Syntheses and fluorescence of RNA conjugates having pyrene-modified adenosine and nitrobenzene-modified uridine base pairs

We prepared RNA duplexes possessing 2′-O-(1-pyrenylmethyl)adenosine and 5-(4-nitrophenyl)uridine base pairs. In the duplexes, pyrene serves as a photo-excitable electron donor and 5-(4-nitrophenyl)uridine acts as an electron acceptor. The donor–acceptor-modified RNA duplexes showed very weak fluorescence originating from the pyrene monomer and excimer emissions, which occur due to electron transfer from the excited pyrene to the nitrobenzene acceptor.