Deciphering the Chemical Basis of Fluorescence of a Selenium‐Labeled Uracil Probe when Bound at the Bacterial Ribosomal A‐Site

Abstract We unveil in this work the main factors that govern turn‐on/off fluorescence of a Se‐modified uracil probe at ribosomal RNA A‐site. Whereas constraint into an “in‐plane” conformation two rings fluorophore is driver for observed turn‐on emission presence antibiotic paromomycin, electrostatics environment plays minor role during process. Our computational strategy clearly indicates that, absence prefers conformations show dark S 1 electronic state with participation nπ* transition contributions between selenium atom and π‐system moiety.