Molecular isomerization triggered by H2S to an NIR accessible first direct visualization of Ca2+-dependent production in living HeLa cells.

Few studies determined the role of intracellular labile Ca2+ in H2S homeostasis. Undoubtedly, fluorescent probes are powerful tools for exploring the question because of their unique advantages: non-destruction, visualization, and multi-levels imaging. Herein, a near-infrared (λem = 687 nm) and methylene blue chromophore-based fluorescent probe (MB1) for H2S was rationally developed. Based on its high sensitivity and selectivity, MB1 was employed to image the concentration change of H2S, upon stimulating it with ionomycin (a specific calcium ionophore). We found that the intracellular labile Ca2+ acted as a promotor for H2S production in living cells. Furthermore, cystathionine γ-lyase (CSE) might have functioned as a positive mediator of Ca2+-dependent H2S production. These direct and visible links for H2S/Ca2+ will help us to understand the complex signaling in a better way.