Guanine-rich single-stranded DNAs and RNAs that fold into G-quadruplexes (GQs) are known to complex tightly with FeII-heme and FeIII-heme (hemin), ubiquitous cellular cofactors. Heme–GQ (DNA) complexes, known as heme·DNAzymes, are able to utilize hydrogen peroxide as an oxidant to vigorously catalyze a variety of one-electron (peroxidase) and two-electron (peroxygenase) oxidation reactions. Herein, we show that complexes of FeII-heme with GQs also robustly catalyze a mechanistically distinct reaction, carbene transfer to an alkene substrate. Significant enhancements were seen in both reaction kinetics and product turnover (∼180) relative to disaggregated FeII-heme in the absence of DNA or in the presence of other DNA folds, such as single-stranded or double-stranded DNA. Heme binds to GQs by end-stacking. Simple, intramolecularly folded GQs are unable to provide a complexly structured “distal side” environment to the bound heme; therefore, such DNAzymes do not display significant product stereoselectivity. However, intermolecular GQs with multiple pendant nucleotides show increasing stereoselectivityin addition to their enhanced catalytic rates. These results recapitulatethe unique functional synergy and highlight the surprising catalyticversatility of complexes formed between heme and DNA/RNA GQs. Ourfindings suggest that heme·DNAzymes and heme·ribozymes mayprove to be useful reagents for carbon–carbon bond forming“green” reactions carried out in vitro and likely withinliving cells.
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机译:折叠成G四链体(GQs)的富含鸟嘌呤的单链DNA和RNA与Fe II sup>-血红素和Fe III sup>-血红素(血红素)紧密复合,无处不在的细胞辅助因子。血红素-GQ(DNA)复合物,称为血红素·DNA酶,能够利用过氧化氢作为氧化剂,大力催化多种单电子(过氧化物酶)和二电子(过氧酶)氧化反应。在本文中,我们表明Fe II sup>-血红素与GQs的配合物也能强有力地催化机理不同的反应,即卡宾转移到烯烃底物上。相对于在不存在DNA或存在其他DNA折叠(例如单链或双链)的情况下,相对于分解的Fe II sup>-血红素,反应动力学和产物转化率(〜180)均显着增强链DNA。血红素通过末端堆叠与GQ结合。简单的分子内折叠的GQ无法为结合的血红素提供结构复杂的“远端”环境。因此,这种DNA酶没有显示出明显的产物立体选择性。但是,具有多个侧链核苷酸的分子间GQ显示出越来越高的立体选择性除了提高催化速率。这些结果概括了独特的功能协同作用,彰显出令人惊讶的催化作用血红素和DNA / RNA GQ之间形成的复合物的多功能性。我们的研究结果表明血红素·DNA酶和血红素·核酶可能被证明是形成碳-碳键的有用试剂体外进行的“绿色”反应可能在活细胞。
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