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Electron spin resonance and electron spin echo modulation (ESEM) spectroscopies have been used to study the location and coordination of silver ionic clusters and silver-alcohol adducts stabilized in y-irradiated Ag-SAPO-5 and Ag-SAPO-11 molecular sieves. It was found that in dehydrated samples silver ionic clusters are not stabilized in contrast to zeolites, but after exposure to methanol, ethanol, and propanol before irradiation Ag2+ and Ag32+ are efficiently stabilized. Besides silver clusters, the formation of organosilver radicals is observed, i.e., Ag'CH20H+. By analyzing the ESEM spectra it was shown that organosilver radicals are located in the 10-ring channels of Ag-SAPO-11 and the 12-ring channels of Ag-SAPO-5 and are coordinated by two nonequivalent methanol molecules. Ag2+ is located in the 6-ring channels and in SAPO-5 interacts with three equivalent CH30H groups, whereas in SAPO-1 1 two methanol molecules are distinctly closer to Ag2+ than the third one. The higher yield and stability of Ag2+ in SAPO-1 1 is associated with the preferential location of Ag+ cations in two adjacent 6-ring channels. This increases the probability of encounter between radiation-induced mobile Ago and AgS

Dinitrosyl non-heme-iron complexes (DNIC) are found in many nitric oxide producing tissues. A prerequisite of DNIC formation is the presence of nitric oxide, iron and thiol/imidazole groups. The aim of this study was to investigate the role of the cellular labile iron pool in the formation of DNIC in erythroid K562 cells. The cells were treated with a nitric oxide donor in the presence of a permeable (salicylaldehyde isonicotinoyl hydrazone) or a nonpermeable (desferrioxamine mesylate) iron chelator and DNIC formation was recorded using electron paramagnetic resonance. Both chelators inhibited DNIC formation up to 50% after 6 h of treatment. To further investigate the role of lysosomal iron in DNIC formation, we prevented lysosomal proteolysis by pretreatment of whole cells with NH4Cl. Pretreatment with NH4Cl inhibited the formation of DNIC in a time-dependent manner that points to the importance of the degradation of iron metalloproteins in DNIC formation in vivo. Fractionation of the cell content after treatment with the nitric oxide donor revealed that DNIC is formed predominantly in the endosomal/lysosomal fraction. Taken together, these data indicate that lysosomal iron plays a crucial role in DNIC formation in vivo. Degradation of iron-containing metalloproteins seems to be important for this process.

Hydroxyalkyl silver radicals, Ag-CH,OH + in y-irradiated Ag-NaA zeolites with adsorbed methanol have been studied by EPR spectroscopy. These adducts, for silver loadings greater than one Ag' per unit cell, are formed directly after irradiation at 77 K. For lower A g + content they appear on annealing above 140 K. It is postulated that the A g + location in the zeolite lattice plays a crucial role in this process, and t w o different mechanisms of Ag-CH,OH+ formation are discussed depending on Ag+ location inside or outside a P-cage.Silver atoms and silver clusters formed in various frozen solutions by ionizing radiation have been extensively studied by EPR spectroscopy. 1-7 Recently radiation-induced silver agglomeration in zeolites has attracted special interest.8-' Much less is known about the organosilver radicals formed during radiation processes. EPR doublets with relatively low silver isotropic hyperfine couplings were first observed in yirradiated frozen methanol solutions: A,,,(Ag) ca. 13.0 mT. A similar doublet was later reported for glassy ethanol samples. l 8 Based on detailed analysis of EPR doublets for CD,OD and 3CH30H samples, Symons" assigned them to covalent organosilver radicals, A g C H 2 0 H + and AgCHCH,OH + having a single electron 0 ' bond between silver and carbon. The same author has proposed that they are formed by Ceaction between. Ag + cations and matrix-derived radicals, C H 2 0 H or CH,CHOH. Besides alcohol glasses Ag doublets with highly reduced A values were only reported for yirradiated frozen solutions of CD,CN + D 2 0 mixtures, A,,,(Ag) = 17.5 mT4 and in glassy dimethylformamide, A,,,(Ag) = 10.0 mT.6The same type of organosilver radicals have also been generated by matrix isolation techniques but only in 1989,85,3963.

Effect of the exposure of poly(butylene adipate-co-terephthalate) (PBAT) to ionizing radiation was studied by means of EPR and diffuse reflection spectroscopy, GC, and gel permeation chromatography. In addition, the influence of radiation-induced processes on mechanical and rheological properties for the doses in the range 0-200 kGy was investigated. The macroscopic consequences of PBAT irradiation included: crosslinking, chain cleavage, and oxidation, which led to the significant modification of physicochemical features. The crosslinking process occurred even under cryogenic conditions and was confirmed by reduction in melt flow index (MFI), increase in viscosity, and weight-average molecular weight with increasing dose. Material degradation during longterm storage was accompanied by deterioration of mechanical properties, increase in MFI, and viscosity reduction. Oxidation of the copolyester had a chain character and increased over time, especially in the case of irradiated PBAT. Despite the presence of aromatic rings dissipating energy, the material is susceptible to ionizing radiation. The regions containing terephthalates are involved in the aging processes; the appropriate mechanisms have been proposed.

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