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pH-equilibration of human hair: Kinetics and pH-dependence of the partition ratios for H+ - and OH- -ions based on a Freundlich isotherm.
Wortmann, Franz J; Hardie, Katie; Schellenberg, Natalja; Jones, Celina; Wortmann, Gabriele; Schulze Zur Wiesche, Erik.
Afiliación
  • Wortmann FJ; Department of Materials, School of Natural Sciences, The University of Manchester, UK; F & GW - Consultants, Aachen, DE. Electronic address: franz.wortmann@manchester.ac.uk.
  • Hardie K; Department of Materials, School of Natural Sciences, The University of Manchester, UK.
  • Schellenberg N; Department of Materials, School of Natural Sciences, The University of Manchester, UK; Henkel AG & Co. KGaA, Hamburg, DE.
  • Jones C; Department of Materials, School of Natural Sciences, The University of Manchester, UK.
  • Wortmann G; Department of Materials, School of Natural Sciences, The University of Manchester, UK; F & GW - Consultants, Aachen, DE.
  • Schulze Zur Wiesche E; Henkel AG & Co. KGaA, Hamburg, DE.
Biophys Chem ; 297: 107010, 2023 06.
Article en En | MEDLINE | ID: mdl-37060741
Hair is an insoluble, fibrous, α-keratinous, protein composite material, providing outer coverage, e.g., for mammals. In the context of a wider study on the effects of pH on human hair properties, we investigated the time-dependence of pH-equilibration study across the acid and the basic pH-range, using appropriate pure solutions of hydrochloric acid and sodium hydroxide. The results show that pH-equilibration follows essentially equal 1st-order kinetics across the pH-range. The characteristic process time does not change significantly and is in the range of 2.5-5 h. The analysis enables to determine the equilibrium uptakes of H+- and OH- -ions. These follow the expected U-shaped path across the pH-range. For both acidic and alkaline conditions, data are well described by two very similar sorption isotherms of the Freundlich-type. In consequence, partition ratios for both ions are highest near neutrality (pH 7: >6000) and drop off strongly towards low and high pHs (<50). Hair is thus a very strong 'sink' for H+ and OH-. This observation fundamentally challenges traditional views of limited ion uptake, namely, in the mid-pH-range due to hindered diffusion. It also does not support considerations on special roles of certain pHs, specific groups of amino acids, or morphological components. Our analysis thus suggests that established views of the interaction of hair and pH need to be reconsidered, The Freundlich isotherm approach appears to provide a versatile tool to refine our understanding of the interactions of hair and possibly other keratinous materials (horn, nail, feathers) with acids and bases.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Ácidos / Ácido Clorhídrico Límite: Animals / Humans Idioma: En Revista: Biophys Chem Año: 2023 Tipo del documento: Article Pais de publicación: Países Bajos
Texto completo
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Imprimir
XML
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Ácidos / Ácido Clorhídrico Límite: Animals / Humans Idioma: En Revista: Biophys Chem Año: 2023 Tipo del documento: Article Pais de publicación: Países Bajos