A novel approach for the synthesis of imidazo and triazolopyridines from dithioesters

Various imidazo- and triazolo-pyridines were synthesised by the intramolecular cyclization of pyridine 2-methylamine and dithioesters under mild conditions.

Molecular evolution of functional nucleic acids with chemical modifications

Nucleic acids are attractive materials for creating functional molecules that have applications as catalysts, specific binders, and molecular switches. Nucleic acids having such functions can be obtained by random screening, typically using in vitro selection methods. These methods have helped explore the potential abilities of nucleic acids and steadily contributed to their evolution, i.e., creation of RNA/DNA enzymes, aptamers, and aptazymes. Chemical modification would be a key means to further increase their performance, e.g., expansion of function diversity, enhancement of activity, and improvement of biostability for biological use. Indeed, in the past two decades, random screening involving chemical modification, post-SELEX chemical modification, and rational design methods have been advanced, and combining and integrating these methods may produce a new class of functional nucleic acids. This review focuses on the effectiveness of chemical modifications on the evolution of nucleic acids as functional molecules and the outlook for related technologies.

Conformation and the sodium ion condensation on DNA and RNA structures in the presence of a neutral cosolute as a mimic of the intracellular media

Water-soluble neutral cosolutes can be used to quantify biomolecular properties in the particular molecular environment occurring in a cell. We studied the conformation and the thermal stability of DNA and RNA structures in the presence of PEG [poly(ethylene glycol)] and smaller cosolutes of glycerol, ethylene glycol, 1,3-propanediol, 2-methoxyethanol, and 1,2-dimethoxyethane. Although the neutral cosolutes destabilized the oligonucleotide duplex and the hairpin structures, the left-handed Z-form duplex was more energetically favored in the cosolute-containing solutions. These observations were due to the contribution of water molecule on the nucleotide structure formations because the cosolutes act as an osmolyte to reduce the water activity of a solution. Moreover, the sodium ion condensation for the duplex and the hairpin formations was reduced in the presence of PEG, while that for the transition from the B-form to the Z-form was unaltered. The CD (circular dichroism) and EPR (electron paramagnetic resonance) spectra demonstrated that the cosolutes changed the helical conformation of the unstructured oligonucleotides, but not those of the ordered structures. The results of the favorable formation of the noncanonical nucleotide structures, and minimized conformational and thermal perturbations of the ordered nucleotide structures in the cosolute-containing solutions implicate the significance of the intracellular environment on DNA and RNA structures in a cell.