H2S donors with optical responses.

Reactive sulfur species, including hydrogen sulfide (H2S), are important biological mediators and play key roles in different pathophysiological conditions. Small molecules that release H2S on demand, often referred to as "H2S donors," constitute a key investigative tool for H2S-related research. A significant challenge, however, is correlating the rate of H2S release from such donors in complex systems with biological outcomes, because release rates are commonly perturbed by different biological environments. In this chapter, we outline an approach to use H2S donors that provide a fluorescent response upon H2S release to address this problem. These compounds leverage the intermediate release of carbonyl sulfide (COS), which is quickly converted to H2S by the endogenous enzyme carbonic anhydrase (CA), to provide activatable donors with an optical response. The described donors are activated by biological thiols and provide a fluorescence response that correlates directly with H2S delivery, which allows for delivered H2S levels to be measured in real time by fluorescence techniques.