[Combinatorial chemistry of nucleic acids: SELEX].

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