Single stranded (ss) oligonucleotides (mainly deoxyribonucleic acid (DNA) or ribonucleic acid (RNA)) originating from in vitro selection, which, starting from random sequence libraries, optimise the nucleic acids for high-affinity binding to a given target.
Note: In vitro selection is an iterative method mainly known as Systematic Evolution of Ligands by EXponential enrichment (SELEX).
Source:
PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1148 (https://doi.org/10.1515/pac-2016-1120)