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Potsdam, Germany

Fainerman V.B.,Medical University Donetsk | Aksenenko E.V.,NASU A. V. Dumansky Institute of Colloid and Water Chemistry | Miller R.,MPI Colloids and Interfaces
Advances in Colloid and Interface Science | Year: 2015

The influence of hexane vapor in the air atmosphere on the surface tension of water and solutions of C10EO8, C n TAB and proteins are presented. For dry air, a fast and strong decrease of surface tension of water was observed. In humid air, the process is slower and the surface tension higher. There are differences between the results obtained by the maximum bubble pressure, pendant drop and emerging bubble methods, which are discussed in terms of depletion and initial surface load. The surface tension of aqueous solutions of β-sasein (BCS), β-lactoglobulin (BLG) and human serum albumin (HSA) at the interfaces with air and air-saturated hexane vapor were measured. The results indicate that the equilibrium surface tension in the hexane vapor atmosphere is considerably lower (at 13-20mN/m) as compared to the values at the interface with pure air.A reorientation model is proposed assuming several states of adsorbed molecules with different molar area values. The newly developed theoretical model is used to describe the effect of alkane vapor in the gas phase on the surface tension. This model assumes that the first layer is composed of surfactant (or protein) molecules mixed with alkane, and the second layer is formed by alkane molecules only. The processing of the experimental data for the equilibrium surface tension for the C10EO8 and BCS solutions results in a perfect agreement between the observed and calculated values. The co-adsorption mechanism of dipalmitoyl phosphatidyl choline (DPPC) and the fluorocarbon molecules leads to remarkable differences in the surface pressure term of cohesion Π coh. This in turn leads to a very efficient fluidization of the monolayer. It was found that the adsorption equilibrium constant for dioctanoyl phosphatidyl choline is increased in the presence of perfluorohexane, and the intermolecular interaction of the components is strong. © 2015 Elsevier B.V.

Gruber K.,Ludwig Maximilians University of Munich | Hermann B.A.,Ludwig Maximilians University of Munich | Seeberger P.H.,MPI Colloids and Interfaces
Angewandte Chemie - International Edition | Year: 2011

Glycans on cell membranes play crucial roles in many cell cell communication processes and the transmission of dangerous diseases like AIDS or malaria. The protein Cyanovirin-N (CV-N) is able to bind and block nonamannose structures found on the surface of the human immunodeficiency virus (HIV) and prevents cell infection. To accurately determine the prophylactic or therapeutic potency of such proteins, specfically designed sensors are required. The cantilever array technique provides advantages like label free detection, short measurement times and up to eight parallel reference channels. A novel cantilever array sensor for the detection of carbohydrate protein interactions is introduced. Parameters that describe sensor quality such as sensitivity, concentration dependence of signal size and specficity of the recognition, are discussed. To this end, a cantilever array was coated with trimannose and nonamannose sugars to create specfic sensing channels. Additional galactose layers were applied on cantilevers of the same array to act as reference and determine the amount of nonspecfic binding. With this setup C V-N concentrations could be detected over five orders of magnitude down to picomolar levels. The sensor differentiates trimannose from nonamannose coatings via smaller and larger sensor signals. Finally, the specficity of CV-N mannose binding was verfied by a competitive inhibition assay. Additional tests with the generic protein Concanavalin A (ConA) demonstrate the versatility of this glycan cantilever array sensor for protein detection. Sensitivity in the nanomolar regime and the dissociation constant are in accordance with literature reports. The specficity of ConA recognition was independently demonstrated by competitive inhibition. As certain medically relevant bacteria also specfically recognize mannose structures, the detection of Escherichia coli (E.coli) is currently investigated. First results indicate that this sensor setup can be expanded successfully from protein to bacteria recognition. The described glycan cantilever array sensor poses a potent and versatile tool to analyze and detect carbohydrate interactions that may advance drug design and diagnostic applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fainerman V.B.,Medical University Donetsk | Aksenenko E.V.,NASU A. V. Dumansky Institute of Colloid and Water Chemistry | Lylyk S.V.,Medical University Donetsk | Lotfi M.,MPI Colloids and Interfaces | And 2 more authors.
Journal of Physical Chemistry B | Year: 2015

The influence of the addition of the nonionic surfactants C12DMPO, C14DMPO, C10OH, and C10EO5 at concentrations between 10-5 and 10-1 mmol/L to solutions of β-casein (BCS) and β-lactoglobulin (BLG) at a fixed concentration of 10-5 mmol/L on the dilational surface rheology is studied. A maximum in the viscoelasticity modulus |E| occurs at very low surfactant concentrations (10-4 to 10-3 mmol/L) for mixtures of BCS with C12DMPO and C14DMPO and for mixtures of BLG with C10EO5, while for mixture of BCS with C10EO5 the value of |E| only slightly increased. The |E| values calculated with a recently developed model, which assumes changes in the interfacial molar area of the protein molecules due to the interaction with the surfactants, are in satisfactory agreement with experimental data. A linear dependence exists between the ratio of the maximum modulus for the mixture to the modulus of the single protein solution and the coefficient reflecting the influence of the surfactants on the adsorption activity of the protein. © 2015 American Chemical Society.

Lotfi M.,MPI Colloids and Interfaces | Lotfi M.,Sharif University of Technology | Karbaschi M.,MPI Colloids and Interfaces | Javadi A.,MPI Colloids and Interfaces | And 7 more authors.
Current Opinion in Colloid and Interface Science | Year: 2014

Dynamic interfacial parameters are the key properties of interfaces in many modern technologies and can be studied in various ways. For applications like foams and emulsions, the dynamics of adsorption and the dilational and shear rheology of liquid-fluid interfaces are investigated most frequently. This work gives an insight into recently developed new experimental approaches, such as fast capillary pressure tensiometry for growing and oscillating drops. These experiments are presented in comparison to more classical techniques like drop profile tensiometry and capillary wave damping. Progress in these experiments based on generated interfacial perturbations can be expected only by a close link to respective CFD simulations. We also present the state of the art of CFD simulations, which have reached a high level during the last decade and provide a substantial basis for dynamic interfacial experiments. © 2014 Elsevier Ltd.

Fainerman V.B.,Medical University Donetsk | Kovalchuk V.I.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Aksenenko E.V.,NASU A. V. Dumansky Institute of Colloid and Water Chemistry | Miller R.,MPI Colloids and Interfaces
Langmuir | Year: 2016

The dilational viscoelasticity of adsorption layer was measured at different frequencies of drop and bubble surface area oscillations for aqueous C12EO5 solutions. The modulus values obtained by the two experimental protocols are the same for - < 15 mN/m, while for higher surface pressures the values from drop experiments exceed those from bubble profile analysis. The nature of this phenomenon was studied using stress deformation experiments. At high surfactant concentrations the magnitude of surface tension variations is essentially higher for drops as compared with bubbles, leading to an increased viscoelasticity modulus for oscillating drops. The observed effects are analyzed quantitatively using a diffusion controlled exchange of matter model. The viscoelasticity moduli for a number of surfactants (different CnEOm and Tritons, C13DMPO, and SDS) are reported, and it is shown that the discrepancies between the data obtained by the two methods for many surfactants agree well with the predictions made here. © 2016 American Chemical Society.

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