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  • 1
    ISSN: 1432-1017
    Keywords: Key words Cholesterol ; DMPC ; Small-angle neutron scattering ; Bilayer rigidity ; Fluctuations ; Unbinding transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The temperature dependence of the small-angle neutron scattering from aqueous multilammellar DMPC lipid bilayers, containing small amounts of cholesterol, is analyzed near the main phase transition by means of a simple geometric model which yields the lamellar repeat distance, the hydrophobic thickness of the bilayer, the interlamellar aqueous spacing, as well as fluctuation parameters. The observation of anomalous swelling behavior in the transition region is interpreted as an indication of bilayer softening and thermally reduced bending rigidity. Our results indicate that the effect of small amounts of cholesterol, ≲3 mole%, is a softening of the bilayers in the transition region, whereas cholesterol contents above this range lead to the well-known effect of rigidification. The possible biological relevance of this result is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1017
    Keywords: Lipid bilayer ; acyl chain ordering ; crystallization ; grain-boundary formation ; interfacial melting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The main gel-fluid phase transition of wet lipid bilayers is examined in terms of a microscopic interaction model which incorporates both trans-gauche isomerism of the lipid acyl chains and crystal orientation variables for the lipid molecules. The model gives two scenarios for the phase behavior of wet lipid bilayers in terms of temperature: (i) chain melting occurs at a higher temperature than crystallization, or (ii) chain melting and crystallization occur at the same temperature. Experimental data for lipid bilayers is consistent with the second scenario. In this case, computer simulation is used to investigate the non-equilibrium behaviour of the model. The numerical data is intepreted in terms of interfacial melting on heating and grain formation on cooling through the main phase transition. Interfacial melting is a non-equilibrium process in which the grains of a polycrystalline bilayer melt inwards from the boundaries. The prediction of interfacial melting in wet lipid bilayers is examined in relation to data from both equilibrium and nonequilibrium measurements, to corresponding phase behavior in monolayers, and to previous theoretical work.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 12 (1985), S. 75-86 
    ISSN: 1432-1017
    Keywords: Lipid bilayer ; phase transition ; clusters ; metastability ; compressibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The softening of wet lipid bilayer membranes during their gel-to-fluid first-order phase transition is studied by computer simulation of a family of two-dimensional microscopic interaction models. The models include a variable number, q, of lipid chain conformational states, where 2≦q≦10. Results are presented as functions of q and temperature for a number of bulk properties, such as internal energy, specific heat, and lateral compressibility. A quantitative account is given of the statistics of the lipid clusters which are found to form in the neighborhood of the transition. The occurrence of these clusters is related to the softening and the strong thermal density fluctuations which dominate the specific heat and the lateral compressibility for the high-q models. The cluster distributions and the fluctuations behave in a manner reminiscent of critical phenomena and percolation. The findings of long-lived metastable states and extremely slow relaxational behavior in the transition region are shown to be caused by the presence of intermediate lipid chain conformational states which kinetically stabilize the cluster distribution and the effective phase coexistence. This has as its macroscopic consequence that the first-order transition apperas as a “continuous” transition, as invariably observed in all experiments on uncharged lecithin bilayer membranes. The results also suggest an explanation of the non-horizontal isotherms of lipid monolayers. Possible implications of lipid bilayer softening and enhanced passive permeability for the functioning of biological membranes are discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1017
    Keywords: lipid membrane ; lipid-protein interactions ; phase diagram ; hydrophobic thickness ; solution theory ; membrane elasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A two-component solution theory is studied which incorporates hydrophobic matching as a major contribution to the lipid-protein interactions in biological membranes. A special geometrical constraint has been discovered which has important implications for the quantitative interpretation of physical effects to lipid-protein interactions. The theory has an advantage over conventional Landau-type phenomenological descriptions in that it accounts for phase separation. A certain class of experimental systems, photosynthetic reaction centre and antenna proteins reconstituted into synthetic lipid membranes of different hydrophobic thicknesses, are considered with a view to determining the parameters of the theory. The theoretical predictions are found to be in good agreement with experimental measurements of shifts in the phase transition temperature.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1017
    Keywords: Key words Lipid bilayer ; Softness ; Swelling ; Cholesterol ; Short-chain lipid ; Bola lipid ; Small-angle neutron scattering ; Calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The effect of the incorporation of small amounts (∼1 mole%) of amphiphilic solutes, such as cholesterol, a short-chain lipid (DC10PC), and a bola lipid, into multilamellar DMPC bilayers is studied by small-angle neutron scattering and differential-scanning calorimetry. The anomalous swelling behavior observed in the transition region of pure DMPC bilayers is interpreted as an indication of bilayer softening and thermally reduced bending rigidity. Small amounts of the solutes are found to maintain or even enhance the bilayer softness. In the case of cholesterol, a systematic study shows that the well-known rigidification effect is observed only for cholesterol concentrations above 3–4 mole%. The results are discussed in relation to the physical properties of internal cell membranes.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-904X
    Keywords: PEG-liposomes ; phospholipase A2 ; enzyme-membrane interaction ; lipopolymer ; degradation ; targeting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2012-11-08
    Description: Interaction between integral membrane proteins and the lipid-bilayer component of biological membranes is expected to mutually influence the proteins and the membrane. We present quantitative evidence of a manifestation of the lipid–protein interactions in liposomal membranes, reconstituted with actively pumping Na+,K+-ATPase, in terms of nonequilibrium shape fluctuations that contain a...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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