Recognition of single- and double-stranded nucleic acids by covalently mercurated oligonucleotides

Metal-mediated base pairs have attracted considerable attention during the past decades for their potential in bio- and nanotechnological applications. The introduction of metal ions into DNA or RNA not only stabilizes various secondary structures but also confers new, metal-based functionalities. In this context, interactions of Hg(II) with nucleic acids containing artificial as well as natural nucleobases have been studied extensively. These studies have yielded promising results but also revealed notable shortcomings, such as off-target metalation and low stability in metal-deficient media. The covalently mercurated oligonucleotides presented in this thesis provide a new alternatives approach for Hg(II)-metal mediated base pairing, aiming to overcome these limitations. In the present study, covalently mercurated natural and artificial nucleosides and corresponding oligonucleotides were synthesized. The binding affinity of mono- and dimercurated nucleosides with natural nucleotides was investigated at the monomer level by NMR studies. At oligomer level, the base-pairing properties of covalently mercurated nucleobases were investigated by measuring UV-melting temperatures of various duplexes and triplexes. Furthermore, the binding mode of a monofacial dimercurated nucleobase was also predicted theoretically by DFT calculations. The results obtained on monomers and oligomers generally agreed well, with the duplexes and triplexes containing the most stable base Hg(II)-mediated base pairs also exhibiting the highest melting temperatures. In some cases, the mercurated duplexes and triplexes were considerably more stable than their counterparts comprising only canonical base pairs

2,6-Dimercuriphenol as a Bifacial Dinuclear Organometallic Nucleobase

A C-nucleoside having 2,6-dimercuriphenol as the base moiety has been synthesized and incorporated into an oligonucleotide. NMR and UV melting experiments revealed the ability of this bifacial organometallic nucleobase surrogate to form stable dinuclear HgII-mediated base triples with adenine, cytosine, and thymine (or uracil) in solution as well as within a triple-helical oligonucleotide. A single HgII-mediated base triple between 2,6-dimercuriphenol and two thymines increased both Hoogsteen and Watson–Crickmelting temperatures of a 15-mer pyrimidine·purine*pyrimidine triple helix by more than 10 oC relative to an unmodified triple helix of the same length. This novel binding mode could be exploited in targeting certain pathogenic nucleic acids as well as in DNA nanotechnology.</p

Organomercury Nucleic Acids: Past, Present and Future

Synthetic efforts towards nucleosides, nucleotides, oligonucleotides and nucleic acids covalently mercurated at one or more of their base moieties are summarized, followed by a discussion of the proposed, realized and abandoned applications of this unique class of compounds. Special emphasis is given to fields in which active research is ongoing, notably the use of Hg-II-mediated base pairing to improve the hybridization properties of oligonucleotide probes. Finally, this minireview attempts to anticipate potential future applications of organomercury nucleic acids

1,8-Dimercuri-6-Phenyl-1H-Carbazole as a Monofacial Dinuclear Organometallic Nucleobase

A C-nucleoside with 6-phenyl-1H-carbazole as the base moiety has been synthesized and incorporated in the middle of an oligonucleotide. Mercuration of this modified residue at positions 1 and 8 gave the first example of an oligonucleotide featuring a monofacial dinuclear organometallic nucleobase. The dimercurated oligonucleotide formed stable duplexes with unmodified oligonucleotides placing either cytosine, guanine, or thymine opposite to the organometallic nucleobase. A highly stabilizing (Delta T-m=7.3 degrees C) Hg-II-mediated base pair was formed with thymine. According to DFT calculations performed at the PDE0DH level of theory, this base pair is most likely dinuclear, with the two Hg-II ions coordinated to O2 and O4 of the thymine base

Fractal-like Hierarchical CuO Nano/Microstructures for Large-Surface-to-Volume-Ratio Dip Catalysts

Dip catalysts are attracting interest in both academia and industry for catalyzing important chemical reactions. These provide excellent stability, better recoverability, recyclability, and easy scale-up. Using the unique microstructures of leaf skeletons, we present a fractal-like hierarchical surface that can be used as a versatile and efficient dip catalyst. Copper oxide microcactuses with nanoscalar features were fabricated onto the Bauhinia racemosa leaf skeletons via a combination of physical vapor deposition, electroplating, and chemical oxidation methods. The coated leaf skeletons have a very high surface area, and the three-dimensional (3D) morphology allows the reactants to encounter the catalytic sites efficiently and move around the reaction mixture swiftly. The fabricated bioinspired leaf skeleton-based dip catalyst was characterized and demonstrated to be very efficient for alcohol dehydrogenation reaction, examined under different experimental conditions. A ceramic 3D-printed catalyst holder was designed to hold the catalysts to avoid any damage caused by the magnetic bars during the reactions. The performance is determined using the reaction yields, and the efficiencies are correlated with microcactus-like structures composed of CuO and the 3D fractal-like shape provided by the leaf skeleton. This strategy can be applied to fabricate other dip catalysts using different materials and designs, suitable for catalyzing numerous other chemical reactions.peerReviewe