M. I. Ibragimova

Quinoid radio-toxin (QRT) induced metabolic changes in mice: an ex vivo and in vivo EPR investigation.

Radio-toxins are toxic metabolites produced by ionizing irradiation and have toxic effects similar to those caused by direct irradiation. We have investigated the effect of a quinoid radio-toxin (QRT) obtained from gamma-irradiated potato tuber on various organs in mice using ex vivo and in vivo EPR spectroscopy. Results indicate a decrease in the activity of ribonucleotide reductase enzyme in spleen of mice treated with 0.2mg QRT. A dose of 2mg QRT was fatal to mice within 45-60 min of treatment. Nitrosyl hemoglobin complexes alpha-(Fe(2+)-NO)alpha-(Fe(2+))beta-(Fe(2+))(2) were detected from spleen, blood, liver, kidney, heart, and lung tissue samples of mice treated with lethal doses of QRT. A significant decrease of pO(2) in liver and brain was observed after administration of QRT at the lethal dose. The time of the appearance of the nitrosyl hemoglobin complex and its intensity varied with the dose of QRT and the type of tissue. These results indicate that the effect of the QRT is more prominent in spleen and to a lesser extent in liver and blood. The QRT action at the lethal doses resulted in an increased hypoxia over time with disruption of compensatory adaptive response. The results indicate similar outcome of QRT as observed with gamma-irradiation.

EPR study of iron status in human body during intensive physical activity

The iron metabolism was studied in serum blood samples collected from 26 professional sportsmen undergoing intensive physical exercises using EPR combined with hematological and biochemical laboratory tests. Only 23% of EPR spectra (n = 6) were practically normal while in the rest spectra additional abnormal absorption lines were detected. Presumably, the significant portion of new signals may be caused by different cytochromes. Moreover, the anisotropic signals with g1 ≅ 2.02; g2 ≅ 1.94 and g3 ≅ 1.86 registered in some spectra pointed to the sulfur-iron centers. There was nearly linear correlation between the concentration of Fe3+ in transferrin (Fe3+-Tf) obtained from the EPR spectra and the serum iron concentration measured by absorption photometry both for sportsmen and controls (healthy individuals and patients with different diseases). At equal serum iron concentrations the Fe3+-Tf level was higher in sportsmen than that in controls. The Pearson correlation coefficient (r) for Fe3+-Tf and serum iron values was equal to 0.89 in sportsmen versus r = 0.97 in controls. Additional new lines in serum EPR spectra of professional sportsmen prove the suitability of EPR assay for scheduled medical exams since routine biochemical and hematological tests are insufficient to discover all abnormalities in iron metabolism under intensive physical exercises.

EPR study of blood of anemic patients with urological cancer

Changes in Fe3+-transferrin (Fe-Tf) and Cu2+-ceruloplasmin (Cu-Cp) concentrations in venous blood sampled from anemic patients with urinary bladder and kidney cancer of stages I–IV were assessed using EPR spectroscopy. In malignancy-associated anemia, the paramagnetic Fe3+ concentration in Tf proved to be below the norm, while in anemic non-oncology patients the Tf iron saturation was normal. Moreover, in patients with malignancy-associated anemia the Cu-Cp on average was nearly twice higher than in healthy volunteers (p < 0.01). Thus, simultaneous EPR measurement of protein-borne paramagnetic centers (such as Fe-Tf and Cu-Cp) in the blood of anemic patients can be used as an express biomarker for urological cancer even at early stages of malignant growth.

Investigation of metabolic changes in blood and tissue of mice γ-irradiated with sublethal doses by direct observation of EPR signals from Hb-NO complexes

The metabolic changes in probes of blood and tissue (spleen, liver and kidney) of mice under total γ-irradiation with the doses varied in the interval of 1–10 Gy at the dose rate of 0.073 Gy/min were studied in the early postirradiation period by ex vivo electron paramagnetic resonance (EPR). It was established that the impact with the lower dose rate leads to more intensive nitric monoxide biosynthesis in comparison with higher dose rates. In the early postirradiation period (from 2 up to 6 h), irradiation with doses higher than 2 Gy brings about an increase of the NO concentration and, hence, the appearance of nitrosyl complexes which were registered directly by EPR in blood and spleen. The observed line is identified as the signal from α-(Fe2+-NO)2β(Fe3+)2 or α-(Fe2+-NO) α(Fe2+)β(Fe3+)2 complexes since the methemoglobin concentration also increases in comparison with the control level. The concentration of Hb-NO complexes in blood and spleen depends on the dose and individual radiosensitivity of the organism. Therefore, the intensity of the Hb-NO signal may serve as a criterion of the radiation injury level during the first hours after the irradiation. 30 h after the impact, the Hb-NO complexes were no longer detected. For the first day, the concentration of Fe3+-transferrin in blood increases with the dose and time passed after the irradiation. The intensity of the EPR signal from Fe3+-transferrin in blood may also serve as a measure of the radiation injury level.

The effect of pulsed laser annealing on the parameters of CdxHg1−xTe photoresistors

The effect of nanosecond-pulse radiation of a Nd laser (pulse duration τ=10 ns, wavelength λ=1.06 µm) at 300 K on the parameters of Cd0.19Hg0.81Te photoresistors was studied. At the optimal energy density W=0.2–0.3 J/cm2, the surface melts to yield a 0.04–0.52-µm-thick inversion layer with increasing sensitivity and detectivity of the photoresistors. At higher energy densities W, the parameters of the photoresistors deteriorate, and the dark resistance grows.

Electrophysical properties of semimagnetic solid solutions Hg1−xMnxTe

A comprehensive study of the electrophysical properties of the semimagnetic ternary solid solution Hg1−xMnxTe, an alternative material to Hg1−xCdxTe, is reported. The charge-carrier scattering, optical, photoelectric, and magnetic properties of the material are investigated. Values are obtained for the effective masses of electrons and holes, the ionization energy of the acceptor level, and the g factor of the charge carriers as functions of the manganese telluride concentration and the densities of electrons and holes at temperatures of 300 and 77 K. It is shown that the methods of radio spectroscopy can be used for diagnostics of the semimagnetic material. Photodiode structures having characteristics close to the values for working in the background-limited regime are obtained by the use of Schottky barriers, diffusion in mercury vapor, and implantation of B+ ions into p-Hg1−xMnxTe samples.

Effect of successive implantation of Ag+(Cu+) and Xe+ ions on the recombination properties of CdxHg1−xTe crystals

The effect of successive double implantation of Ag+(Cu+) and Xe+ ions on the recombination properties of CdxHg1−xTe (0.2<x<0.3) crystals has been investigated. It is shown that after implantation of ions of one chemical element, followed by diffusion thermal annealing at temperatures below 150–200 K, recombination through local levels lying 30±5 meV below the conduction band bottom dominates. Successive double implantation of Ag+(Cu+) and Xe+ ions followed by diffusion thermal annealing changes the course of the temperature dependence of the lifetime of the nonequilibrium charge carriers. It was determined that for CdxHg1−xTe crystals with x⋍0.20–0.25 in the temperature interval 700–200 K the lifetime of the nonequilibrium charge carriers is low (τ<0.15 µs) and does not depend on the temperature. For CdxHg1−xTe crystals with x⋍0.3 recombination of nonequilibrium charge carriers occurs through two types of levels: in the temperature range 140–200 K — deep levels Et1⋍Ec−51 meV and at lower temperatures (77–140 K) — through shallower levels Et2⋍Ec−(16±2) meV.

PECULIARITIES OF CARRIER RECOMBINATION IN CDXHG1-XTE IMPLANTED CONSECUTIVELY WITH AG+ (CU+) AND XE+ IONS

Abstract The influence of consecutive implantation of Ag+ (Cu+) and Xe+ ions on recombination processes in CdxHg1−xTe has been studied. It has revealed that after an implantation with a certain kind of ions followed by diffusion thermal annealing (DTA) at temperatures lower than 150–200 K there dominates a recombination through levels 30±5 meV below the bottom of the conduction band. After a consecutive double implantation of Ag+ (Cu+) and Xe+ ions followed by DTA the measured carrier minority lifetime τ versus temperature changes and strongly depends on the value of x. For CdxHg1−xTe with x ≤ 0.25 τ( 1 T ) is rather small (