Understanding the biological roles of RNAs requires analytical methods for detecting them selectively. This is particularly important for short RNAs with roles in the regulation of gene expression, such as microRNAs, for which accurate detection can be critical for medical diagnostics.

Simone Egetenmeyer and Clemens Richert, University of Stuttgart, Germany, describe a covalently attached quinolone cap for the 5′-terminus of oligonucleotides that increases base pairing fidelity. The cap binds tightly to the helix when a canonical base pair is formed, but provides little stabilization in cases of a mismatch. The cap increases the melting point of duplexes with RNA by up to 13.8 °C and improves mismatch discrimination at the terminus for each of the 12 possible non-Watson–Crick pairings.

With the new 5’-cap, closely related microRNAs can be detected selectively whereas conventional probes fail to provide sufficient selectivity.

• A 5’-Cap for DNA Probes Binding RNA Target Strands
  S. Egetenmeyer, C. Richert,
  Chem. Eur. J. 2011.
  DOI: 10.1002/chem.201101828