In this manuscript the catalytic ability of RNA is examined and compared to
other biopolymers. Despite having considerably fewer catalytically enablin
g properties when compared to proteins, the power of in vitro selection has
allowed for RNA and DNA catalysts to be isolated. RNA catalysis has been e
xpanded by incorporating modified bases to enrich the structural and functi
onal diversity of RNA. Successful examples of new IVA chemistry using base
modifications include carbon-carbon bond forming reactions and creation of
highly specific active sites that are capable of recognizing small organic
molecules without the need for nucleic acid templating or intercalation. In
fact, the scope of functional modifications available for use in the RNA p
latform may eventually surpass those that are found in proteins and there a
re already hints that well chosen modifications allow nucleic acid catalyst
s to take advantage of mechanisms not available to selected protein catalys
ts for similar reactions. The chemical versatility of RNA is just emerging
and future research directions will likely entail more creative methods for
functional modification that will lead to new catalysts. (C) 1998 John Wil
ey & Sons, Inc.