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Haike Yan - One of the best experts on this subject based on the ideXlab platform.

  • solubility of Behenic Acid in supercritical co2 with n pentane or n octane cosolvents
    Journal of Chemical & Engineering Data, 1999
    Co-Authors: Bing Guan, Zhimin Liu, Buxing Han, Haike Yan
    Abstract:

    Solubilities of Behenic Acid in supercritical (SC) CO{sub 2} with n-pentane or n-octane cosolvents were measured at 308.15 K, 318.15 K, and 328.15 K in the pressure range from 9.0 MPa to 16.0 MPa and cosolvent concentration range from 0 mol % to 7.5 mol %. The effects of cosolvent concentration, pressure, and temperature on solubility were investigated.

  • solubility of Behenic Acid in supercritical carbon dioxide with ethanol
    Journal of Supercritical Fluids, 1999
    Co-Authors: Bing Guan, Zhimin Liu, Buxing Han, Haike Yan
    Abstract:

    Abstract The solubilities of Behenic Acid in supercritical CO2 with and without ethanol cosolvent were determined at 308.15 K and 318.15 K in the pressure range from 8.0 to 16.0 MPa, and the concentration of cosolvent ranged from 0 to 6.5 mol%. The corresponding density of the fluid phase was also determined. The effects of the cosolvent concentration, fluid density, pressure, and temperature on the solubility are discussed. The solubility increases with ethanol concentration, pressure, and the apparent density d1 (moles of CO2 per liter of the fluid) of CO2 at higher ethanol concentrations.

Jean-marc Valleton - One of the best experts on this subject based on the ideXlab platform.

  • Local surface pressure gradients observed during the transfer of mixed Behenic Acid/pentadecanoic Acid Langmuir films
    Journal of Biological Physics and Chemistry, 2001
    Co-Authors: Stéphane Alexandre, Céline Lafontaine, Jean-marc Valleton
    Abstract:

    Fatty Acids are good candidates for modelling biological membranes and the interactions occurring between lipids and proteins [1-2]. In particular, it is possible to form Langmuir films at the air/water interface when the hydrophobic chains are long enough to ensure a high water insolubility of the fatty Acids. When transferred on a solid substrate by the Langmuir-Blodgett technique [3], the films can be studied by different spectroscopies, and by scanning force microscopy [1]. A problem of interest is to study the formation of lipid domains which may play a key role in biological processes [4]. It is possible to model this behaviour in Langmuir monolayers, by using at least two lipids [5-8], for example two fatty Acids differing only by their chain length [9]. In this paper we report an initial study of Langmuir films constituted of two fatty Acids, Behenic Acid and pentadecanoic Acid. These first investigations led us to obtain original results, and in particular to observe a great rigidity of the mixed film. Scanning force microscopy confirmed the existence of microscopic domains stable for long times in these mixed films transferred on muscovite. The existence of pressure gradients in the film is discussed.

  • local surface pressure gradients observed during the transfer of mixed Behenic Acid pentadecanoic Acid langmuir films
    Journal of Biological Physics and Chemistry, 2001
    Co-Authors: Stéphane Alexandre, Céline Lafontaine, Jean-marc Valleton
    Abstract:

    Fatty Acids are good candidates for modelling biological membranes and the interactions occurring between lipids and proteins [1-2]. In particular, it is possible to form Langmuir films at the air/water interface when the hydrophobic chains are long enough to ensure a high water insolubility of the fatty Acids. When transferred on a solid substrate by the Langmuir-Blodgett technique [3], the films can be studied by different spectroscopies, and by scanning force microscopy [1]. A problem of interest is to study the formation of lipid domains which may play a key role in biological processes [4]. It is possible to model this behaviour in Langmuir monolayers, by using at least two lipids [5-8], for example two fatty Acids differing only by their chain length [9]. In this paper we report an initial study of Langmuir films constituted of two fatty Acids, Behenic Acid and pentadecanoic Acid. These first investigations led us to obtain original results, and in particular to observe a great rigidity of the mixed film. Scanning force microscopy confirmed the existence of microscopic domains stable for long times in these mixed films transferred on muscovite. The existence of pressure gradients in the film is discussed.

  • mixed langmuir films of glucose oxidase and Behenic Acid structure and dynamics
    Journal of Colloid and Interface Science, 1996
    Co-Authors: Nicolas Dubreuil, Stéphane Alexandre, Catherine Fiol, Jean-marc Valleton
    Abstract:

    Abstract The formation of Behenic Acid monolayers at the air/water interface has been studied in the presence of glucose oxidase. When the enzyme is present in the subphase, spreading of Behenic Acid at the air/water interface leads to the formation of a mixed film of glucose oxidase and Behenic Acid. The pressure–area isotherms performed with various concentrations of the enzyme in the subphase showed the incorporation of the enzyme in the monolayer. The dynamics of the mixed films was studied by following the evolution of the film area at a constant pressure and the evolution of the pressure at a constant area. Glucose oxidase dramatically stabilizes the Behenic Acid film. A limit pressure of incorporation of glucose oxidase in the Behenic Acid film at the air/water interface was observed at 28 m N /m.

  • characterization of Behenic Acid glucose oxidase langmuir blodgett films by spectrophotometry a tentative model of their organization
    Thin Solid Films, 1995
    Co-Authors: Catherine Fiol, Nicolas Dubreuil, Stéphane Alexandre, Jean-marc Valleton
    Abstract:

    Abstract Mixed Behenic Acid/glucose oxidase ( BA GOx ) films were transferred onto CaF2 slides and gold substrates and characterized by IR and/or UV-visible spectroscopies. The results obtained were confirmed by the study of pressure-area isotherms and led to a diagrammatic model of the structure elaborated by Langmuir—Blodgett technology. This structure could present some domains with GOx organized as islets.

  • Characterization of Enzymic Structures in Mixed Langmuir-Blodgett Films by Scanning Force Microscopy
    Langmuir, 1995
    Co-Authors: Nicolas Dubreuil, Stéphane Alexandre, Catherine Fiol, Françoise Sommer, Jean-marc Valleton
    Abstract:

    Mixed Langmuir films in which Behenic Acid and glucose oxidase are associated have been transferred by a vertical procedure onto pyrolytic graphite. The resulting films have been studied by scanning force microscopy in the classical contact mode and the tapping mode, from the micrometer to the nanometer scale. Enzymatic structures as well as Behenic Acid molecules have been observed.

Michel Pezolet - One of the best experts on this subject based on the ideXlab platform.

  • infrared study of the molecular orientation in ultrathin films of Behenic Acid methyl ester comparison between single langmuir blodgett monolayers and spin coated multilayers
    Langmuir, 2003
    Co-Authors: Isabelle Pelletier, Thierry Buffeteau, Isabelle Laurin, And Bernard Desbat, Michel Pezolet
    Abstract:

    Single Langmuir−Blodgett (LB) monolayers of Behenic Acid methyl ester (BAME) were studied by infrared spectroscopy. Anisotropic optical constants of this system were calculated from a perpendicular-polarized attenuated total reflectance spectrum and a parallel-polarized reflection−absorption spectrum and were compared to those obtained, in a previous article, for spin-coated multilayers (Pelletier, I.; Bourque, H.; Buffeteau, T.; Blaudez, D.; Desbat, B.; Pezolet, M. J. Phys. Chem. B 2002, 106, 1968). These optical constants were used to calculate the tilt angle of the alkyl chains in both types of films deposited on solid substrates and to simulate polarization modulation reflection−absorption spectra of the Langmuir film at the air/water interface. The results indicate that the molecular tilt angle is near 30° for spin-coated multilayers, while single LB monolayers have a tilt angle of 11 ± 2°. A similar orientation of the alkyl chains is obtained on single monolayers deposited onto solid substrates or s...

  • study by infrared spectroscopy of ultrathin films of Behenic Acid methyl ester on solid substrates and at the air water interface
    Journal of Physical Chemistry B, 2002
    Co-Authors: Isabelle Pelletier, Helene Bourque, Thierry Buffeteau, D Blaudez, Bernard Desbat, Michel Pezolet
    Abstract:

    Ultrathin films of Behenic Acid methyl ester (BAME) deposited by spin coating on solid substrates or spread at the air/water interface were studied by infrared spectroscopy and Brewster angle microscopy. Anisotropic optical constants of BAME were determined from a transmittance spectrum at normal incidence and a parallel-polarized reflectance spectrum at grazing incidence. A transmittance spectrum recorded at oblique incidence (60°) was used to validate these optical constants. The anisotropic extinction coefficients and the polarized ATR spectra were used to calculate the tilt angle of several transition moments and also the molecular tilt angle of BAME molecules assuming an all-trans conformation of the alkyl chain. The results indicate that the alkyl chain of the fatty Acid ester is tilted and that the molecular tilt angle is close to 30°. PM-IRRAS spectra of BAME at the air/water interface were also recorded as a function of the surface pressure. The splitting of the methylene bending mode shows that ...

Helmuth Mohwald - One of the best experts on this subject based on the ideXlab platform.

  • langmuir monolayers with a cf group in the hydrophilic head monolayers of trifluoroethyl ester of Behenic Acid
    The Journal of Physical Chemistry, 1996
    Co-Authors: Jordan G Petrov, Helmuth Mohwald
    Abstract:

    Insoluble monolayers of the trifluoroethyl ester of Behenic Acid possessing a terminal CF3 group of the ester radical of the hydrophilic head are studied at the air−water interface. The surface pressure−area isotherms show a formation of condensed monolayer. The relatively low collapse pressure and significant reduction with time of the molecular area at constant surface pressure illustrate considerable decrease of the monolayer stability when compared to the one of the ethyl behenate monolayers. The CF3 terminal of the ester radical reverses the sign of the surface potential and the vertical dipole moment component; negative values of ΔV and μ⊥ are obtained for the trifluoroethyl behenate monolayer, while positive values of ΔV and μ⊥ are characteristic for other neutral behenyl chain derivatives such as methyl and ethyl behenate, behenyl alcohol, undissociated Behenic Acid, and behenyl amine. This fact demonstrates the determining role of the hydrophilic head for these electrostatic properties. The new r...

  • Langmuir monolayers with a CF₃ group in the hydrophilic head. Monolayers of trifluoroethyl ester of Behenic Acid
    The Journal of Physical Chemistry, 1996
    Co-Authors: Jordan G Petrov, Helmuth Mohwald
    Abstract:

    Insoluble monolayers of the trifluoroethyl ester of Behenic Acid possessing a terminal CF3 group of the ester radical of the hydrophilic head are studied at the air−water interface. The surface pressure−area isotherms show a formation of condensed monolayer. The relatively low collapse pressure and significant reduction with time of the molecular area at constant surface pressure illustrate considerable decrease of the monolayer stability when compared to the one of the ethyl behenate monolayers. The CF3 terminal of the ester radical reverses the sign of the surface potential and the vertical dipole moment component; negative values of ΔV and μ⊥ are obtained for the trifluoroethyl behenate monolayer, while positive values of ΔV and μ⊥ are characteristic for other neutral behenyl chain derivatives such as methyl and ethyl behenate, behenyl alcohol, undissociated Behenic Acid, and behenyl amine. This fact demonstrates the determining role of the hydrophilic head for these electrostatic properties. The new r...

Bing Guan - One of the best experts on this subject based on the ideXlab platform.

  • solubility of Behenic Acid in supercritical co2 with n pentane or n octane cosolvents
    Journal of Chemical & Engineering Data, 1999
    Co-Authors: Bing Guan, Zhimin Liu, Buxing Han, Haike Yan
    Abstract:

    Solubilities of Behenic Acid in supercritical (SC) CO{sub 2} with n-pentane or n-octane cosolvents were measured at 308.15 K, 318.15 K, and 328.15 K in the pressure range from 9.0 MPa to 16.0 MPa and cosolvent concentration range from 0 mol % to 7.5 mol %. The effects of cosolvent concentration, pressure, and temperature on solubility were investigated.

  • solubility of Behenic Acid in supercritical carbon dioxide with ethanol
    Journal of Supercritical Fluids, 1999
    Co-Authors: Bing Guan, Zhimin Liu, Buxing Han, Haike Yan
    Abstract:

    Abstract The solubilities of Behenic Acid in supercritical CO2 with and without ethanol cosolvent were determined at 308.15 K and 318.15 K in the pressure range from 8.0 to 16.0 MPa, and the concentration of cosolvent ranged from 0 to 6.5 mol%. The corresponding density of the fluid phase was also determined. The effects of the cosolvent concentration, fluid density, pressure, and temperature on the solubility are discussed. The solubility increases with ethanol concentration, pressure, and the apparent density d1 (moles of CO2 per liter of the fluid) of CO2 at higher ethanol concentrations.