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  • 1
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    Hierarchical self-assembly of F-actin and cationic lipid complexes: stacked three-layer tubule networks (2000)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2000-06-17
    Description: We describe a distinct type of spontaneous hierarchical self-assembly of cytoskeletal filamentous actin (F-actin), a highly charged polyelectrolyte, and cationic lipid membranes. On the mesoscopic length scale, confocal microscopy reveals ribbonlike tubule structures that connect to form a network of tubules on the macroscopic scale (more than 100 micrometers). Within the tubules, on the 0.5- to 50-nanometer length scale, x-ray diffraction reveals an unusual structure consisting of osmotically swollen stacks of composite membranes with no direct analog in simple amphiphilic systems. The composite membrane is composed of three layers, a lipid bilayer sandwiched between two layers of actin, and is reminiscent of multilayered bacterial cell walls that exist far from equilibrium. Electron microscopy reveals that the actin layer consists of laterally locked F-actin filaments forming an anisotropic two-dimensional tethered crystal that appears to be the origin of the tubule formation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wong, G C -- Tang, J X -- Lin, A -- Li, Y -- Janmey, P A -- Safinya, C R -- AR38910/AR/NIAMS NIH HHS/ -- GM59288/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2000 Jun 16;288(5473):2035-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Materials Department, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10856215" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/*chemistry/ultrastructure ; Anisotropy ; Cations ; Crystallization ; Electrochemistry ; Electrolytes ; Fatty Acids, Monounsaturated/chemistry ; Freeze Fracturing ; Lipid Bilayers/*chemistry ; Microscopy, Confocal ; Microscopy, Electron ; Molecular Conformation ; Protein Conformation ; Quaternary Ammonium Compounds/chemistry ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    Structure of DNA-cationic liposome complexes: DNA intercalation in multilamellar membranes in distinct interhelical packing regimes (1997)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1997-02-07
    Description: Cationic liposomes complexed with DNA (CL-DNA) are promising synthetically based nonviral carriers of DNA vectors for gene therapy. The solution structure of CL-DNA complexes was probed on length scales from subnanometer to micrometer by synchrotron x-ray diffraction and optical microscopy. The addition of either linear lambda-phage or plasmid DNA to CLs resulted in an unexpected topological transition from liposomes to optically birefringent liquid-crystalline condensed globules. X-ray diffraction of the globules revealed a novel multilamellar structure with alternating lipid bilayer and DNA monolayers. The lambda-DNA chains form a one-dimensional lattice with distinct interhelical packing regimes. Remarkably, in the isoelectric point regime, the lambda-DNA interaxial spacing expands between 24.5 and 57.1 angstroms upon lipid dilution and is indicative of a long-range electrostatic-induced repulsion that is possibly enhanced by chain undulations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Radler, J O -- Koltover, I -- Salditt, T -- Safinya, C R -- New York, N.Y. -- Science. 1997 Feb 7;275(5301):810-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Materials Department, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9012343" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteriophage lambda ; Cations ; Chemistry, Physical ; DNA/*chemistry ; DNA, Viral/*chemistry ; Fatty Acids, Monounsaturated ; Isoelectric Point ; Light ; Lipid Bilayers ; *Liposomes ; Microscopy, Fluorescence ; Microscopy, Interference ; *Nucleic Acid Conformation ; Phosphatidylcholines ; Phosphatidylethanolamines ; Physicochemical Phenomena ; Plasmids ; Quaternary Ammonium Compounds ; Scattering, Radiation ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    An inverted hexagonal phase of cationic liposome-DNA complexes related to DNA release and delivery (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-07-04
    Description: A two-dimensional columnar phase in mixtures of DNA complexed with cationic liposomes has been found in the lipid composition regime known to be significantly more efficient at transfecting mammalian cells in culture compared to the lamellar (LalphaC) structure of cationic liposome-DNA complexes. The structure, derived from synchrotron x-ray diffraction, consists of DNA coated by cationic lipid monolayers and arranged on a two-dimensional hexagonal lattice (HIIC). Two membrane-altering pathways induce the LalphaC --〉 HIIC transition: one where the spontaneous curvature of the lipid monolayer is driven negative, and another where the membrane bending rigidity is lowered with a new class of helper-lipids. Optical microscopy revealed that the LalphaC complexes bind stably to anionic vesicles (models of cellular membranes), whereas the more transfectant HIIC complexes are unstable and rapidly fuse and release DNA upon adhering to anionic vesicles.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Koltover, I -- Salditt, T -- Radler, J O -- Safinya, C R -- New York, N.Y. -- Science. 1998 Jul 3;281(5373):78-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Materials Department, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9651248" target="_blank"〉PubMed〈/a〉
    Keywords: Birefringence ; Cations ; *DNA/chemistry ; Endocytosis ; Endosomes/chemistry ; Fatty Acids, Monounsaturated/chemistry ; Hexanols/chemistry ; Lipid Bilayers ; Liposomes/*chemistry ; Membrane Fusion ; Phosphatidylcholines/chemistry ; Phosphatidylethanolamines/chemistry ; Quaternary Ammonium Compounds/chemistry ; *Transfection ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Materials chemistry: Liposomes derived from molecular vases (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-09-22
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Safinya, Cyrus R -- Ewert, Kai K -- England -- Nature. 2012 Sep 20;489(7416):372-4. doi: 10.1038/489372b.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22996547" target="_blank"〉PubMed〈/a〉
    Keywords: *Drug Delivery Systems ; Hydrophobic and Hydrophilic Interactions ; Lipid Bilayers/chemical synthesis/chemistry ; Liposomes/chemical synthesis/*chemistry ; Surface-Active Agents/chemical synthesis/chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
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    X-ray Scattering Studies of Aligned, Stacked Surfactant Membranes (1988)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1988-12-09
    Description: X-ray scattering studies were performed to understand the structure and correlations in the lamellar phases of thick, freely suspeded films of (i) the hydrated phospholipid dimyristoylphosphotidylcholine (DMPC) and (ii) the ternar system consisting of the surfactant sodium dodecyl sulfate (SDS), cosurfactant (pentanol), and water. The films were drawn in a temperature- and humidity-controlled environment, where the layers were oriented to within 0.1 degrees . In the DMPC system, this made it possible to directly observe the orientation of the P(beta') modulation and to identify phase L(beta') as three distinct phases distinguished by the direction of chain tilt with respect to the lattice. In the L(alpha) phase of the ternary system, power law behavior of the (0,0,L) structure factor arising from the algebraic decay of layer correlatios was observed in single crystals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sirota, E B -- Smith, G S -- Safinya, C R -- Plano, R J -- Clark, N A -- New York, N.Y. -- Science. 1988 Dec 9;242(4884):1406-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17802136" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Existence of a flat phase in red cell membrane skeletons (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-02-12
    Description: Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membranes exhibit solid-like elastic behavior in the plane of the membrane. The spectrin skeleton of red blood cells was studied as a model tethered membrane. The static structure factor of the skeletons, measured by small-angle x-ray and light scattering, was fitted with a structure factor predicted with a model calculation. The model describes tethered membrane sheets with free edges in a flat phase, which is a locally rough but globally flat membrane configuration. The fit was good for large scattering vectors. The membrane roughness exponent, zeta, defined through h alpha L zeta, where h is the average amplitude of out-of-plane fluctuations and L is the linear membrane dimension, was determined to be 0.65 +/- 0.10. Computer simulations of model red blood cell skeletons also showed this flat phase. The value for the roughness exponent, which was determined from the scaling properties of membranes of different sizes, was consistent with that from the experiments.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schmidt, C F -- Svoboda, K -- Lei, N -- Petsche, I B -- Berman, L E -- Safinya, C R -- Grest, G S -- New York, N.Y. -- Science. 1993 Feb 12;259(5097):952-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cellular and Developmental Biology, Harvard University, Cambridge, MA 02138.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8438153" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry, Physical ; Computer Simulation ; Electrochemistry ; Erythrocyte Membrane/chemistry/*ultrastructure ; Light ; Mathematics ; Models, Molecular ; Physicochemical Phenomena ; Scattering, Radiation ; Spectrin/chemistry/*ultrastructure ; X-Rays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
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  • 7
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    Structure of membrane surfactant and liquid crystalline smectic lamellar phases under flow (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-07-30
    Description: Synchrotron x-ray scattering studies were performed to probe the nonequilibrium structures of two layered systems at high shear rates: the smectic-A phase of the thermotropic liquid crystal 4-cyano-4'-octylbiphenyl (8CB) and the lamellar L(alpha) phases of surfactant membranes composed of sodium dodecyl sulfate and pentanol. Whereas the lamellar surfactant phases oriented primarily with their layers parallel to the shearing plates, as expected intuitively, in the corresponding high shear regime, the smectic-A liquid crystalline material oriented with the layers perpendicular to the shearing plates. A careful numerical study revealed that this surprising layer orientation results from nonlinear dynamics of the liquid crystal director and is caused by the flow distortion of thermal fluctuations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Safinya, C R -- Sirota, E B -- Bruinsma, R F -- Jeppesen, C -- Plano, R J -- Wenzel, L J -- New York, N.Y. -- Science. 1993 Jul 30;261(5121):588-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17758168" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    A phase of liposomes with entangled tubular vesicles (1994)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1994-11-18
    Description: An equilibrium phase belonging to the family of bilayer liposomes in ternary mixtures of dimyristoylphosphatidylcholine (DMPC), water, and geraniol (a biological alcohol derived from oil-soluble vitamins that acts as a cosurfactant) has been identified. Electron and optical microscopy reveal the phase, labeled Ltv, to be composed of highly entangled tubular vesicles. In situ x-ray diffraction confirms that the tubule walls are multilamellar with the lipids in the chain-melted state. Macroscopic observations show that the Ltv phase coexists with the well-known L4 phase of spherical vesicles and a bulk L alpha phase. However, the defining characteristic of the Ltv phase is the Weissenberg rod climbing effect under shear, which results from its polymer-like entangled microstructure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chiruvolu, S -- Warriner, H E -- Naranjo, E -- Idziak, S H -- Radler, J O -- Plano, R J -- Zasadzinski, J A -- Safinya, C R -- GM47334/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Nov 18;266(5188):1222-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Materials Research Laboratory, University of California, Santa Barbara 93106.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7973704" target="_blank"〉PubMed〈/a〉
    Keywords: Dimyristoylphosphatidylcholine/*chemistry ; Lipid Bilayers/*chemistry ; Liposomes/*chemistry ; Microscopy, Electron ; Scattering, Radiation ; Temperature ; Terpenes/*chemistry ; X-Ray Diffraction ; X-Rays
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Lamellar biogels: fluid-membrane-based hydrogels containing polymer lipids (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-02-16
    Description: A class of lamellar biological hydrogels comprised of fluid membranes of lipids and surfactants with small amounts of low molecular weight poly(ethylene glycol)-derived polymer lipids (PEG-lipids) were studied by x-ray diffraction, polarized light microscopy, and rheometry. In contrast to isotropic hydrogels of polymer networks, these membrane-based birefringent liquid crystalline biogels, labeled L-alpha,g, form the gel phase when water is added to the liquid-like lamellar L-alpha phase, which reenters a liquid-like mixed phase upon further dilution. Furthermore, gels with larger water content require less PEG-lipid to remain stable. Although concentrated (approximately 50 weight percent) mixtures of free PEG (molecular weight, 5000) and water do not gel, gelation does occur in mixtures containing as little as 0.5 weight percent PEG-lipid. A defining signature of the L-alpha,g regime as it sets in from the fluid lamellar L-alpha phase is the proliferation of layer-dislocation-type defects, which are stabilized by the segregation of PEG-lipids to the defect regions of high membrane curvature that connect the membranes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Warriner, H E -- Idziak, S H -- Slack, N L -- Davidson, P -- Safinya, C R -- New York, N.Y. -- Science. 1996 Feb 16;271(5251):969-73.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Materials Research Laboratory, Materials Department, University of California, Santa Barbara 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8584932" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry, Physical ; Dimyristoylphosphatidylcholine/chemistry ; Gels ; *Lipid Bilayers ; Lipids/*chemistry ; Membrane Fluidity ; Microscopy, Polarization ; Molecular Weight ; Pentanols/chemistry ; Phosphatidylethanolamines/*chemistry ; Physicochemical Phenomena ; Polyethylene Glycols/*chemistry ; Surface-Active Agents/chemistry ; Viscosity ; Water ; X-Ray Diffraction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Lipid tubule self-assembly: length dependence on cooling rate through a first-order phase transition (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-03-17
    Description: The formation kinetics and self-assembly of multilamellar tubules of the diacetylenic phospholipid 1,2-bis(tricosa-10,12-diynoyl)-sn-glycerol-3-phosphocholine formed under controlled cooling rates were studied by x-ray diffraction and optical, atomic force, and scanning electron microscopy. Tubule formation was driven by a reversible first-order phase transition from an intralamellar, chain-melted L(alpha) phase to a chain-frozen L(beta), phase. These observations are the basis of a highly efficient method of tubule production in which tubule lengths can be controlled, between 1 and 100 micrometers, by varying the cooling rate. These tubules can be made in suspensions with 10 percent lipid by mass, far exceeding the lipid solubility limit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Thomas, B N -- Safinya, C R -- Plano, R J -- Clark, N A -- New York, N.Y. -- Science. 1995 Mar 17;267(5204):1635-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17808182" target="_blank"〉PubMed〈/a〉
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    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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