase transition occurs as a consequence of decoupling between the two leaflets of the bilayer due to enhanced stabilization of the lower leaflet with either the support or the water entrained between the support and the bilayer. Addition of the transmembrane protein gramicidin A or construction of a highly defected gel phase results in elimination of this decoupling and removal of the secondary phase transition.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Z Vivian
authors.initials: ZV
authors.lastname: Feng
authors.forename: Tighe A
authors.initials: TA
authors.lastname: Spurlin
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Gewirth
mesh_terms: D005782:Gels / Q000032:analysis / Q000737:chemistry; D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry*; D046911:Macromolecular Substances / Q000032:analysis / Q000737:chemistry; D008560:Membrane Fluidity; D018625:Microscopy, Atomic Force / Q000379:methods*; D008968:Molecular Conformation; D044367:Phase Transition; D010743:Phospholipids / Q000032:analysis* / Q000737:chemistry*; D013696:Temperature
chemical_list: D005782:Gels; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D010743:Phospholipids