Characterization of defects generated by di-and trivalent cations in the potassium-dihydrophosphate structure and their influence on growth kinetics and face morphology

Different types of defect sites generated by the impurities of divalent (M²⁺) and trivalent (M³⁺) metals in the structure of potassium dihydrophosphate KH₂PO₄ (KDP) were revealed by crystal-chemical analysis and computer simulation. These sites cause different deformations of the crystal matrix by generating different local strains, which enhance the inhibiting effect of impurity atoms adsorbed on the surface. This fact accounts for the different influence of di-and trivalent cations on the growth kinetics and face morphology of KDP crystals. The effect of the M³⁺ ions is associated primarily with their adsorption on the face surfaces, whereas the influence of the M²⁺ ions results from their insertion into the surface layer of the crystal.     

Experimental studies and theoretical calculations of partition coefficients of isovalent impurities in lithium chloride

Using the method of directed crystallization, partition coefficients have been determined for sodium, potassium, rubidium, cesium and silver in lithium chloride. A theoretical calculation of impurity partition coefficients has been made for the systems investigated with due regard for excess functions of mixing in solid solutions and melts. In the LiCl–Cs system, an abrupt jump of the CsCl partition coefficient has been detected in the range of very low CsCl concentrations in the melt. This effect is explained by the interaction of the cesium umpurity with the cation vacancies.     

Antibodies-Abzymes with Antioxidant Activities in Two Th and 2D2 Experimental Autoimmune Encephalomyelitis Mice during the Development of EAE Pathology

The exact mechanisms of multiple sclerosis development are still unknown. However, the development of EAE (experimental autoimmune encephalomyelitis) in Th and 2D2 mice is associated with the infringement of the differentiation profiles of bone marrow hematopoietic stem cells which are bound with the production of compounds that are harmful for human autoantibodies-abzymes that hydrolyze myelin oligodendrocyte glycoprotein, myelin basic protein, and DNA. It showed that autoimmune patients’ antioxidant IgG antibodies oxidise some compounds due to their peroxidase (H₂O₂-dependent) and oxidoreductase (H₂O₂-independent) activities more effectively than those in healthy humans can. It was interesting to identify whether the redox activities of the antibodies change during the development of autoimmune diseases. Here, we analyzed the change in these redox activities of the IgGs from the blood of Th and 2D2 mice, which corresponded to different stages of the EAE development. The peroxidase activity in the oxidation of ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) in the Th (4-fold) and 2D2 (2-fold) mice IgGs, on average, is higher than the oxidoreductase activity is. The peroxidase activity of the Th (1.9-fold) and 2D2 (3.5-fold) mice IgGs remarkably increased during the 40 days of the spontaneous development of EAE. Forty days after the immunization of the MOG peroxidase activity, the IgGs of the Th and 2D2 mice increased 5.6–6.0 times when they were compared with those that presented no increase (3 months of age). The mice IgGs were oxidized with 3,3′-diaminobenzidine (2.4–4.3-fold) and o-phenylenediamine (139–143-fold) less efficiently than they were with ABTS. However, the temper of the change in the IgG activity in the oxidation of these substrates during the spontaneous and MOG-induced development of EAE was close to that which occurred for ABTS. All of the data show that the IgG peroxidase and oxidoreductase activities of EAE mice can play an important role in their protection from toxic compounds and oxidative stress.     

Immunochromatographic assay for the detection of ochratoxin A

The detection of mycotoxins—toxic contaminants of fungal origin—is an important problem in the food and feed quality control. An immunochromatographic system was developed for the detection of ochratoxin A (OTA), which is one of the priority contaminants in grain. Monoclonal antibodies against OTA and their conjugates with colloidal gold nanoparticles were prepared. The detection is based on the competition of OTA in a sample and an OTA-protein conjugate immobilized on a test strip for the binding to anti-bodies on the colloidal particle surface. The method was tested in the analysis of plant extracts (maize and barley extracts). It was shown that OTA can be detected in a medium with a high content of an organic solvent (up to 35% of methanol). The disappearance of the line in the test zone is visually detected at OTA concentrations starting from 50 ng/mL. In the case of the video-digital detection of changes in the color intensity of the test zone, the limit of detection of OTA is 5 ng/mL. The duration of the assay is 10 min.     

Principles and criteria for the choice and refinement of structural models in inorganic crystal chemistry

A hierarchical approach to the choice of the most probable structural models of a compound with a specified chemical composition and to the subsequent refinement of these models with the use of different methods is analyzed. Most attention is given to one of the first stages of the choice of the starting model (on the basis of the principles of total and local crystal electroneutrality) and to the solution of the problem of construction and determination of the bond graphs and connectivity matrices. Simple criteria for the most stable configurations of chemical bonds are introduced reasoning from the principles of minimum dissymmetrization and maximum informational entropy.     

Distortion of V<Superscript><Emphasis Type="Italic">z</Emphasis>+</Superscript>O<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> coordination polyhedra and parameters of the bond valence model for V-O bonds in inorganic crystals

The dependences of average V-O distances in inorganic compounds of vanadium of different valence on the degree of distortion of coordination polyhedra have been obtained by careful statistical treatment of modern structural data banks. Values of bond lengths in undistorted (regular) polyhedra are recommended. Theoretical analysis of the statistical data made it possible to calculate the most likely values of the parameters of the bond valence model: the interatomic distance for the single (two-electron) bond, corresponding to the single valence, and the bond softness parameter. Calculations of the sums of bond valences for some complicated cases (different coordination numbers, mixed vanadium valence) confirmed reliability of the recommended parameters.