Investigation of radiation defects in steatite ceramics SK-1 and SNC by the EPR method

The EPR spectra of γ- and n-γ-reactor irradiated steatite ceramics SK-1 and SNC has been studied. It is shown that structural defects of the E ′-center type are created in the structure of the SK-1 and SNC ceramics under the action of high doses of γ-irradiation. After n-γ-irradiation and additional annealing, paramagnetic defect centers such as interstitial Me2++e− ions are created in the structure of the SNC ceramics, which are caused by amorphization of the ceramic crystal phase and the creation of a Mg enriched glass phase at the interface between crystalline and amorphous phases.

Photochemical synthesis of 4H-thieno[3,2-c]chromene and their optical properties

4 - [(2-Iodalyloxy) methyl] thiophene-2-carbaldehyde and 5-iodo-4- (aryloxymethyl)thiophene-2-carbaldehydes were obtained by interaction of phenols with 4-chloromethylthiophene-2-carbaldehyde and its 5-iodosubstituted derivative. These compounds underwent ring closure upon irradiation with UV light (254 nm) to form 4H-thieno[3,2-c]chromene-2-carbaldehyde in high yield. The formation of intermediate radical species was detected by EPR method. Comparative analysis of the ring closure methods showed that the photochemical cyclization of 5-iodo-4-(aryloxymethyl) thiophene-2-carbaldehyde is more rational than the Pd-catalyzed intramolecular arylation. A series of substituted 4H-thieno[3,2-c]chromene-2-carbaldehydes was synthesized by the photochemical cyclization of the corresponding precursors. The photophysical properties of the synthesized compounds were studied. The obtained 4H-thieno[3,2-c]chromene-2-carbaldehydes can be used as covert marking pigments.

Concentration of Fe(3+)-Triapine in BEAS-2B Cells

An electron paramagnetic resonance (EPR) method was used to determine the concentration of the antitumor agent Triapine in BEAS-2B cells when Triapine was bound to iron (Fe). Knowledge of the concentration of Fe-Triapine in tumor cells may be useful to adjust the administration of the drug or to adjust iron uptake in tumor cells. An EPR spectrum is obtained for Fe(3+)-Triapine, Fe(3+)(Tp)2+, in BEAS-2B cells after addition of Fe(3+)(Tp)2+. Detection of the low spin signal for Fe(3+)(Tp)2+ shows that the Fe(3+)(Tp)2+ complex is intact in these cells. It is proposed that Triapine acquires iron from transferrin in cells including tumor cells. Here, it is shown that iron from purified Fe-transferrin is transferred to Triapine after the addition of ascorbate. To our knowledge, this is the first time that the EPR method has been used to determine the concentration of an iron antitumor agent in cells.

Treatment of Cells and Tissues with Chromate Maximizes Mitochondrial 2Fe2S EPR Signals

In a previous study on chromate toxicity, an increase in the 2Fe2S electron paramagnetic resonance (EPR) signal from mitochondria was found upon addition of chromate to human bronchial epithelial cells and bovine airway tissue ex vivo. This study was undertaken to show that a chromate-induced increase in the 2Fe2S EPR signal is a general phenomenon that can be used as a low-temperature EPR method to determine the maximum concentration of 2Fe2S centers in mitochondria. First, the low-temperature EPR method to determine the concentration of 2Fe2S clusters in cells and tissues is fully developed for other cells and tissues. The EPR signal for the 2Fe2S clusters N1b in Complex I and/or S1 in Complex II and the 2Fe2S cluster in xanthine oxidoreductase in rat liver tissue do not change in intensity because these clusters are already reduced; however, the EPR signals for N2, the terminal cluster in Complex I, and N4, the cluster preceding the terminal cluster, decrease upon adding chromate. More surprising to us, the EPR signals for N3, the cluster preceding the 2Fe2S cluster in Complex I, also decrease upon adding chromate. Moreover, this method is used to obtain the concentration of the 2Fe2S clusters in white blood cells where the 2Fe2S signal is mostly oxidized before treatment with chromate and becomes reduced and EPR detectable after treatment with chromate. The increase of the g = 1.94 2Fe2S EPR signal upon the addition of chromate can thus be used to obtain the relative steady-state concentration of the 2Fe2S clusters and steady-state concentration of Complex I and/or Complex II in mitochondria.

ELDOR-detected NMR beyond hyperfine couplings: a case study with Cu(ii)-porphyrin dimers

The pulse EPR method ELDOR-detected NMR gives information about electron–electron couplings in Cu(ii) porphyrin dimers.