Selecting Fully‐Modified XNA Aptamers Using Synthetic Genetics

Abstract This unit describes the application of “synthetic genetics,” i.e., the replication of xeno nucleic acids (XNAs), artificial analogs of DNA and RNA bearing alternative backbone or sugar congeners, to the directed evolution of synthetic oligonucleotide ligands (XNA aptamers) specific for target proteins or nucleic acid motifs, using a cross‐chemistry selective exponential enrichment (X‐SELEX) approach. Protocols are described for synthesis of diverse‐sequence XNA repertoires (typically 10 14 molecules) using DNA templates, isolation and panning for functional XNA sequences using targets immobilized on solid phase or gel shift induced by target binding in solution, and XNA reverse transcription to allow cDNA amplification or sequencing. The method may be generally applied to select fully‐modified XNA aptamers specific for a wide range of target molecules. © 2018 by John Wiley & Sons, Inc.