Aptamer

Aptamers are oligomers of RNA or DNA that spontaneously fold into specific three-dimensional shapes that can bind defined targets. The specificity of the shape of the binding site arises from the base sequence of the aptamer, which determines the base-pairing pattern of the oligomer.

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2009, Corinne Ravelet, Eric Peyrin, Chapter 10: Aptamers in Affinity Separations: Stationary Separation, Yingfu Li, Yi Lu (editors), Functional Nucleic Acids for Analytical Applications, page 271, The use of DNA or RNA aptamers as tools in analytical chemistry is a very promising field of research because of their capabilities to bind specifically the target molecules with an affinity similar to that of antibodies.

Source: wiktionary

The field of aptamer research is also more targeted, with many more catalytic aptamers being examined rather than for binding alone.

Source: wiktionary

2015, Caroli J et al, "APTANI: a computational tool to select aptamers through sequence-structure motif analysis of HT-SELEX data", Bioinformatics, 32 (2): 161-164, "3 Results". To test APTANI performances and validate its findings, we analyzed a sequence library corresponding to an HT-SELEX experiment designed to isolate aptamers specific for murine IL4Ra (Roth et al., 2012).

Source: wiktionary