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The formation of beta-lactoglobulin (BLG)/sodium polystyrene sulfonate (PSS) complexes decelerates the change in the surface properties of the mixed solutions with the surface age and increases the steady-state dilational surface elasticity in a narrow PSS concentration range. At the same time, the changes in the surface properties are accelerated in the dispersions of BLG fibrils with and without PSS due to the influence of small peptides coexisting with fibrils. A decrease in the peptide concentration as a result of the dispersion purification leads to slower changes in the surface properties at low PSS concentrations. The increase in the polyelectrolyte concentration results in an increase in the steady-state surface elasticity due to the fibril/PSS complex formation and in very slow changes in the surface properties if the polyelectrolyte exceeds a certain critical value. The latter effect is a consequence of the formation of large aggregates and of an increase in the electrostatic adsorption barrier. The consecutive adsorption of BLG fibrils and PSS leads to the formation of regular multilayers at the liquid–gas interface. The multilayer properties change noticeably with an increase in the number of layers from four to six in agreement with previous results on the multilayers of PSS with an oppositely charged synthetic polyelectrolyte, presumably due to the heterogeneity of the first PSS layer. The dynamic elasticity of the multilayers approaches 250 mN/m, indicating that they can effectively stabilize foams and emulsions. [ABSTRACT FROM AUTHOR]

Kinetic dependences have been determined for the surface tension, dilatational dynamic surface elasticity, and ellipsometric angles of solutions of styrene copolymers with 4-vinylbenzyl chloride modified with N,N-dimethyldodecylamine. The micromorphology of the adsorbed and spread layers of these polyelectrolytes has also been studied. All kinetic dependences of the dynamic surface elasticity have turned out to be monotonic in contrast to those observed for previously studied solutions of polyelectrolytes free of polystyrene fragments. The peculiarities of the surface properties of the studied solutions may be related to the formation of microaggregates in the surface layers, because these microaggregates suppress the formation of loops and tails of polymer chains at the interfaces, and, consequently, decrease the surface elasticity after the local maximum. Atomic force microscopy data also indicate the formation of aggregates with sizes in the Z direction of 1–4 nm in the surface layers. The obtained results confirm the conclusions previously made about the formation of aggregates in the surface layers of solutions of polyelectrolytes containing fragments of sodium poly(styrene sulfonate). A 2D phase transition to a denser surface phase and the formation of aggregates with a size of 40 nm in the Z direction have been observed at surface pressures of 25–30 mN/m for the layers of the studied styrene-free polyelectrolyte spread over an aqueous substrate. [ABSTRACT FROM AUTHOR]

The formation of a fibrin film at the sites of cuts and wounds is a complex biochemical process that involves fibrinogen and thrombin as the main components, as well as other enzymes and proteins. Dynamic surface properties of adsorption films obtained from the solution, which contains factors VIII, XIIIa, von Willebrand factor and fibronectin, differ from the fibrinogen adsorption films and fibrin films obtained from a solution containing only fibrinogen and thrombin. Their dynamic surface elasticities exceed the corresponding values for fibrinogen (80 and 55 mN/m, respectively); however, they appear to be lower than value for fibrin prepared from pure components (115 mN/m). The surface pressures achieved for the adsorption films obtained from hemostatic glue (27 mN/m) exceed those for both aforementioned systems (14 mN/m). As follows from the Brewster angle microscopy and scanning electron microscopy data, significant changes in the morphology of the resulting films are responsible for the observed effect. [ABSTRACT FROM AUTHOR]

The formation of beta-lactoglobulin (BLG)/sodium polystyrene sulfonate (PSS) complexes decelerates the change in the surface properties of the mixed solutions with the surface age and increases the steady-state dilational surface elasticity in a narrow PSS concentration range. At the same time, the changes in the surface properties are accelerated in the dispersions of BLG fibrils with and without PSS due to the influence of small peptides coexisting with fibrils. A decrease in the peptide concentration as a result of the dispersion purification leads to slower changes in the surface properties at low PSS concentrations. The increase in the polyelectrolyte concentration results in an increase in the steady-state surface elasticity due to the fibril/PSS complex formation and in very slow changes in the surface properties if the polyelectrolyte exceeds a certain critical value. The latter effect is a consequence of the formation of large aggregates and of an increase in the electrostatic adsorption barrier. The consecutive adsorption of BLG fibrils and PSS leads to the formation of regular multilayers at the liquid–gas interface. The multilayer properties change noticeably with an increase in the number of layers from four to six in agreement with previous results on the multilayers of PSS with an oppositely charged synthetic polyelectrolyte, presumably due to the heterogeneity of the first PSS layer. The dynamic elasticity of the multilayers approaches 250 mN/m, indicating that they can effectively stabilize foams and emulsions.

The surface properties of mixed solutions containing an anionic polyelectrolyte, carboxymethylchitosan (CMCH), and a cationic gemini surfactant, 1,2-bis(dodecyldimethlyammonio)hexane dibromide (C12C6C12), were studied by measuring the surface tension and the dynamic surface elasticity. The association behaviors in the solutions were also measured by fluorescence probe technique. The results showed that the adsorption layer transformed from pure elastic 2D layer to visco-elastic 3D layer with increase in surfactant concentration. The microparticles in the 3D layer were adsorbed from the adjacent bulk to the surface but not formed directly in the surface layer as it was sometimes assumed in other polyelectrolyte/surfactant systems. The stress relaxation mechanism were supposed to be the mass exchange between the unstructured thinner film surrounding the microparticles and the adjacent bulk during the surface compression or expansion. These surface properties of CMCH/C12C6C12 solutions were influenced strongly by the association in the bulk solution. The adsorption layers of mixed solutions of an anionic polyelectrolyte, Carboxymethylchitosan, and a cationic gemini surfactants, 1,2-bis(dodecyldimethlyammonio)hexane dibromide, have various structures at a given polyelectrolyte concentration and different surfactant concentrations. Association in the bulk solution influences strongly the adsorption at the surface. [ABSTRACT FROM AUTHOR]

The review discusses the mechanism of formation of protein/surfactant adsorption layers at the liquid – gas interface. The complexes of globular proteins usually preserve their compact structure a low surfactant concentrations. Therefore a simple kinetic model of the adsorption of charged compact nanoparticles is discussed first and compared with experimental data. The increase of surfactant concentrations results in various conformational transitions in the surface layer. One can obtain information on the changes of the adsorption layer structure using the dilational surface rheology. The kinetic dependencies of the dynamic surface elasticity are strongly different for the adsorption of unfolded macromolecules and compact globules, and have local maxima in the former case corresponding to different steps of the adsorption. These distinctions allow tracing the changes of the tertiary structure of protein/surfactant complexes in the surface layer. The adsorption from mixed solutions of ionic surfactants with β-casein, β-lactoglobulin, bovine serum albumin and myoglobin is discussed with some details. [ABSTRACT FROM AUTHOR]

The dynamic surface elasticity of the solution of carboxymethylchitosan (CMCH) and cetyltrimethylammonium bromide (C16TAB) was measured as a function of the surfactant concentration and the surface age by the oscillating drop method. The results showed that the surface layer of the CMCH/C16TAB solution transformed from loose to structured with the increase in the surfactant concentration. The surface elasticity versus the surface pressure curve during the adsorption showed different features at different surfactant concentration ranges, which was connected with the structural transformation of the surface layer. Our results show that the measurement of dynamic surface dilational properties is a powerful tool for studying the surface kinetics, which is helpful for dealing non-equilibrium systems in industry. [ABSTRACT FROM AUTHOR]

Abstract: Experimental results on the dynamic dilational surface elasticity of protein solutions are analyzed and compared. Short reviews of the protein behavior at the liquid–gas interface and the dilational surface rheology precede the main sections of this work. The kinetic dependencies of the surface elasticity differ strongly for the solutions of globular and non-globular proteins. In the latter case these dependencies are similar to those for solutions of non-ionic amphiphilic polymers and have local maxima corresponding to the formation of the distal region of the surface layer (type I). In the former case the dynamic surface elasticity is much higher (>60mN/m) and the kinetic dependencies are monotonical and similar to the data for aqueous dispersions of solid nanoparticles (type II). The addition of strong denaturants to solutions of bovine serum albumin and β-lactoglobulin results in an abrupt transition from the type II to type I dependencies if the denaturant concentration exceeds a certain critical value. These results give a strong argument in favor of the preservation of the protein globular structure in the course of adsorption without any denaturants. The addition of cationic surfactants also can lead to the non-monotonical kinetic dependencies of the dynamic surface elasticity indicating destruction of the protein tertiary and secondary structures. The addition of anionic surfactants gives similar results only for the protein solutions of high ionic strength. The influence of cationic surfactants on the local maxima of the kinetic dependencies of the dynamic surface elasticity for solutions of a non-globular protein (β-casein) differs from the influence of anionic surfactants due to the heterogeneity of the charge distribution along the protein chain. In this case one can use small admixtures of ionic surfactants as probes of the adsorption mechanism. The effect of polyelectrolytes on the kinetic dependencies of the dynamic surface elasticity of protein solutions is weaker than the effect of conventional surfactants but exceeds the error limits. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Recent studies show strong influence of the dilational surface rheological properties on the stability and dynamics of foam and emulsions. On the other hand, the dilational dynamic surface elasticity proved to be highly sensitive to conformational transitions of macromolecules at fluid–fluid interfaces and can be used to investigate the adsorption mechanism and aggregate formation in the surface layer. The intention of this review consists in the discussion of recent progress in the dialtional surface rheology of solutions of non-ionic homopolymers, block copolymers, polyelectrolytes, polyelectrolyte/surfactant and protein/surfactant complexes. [Copyright &y& Elsevier]

Abstract: Frutalin is a homotetrameric α-d-galactose (d-Gal)-binding lectin that activates natural killer cells in vitro and promotes leukocyte migration in vivo. Because lectins are potent lymphocyte stimulators, understanding the interactions that occur between them and cell surfaces can help to the action mechanisms involved in this process. In this paper, we present a detailed investigation of the interactions of frutalin with phospho- and glycolipids using Langmuir monolayers as biomembrane models. The results confirm the specificity of frutalin for d-Gal attached to a biomembrane. Adsorption of frutalin was more efficient for the galactose polar head lipids, in contrast to the one for sulfated galactose, in which a lag time is observed, indicating a rearrangement of the monolayer to incorporate the protein. Regarding ganglioside GM1 monolayers, lower quantities of the protein were adsorbed, probably due to the farther apart position of d-galactose from the interface. Binary mixtures containing galactocerebroside revealed small domains formed at high lipid packing in the presence of frutalin, suggesting that lectin induces the clusterization and the forming of domains in vitro, which may be a form of receptor internalization. This is the first experimental evidence of such lectin effect, and it may be useful to understand the mechanism of action of lectins at the molecular level. [Copyright &y& Elsevier]