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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.


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.


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.


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.


Noskov B.A.,Saint Petersburg State University | Mikhailovskaya A.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
Langmuir | Year: 2010

Measurements of the surface dilational elasticity close to equilibrium did not indicate significant distinctions in the surface conformation of different forms of bovine serum albumin (BSA) in a broad pH range. At the same time, the protein denaturation in the surface layer under the influence of guanidine hydrochloride led to strong changes in the kinetic dependencies of the dynamic surface elasticity if the denaturant concentration exceeded a critical value. It was shown that the BSA unfolding at the solution surface occurred at lower denaturant concentrations than in the bulk phase. In the former case, the unfolding resulted in the formation of loops and tails at surface pressures above 12 mN/m. The maximal values of the dynamic surface elasticity almost coincided with the corresponding data for the recently investigated solutions of β-lactoglobulin, thereby indicating a similar unfolding mechanism. © 2010 American Chemical Society.


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.


Yazhgur P.A.,Saint Petersburg State University | Noskov B.A.,Saint Petersburg State University | Liggieri L.,CNR Institute for Energetics and Interphases | Lin S.-Y.,National Taiwan University of Science and Technology | And 3 more authors.
Soft Matter | Year: 2013

The adsorption films of silica nanoparticles modified by a cationic surfactant (cetyltrimethylammonium bromide, CTAB) at the air-water interface were investigated by the dilational surface rheology and optical methods. Special attention was paid to the slow changes of surface properties with the surface age. The surface tension and dynamic dilational surface elasticity were measured as a function of CTAB concentration. The whole surfactant concentration range can be divided into four regions characterized by different surface rheological behavior. Depending on the CTAB concentration, the surface elasticity close to the equilibrium may reach extremely high values (∼1000 mN m-1) and strongly depends on the applied surface strain. This occurs at surfactant concentrations below the region where the dispersion becomes turbid, indicating particle aggregation in the bulk. The Brewster angle microscopy and ellipsometry show that the adsorption layer becomes fragile and inhomogeneous in this region. © 2013 The Royal Society of Chemistry.


Sankaranarayanan K.,CSIR - Central Electrochemical Research Institute | Dhathathreyan A.,CSIR - Central Electrochemical Research Institute | Kragel J.,MPI fur Kolloid und Grenzflachenforschung | Miller R.,MPI fur Kolloid und Grenzflachenforschung
Journal of Physical Chemistry B | Year: 2012

This study describes the folding and organization of myoglobin (Mb) at the solution/air interface at different pH values of 2.5, 3.5, 5.5, 7.5, and 8.5. Dynamic surface tension and the associated dilational and shear viscoelasticity for Mb at these pHs have been studied using a sinusoidal surface compression and expansion for frequencies ranging from 0.01 to 0.4 Hz. The changes in dilational viscosity, elasticity, and fluorescence lifetime measurements have been related to the conformational changes of the protein films at the interface. It is observed that while acid-induced denaturation of the protein does not lead to large changes in dilational properties, the shear properties on the other hand are strongly influenced by it, and the protein behaves like a shear-thickening fluid. At higher pH, particularly at the isoelectric point, Mb is pseudoplastic indicating an increase in the shear viscosity. These results are strongly suggestive of formation of hydrophobic clusters at the protein-buffer interface because of the change in the overall charge distributions. © 2011 American Chemical Society.


Pussak D.,MPI fur Kolloid und Grenzflachenforschung | Ponader D.,MPI fur Kolloid und Grenzflachenforschung | Mosca S.,MPI fur Kolloid und Grenzflachenforschung | Ruiz S.V.,MPI fur Kolloid und Grenzflachenforschung | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2013

Elastic sensors: A simple method is presented for the measurement of specific biomolecular interactions with soft colloidal hydrogel particles (SCPs) as sensors. Carbohydrate/lectin interactions (see picture; green: carbohydrate molecules) were studied by optical detection of the mechanical deformation of the particles on a lectin surface. The affinity of various carbohydrate inhibitors could also be readily determined. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Mohwald H.,MPI fur Kolloid und Grenzflachenforschung
Colloid and Polymer Science | Year: 2010

This article deals with topics where I expect special future challenges, exemplifying these by experiments out of my own department. One area where I expect large progress also in view of many technical developments in the past concerns the understanding of the structure of fluid interfaces at the atomic level. It is shown by nonlinear optical spectroscopies that the free water surface is ice-like and can be "liquefied" by ion adsorption. X-ray fluorescence from the interface demonstrates that ion binding is very specific which cannot be explained by existing theories. A second major area are nonequilibrium features, and one of the old and new ones here is nucleation and growth. This presentation concentrates on effects produced by ultrasound, a well-defined trigger of gas bubble formation. It exhibits high potential for chemistry at extreme conditions but with a reactor at normal conditions. It has special importance for treatment of surfaces that can be also manipulated via controlled surface energies. A third area will concern complex and smart systems with multiple functions in materials and biosciences. As next generation, I anticipate those with feedback control, and examples on this are self-repairing coatings. © The Author(s) 2009.

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