Abstract
The copper–phenanthroline complex CuI(Phen)2 was the first artificial nuclease studied in biology. The mechanism responsible for this activity involves CuII(Phen)2 and H2O2. Even if H2O2/Cu systems have been extensively studied in biology and oxidative chemistry, most of these studies were carried out at physiological pH only, and little information is available on the generation of radicals by the H2O2/CuII-Phen system. In the context of paper pulp bleaching to improve the bleaching ability of H2O2, this system has been investigated, mostly at alkaline pH, and more recently at near-neutral pH in the case of dyed cellulosic fibers. Hence, this paper aims at studying the production of radicals with the H2O2/CuII-Phen system at near-neutral and alkaline pHs. Using the EPR/spin-trapping method, HO• formation was monitored to understand the mechanisms involved. DMPO was used as a spin-trap to form DMPO–OH in the presence of HO•, and two HO• scavengers were compared to identify the origin of the observed DMPO–OH adduct, as nucleophilic addition of water onto DMPO leads to the same adduct. H2O2 decomposition was enhanced by the addition of CuII–Phen (and only slightly by addition of CuSO4), reaching a level similar to the Fenton reagent at near-neutral pH. This evidences the role of Phen, which improves the effect of CuII by tuning the electronic structure and structural properties of the corresponding CuII complexes.
Highlights
Accepted: 10 January 2021In 1979, Cu+2 was discovered to display nuclease activity [1], by cleaving the phosphodiester bonds of DNA or RNA
In the presence of DMPO, the EPR spectrum of a solution of Cu–Phen displays features corresponding to three different radical adducts: DMPO–OH, DMPO–R, and a radical showing triplet splitting lines (Figure 3a)
The addition of dimethyl sulfoxide (DMSO) does not reduce the DMPO–OH signal, indicating that DMPO–OH does not originate from the trapping of HO, but from nucleophilic addition of water
Summary
In 1979, Cu+ (phenanthroline) (the molecular structure of phenanthroline is presented in Figure 1) was discovered to display nuclease activity [1], by cleaving the phosphodiester bonds of DNA or RNA. The scission of DNA occurs in the presence of two co-reactants: Cu+ (phenanthroline) and H2 O2 [2,3]. According to Sigman [2], the Cu+ (phenanthroline) complex coordinates to DNA and the oxidation of this coordinate by H2 O2 further generates a cupric hydroxyl radical-like coordinate, responsible for the DNA scission. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copper–phenanthroline coordinates (Cu–Phen) represent the first artificial nucleases studied in biology.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
