PHENYL-SUBSTITUTED COPPER DI-SCHIFF BASE, A POTENT CU2ZN2 SUPEROXIDE-DISMUTASE MIMIC SURVIVING COMPETITIVE BIOCHELATION

yridyl-phenyl)methylene-1,4-butanediamine]-(N,N',N '',N''')-copper(II) , Cu(II)PuPhePy, a copper(II) di-Schiffbase in both its chloride and p erchlorate form, has been prepared and crystallized with a yield of 50 +/-10%. IR spectra confirmed the successful preparation. The electroni c absorption epsilon(690) was 136 M(-1) cm(-1). The EPR parameters g(p erpendicular to)=2.048 and g(parallel to)=2.217 were in dose agreement with the respective values of intact Cu2Zn2 SOD. Comparison of the cr ystal structures of this complex and the copper binding centre of Cu2Z n2 SOD revealed a virtually identical coordination chemistry. The puls e-radiolytically-determined superoxide dismutation proceeded even in t he presence of a fourfold molar excess of EDTA at a rate of 0.48x10(9) M(-1) s(-1). In the indirect nitroblue tetrazolium assay 0.27 mu M of Cu(II)PuPhePy(ClO4)(2) were required to cause 50% inhibition. The the rmodynamic stability constant logK=18.33+/-0.77 was calculated from CD data. The stability being two orders of magnitude higher than that of serum albumin, a competitive biological Cu(II) chelator and its 'mode l' EDTA was deduced. Of all the many superoxide dismutase mimics exami ned, the present Cu complex is in closest agreement in both structure and catalytic function with the active centre of intact Cu2Zn2 SOD.