Zeolites as model solids for investigations on the role of iron at the solid-liquid interface in particulate toxicity

In order to investigate the molecular mechanism whereby iron in asbestos an d in other iron containing fibres plays a crucial role in fibre induced car cinogenicity, two Fe2+-exchanged zeolites (Y and H-ZSM-5) have been prepare d and used as model solids. Fe-Y was active both in free radical generation via hydrogen abstraction and in single strand DNA damage, but lost both th ese properties when oxidized by hydrogen peroxide. Fe-ZSM-5, on the other h and, was nearly inactive. Iron chelators and reductants (ascorbate, citrate and EDTA) enhance the activity in DNA single strand breaks. Moreover, they reactivate oxidized Fe-Y and activate Fe-ZSM-5. Iron is mobilized and Fe3 is partially reduced to Fe2+. The most pronounced effect was found when ci trate was present together with ascorbate. I-I-abstraction turns out to be a rather general reaction, occurring also with peptides as target molecules . In this case EPR spectra show that more than one type of radical moiety i s generated.