Szostak, Jack

JACK W. SZOSTAK, Howard Hughes Medical Institute, Harvard University 

I acknowledge Jennifer Doudna, Michael Famulok, and Jack Szostak for helpful discussions during the preparation of the manuscript, and David Bartel for insights into the importance of fidelity in template-directed polymerizations. 

The SELEX technology (Systematic Evolution of Ligands by Exponential enrichment) was introduced by Larry Gold and Jack Szostak [1, 2] and provides a powerful tool for the in vitro selection of nucleic acids (aptamers) from combinatorial DNA or RNA libraries against a target molecule. 

This creates a dilemma of a different sort. How are we to demonstrate ribozyme activities that no longer exist Perhaps we must design our own ribozymes to demonstrate the full potential for RNA to act as an enzyme. This approach is being used by Jack Szostak and Gerald Joyce, who indepen- 

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