Visualization and Quantification of Base-Level SO2 in Live Cells without Intracellular Background Interference Using Sensitive 19F-NMR

Sulfur dioxide (SO 2 ), as an endogenous gasotransmitter, is involved in a variety of physiological processes in living systems, however, distinction and quantification of base-level SO 2 in live cells pose great challenges for the current analytical techniques. We report an efficient way to visualize and quantify base-level SO 2 in different live mammalian cells by 19 F-NMR. This method relies on a high-performance 19 F-probe ( P1-CF 3 ) that reacts with the reactive sulfur species (RSS) in the generation of distinct chemical shift profiles, which are well-resolved in the NMR spectrum. The quantitative reaction of the 19 F-probe with SO 2 is fast and produces a stable addition product that is well distinguishable between the intra- and extracellular environment. The high performance of this method discloses that the base-level SO 2 in live cells varies greatly in different cell lines. The high accuracy and precision of RSS measurement by the reactive 19 F NMR probe allow simultaneous quantification of base-level SO 2 in living cells and culture medium in real time without interference from other RSS and potential competitors and also without background signals.