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Confinement of a hydrophilic polymer in membrane lyotropic phases. J Colloid Interface Sci 2009; 331:185-90. [DOI: 10.1016/j.jcis.2008.11.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 11/08/2008] [Accepted: 11/11/2008] [Indexed: 11/15/2022]
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2
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The sponge phase of a mixed surfactant system. J Colloid Interface Sci 2007; 308:485-90. [PMID: 17266977 DOI: 10.1016/j.jcis.2007.01.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Revised: 01/05/2007] [Accepted: 01/06/2007] [Indexed: 11/25/2022]
Abstract
We study the sponge phase of the mixed non-ionic/ionic surfactant system C14DMAO-TTAB-hexanol-brine. Our aim is to determine if this phase exists in this mixed system and if it preserves or changes its structure when the relative amount of the charged surfactant is increased in the mixture. SAXS, FFEM, and conductivity results show that for the same bilayer volume fraction the sponge phase preserves its global structure. We propose a method to determine the geometrical obstruction factor from electrical conductivity measurements in ionic sponge phases. Analysis of lamellar phases in the same system shows that the bilayer thickness increases when the ionic surfactant concentration is increased.
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Amphiphilic diblock copolymers with adhesive properties: I. Structure and swelling with water. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2006; 20:273-87. [PMID: 16838088 DOI: 10.1140/epje/i2005-10130-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 06/07/2006] [Indexed: 05/10/2023]
Abstract
We study asymmetric block copolymers with the simple diblock AB architecture, in the case where the longer block A is both hydrophobic and "soft", whereas the shorter block B is hydrophilic and "hard". Materials with such a particular combination of physico-chemical and mechanical properties have distinctive advantages, in particular for designing water-compatible adhesive materials. The phase diagram is established, combining NMR and SAXS characterisations of the materials. The swelling with water is monitored through gravimetry and "time-resolved" SAXS. Indications of maintained adhesive properties in a wet environment are given.
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A structural description of microemulsions. Small-angle neutron scattering and electrical conductivity study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100449a020] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Study of the surface tension of polymer solutions: theory and experiments. Good solvent conditions. Macromolecules 2002. [DOI: 10.1021/ma00235a010] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Interactions and aggregation in microemulsions. A small-angle neutron scattering study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100456a017] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Highly curved defects in lyotropic (nonionic) lamellar phases. Origin and role in hydration process. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j150660a010] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Binary separation in very thin nematic films: thickness and phase coexistence. PHYSICAL REVIEW LETTERS 2001; 87:125701. [PMID: 11580524 DOI: 10.1103/physrevlett.87.125701] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2001] [Indexed: 05/23/2023]
Abstract
The behavior as a function of temperature of very thin films (10 to 200 nm) of pentylcyanobiphenyl on silicon substrates is reported. In the vicinity of the nematic-isotropic transition we observe a coexistence of two regions of different thicknesses: thick regions are in the nematic state while thin ones are in the isotropic state. Moreover, the transition temperature is shifted downward following a 1/h(2) law ( h is the film thickness). Microscope observations and small-angle x-ray scattering allowed us to draw a phase diagram which is explained in terms of a binary first-order phase transition where thickness plays the role of an order parameter.
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Self diffusion and spectral modifications of a membrane protein, the Rubrivivax gelatinosus LH2 complex, incorporated into a monoolein cubic phase. Biophys J 2001; 81:1613-23. [PMID: 11509374 PMCID: PMC1301639 DOI: 10.1016/s0006-3495(01)75815-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The light-harvesting complex LH2 from a purple bacterium, Rubrivivax gelatinosus, has been incorporated into the Q230 cubic phase of monoolein. We measured the self-diffusion of LH2 in detergent solution and in the cubic phase by fluorescence recovery after photobleaching. We investigated also the absorption and fluorescence properties of this oligomeric membrane protein in the cubic phase, in comparison with its beta-octyl glucoside solution. In these experiments, native LH2 and LH2 labeled by a fluorescent marker were used. The results indicate that the inclusion of LH2 into the cubic phase induced modifications in the carotenoid and B800 binding sites. Despite these significant perturbations, the protein seems to keep an oligomeric structure. The relevance of these observations for the possible crystallization of this protein in the cubic phase is discussed.
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Dramatic rigidification of a peptide-decorated lamellar phase. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:041903. [PMID: 11308873 DOI: 10.1103/physreve.63.041903] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2000] [Indexed: 05/23/2023]
Abstract
We have performed small-angle x-ray scattering on a lamellar (L(alpha)) phase made of a nonionic surfactant (C12E4), decane, and water, after the insertion of a triblock peptide. The hydrophilic part of the peptide is rigid and organized in an alpha helix in the presence of membranes. Surface tension measurements and spectrofluorometry show that the peptide lies on the membrane surface. The Caillé parameter eta and the smectic compressibility modulus (-)B decrease with peptide concentration, whereas the membrane bending rigidity kappa increases threefold for mole ratio of peptide to surfactant as low as 5.2 x 10(-4). The published models for rigid inclusions in membranes cannot account for this dramatic rigidification. However, experimental results are well fitted by a Heuristic renormalization of the membrane thickness.
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Interaction between the lipoamide-containing H-protein and the lipoamide dehydrogenase (L-protein) of the glycine decarboxylase multienzyme system 2. Crystal structures of H- and L-proteins. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:2890-8. [PMID: 10806386 DOI: 10.1046/j.1432-1033.2000.01330.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The glycine decarboxylase complex consists of four different component enzymes (P-, H-, T- and L-proteins). The 14-kDa lipoamide-containing H-protein plays a pivotal role in the complete sequence of reactions as its prosthetic group (lipoic acid) interacts successively with the three other components of the complex and undergoes a cycle of reductive methylamination, methylamine transfer and electron transfer. With the aim to understand the interaction between the H-protein and its different partners, we have previously determined the crystal structure of the oxidized and methylaminated forms of the H-protein. In the present study, we have crystallized the H-protein in its reduced state and the L-protein (lipoamide dehydrogenase or dihydrolipoamide dehydrogenase). The L-protein has been overexpressed in Escherichia coli and refolded from inclusion bodies in an active form. Crystals were obtained from the refolded L-protein and the structure has been determined by X-ray crystallography. This first crystal structure of a plant dihydrolipoamide dehydrogenase is similar to other known dihydrolipoamide dehydrogenase structures. The crystal structure of the H-protein in its reduced form has been determined and compared to the structure of the other forms of the protein. It is isomorphous to the structure of the oxidized form. In contrast with methylaminated H-protein where the loaded lipoamide arm was locked into a cavity of the protein, the reduced lipoamide arm appeared freely exposed to the solvent. Such a freedom is required to allow its targeting inside the hollow active site of L-protein. Our results strongly suggest that a direct interaction between the H- and L-proteins is not necessary for the reoxidation of the reduced lipoamide arm bound to the H-protein. This hypothesis is supported by biochemical data [Neuburger, M., Polidori, A.M., Piètre, E., Faure, M., Jourdain, A., Bourguignon, J., Pucci, B. & Douce, R. (2000) Eur. J. Biochem. 267, 2882-2889] and by small angle X-ray scattering experiments reported herein.
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Abstract
We have used a lamellar phase made of a nonionic surfactant, dodecane and water, as a model membrane to investigate its interactions with macromolecular inclusions bringing together two membranes, i.e., acting as macromolecular snaps. In systems devoid of inclusions, the interlamellar distance depends on the total volume fraction of membranes Phi. We show that, in presence of a transmembrane protein, or of several de novo designed peptides of different length and composition, the lamellar phase undergoes a binding transition. Under such conditions, the interlamellar distance is no longer proportional to Phi(-1), but rather to the surface concentration of snaps within the membrane. It also appears that, in the presence of the hydrophobic segment of peptide snaps, the length of the inclusions must be at least equal to the hydrophobic length of the membrane to be active. Experimental results have been precisely fitted to a model of thermally stabilized membranes, decorated with snaps. However, in the presence of inclusions, the parameter describing the interactions between membranes, has to take into account the length of the inclusion to preserve good predictive capabilities.
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Organization of cyanobiphenyl liquid crystal molecules in prewetting films spreading on silicon wafers. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1999; 59:6808-18. [PMID: 11969668 DOI: 10.1103/physreve.59.6808] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/1998] [Revised: 02/16/1999] [Indexed: 04/18/2023]
Abstract
We observe prewetting films of 8CB (4'-n-octyl-4-cyanobiphenyl) spreading at room temperature on silicon wafers by ellipsometry and x-ray reflectivity. Ellipsometry indicates the formation of a nondense monolayer spreading in front of a 45-A-thick film. X-ray reflectivity, performed using a ribbon geometry for the liquid crystal (LC) reservoir, allows us to determine the organization of the 8CB molecules in the homogenous film. It consists of a trilayer stacking with a smecticlike bilayer standing above a polar monolayer with tilted molecules. We show that the thickness of the bilayer is equal to the smectic periodicity in the bulk material and that the tilt angle of the molecules in contact with the solid surface is close to 60 degrees, in good agreement with second-harmonic generation studies reported by other groups. Such organization can be precisely determined using x-ray reflectivity because it induces a modulation of the electron density along the normal to the surface. Furthermore, a study of the ellispometric profile of a drop heated in the nematic phase, where we observe a complete spreading of the LC, shows the complex structuration of the LC close to the solid interface. In particular, the spreading behavior of the trilayer compared to the subsequent smecticlike bilayers indicates the existence of specific interaction between the trilayer and silicon wafer.
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Contributory presentations/posters. J Biosci 1999. [DOI: 10.1007/bf02989373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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(CdSe)ZnS Core−Shell Quantum Dots: Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites. J Phys Chem B 1997. [DOI: 10.1021/jp971091y] [Citation(s) in RCA: 3479] [Impact Index Per Article: 128.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Abstract
The glycine decarboxylase complex consists of four different component enzymes (P-, H-, T- and L-proteins). The 14-kDa lipoamide-containing H-protein plays a pivotal role in the complete sequence of reactions since its prosthetic group (lipoic acid) interacts successively with the three other components of the complex and undergoes a cycle of reductive methylamination, methylamine transfer and electron transfer. The X-ray crystal structure of different forms of the H-protein has shown a unique conformation of the protein. This leads to the hypothesis of a three-dimensional recognition of the H-protein by the other components of the system and also by the ligase which lipoylates the H-protein. Striking structural similarities are observed between the H-protein and other lipoate domains of 2-oxo acid dehydrogenases and with the biotin carrier protein of acetyl-CoA carboxylase. In the H-protein, the lipoamide arm is free to move in the solvent when oxidized but is pivoted and tightly bound into a cleft at the protein surface when methylamine-loaded. This implies that the H-protein and the T-component form a stable complex during the catalytic transfer of the methylene unit to the tetrahydrofolate cofactor of the T-protein. This complex has been detected by small angle scattering experiments. In conclusion, in the glycine decarboxylase system, the lipoamide arm does not swing freely from one catalytic site to another as was proposed in other systems.
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Characterization of CdSe nanocrystallite dispersions by small angle x‐ray scattering. J Chem Phys 1996. [DOI: 10.1063/1.472854] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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28
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Squeezing of Oil-Swollen Surfactant Bilayers by a Membrane Protein. PHYSICAL REVIEW LETTERS 1996; 77:3485. [PMID: 10062232 DOI: 10.1103/physrevlett.77.3485] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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29
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Nonionic Surfactant Reverse Micelles of C12E4 in Dodecane: Temperature Dependence of Size and Shape. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960628p] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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30
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Swelling behavior and local topology of an L3 (sponge) phase. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1996; 54:1774-1778. [PMID: 9965256 DOI: 10.1103/physreve.54.1774] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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31
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Polymer confinement in surfactant bilayers of a lyotropic lamellar phase. PHYSICAL REVIEW LETTERS 1995; 74:4237-4240. [PMID: 10058450 DOI: 10.1103/physrevlett.74.4237] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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32
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A small angle X-ray scattering investigation of the structure of a ternary water-in-oil microemulsion. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0166-6622(92)80219-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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33
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Anisotropy of a flexible polymeric chain in a nematic field : neutron scattering versus magnetic resonance. ACTA ACUST UNITED AC 1985. [DOI: 10.1051/jphys:019850046070122700] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Study of the surface tension of polymer solutions: theory and experiments in theta solvent conditions. ACTA ACUST UNITED AC 1983. [DOI: 10.1051/jphys:019830044090103500] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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38
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Structure of microemulsions: use of a variable-contrast method applied to neutron scattering. J Appl Crystallogr 1978. [DOI: 10.1107/s0021889878014016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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39
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A structural description of liquid particle dispersions: Ultracentrifugation and small angle neutron scattering studies of microemulsions. J Chem Phys 1978. [DOI: 10.1063/1.436979] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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40
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Study of structure and electrical conductivity in microemulsions : Evidence for percolation mechanism and phase inversion. ACTA ACUST UNITED AC 1978. [DOI: 10.1051/jphyslet:019780039024048700] [Citation(s) in RCA: 157] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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41
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Neutron diffraction patterns of labelled polymer chains in the bulk. J Appl Crystallogr 1974. [DOI: 10.1107/s0021889874009162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
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45
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Study of polymer solution by small-angle neutron scattering in the intermediate momentum range. J Appl Crystallogr 1974. [DOI: 10.1107/s0021889874009198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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46
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