Bifunctional binding and catalysis

Cyclodextrin dimers can show very strong binding of appropriate substrates, and also significant geometric recognition. When the link between the two cyclodextrin rings carries a catalytic group, good turnover catalysis can be observed. The binding and catalytic properties are comparable with those of some catalytic antibodies. When a cyclodextrin binding group carries two catalytic groups, cooperative bifunctional catalysis can be observed. The details of this process are best understood in a mimic of ribonuclease, but other reactions that show bifunctional catalysis by these enzyme mimics are also being explored. The design of these catalysts was strongly influenced by detailed mechanistic studies of bifunctional catalysed cleavage and isomerization of RNA. A brief description of this evidence for the mechanism is presented. Recent findings on the properties of an isomer of DNA are also discussed.