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Mikhailovskaya A.A.,Saint Petersburg State University | Noskov B.A.,Saint Petersburg State University | Lin S.-Y.,National Taiwan University of Science and Technology | Loglio G.,University of Florence | Miller R.,MPI fur Kolloid und Grenzflachenforschung
Journal of Physical Chemistry B | Year: 2011

The dynamic dilatational surface elasticity of mixed solutions of globular proteins (β-lactoglobulin (BLG) and bovine serum albumin (BSA)) with cationic (dodecyltrimethylammonium bromide (DTAB)) and anionic (sodium dodecyl sulfate (SDS)) surfactants was measured as a function of the surfactant concentration and surface age. If the cationic surfactant concentration exceeds a certain critical value, the kinetic dependencies of the dynamic surface elasticity of BLG/DTAB and BSA/DTAB solutions become nonmonotonous and resemble those of mixed solutions of proteins with guanidine hydrochloride. This result indicates not only the destruction of the protein tertiary structure in the surface layer of mixed solution but also a strong perturbation of the secondary structure. The corresponding kinetic dependencies for protein solutions with added anionic surfactants are always monotonous, thereby revealing a different mechanism of the adsorption layer formation. One can assume that the secondary structure is destroyed to a lesser extent in the latter case and hinders the formation of loops and tails at the interface. The increase of the solution's ionic strength by the addition of sodium chloride results in stronger changes of the protein conformations in the surface layer and the appearance of a local maximum in the kinetic dependencies of the dynamic surface elasticity in a relatively narrow range of SDS concentration. © 2011 American Chemical Society. Source


Noskov B.A.,Saint Petersburg State University | Loglio G.,MPI fur Kolloid und Grenzflachenforschung | Miller R.,University of Florence
Advances in Colloid and Interface Science | Year: 2011

Recent application of the methods of surface dilational rheology to solutions of the complexes between synthetic polyelectrolytes and oppositely charged surfactants (PSC) gave a possibility to determine some steps of the adsorption layer formation and to discover an abrupt transition connected with the formation of microaggregates at the liquid surface. The kinetic dependencies of the dynamic surface elasticity are always monotonous at low surfactant concentrations but can have one or two local maxima in the range beyond the critical aggregation concentration. The first maximum is accompanied by the generation of higher harmonics of induced surface tension oscillations and caused by heterogeneities in the adsorption layer. The formation of a multilayered structure at the surface for some systems leads to the second maximum in the dynamic surface elasticity. The hydrophobicity and charge density of a polymer chain influence strongly the surface structure, resulting in a variety of dynamic surface properties of PSC solutions. Optical methods and atomic force microscopy give additional information for the systems under consideration. Experimental results and existing theoretical frameworks are reviewed with emphasis on the general features of all studied PSC systems. © 2011 Elsevier B.V. All rights reserved. Source


Mikhailovskaya A.A.,Saint Petersburg State University | Noskov B.A.,Saint Petersburg State University | Nikitin E.A.,Saint Petersburg State University | Lin S.-Y.,National Taiwan University of Science and Technology | And 2 more authors.
Food Hydrocolloids | Year: 2014

The dilational surface rheology is applied to solutions of globular proteins (bovine serum albumin and β-lactoglobulin) in presence of urea. The kinetic dependencies of the dynamic dilational surface elasticity become non-monotonic if the denaturant concentration exceeds a certain critical value indicating the adsorption of unfolded protein molecules. The unfolding in the surface layer occurs at lower urea concentrations than in the bulk phase similar to the case of mixed solutions of the proteins and guanidine hydrochloride. At the same time, the influence of urea on the dilational surface rheological properties of protein solutions has some peculiarities. In particular, the high values of the dynamic surface elasticity close to equilibrium indicate the limited flexibility of unfolded BLG molecules in the surface layer. © 2012 Elsevier Ltd. Source


Milyaeva O.Y.,Saint Petersburg State University | Noskov B.A.,Saint Petersburg State University | Lin S.-Y.,National Taiwan University of Science and Technology | Loglio G.,University of Florence | Miller R.,MPI fur Kolloid und Grenzflachenforschung
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

The dynamic surface elasticity of mixed solutions of bovine serum albumin (BSA) and poly(diallyldimethylammonium chloride) (PDADMAC) was measured as a function of the surface age, polyelectrolyte concentration and solution pH. The addition of polyelectrolyte does not influence the dynamic surface properties of protein solution at pH below the isoelectric point of BSA. At the same time, one can observe significant changes of the kinetic dependencies of the surface pressure and surface elasticity under the influence of polyelectrolyte at higher pH indicating the interaction between the components. The acceleration of the changes of the surface properties can be connected with the decrease of the electric adsorption barrier due to the decrease of the total charge of the protein/polyelectrolyte complex. The local maximum of the kinetic dependencies of the dynamic surface elasticity at pH higher than the isoelectric point indicates partial destruction of the protein tertiary structure at high surface pressures. © 2013 Elsevier B.V. Source


Bykov A.G.,Saint Petersburg State University | Noskov B.A.,Saint Petersburg State University | Loglio G.,University of Florence | Lyadinskaya V.V.,Saint Petersburg State University | Miller R.,MPI fur Kolloid und Grenzflachenforschung
Soft Matter | Year: 2014

The dependence of the dilational surface elasticity on the surface pressure of the spread monolayers of polystyrene microparticles is studied at the water-air interface. The surface rheological measurements together with the data from optical methods allow the division of the whole range of surface pressures into three zones characterized by different monolayer structures. The extremely high surface elasticity (∼500 mN m-1) at surface pressures close to 30 mN m-1 is similar to the results for the adsorption layer of the complexes formed between silica particles and surfactant molecules and is probably caused by strong hydrophobic attraction between the particles. At the same time, some other characteristic features of the viscoelasticity of the monolayers of polysterene microparticles differ strongly from the properties of previously studied systems. This journal is © the Partner Organisations 2014. Source

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