A Step Toward Wholly Synthetic Enzymes
One step beyond the combination of a protein binding agent with a synthetic catalyst is the construction of a completely synthetic enzyme. That term could encompass a variety of species, but perhaps the best definition is that it is a synthetic molecule with a cavity for binding a substrate and one or more catalytic groups attached.
A great deal of work has been accomplished in the design of organic molecules with binding cavities. These materials, called cavitands by Donald J. Cram of the University of California, Los Angeles, have been discussed previously (Science, 11 March 1983, p. 1177). Unfortunately, there has been little reported success in attaching catalytic groups to the cavitands.
The one area where there has been success involves a family of materials called cyclodextrins. These are doughnut-shaped molecules typically containing six ( -cyclodextrin), seven ( -cyclodextrin), or eight ( -cyclodextrin) glucose molecules. These contain a cavity that is 7 angstroms...