Combinatorial chemistry of nucleic acids: SELEX

A method of irrational oligonucleotide design, SELEX, is considered. Indivi dual SELEX products, aptamers, are small molecules (40-100 nt) that have a unique three-dimensional structure, which provides for their specific and h igh-affinity binding to targets varying from low-molecular-weight ligands t o proteins. Thus, the sophisticated biosynthesis of recognizing protein ele ments, antibodies, can be emulated in vitro via selection and synthesis of principally new recognizing elements based on nucleic acids.