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M. A Winnik - One of the best experts on this subject based on the ideXlab platform.

  • Exchange mechanisms for sodium dodecyl sulfate micelles: High Salt Concentration.
    Journal of the American Chemical Society, 2004
    Co-Authors: Yahya Rharbi, Liusheng Chen, M. A Winnik
    Abstract:

    Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of Salt show that the “observed” rate constant kobs for solute exchange varies by over 6 orders of magnitude as the free sodium ion Concentration [Na+]aq is varied between 10 and 850 mM. There is a sharp break in the log−log plot of kobs versus [Na+]aq in the range of [Na+]aq = 200 mM, with the exchange rate showing a weaker dependence on [Na+]aq above this Concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At Higher Salt Concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at High Salt Concentrations. The fission rate appears to level off for Salt Concentrations abo...

  • Exchange mechanisms for sodium dodecyl sulfate micelles : High Salt Concentration
    Journal of the American Chemical Society, 2004
    Co-Authors: Yahya Rharbi, C. Liusheng, M. A Winnik
    Abstract:

    Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of Salt show that the “observed” rate constant kobs for solute exchange varies by over 6 orders of magnitude as the free sodium ion Concentration [Na+]aq is varied between 10 and 850 mM. There is a sharp break in the log−log plot of kobs versus [Na+]aq in the range of [Na+]aq = 200 mM, with the exchange rate showing a weaker dependence on [Na+]aq above this Concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At Higher Salt Concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at High Salt Concentrations. The fission rate appears to level off for Salt Concentrations above 300−400 mM. These fission and fusion processes are related in an intimate way to the changes in the size and shape of the SDS micelles with increasing Salt Concentration.

Yahya Rharbi - One of the best experts on this subject based on the ideXlab platform.

  • Exchange mechanisms for sodium dodecyl sulfate micelles: High Salt Concentration.
    Journal of the American Chemical Society, 2004
    Co-Authors: Yahya Rharbi, Liusheng Chen, M. A Winnik
    Abstract:

    Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of Salt show that the “observed” rate constant kobs for solute exchange varies by over 6 orders of magnitude as the free sodium ion Concentration [Na+]aq is varied between 10 and 850 mM. There is a sharp break in the log−log plot of kobs versus [Na+]aq in the range of [Na+]aq = 200 mM, with the exchange rate showing a weaker dependence on [Na+]aq above this Concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At Higher Salt Concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at High Salt Concentrations. The fission rate appears to level off for Salt Concentrations abo...

  • Exchange mechanisms for sodium dodecyl sulfate micelles : High Salt Concentration
    Journal of the American Chemical Society, 2004
    Co-Authors: Yahya Rharbi, C. Liusheng, M. A Winnik
    Abstract:

    Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of Salt show that the “observed” rate constant kobs for solute exchange varies by over 6 orders of magnitude as the free sodium ion Concentration [Na+]aq is varied between 10 and 850 mM. There is a sharp break in the log−log plot of kobs versus [Na+]aq in the range of [Na+]aq = 200 mM, with the exchange rate showing a weaker dependence on [Na+]aq above this Concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At Higher Salt Concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at High Salt Concentrations. The fission rate appears to level off for Salt Concentrations above 300−400 mM. These fission and fusion processes are related in an intimate way to the changes in the size and shape of the SDS micelles with increasing Salt Concentration.

Loïc J. Blum - One of the best experts on this subject based on the ideXlab platform.

  • Investigations of the Enhancer Effect of a High‐Salt Concentration Medium on the Luminol Chemiluminescent Reaction
    Photochemistry and Photobiology, 1997
    Co-Authors: Agnès Berger Collaudin, Loïc J. Blum
    Abstract:

    The enhancer effect of a High-Salt Concentration medium on the luminol chemiluminescence reaction catalyzed by either soluble or immobilized peroxidase has been investigated. Some widely used Salts were tested at High Concentration (up to 3 mol L): potassium chloride, sodium chloride, ammonium sulfate and calcium chloride. The magnitude of the light intensity enhancement depends on the nature of the Salt and on the form of the peroxidase, i.e. free in solution or immobilized. The enhancement is observed whether the catalyst of the chemiluminescence reaction is peroxidase or ferricyanide. Both the enhanced or nonenhanced luminol chemiluminescence spectra have a maximum wavelength emission at around 425 nm. The results reported in this study are in favor of an action of the Salts on the nonenzymatic steps of the luminol chemiluminescence reaction rather than a modification of the enzymatic process.

  • Enhanced luminescent response of a fibre-optic sensor for H2O2 by a High-Salt-Concentration medium
    Sensors and Actuators B: Chemical, 1997
    Co-Authors: Agnès Berger Collaudin, Loïc J. Blum
    Abstract:

    Abstract A sensitive H 2 O 2 biosensor based on the luminol-peroxidase system has been developed. Enhancement of the light emission is obtained with a novel approach consisting of the use of a High-Salt-Concentration reaction medium. This enhancement phenomenon is just as effective on soluble peroxidase as on immobilized peroxidase. The magnitude of enhancement depends on the hydrogen peroxide Concentration. With the biosensor associated with the FIA system, it varies from one to eight in the presence of 3 M KCl and from three to eight in the presence of 3 M NaCl for the range 6.25 pmol-25 nmol of injected H 2 O 2 . With KCl or NaCl, at a Concentration of 3 M, the coefficient of variation is 3.7 or 2.9%, respectively, for 40 replicates of 250 pmol H 2 O 2 . After 80 assays performed within two days, no decrease of the biosensor response is perceptible. After four days of intensive use, the biosensor response represents 83% of the initial value.

R. Martínez-garcía - One of the best experts on this subject based on the ideXlab platform.

  • Effect of the particle surface charge density on the colloidal aggregation mechanism.
    Physical review. E Statistical physics plasmas fluids and related interdisciplinary topics, 1996
    Co-Authors: A. Fernández-barbero, Miguel A. Cabrerizo-vílchez, R. Martínez-garcía, Roque Hidalgo-alvarez
    Abstract:

    We have studied the influence of the surface charge density of polymer colloids on the aggregation processes induced at a High Salt Concentration. In this way, the effect of the residual interaction between the particles on the aggregation mechanism was studied. The time dependence of the detailed cluster-size distribution and the time-independent scaling distribution were obtained by single particle light scattering. We found a change in the aggregation mechanism, expressed as a variation of the m exponent value, when the surface charge was modified.

  • Dynamic scaling in colloidal fractal aggregation: Influence of particle surface charge density
    Trends in Colloid and Interface Science X, 1
    Co-Authors: A. Fernández-barbero, Miguel A. Cabrerizo-vílchez, R. Martínez-garcía
    Abstract:

    We have studied the influence of the surface charge density of polymer colloids on aggregation processes induced at a High Salt Concentration. In this way, the effect of the residual interaction between the particles on the aggregation mechanism was studied. The time dependence of the detailed cluster-size distribution and the time-independent scaling distribution were obtained by single particle light scattering. We found a change in the aggregation mechanism, expressed as a variation of the μ exponent value, when the surface charge is modified.

Agnès Berger Collaudin - One of the best experts on this subject based on the ideXlab platform.

  • Investigations of the Enhancer Effect of a High‐Salt Concentration Medium on the Luminol Chemiluminescent Reaction
    Photochemistry and Photobiology, 1997
    Co-Authors: Agnès Berger Collaudin, Loïc J. Blum
    Abstract:

    The enhancer effect of a High-Salt Concentration medium on the luminol chemiluminescence reaction catalyzed by either soluble or immobilized peroxidase has been investigated. Some widely used Salts were tested at High Concentration (up to 3 mol L): potassium chloride, sodium chloride, ammonium sulfate and calcium chloride. The magnitude of the light intensity enhancement depends on the nature of the Salt and on the form of the peroxidase, i.e. free in solution or immobilized. The enhancement is observed whether the catalyst of the chemiluminescence reaction is peroxidase or ferricyanide. Both the enhanced or nonenhanced luminol chemiluminescence spectra have a maximum wavelength emission at around 425 nm. The results reported in this study are in favor of an action of the Salts on the nonenzymatic steps of the luminol chemiluminescence reaction rather than a modification of the enzymatic process.

  • Enhanced luminescent response of a fibre-optic sensor for H2O2 by a High-Salt-Concentration medium
    Sensors and Actuators B: Chemical, 1997
    Co-Authors: Agnès Berger Collaudin, Loïc J. Blum
    Abstract:

    Abstract A sensitive H 2 O 2 biosensor based on the luminol-peroxidase system has been developed. Enhancement of the light emission is obtained with a novel approach consisting of the use of a High-Salt-Concentration reaction medium. This enhancement phenomenon is just as effective on soluble peroxidase as on immobilized peroxidase. The magnitude of enhancement depends on the hydrogen peroxide Concentration. With the biosensor associated with the FIA system, it varies from one to eight in the presence of 3 M KCl and from three to eight in the presence of 3 M NaCl for the range 6.25 pmol-25 nmol of injected H 2 O 2 . With KCl or NaCl, at a Concentration of 3 M, the coefficient of variation is 3.7 or 2.9%, respectively, for 40 replicates of 250 pmol H 2 O 2 . After 80 assays performed within two days, no decrease of the biosensor response is perceptible. After four days of intensive use, the biosensor response represents 83% of the initial value.