Print Email Facebook Twitter Importance of physical vs. chemical interactions in surface shear rheology Title Importance of physical vs. chemical interactions in surface shear rheology Author Wierenga, P.A. Kosters, H. Egmond, M.R. Voragen, A.G.J. de Jongh, H.H.J. TNO Kwaliteit van Leven Publication year 2006 Abstract The stability of adsorbed protein layers against deformation has in literature been attributed to the formation of a continuous gel-like network. This hypothesis is mostly based on measurements of the increase of the surface shear elasticity with time. For several proteins this increase has been attributed to the formation of intermolecular disulfide bridges between adsorbed proteins. However, according to an alternative model the shear elasticity results from the low mobility of the densely packed proteins. To contribute to this discussion, the actual role of disulfide bridges in interfacial layers is studied. Ovalbumin was thiolated with S-acetylmercaptosuccinic anhydride (S-AMSA), followed by removal of the acetylblock on the sulphur atom, resulting in respectively blocked (SX) and deblocked (SH) ovalbumin variants. This allows comparison of proteins with identical amino acid sequence and similar globular packing and charge distribution, but different chemical reactivity. The presence and reactivity of the introduced, deblocked sulfhydryl groups were confirmed using the sulfhydryl-disulfide exchange index (SEI). Despite the reactivity of the introduced sulfhydryl groups measured in solution, no increase in the surface shear elasticity could be detected with increasing reactivity. This indicates that physical rather than chemical interactions determine the surface shear behaviour. Further experiments were performed in bulk solution to study the conditions needed to induce covalent aggregate formation. From these studies it was found that mere concentration of proteins (to 200 mg/mL, equivalent to a surface concentration of around 2 mg/m2) is not sufficient to induce significant aggregation to form a continuous network. In view of these results, it was concluded that the adsorbed layer should not be considered a gelled network of aggregated material (in analogy with three-dimensional gels formed from heating protein solutions). Rather, it would appear that the adsorbed proteins form a highly packed system of proteins with net-repulsive interactions. © 2005 Elsevier B.V. All rights reserved. Subject NutritionFood technologyAir-water interfaceChemical modificationOvalbuminSurface rheologyThiolationElasticityGelsProteinsShear stressSurface chemistryAir-water interface]OvalbuminSurface rheologyThiolationRheologydisulfideovalbuminadsorptionanimalarticlechemistrychickenelasticityflow kineticsprotein conformationsurface propertyAdsorptionAnimalsChickensDisulfidesElasticityOvalbuminProtein ConformationRheologySurface Properties To reference this document use: http://resolver.tudelft.nl/uuid:5a53d30d-41dd-451a-8630-d6b5f1c21be4 DOI https://doi.org/10.1016/j.cis.2005.11.001 TNO identifier 239137 ISSN 0001-8686 Source Advances in Colloid and Interface Science, 119 (2-3), 131-139 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.