title: Dynamics of Crowding-Induced Mixing in Phase Separated Lipid Bilayers.
abstract: We use fluorescence microscopy to examine the dynamics of the crowding-induced mixing transition of liquid ordered (Lo)-liquid disordered (Ld) phase separated lipid bilayers when the following particles of increasing size bind to either the Loor Ldphase: Ubiquitin, green fluorescent protein (GFP), and nanolipoprotein particles (NLPs) of two diameters. These proteinaceous particles contained histidine-tags, which were phase targeted by binding to iminodiacetic acid (IDA) head groups, via a Cu2+chelating mechanism, of lipids that specifically partition into either the Lophase or Ldphase. The degree of steric pressure was controlled by varying the size of the bound particle (10-240 kDa) and the amount of binding sites present (i.e., DPIDA concentrations of 9 and 12 mol%) in the supported lipid multibilayer platform used here. We develop a mass transfer-based diffusional model to analyze the observed Lophase domain dissolution that, along with visual observations and activation energy calculations, provides insight into the sequence of events in crowding-induced mixing. Our results suggest that the degree of steric pressure and target phase influence not only the efficacy of steric-pressure induced mixing, but the rate and controlling mechanism for which it occurs.
authors.affiliation: Department of Chemical Engineering, University of California Davis , Davis, California 95616, United States.
authors.forename: Wade F
authors.initials: WF
authors.lastname: Zeno
authors.affiliation: Department of Chemical Engineering, University of California Davis , Davis, California 95616, United States.
authors.forename: Tristan J
authors.initials: TJ
authors.lastname: Johnson
authors.affiliation: Sandia National Laboratories , P.O. Box 969, Livermore, California 94551, United States.
authors.forename: Darryl Y
authors.initials: DY
authors.lastname: Sasaki
authors.affiliation: Department of Materials Science and Engineering, University of California Davis , Davis, California 95616, United States.
authors.forename: Subhash H
authors.initials: SH
authors.lastname: Risbud
authors.affiliation: Department of Chemical Engineering, University of California Davis , Davis, California 95616, United States.
authors.forename: Marjorie L
authors.initials: ML
authors.lastname: Longo
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry / Q000302:isolation & purification*; D008074:Lipoproteins / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D056004:Molecular Dynamics Simulation; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D025801:Ubiquitin / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008074:Lipoproteins; D025801:Ubiquitin