Rational design of cysteine-specific ratiometric probe based on steric hindrance effect and its biological application

Based on our previous work, we modified the coumarin derivate with orthotopic pinacol which can promote the specificity of the probe toward Cysteine (Cys) via steric-hinerance effect to develop a new Cys specific ratiometric fluorescent probe with α , β -unsaturated ketone as the reaction site. The nucleophilic addition reaction between Cys and α , β -unsaturated ketone rearranged the conjugation system of the probe which induced the hypochromatic shift of the fluorescent emission. The probe features good water solubility and the detection process reaches equilibrium within 10 min. Notably, the fast response would provide better precision because of the oxidizable nature of Cys. The fluorescence ratio of the probe increased 9-fold after the reaction and the corresponding detection limit was calculated to be 14  μ M. Furthermore, bioimaging experiment results indicated that the probe could detect exogenous and endogenous Cys specifically through the ratiometric manner.