Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine

Abstract

Fluorogenic RNA aptamers such as Chili display strong fluorescence enhancement upon aptamer–ligand complex formation. Here, the authors provide insights into the mechanism of fluorescence activation of Chili by solving the crystal structures of Chili with its bound positively charged ligands DMHBO+ and DMHBI+, and they reveal that Chili uses an excited state proton transfer mechanism based on time-resolved optical spectroscopy measurements.