New Fluorescent Chemodosimetric Mechanism for Selective Recognition of Selenocysteine by Dansyl-Appended Ruthenium Nitrosyl Complexes

Abstract

Selenocysteine (Sec) is a biologically essential amino acid that serves as a crucial component in selenoproteins that play a key role in various cellular functions. Thus, developing a reliable and rapid method for detecting Sec in physiological media is of paramount importance. This report introduces for the first time a novel fluorescent chemodosimetric mechanism for the selective recognition of Sec using dansyl-appended ruthenium nitrosyl complexes. These complexes consist of a tetradentate ligand featuring a π-extended system (L = N,N′-bis(2-hydroxy-1-naphthylidene)-1,2-phenylenediamine) and a monodentate ligand derived from the conjugated dansyl group, which acts as a strong fluorescent signaling unit (ID = dansyl-imidazole, BD = dansyl-benzimidazole). The reaction between Sec and the complexes {RuNO}⁶ = [RuL(NO)(ID)]Cl or [RuL(NO)(BD)]Cl in an aqueous phase enhances fluorescence; as a result, it releases NO^• that has been demonstrated through fluorimetric titrations, UV–vis titrations, ⁷⁷Se NMR, EPR, IR, MS, and electronic density calculations. [RuL(NO)(ID)]Cl and [RuL(NO)(BD)]Cl quantitatively detect Sec within a micromolar concentration range, achieving the limit of detection as low as 0.31 and 0.12 μM, respectively, within just 5 min. Remarkably, these chemodosimeters can also be conveniently employed to detect Sec in living Saccharomyces cerevisiae cells.