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Berejnov V. | Berejnov V. V. | Berejnov Viatcheslav | Berejnov Viatcheslav V.

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Self pinning protein-laden drops

Berejnov Viatcheslav V.
14 Apr 2008 physics.chem-ph physics.flu-dyn arxiv.org/abs/0804.2100

Proteins dissolved in a drop induce and enhance the pinning of the drop contact line. This effect dramatically increases volume of drops that are vertically pinned on a flat siliconized substrate. The drop pinning behavior exhibits two regimes: for low protein content in a drop the pinning increases as the contact angle hysteresis increases, and for high protein content the pinning decreases as the surface tension of the protein solution decreases.

Protein and ionic surfactants - promoters and inhibitors of contact line pinning

Berejnov Viatcheslav V.
03 Apr 2007 physics.chem-ph physics.flu-dyn arxiv.org/abs/0704.0434

We report a new effect of surfactants in pinning a drop contact line, specifically that lysozyme promotes while lauryl sulfate inhibits pinning. We explain the pinning disparity assuming difference in wetting: the protein-laden drop wets a "clean" surface and the surfactant-laden drop wets an auto-precursored surface.

Effect of transient pinning on stability of drops sitting on an inclined plane

Berejnov Viatcheslav V., Thorne Robert E.
23 Sep 2006 physics.flu-dyn arxiv.org/abs/physics/0609208

We report on new instabilities of the quasi-static equilibrium of water drops pinned by a hydrophobic inclined substrate. The contact line of a statically pinned drop exhibits three transitions of partial depinning: depinning of the advancing and receding parts of the contact line and depinning of the entire contact line leading to the drop's translational motion. We find a region of parameters where the classical Macdougall-Ockrent-Frenkel approach fails to estimate the critical volume of the statically pinned inclined drop.

Transparent Lyotropic Ferronematics

Berejnov V. V., Raikher Yu. L.
19 Mar 2001 cond-mat.soft cond-mat.mtrl-sci arxiv.org/abs/cond-mat/0103383

Transparent lyotropic ferronematic dispersions are synthesized by admixing a cationic ferrofluid to the lyotropic liquid crystal PL/1D/Wt. The transparency is spontaneous and time-independent. It is observed in zero magnetic field in white and polarized light for disordered layers of ferroliquid crystals of thicknesses ~1 cm in both isotropic and nematic phases. Justification of the low extinction of light in the systems of the lyotropic origin is presented.

Measurements of Protein-Protein Interactions by Size Exclusion Chromatography

Bloustine J., Berejnov V., Fraden S.
12 Jun 2003 cond-mat.soft q-bio.QM arxiv.org/abs/cond-mat/0306346

A method is presented for determining second virial coefficients B_2 of protein solutions from retention time measurements in size exclusion chromatography (SEC). We determine B_2 by analyzing the concentration dependance of the chromatographic partition coefficient. We show the ability of this method to track the evolution of B_2 from positive to negative values in lysozyme and bovine serum albumin solutions. Our SEC results agree quantitatively with data obtained by light scattering.

Enhancing protein drop stability for crystallization by chemical patterning

Berejnov Viatcheslav, Thorne Robert E.
12 Apr 2006 cond-mat.soft cond-mat.mtrl-sci arxiv.org/abs/cond-mat/0604326

Motion of protein drops on crystallization media during routine handling is a major factor affecting the reproducibility of crystallization conditions. Drop stability can be enhanced by chemical patterning to more effectively pin the drop's contact line. As an example, a hydrophilic area is patterned on an initially flat hydrophobic glass slide. The drop remains confined to the hydrophilic area, and the maximum drop size that remains stable when the slide is rotated to the vertical position increases. This simple method is readily scalable and has the potential to significantly improve outcomes in hanging and sitting drop crystallization.

Effects of cryoprotectant concentration and cooling rate on vitrification of aqueous solutions

Berejnov Viatcheslav, Husseini Naji S., Alsaied Osama A., Thorne Robert E.
13 Apr 2006 physics.bio-ph physics.chem-ph arxiv.org/abs/physics/0604109

Vitrification of aqueous cryoprotectant mixtures is essential in cryopreservation of proteins and other biological samples. We report systematic measurements of critical cryoprotective agent (CPA) concentrations required for vitrification during plunge cooling from T=295 K to T=77 K in liquid nitrogen. Measurements on fourteen common CPAs including alcohols (glycerol, methanol, isopropanol), sugars (sucrose, xylitol, dextrose, trehalose), PEGs (ethylene glycol, PEG 200, PEG 2 000, PEG 20 000), glycols (DMSO, MPD), and salt (NaCl) were performed for volumes ranging over four orders of magnitude from ~nL to 20 mkL, and covering the range of interest in protein crystallography. X-ray diffraction measurements on aqueous glycerol mixtures confirm that the polycrystalline-to-vitreous transition occurs within a span of less than 2% w/v in CPA concentration, and that the form of polycrystalline ice (hexagonal or cubic) depends on CPA concentration and cooling rate. For most of the studied cryoprotectants, the critical concentration decreases strongly with volume in the range from ~5 mkL to ~0.1 mkL, typically by a factor of two. By combining measurements of the critical concentration versus volume with cooling time versus volume, we obtain the function of greatest intrinsic physical interest: the critical CPA concentration versus cooling rate during flash cooling. These results provide a basis for more rational design of cryoprotective protocols, and should yield insight into the physics of glass formation in aqueous mixtures.

Comment on "Self-Running Droplet: Emergence of Regular Motion from Nonequilibrium Noise"

Berejnov V., Leshansky A.
14 Apr 2006 physics.flu-dyn arxiv.org/abs/physics/0604113

In a recent Letter (Y. Sumino et al., PRL 94, 068301 (2005)) a spontaneous motion of an oil droplet in the surrounding aqueous media along a glass surface was reported. The authors suggested that the self-locomotion is driven by a difference in wettability between the front and the rear of a droplet sustained by its translational motion. We disagree with the author's explanations. We analyzed the supplementary materials provided by Sumino et al. and found that their data did not support their conclusions. We provide an interpretation of the experimental data of Sumino et al. and the underlying physical mechanism of the self-locomotion.

Effect of transient pinning on stability of drops sitting on an inclined plane

Berejnov Viatcheslav V., Thorne Robert E.
23 Sep 2006 physics.flu-dyn arxiv.org/abs/physics/0609208

We report on new instabilities of the quasi-static equilibrium of water drops pinned by a hydrophobic inclined substrate. The contact line of a statically pinned drop exhibits three transitions of partial depinning: depinning of the advancing and receding parts of the contact line and depinning of the entire contact line leading to the drop's translational motion. We find a region of parameters where the classical Macdougall-Ockrent-Frenkel approach fails to estimate the critical volume of the statically pinned inclined drop.

A lyotropic ferrocolloid (ferronematic) based on a potassium laurate/1-decanole/water ternary solution

Berejnov V. V., Cabuil V., Perzynski R., Raikher Yu. L.
21 Mar 2007 cond-mat.soft cond-mat.mtrl-sci arxiv.org/abs/cond-mat/0703537

A lyotropic ferrocolloid is synthesized by mixing of a cationic ferrofluid and potassium laurate/1-decanol/water ternary solution. Conditions of existence of a nematic phase in this mixture, other mesophases, and their phase diagrams in the vicinity of the nematic one are obtained and characterized quantitatively. Inside of the nematic zone the lyotropic ferrocolloid becomes a ferronematic, i.e., a liquid crystal with remarkably strong magnetic properties. We found that the pH and the component concentrations dramatically affect the amount of magnetic particles stably suspended in a lyotropic carrier. Magnetization and magnetic susceptibility of synthesized ferronematics are measured depending on the concentration of dispersed magnetic particles.