A tridentate “click” nucleoside for metal-mediated base pairing

CuII-mediated DNA base pairing of a triazole-4-carboxylate nucleoside prepared by click chemistry

Artificial metal-mediated DNA base pairing is a promising strategy for creating highly functionalized DNA supramolecules. Here we report a novel ligand-type triazole-4-carboxylate (TazC) nucleoside that is readily prepared by the click reaction. TazC nucleosides were found to form a stable TazC-Cu^II-TazC base pair inside DNA duplexes, resulting in Cu^II-specific duplex stabilization (ΔT_m = +7.7 °C). This study demonstrates that the triazole derivatives are useful in the development of metal-mediated base pairing.

Homogeneous Catalysis: A Powerful Technology for the Modification of Important Biomolecules

Homogeneous catalysis plays an important and ubiquitous role in the synthesis of simple and complex molecules, including drug compounds, natural products, and agrochemicals. In recent years, the wide-reaching importance of homogeneous catalysis has made it an indispensable tool for the modification of biomolecules, such as carbohydrates (sugars), amino acids, peptides, nucleosides, nucleotides, and steroids. Such a synthetic strategy offers several advantages, which have led to the development of new molecules of biological relevance at a rapid rate relative to the number of available synthetic methods. Given the powerful nature of homogeneous catalysis in effecting these synthetic transformations, this Focus Review has been compiled to highlight these important developments.

Sequence-Dependent Duplex Stabilization upon Formation of a Metal-Mediated Base Pair

An artificial nucleoside surrogate with 1H-imidazo[4,5-f][1,10]phenanthroline (P) acting as an aglycone has been introduced into DNA oligonucleotide duplexes. This nucleoside surrogate can act as a bidentate ligand, and so is useful in the context of metal-mediated base pairs. Several duplexes involving a hetero base pair with an imidazole nucleoside have been investigated. The stability of DNA duplexes incorporating the respective Ag(I) -mediated base pairs strongly depends on the sequence context. Quantum mechanical/molecular mechanical (QM/MM) calculations have been performed in order to gain insight into the factors determining this sequence dependence. The results indicated that, in addition to the stabilizing effect that results from the formation of coordinative bonds, destabilizing effects may occur when the artificial base pair does not fit optimally into the surrounding B-DNA duplex.

Single-Molecule Force Spectroscopy of an Artificial DNA Duplex Comprising a Silver(I)-Mediated Base Pair

Single-molecule force spectroscopy measurements of a DNA duplex comprising an artificial metal-mediated base pair are reported. The measurements reveal that DNA duplexes comprising one central imidazole:imidazole mispair rupture at lower forces than a related duplex with canonical base pairs only. In contrast, DNA duplexes with one central imidazole-Ag(+)-imidazole base pair (formed by the addition of Ag(+) to the aforementioned duplex with the mispair) rupture at higher forces. These measurements indicate for the first time that the increase in thermal stability of a nucleic acid duplex that is observed upon the formation of a metal-mediated base pair is accompanied by a concomitant mechanical stabilization. In fact, the mechanical stabilization even exceeds the thermal one. This result indicates that nucleic acids with metal-mediated base pairs should be ideal building blocks for rigid functionalized DNA nano-objects.