The development of agents capable of cleaving RNA and DNA has attracted considerable attention from researchers in the last few years, because of the immediate and very important applications they can find in the emerging fields of biotechnology and pharmacology. There are essentially two classes of these agents - nucleases that occur naturally inside cells and synthetically produced artificial nucleases. The first class includes protein enzyme nucle ases and catalytic RNA structured ribozymes that perform cleavage of the phosphodiester bonds in nucleic acids according to a hydrolytic pathway...