Comparison of the Overall Motion Correlation Times of Several Mammalian Serum Albumins in Dilute Solutions Determined on the Basis of Maxwell Effect and the Debye-Stokes-Einstein Equation.

One of the rarely used ways of determining the overall motion correlation time of proteins is method based on the Maxwell effect. This effect consists in the appearance of a stimulated birefringence in liquids or solutions and induced by the mechanical force like shear stress in a streamline flow. To determine the overall motion correlation time for protein in dilute solution is sufficient to know the molecular mass and the ratio of the principal axes of protein, and an intrinsic viscosity. The intrinsic viscosity has been measured using an Ubbelohde-type capillary microviscometer immersed in a water-bath controlled thermostatically in the range from 5°C to 45°C for six mammalian albumins. To check the influence of solution pH on the overall motion correlation time the intrinsic viscosity value of the human serum albumin in solutions at the isoelectric point and beyond of it was measured. The thus obtained correlation times were compared with the times determined on the basis of the Debye-Stokes-Einstein equation.

The Glass Transition Temperature and Temperature Dependence of Activation Energy of Viscous Flow of Ovalbumin

The paper presents the results of viscosity determinations on aqueous solutions of ovalbumin at a wide range of concentrations and at temperatures ranging from 5°C to 55°C. On the basis of these measurements and three models of viscosity for glass-forming liquids: Avramov’s model, free-volume model and power-law model, the activation energy of viscous flow for solutions and ovalbumin molecules, at different temperatures, was calculated. The obtained results show that activation energy monotonically decreases with increasing temperature both for solutions and ovalbumin molecules. The influence of the energy of translational heat motion, protein-protein and protein-solvent interactions, flexibility and hydrodynamic radius of ovalbumin on the rate of decrease in activation energy with temperature has been discussed. One of the parameters in the Avramov’s equation is the glass transition temperature Tg. It turns out that the Tg of ovalbumin solutions increases with increasing concentration. To obtain the glass transition temperature of the dry ovalbumin, a modified Gordon-Taylor equation is used. Thus determined the glass transition temperature for dry ovalbumin is equal to (231.8 ± 6.1) K.

Incorporation of Ag Nanoparticles Into Micelles. Stability Studies of Self-Organized Nanoparticlesmicelles Structures

In this paper we present the results of measured physical parameters of self-organized structures consisting of hydrophobic functionalized silver nanoparticles and amphiphilic molecules capable of micelles formation. Those systems may be considered as simple models for transfer of nanoparticles through the biological membrane. Three different surfactants were used: negatively charged sodium dodecyl sulphite, SDS, neutral Triton X-100 and positively charged tetredodecyltrimethyl ammonium bromide, TTABr. We have found that hydrophobic functionalized Ag nanoparticles are encapsulated in neutral Triton X-100 micelles with a diameter of 10 nm without significant change in the size of the micelles. The efficiency of encapsulation of Ag by SDS micelles is lower compared to Triron X-100 and no incorporation of Ag nanoparticles into TTABr occurs. Obtained results indicate that in aqueous environment ionic properties of molecules creating micelles and concentration ratios between components determine the efficiency and kinetics of two competitive processes association or aggregation of nanoparticles and encapsulation of Ag nanoparticles within micelles.

Sodium chloride-induced conformational change in tRNA as measured by circular dichroism

The effect of 0.01-1 M sodium ions on the conformation of the folded brewer’s yeast tRNAPhe was examined by circular dichroism method in the region 200-350 nm. The minimum peak at about 210 nm for tRNA solution with 50 mM sodium chloride showed a decrease in magnitude by 26-30% in comparison to that recorded for the solution of higher NaCl content. The depths of the peaks at 225 nm and 233 nm for two solutions with the lowest sodium chloride concentrations (cNaCl = 10mM, cNaCl = 50mM) were changed by 3-10% relative to the those in the spectra of other samples, for the 260 nm maximum peak a decrease in height was 21-25%. In the region 300-350 nm no significant difference was observed. The results point to a strong relationship between concentration of sodium ions and stabilization process of secondary and tertiary tRNA structure, which indicates the influence of sodium ions on stacking and base-pairing interactions.

Testing Sorption Properties of Halloysite by Means of the Laser Interferometry Method

The objective of the present study has been to test the laser interferometry method in terms of its usability for investigating sorption properties of minerals. This method was used to test the absorption capacity of halloysite with reference to glucose, which is often found in industrial wastewater and whose excess can disturb the environmental eco-balance. The sorption capacity of halloysite was thus determined indirectly, basing on the comparison of concentration profiles as well as time characteristics of glucose quantities released from the control solution and from the solution incubated with a halloysite adsorbent. An analysis of glucose diffusion was conducted in a two-chamber membrane system. On the basis of the obtained concentration profiles, the evolution of the concentration field was determined; so were the removal efficiency (%) and the amount of glucose adsorbed at equilibrium (qe, mg/g). The obtained results confirm good sorption properties of halloysite with respect to the investigated substance as well as usability of the method for this kind of investigations. The presented tests suggest that the measurement set-up can be optimised in such as way that visual rendering and testing the kinetics of the adsorbed substance direct release from the studied material become possible.

Mechanism of Gallstones Formation in Women During Menopause (EPR Study)

The worldwide incidence of gallbladder disease is highly variable. Identification of metabolic alterations like cholesterol metabolism or free radicals may provide insight into the formation of gallstones and provide a basis for prognostic markers. The aim of the study was to identify the pathogenesis and prognostic value of metabolic disorders in gallstone formation in menopausal women. Methods: Menopause-aged women with (group I, 58 patients) and without gallstone disease (group II, 25 patients) were investigated. In each group blood lipid metabolism and blood redox parameters (free Mn2+-ions) and antioxidant system activity (ceruloplasmine/Fe3+-transferrin) were studied using micro enzymatic method and Electron Pramagnetic Resonance (EPR) spectroscopy. Surgically removed gall bladder stones were studied by routine laboratory methods (cholesterol and bilirubin content) and EPR spectroscopy. In model experiments in vitro purified bilirubin was irradiated with visible light in different conditions (in presence and without oxygen). Results: Intensive signal of oxidized bilirubin free radical was detected in the EPR spectra of gallstones. Reduced activity of blood antioxidant ceruloplasmin/F3+-transferrin system and increased content of prooxidants Mn2+-ions were detected in menopausal women blood with gallstone disease. In vitro experiments demonstrated, that prolonged exposure of bilirubin to visible light in the presence of oxygen induces formation of the bilirubin free radicals (EPR signal g= 2.003 AH = 1.0 mT); irradiation of bilirubin in vacuum was not associated with generation of free radicals. Correlation analysis revealed statistically significant correlation between EPR signal intensity of bilirubin free radical in gallstones, activity of ceruloplazmin/F3+-transferrin antioxidant system and content of free Mn 2+ ions in patients' blood (r=-0.5725, p=0.0324; r=0.7805, p=0.0010, respectively). The tight correlation between marker of oxidative stress, Mn 2+ ions EPR signal intensity and HDL-, LDL-cholesterol content in blood (r = 0.910629, p = 0.0324; r = 0.029477, p = 0.0010, respectively) was also revealed. Conclusion: The results of the present study demonstrated the pathophysiological significance of alterations of blood redox-homeostasis during menopause in the gallstone formation. The risk of bilirubin oxidation, which plays a crucial role in the gallstones formation, increases with intensification of oxidative stress. Crystallization of cholesterol in polymeric network of oxidized bilirubin may contribute to gallstone formation.

Nanoparticle Tracking Analysis of Latex Standardized Beads

The most popular technique for particle size characterization is the dynamic light scattering (DLS). In recent years new advanced method based on counting each single particle movement was introduced giving perspective for measurement of each component of mixture. This study presents some advantages of nanoparticle tracking analysis (NTA) method in comparison to DLS. For tests standard polystyrene beds were chosen vary diameter of 22, 61 and 150 nm and its mixtures. Experiments showed that the particles size resolution allows to distinguish each population in two population suspension opposed to DLS. The NTA method permits to eliminate the negative effects i.e. dust or aggregates in sample during post processing, that permits to use it in a variety of studies.