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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.