Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Effect of natural polysaccharides and oligosaccharides on the permeability of cell membranes

Glycyrrhizic acid, arabinogalactan, and β-cyclodextrin are capable of forming complexes with various drug compounds significantly enhancing their solubility and bioavailability. To elucidate the mechanism of action of oligo- and polysaccharides, the exchange time of transporting formate ions through the membrane of myeloblastic leukemia cells (K562) was measured by NMR spectroscopy with the addition of paramagnetic ions. It was found that glycyrrhizic acid and arabinogalactan substantially increased the membrane permeability.     

Temperature dependence of radiation hardness of lead tungstate (PWO) scintillation crystals

Influence of irradiation on the light yield of PWO (lead tungstate, PbWO₄) scintillation crystals was studied in the temperature range from ?25 °C to +60 °C. Light output and optical transmittance were simultaneously measured as a function of time under irradiation in PWO single crystals grown in first and second recrystallization cycle of raw material, doped with different lanthanides and annealed in different conditions. Increased sensitivity to irradiation and slower recovery of the initial light yield were observed at decreased temperatures. The model of tungsten oxide clusters in a regular PWO lattice is used to interpret the experimental results, and dynamics of the light yield under irradiation at different temperatures are qualitatively explained using rate equations describing composition changes in the clusters.     

Membrane-modifying activity of glycyrrhizic acid

Owing to amphiphilicity, glycyrrhizic acid is capable of forming complexes with a variety of hydrophobic therapeutic compounds. This is accompanied by a significant decrease in the therapeutic dose of the drug. In addition, glycyrrhizic acid has a strong influence on the permeability and elasticity of cell membranes. To elucidate the molecular and cellular mechanisms of the effects observed, the effect of glycyrrhizic acid on the dynamics of lipids inside the membrane was investigated by NMR relaxation. It was found that glycyrrhizic acid can be incorporated into the membrane increasing the mobility of lipids.     

Phosphorylation of trivalent metal tris(3-bromo-2,4-pentanedionates)

Reactions of chromium(III) and cobalt (III) tris(3-bromo-2,4-pentandionates) with sodium dibutyl phosphate, sodium dibutylphosphinate, sodium dibutyl dithiophosphate, and sodium dibutyldithiophosphinate were studied. Oxygen-containing derivatives of phosphorus acids give metal polyphosphates and polyphosphonates, and in the case of sodium dibutyl phosphate, a bromine substitution product was isolated in 3% yield. The reactions of the chelates with sodium dibutyl dithiophosphate and sodium dibutyldithiophosphinate, substitution products were isolated in 54% and 65% yields, respectively. The reactions all involved reductive dehalogenation along with substitution.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1472–1475.Original Russian Text Copyright © 2004 by Shapkin, Apanasenko, Skobun, Ivanova.This revised version was published online in April 2005 with a corrected cover date.