Glen Research provides RNA and DNA phosphoramidites for researchers seeking high affinity aptamers using systematic evolution of ligands by exponential enrichment (SELEX) methods. Aptamer discovery has been advanced by incorporating technologies to modify the nucleotide base, sugar, and the internucleotide phosphodiester linkage. Unnatural mirror image enantiomer DNA phosphoramidites are now available for the development of Spiegelmer aptamers with enhanced biological stability. Recent research findings that cell-based SELEX methods can identify aptamers to live cell’s surface structures, which are relevant to cell signaling pathway control, have opened a new route to drug discovery.