Modified Nucleic Acid for Systematic Evolution of RNA Ligands by Exponential Enrichment

Various types of modified nucleic acid were tested for systematic evolution of ligands by exponential enrichment (SELEX) or in vitro evolution. T7 RNA polymerase accepted cytidine triphosphate with a biotinyl group at the N ⁴ -position of cytosine, adenosine triphosphate with an aminohexyl group at the N ⁶ -position of adenine, and 2T-amino-2′-deoxyuridine triphosphate as substrates for transcription of DNA containing a random sequence. However, uridine triphosphate with a nitroveratryloxy group at the 2′-position and adenosine triphosphate with an aminohexyl group at the 8-position of adenine were not accepted. The transcribed products served as templates for the production of cDNA by reverse transcription. These findings indicate that some modified nucleotides can be applied to the present SELEX protocol.