Chemical nucleases.

Substantial progress is being made in the synthesis of functional mimics of metallonuclease enzymes, although a comparison with enzyme-promoted rates of reaction shows considerable room for future improvement. Improved ligand design allows facile substrate binding to metal ion catalysts, while maintaining the stability of the metal complex. The execution of double-strand cleavage of DNA under hydrolytic conditions has been reported and new levels of activity achieved. Finally, considerable progress has been made in identifying the molecular determinants for site-selective cleavage of RNA (in particular) and the design of ligands to achieve targeted recognition and cleavage.