MPI Colloids and Interfaces

Potsdam, Germany

MPI Colloids and Interfaces

Potsdam, Germany
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Miller R.,MPI Colloids and Interfaces | Aksenenko E.V.,NASU A. V. Dumansky Institute of Colloid and Water Chemistry | Kovalchuk V.I.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Fainerman V.B.,Donetsk National Medical University
Physical Chemistry Chemical Physics | Year: 2017

The dynamic and equilibrium surface tension for drops of aqueous C14EO8 solutions at the interface to pure air or pentane, hexane, heptane and toluene saturated air, and the dynamic surface tension of pure water at these interfaces are presented. Two theoretical models were employed: both assuming a diffusion controlled adsorption of the surfactant, and either a diffusion or kinetic barrier governed adsorption of the alkanes. The experimental results are best described by the model which implies a diffusion control for the C14EO8 molecules and the existence of a kinetic barrier for the alkane molecules. The desorption of alkanes from the surface layer after equilibration and their subsequent removal from the measuring cell was studied as well. The desorption process was shown to be slow for heptane and hexane. However, for the pentane vapor the desorption is quite rapid, and after the desorption commences the surface tension becomes equal to that at the interface with pure air. © 2017 the Owner Societies.


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 | Aksenenko E.V.,NASU A. V. Dumansky Institute of Colloid and Water Chemistry | Kovalchuk V.I.,NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry | Miller R.,MPI Colloids and Interfaces
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2016

The drop profile method is used to study the influence of hexane vapor in the air atmosphere on the surface tension of water. It was shown that the results depend essentially on the air humidity. At the interface with dry air a fast and strong decrease of surface tension was observed. In humid air and in a measurement cell filled with water, the process is slower and the resulting surface tension is higher. The experimental conditions are defined at which stable results can be measured.A new theoretical model is developed to describe the influence of alkane vapor in the gas phase on the surface tension of aqueous solutions of the reorientable surfactant C10EO8. This model assumes that a first interfacial layer is composed by surfactants mixed with alkane, and a second layer which is formed by alkane only. The experimental equilibrium surface tension data for the studied C10EO8 solutions agree very well with those calculated from the given model. © 2016 Elsevier B.V.


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

Proteins and their mixtures with surfactants are widely used in many applications. The knowledge of their solution bulk behavior and its impact on the properties of interfacial layers made great progress in the recent years. Different mechanisms apply to the formation process of protein/surfactant complexes for ionic and non-ionic surfactants, which are governed mainly by electrostatic and hydrophobic interactions. The surface activity of these complexes is often remarkably different from that of the individual protein and has to be considered in respective theoretical models. At very low protein concentration, small amounts of added surfactants can change the surface activity of proteins remarkably, even though no strongly interfacial active complexes are observed. Also small added amounts of non-ionic surfactants change the surface activity of proteins in the range of small bulk concentrations or surface coverages. The modeling of the equilibrium adsorption behavior of proteins and their mixtures with surfactants has reached a rather high level. These models are suitable also to describe the high frequency limits of the dilational viscoelasticity of the interfacial layers. Depending on the nature of the protein/surfactant interactions and the changes in the interfacial layer composition rather complex dilational viscoelasticities can be observed and described by the available models. The differences in the interfacial behavior, often observed in literature for studies using different experimental methods, are at least partially explained by a depletion of proteins, surfactants and their complexes in the range of low concentrations. A correction of these depletion effects typically provides good agreement between the data obtained with different methods, such as drop and bubble profile tensiometry. © 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 | 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.


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.


Fainerman V.B.,Medical University Donetsk | Lotfi M.,MPI Colloids and Interfaces | Lotfi M.,Sharif University of Technology | Javadi A.,MPI Colloids and Interfaces | And 5 more authors.
Langmuir | Year: 2014

The influence of the addition of the nonionic surfactants dodecyl dimethyl phosphine oxide (C12DMPO), tetradecyl dimethyl phosphine oxide (C14DMPO), decyl alcohol (C10OH), and C10EO5 at concentrations between 10-5 and 10-1 mmol/L to solutions of -casein (BCS) and -lactoglobulin (BLG) at a fixed concentration of 10-5 mmol/L on the surface tension is studied. It is shown that a significant decrease of the water/air surface tension occurs for all the surfactants studied at very low concentrations (10-5-10-3 mmol/L). All measurements were performed with the buoyant bubble profile method. The dynamics of the surface tension was simulated using the Fick and Ward-Tordai equations. The calculation results agree well with the experimental data, indicating that the equilibration times in the system studied do not exceed 30 000 s, while the time required to attain the equilibrium on a plane surface is by one order of magnitude higher. To achieve agreement between theory and experiment for the mixtures, a supposition was made about the influence of the concentration of nonionic surfactant on the adsorption activity of the protein. The adsorption isotherm equation of the protein was modified accordingly, and this corrected model agrees well with all experimental data. © 2014 American Chemical Society.


PubMed | NASU A. V. Dumansky Institute of Colloid and Water Chemistry, MPI Colloids and Interfaces, NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry and Donetsk National Medical University
Type: | Journal: Physical chemistry chemical physics : PCCP | Year: 2017

The dynamic and equilibrium surface tension for drops of aqueous C


PubMed | NASU A. V. Dumansky Institute of Colloid and Water Chemistry, MPI Colloids and Interfaces, NASU F. D. Ovcharenko Institute of Biocolloidal Chemistry and Medical University Donetsk
Type: Journal Article | Journal: Langmuir : the ACS journal of surfaces and colloids | 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.

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