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Adsorption Step

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Raoul Zana – One of the best experts on this subject based on the ideXlab platform.

Xiaofeng Ren – One of the best experts on this subject based on the ideXlab platform.

Reinaldo Simões Gonçalves – One of the best experts on this subject based on the ideXlab platform.

Jiechao Yin – One of the best experts on this subject based on the ideXlab platform.

  • Cholesterol is important for a post-Adsorption Step in the entry process of transmissible gastroenteritis virus.
    Antiviral research, 2010
    Co-Authors: Jiechao Yin, Joerg Glende, Christel Schwegmann-wessels, Luis Enjuanes, Georg Herrler, Xiaofeng Ren
    Abstract:

    Cholesterol is a major constituent of detergent-resistant membrane microdomains (DRMs). We localized transmissible gastroenteritis virus (TGEV) spike (S) protein in DRMs in the viral envelope. Though S protein was not solubilized by cold non-ionic detergents, this behavior was unchanged when cholesterol was depleted from viral membrane by methyl-β-cyclodextrin (MβCD) and the protein did not comigrate with cellular DRM marker proteins in flotation analyses. Therefore, the S protein is not anchored in the viral membrane DRMs as they are known to occur in the plasma membrane. Cholesterol depletion from viral membrane may not affect the Adsorption process as neither the sialic acid binding activity nor the binding to aminopeptidase N was reduced post-MβCD treatment. Reduced infectivity of cholesterol-depleted TGEV was observed only when the Adsorption process occurred at 37°C but not when the virus was applied at 4°C. Cholesterol is important for a post-Adsorption Step, allowing membrane rearrangements that facilitate virus entry.

M Chorro – One of the best experts on this subject based on the ideXlab platform.

  • Investigations of First Adsorption Step of Cationic Dimeric (Gemini) Surfactants onto Silica Surfaces by Analytical and Calorimetric Methods
    Journal of Colloid and Interface Science, 2001
    Co-Authors: L. Grosmaire, M Chorro, C Chorro, S Partyka, Raoul Zana
    Abstract:

    Abstract This paper reports new results on the Adsorption of cationic dimeric surfactants (12– s –12 surfactants, where s is the carbon number of the polymethylene spacer) on adsorbents with different surface functions, namely raw and HCl-treated silica. These results were obtained by traditional methods (Adsorption isotherms, electrophoretic mobility, and chemical analysis of the equilibrated supernatant) and microcalorimetry. The results showed that the stoichiometry of the first Step of the Adsorption (ion-exchange Step) varies strongly with the spacer carbon number. The binding of one surfactant to the surface brings about the release of between 1 and 2 sodium ions as the spacer carbon number is increased from 2 to 10. Thus the surfactant binding to the surface involves one head group for the 12–2–12 surfactant (short spacer) and two head groups for the 12–10–12 surfactant (long spacer). These results suggest the use of dimeric surfactants as molecular rulers to study the distribution of charged sites on surfaces. The microcalorimetric experiments clearly showed the two Adsorption Steps. The ion-exchange Step gives rise to an endothermal effect having an amplitude that depends strongly on the spacer carbon number. The second Adsorption Step associated with the formation of surfactant aggregates gives rise to an exothermal effect that also depends on s .

  • Adsorption mechanism of conventional and dimeric cationic surfactants on silica surface effect of the state of the surface
    Joint International Conference on Information Sciences, 1999
    Co-Authors: M Chorro, C Chorro, O Dolladille, S Partyka, Raoul Zana
    Abstract:

    Abstract The aim of this study was to investigate the effect of the state of the silica surface and of the surfactant molecular structure on the Adsorption of cationic surfactants onto silica. Thus, the Adsorption of DTAB (dodecyltrimethylammonium bromide) and of the dimeric surfactant 12-2-12 (ethanediyl-1,2-bis(dodecyldimethylammonium bromide)) on raw silica (SiNa) and on HCl-washed silica (SiH) has been investigated under “free” system conditions. The amount of surfactant adsorbed (Adsorption isotherm), the sodium ion and bromide ion concentrations and the pH in the equilibrated supernatant, and the silica particle electrophoretic mobility have been measured along the isotherms. The Adsorption mechanisms of the two surfactants on the raw and washed silica are qualitatively similar. Nevertheless, important quantitative differences are observed which are all due to (i) the larger number of surface sites present at the surface of SiNa with respect to SiH and (ii) the larger ionic strength of the supernatant in SiNa/surfactant systems with respect to SiH/surfactant systems, due to the much larger amount of sodium ions released by SiNa upon surfactant binding. Thus, the amounts of surfactant adsorbed at the point of zero charge and at saturation of the silica particles, of sodium ions released by the surface and the decrease of critical micelle concentration (cmc) in the supernatant with respect to pure water are all larger for the raw silica than for the treated silica. For the four silica/surfactant systems investigated, the first Adsorption Step corresponds to the Adsorption of individual surfactant ions on the negative sites of the silica surface. It is driven by electrostatic interactions and strongly dependent on the number of surface sites and ionic strength associated to the released ions. At the end of the first Adsorption Step, which is clearly seen with SiH/surfactant systems, the second Adsorption Step starts. This Step is driven by hydrophobic interaction between surfactant alkyl chains and results in the formation of surface aggregates. The surfactant Adsorption on the surface is shown to continue even after the cmc in the supernatant is reached.