Wang, L.; Sivakumar, A.; Zhang, R.; Cho, S.; Kim, Y.; Aggarwal, T.; Wang, L.; Izgu, E. C.

Activity-based detection of hydrogen sulfide in live cells can expand our understanding of its reactivity and complex physiological effects. We have discovered a highly efficient method for fluorescent probe activation, which is driven by H2S-triggered 1,6-elimination of an -CF3-benzyl to release resorufin. In detecting intracellular H2S, 4-azido-(-CF3)-benzyl resorufin offers significantly faster signal generation and improved sensitivity compared to 4-azidobenzyl resorufin. Computed free energy profiles for the 1,6-elimination process support the hypothesis that a benzylic CF3 group can reduce the activation energy barrier toward probe activation. This novel probe design allows for near-real-time detection of H2S in HeLa cells under stimulation conditions.