Reactive oxygen species (ROS) are transient, highly reactive intermediates or byproducts produced during oxygen metabolism. However, when innate mechanisms are unable to cope with sequestration of surplus ROS, it causes oxidative stress, where excess ROS damage biomolecules. Oxidized phosphatidylserine (PS), a pro-apoptotic “eat me” signal, is produced in response to elevated ROS, yet, little is known of its chemical composition and metabolism. Here, we report a small molecule that generates ROS in different mammalian cells, using which we detect, characterize and study oxidized PS in mammalian cells. We describe a chemical genetic screen to identify enzymes that regulate oxidized PS in mammalian cells, and find that the lipase ABHD12 hydrolyzes oxidized PS. We validate these findings in different physiological settings including primary peritoneal macrophages, and brains from Abhd12–/– knockout mice under inflammatory stress, and in the process functionally annotate an enzyme capable of regulating oxidized PS in vivo.

Hydrogen sulfide (HS) is a mediator of a number of cellular processes, and modulating cellular levels of this gas has emerged as an important therapeutic area. Localized generation of HS is thus very useful but highly challenging. Here, we report pivaloyloxymethyl-based carbonothioates and carbamothioates that are activated by the enzyme, esterase, to generate carbonyl sulfide (COS), which is hydrolyzed to HS.

Fluoroquinolones (FQs) are among the front-line antibiotics used to treat severe infections caused by Gram-negative bacteria. However, recently, due to toxicity concerns, their use has been severely restricted. Hence, efforts to direct delivery of this antibiotic specifically to bacteria/site of infection are underway. Here, we report a strategy that uses a bacterial enzyme for activation of a prodrug to generate the active antibiotic. The ciprofloxacin-latent fluorophore conjugate 1, which is designed as a substrate for nitroreductase (NTR), a bacterial enzyme, was synthesized. Upon activation by NTR, release of Ciprofloxacin (CIP) as well as a fluorescence reporter was observed. We provide evidence for the prodrug permeating bacteria to generate a fluorescent signal and we found no evidence for activation in mammalian cells supporting selectivity of activation within bacteria. As a testament to its efficacy, 1 was found to have potent bactericidal activity nearly identical to CIP and significantly reduced the bacterial burden in a neutropenic mouse thigh infection model, again, at comparable potency with CIP, a clinically used FQ. Thus, together, we have developed a small molecule that facilitates bacteria-specific fluoroquinolone delivery.

A series of cell-permeable esterase-sensitive sulfonates that undergo self-immolation to produce sulfur dioxide (SO), a gaseous pollutant with new and emerging biological roles, is reported. These compounds should facilitate the study SO biology and will lay the platform for newer stimuli-responsive donors of this gas.

Here, we report the design, synthesis, and evaluation of arylboronate ester based diazeniumdiolates (BORO/NO), a class of nitric oxide (NO) donors activated by hydrogen peroxide (H2O2), a reactive oxygen species (ROS), to generate NO. We provide evidence for the NO donors' ability to permeate bacteria to produce NO when exposed to H2O2 supporting possible applications for BORO/NO to study molecular mechanisms of NO generation in response to elevated ROS.