Copper-ligand interactions and physiological free radical processes. Part 2. Influence of Cu2+ ions on Cu(+)-driven .OH generation and comparison with their effects on Fe(2+)-driven .OH production.
In our search to establish a reference .OH production system with respect to which the reactivity of copper(II) complexes could then be tested, the influence of free Cu2+ ions on the Cu+/H2O2 reaction has been investigated. This influence depends on the CCu2+/CCu+ ratio. At low Cu2+ concentrations, .OH damage to various detector molecules decreases with increasing Cu2+ concentrations until CCu2+/CCu+ reaches unity. Above this value, .OH damage increases sharply until CCu2+/CCu+ becomes equal to 5 with salicylate and 2 with deoxyribose, ratios for which the protective effect of Cu2+ cancels. Finally, at higher concentrations, Cu2+ ions logically add their own .OH production to that normally expected from Cu+ ions. The possible origin of this unprecedented alternate effect has been discussed. The possible influence of Cu+ ions on the generation of .OH radicals by water gamma radiolysis has also been tested and, as already established for Cu2+ in a previous work, shown to be nonexistent. This definitely confirms that either form of ionised copper cannot scavenge .OH radicals in the absence of a ligand.
Maestre
P
P
INSERM U305, Equipe Bioréactifs: Spéciation et Biodisponibilité, Université Paul Sabatier, Toulouse, France.
Lambs
L
L
Thouvenot
J P
JP
Berthon
G
G
D002413:Cations, Divalent; D003300:Copper; D003497:Cyclic N-Oxides; D004247:DNA / Q000737:chemistry*; D003855:Deoxyribose / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005720:Gamma Rays; D017665:Hydroxyl Radical; D006900:Hydroxylation; D007501:Iron; D007700:Kinetics; D012459:Salicylates; D020156:Salicylic Acid; D013113:Spin Labels
D002413:Cations, Divalent; D003497:Cyclic N-Oxides; D012459:Salicylates; D013113:Spin Labels; D017665:Hydroxyl Radical; D003855:Deoxyribose; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D003300:Copper; D004247:DNA; D007501:Iron; D020156:Salicylic Acid