How Well Should the Active Site and the Specific Recognition Be Defined for Proficient Catalyses

How Well Should the Active Site and the Specific Recognition Be Defined for Proficient Catalyses? —Effective and Cooperative Polyphenol/Catechol Oxidation and Oxidative DNA Cleavage by a Copper(II)-Binding and H-bonding Copolymer

Vasiliki Lykourinou,^[a] Ahmed I. Hanafy,^[a,b] Giordano F. Z. da Silva,^[a] Kirpal S. Bisht,^[a] Randy W. Larsen,^[a] Brian T. Livingston,^[c] Alexander Angerhofer,^[d] and Li-June Ming^[a]*

[a] Dr. Vasiliki Lykourinou, Dr. Ahmed I. Hanafy, Giordano F. Z. da Silva, Prof. Kirpal S. Bisht, Prof. Randy W. Larsen, and Prof. Li-June Ming*
Department of Chemistry
University of South Florida
4202 Fowler Avenue, Tampa, FL 33620, USA
Fax: (+) 01-813-974-1733
E-mail: ming@shell.cas.usf.edu

[b] Dr. Ahmed I. Hanafy
Department of Chemistry, Faculty of Science
Al-Azhar University
Nasr City, Cairo, Egypt

[c] Prof. Brian T. Livingston
Department of Biology
University of South Florida

[d] Prof. Alexander Angerhofer
Department of Chemistry
University of Florida
Gainesville, FL 32611

Abstract: Despite the mainly inhomogeneous and unstructured nature of linear polymers, the Cu^II complex of a vinyl pyridine-acrylamide copolymer exhibits very efficient 2-electron catalysis toward the oxidation of catechol and derivatives to form quinones with and without 80 mM (0.27%) H₂O₂, showing remarkable (0.114–2.67) × 10⁵and (2.83–9.60) × 10⁴-fold rate enhancements, respectively, in terms of first-order rate constant relative to auto-oxidation of the substrates in an aqueous environment under mild conditions. Metal-binding profiles suggest the presence of cooperativity in the catalysis. The oxidation catalysis is inhibited by the di-copper tyrosinase-specific kojic acid. Moreover, electron paramagnetic resonance spectra reveal magnetic interaction of the Cu^II ions. Based on the results, the catalysis by this Cu^II-polymer seems to be consistent with the mechanism of type-3 di-copper oxidases. This complex also shows effective single- and double-stranded DNA cleavage in the presence of 1.0% H₂O₂. These studies suggest this Cu^II-polymer complex can serve as a unique “chemical nuclease” and a versatile chemical system for further exploration of Cu-oxygen chemistry.