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The reactions between some Ni(II) oligopeptides (Gly-His-Lys, (Gly)4, Asp-Ala-His-Lys, Gly-Gly-His, beta Ala-His, and serum albumin) and reduced oxygen species have been characterized by spin-trapping experiments using DMPO and Me2SO. Most of the peptides possessed superoxide dismutase- and catalase-like activities leading to the formation of either oxene [NiO]2+ or, in the case of beta Ala-His, hydroxyl radicals. Both these species may affect DNA integrity through distinct mechanisms.

A spin-labelled derivative of 9-aminoacridine, the AATEMPO, was studied with respect to its localization in KB cells in vivo. It was found that both nuclear and mitochondrial DNAs were targets for this intercalating dye. The observed speed of intercalation and the absence of a blocked signal in cellular membranes suggested that no receptor -or carrier- proteins were implied in the penetration process. No changes in cell membrane fluidity were observed following the administration of m-AMSA, the unlabelled structural analog, to the living cells, which seemed to exclude the plasma membrane as a possible site of action of 9-aminoacridines. Side effects of phenol/chloroform mixtures and high-salt concentrations on the intercalation phenomenon were also described.

A model incorporating the metal chelating moiety of bleomycin and an anilinoacridine ring able to intercalate in DNA has been synthesized. The copper(II) complex of that molecule has been studied using circular dichroism and electron spin resonance by comparison with bleomycin. The introduction of the anilinoacridine ring involves a modification in the geometry of the complex. A distortion of the square-pyramidal form (type II complex) gives rise to a type I complex in which the metallic atom is drawn out of the plane of the four square-planar ligands and displaced slightly towards the fifth ligand.

Methyl 2-(2-aminoethyl)-aminomethyl-pyridine-6-carboxyl-histidinate (AMPHIS), a synthetic analogue of the chelating part of bleomycin (BLM), has been studied for its metal binding properties. Electron spin resonance parameters of AMPHIS-Cu(II) and BLM-Cu(II) have been found to be closely similar likewise spectra of oxygen radicals spin-adducts induced by AMPHIS-Fe(II)-O2 and BLM-Fe(II)-O2 systems. Thus, AMPHIS could constitute a very useful tool for the study of BLM mode of action.