The Redox Aqueous Chemistry of Cu^II/IATP

Copper proteins have diverse roles in biological electron transport and oxygen transportation, processes that exploit the easy interconversion of Cu(I) and Cu(II). As such, copper ions can act as both antioxidant and pro-oxidant species. Free radicals occur naturally in human body and can damage cell walls, interact with genetic material, and contribute to the development of a number of health problems. Recent studies suggest that the catalytic cycle of the Menkes’ protein begins with the binding of copper ions to high affinity binding sites in the transmembrane channel, followed by ATP binding and transient phosphorylation.

Our study focuses on the interaction of ATP with both Cu(II) and Cu(I) ions and the redox activity of the latter formed complexes in general, and their reactions with methyl radicals- the simplest example for ^.R formed in biological tissues. The methyl radicals were produced in vitro by continuous radiolysis of N₂O saturated aqueous solutions containing DMSO.

While Cu(II)ATP was prepared by mixing the reagents at neutral pH (excess of ATP), the Cu(I) ATP was prepared by comproportionation of Cu(II)ATP, ATP and Cu(0), as CV experiments showed thermodynamic stabilization of the Cu(II)ATP/Cu(I)ATP with E_1/2 ~ +0.078V vs. Ag/AgCl.

Cu(I)ATP reacted with ^.CH₃ in a process in which the presumable metal carbon s bond transient formed, ATPCu(II)-CH₃ decomposed heterolytically to give methane and Cu(II)ATP as the major products.

Its divalent analogue produced ATPCu(III)-CH₃, which decomposed to give methane and ethane as minor products while the major products were methanol together with Cu(I)ATP.

Detailed data and mechanisms of reactions will be presented.