Expanding the catalytic repertoire of DNAzymes by modified nucleosides.

Modified nucleoside triphosphates (dNTPs) are a versatile platform for the generation of high-density functionalized nucleic acids. The enzymatic polymerization of dNTPs allows the introduction of sensible functionalities that might not be compatible with the standard automated synthesis of oligonucleotides. Their application to in vitro selections, an elegant chemical approach to Darwinian evolution, delivers modified aptamers and catalytic nucleic acids with potentially enhanced properties. This review article highlights some recent synthetic examples of dNTPs bearing functionalities that are either found in the active site of protein enzymes or have been employed in organocatalysis and further underscores their usefulness in the development of some modified catalytic nucleic acids with special emphasis on M(2+)-independent RNA-cleaving DNAzymes.