Efficient single-strand cleavage of DNA mediated by a MnIIIMnIV-based artificial nuclease

Abstract

A water-soluble Mn^IV 1,4,7-triazacyclononane complex, [Mn^IV₂L₂(μ-O)₂](ClO₄)₂·2H₂O (1), was prepared to serve as a nuclease mimic (L = 1,4,7-triazacyclononane-N-acetate). Complex 1 was readily synthesized from the highly water soluble ligand (L), with Mn^III salt, [Mn₃O(MeCO₂)₇]·3H₂O in basic condition, and characterized by X-ray, IR, electronic spectroscopy, cyclic voltammetry and magnetic susceptibility as well as ESI-MS. The bond valence sum (BVS) analysis and magnetic data suggest that 1 is a Mn^IV–μ-O₂–Mn^IV species. The electrospray mass spectrum and electronic spectrum of 1 in aqueous solution indicates that dinuclear Mn complex [Mn^IIIMn^IVL₂(μ-O)₂]⁺ (2) is the active species. A predominantly hydrolytic cleavage mechanism was confirmed through experiments performed in the presence of various radical scavengers, T4 ligase and under anaerobic conditions. The kinetic aspects of DNA cleavage under pseudo- or true-Michaelis–Menten conditions were also detailed, kinetic parameters (k_cat, K_M, V_max) were calculated to be 6.27 h⁻¹, 7.35 × 10⁻⁵ M, 4.6 × 10⁻⁴ M h⁻¹; 0.683 h⁻¹, 1.93 × 10⁻⁵ M, 1.32 × 10⁻⁵ M h⁻¹ for 2, respectively.