H2S is a well-known toxic gas and also a gaseous signaling molecule involved in many biological processes. Advanced chemical tools that can regulate H2S levelsin vivoare useful for understanding H2S biology as well as its potential therapeutic effects. To this end, we have developed a series of 7-nitro-1,2,3-benzoxadiazole (NBD) amines as potential H2S scavengers. The kinetic studies of thiolysis reactions revealed that incorporation of positively-charged groups onto the NBD amines greatly increased the rate of the H2S-specific thiolysis reaction. We demonstrate that these reactions proceed effectively, with second order rate constants (k(2)) of >116 M(-1)s(-1)at 37 degrees C forNBD-S8. Additionally, we demonstrate thatNBD-S8can effectively scavenge enzymatically-produced and endogenous H2S in live cells. Furthering the biological significance, we demonstrateNBD-S8mediates scavenging of H2S in mice.

Hydrogen sulfide (H2S) is an endogenously produced gaseous signaling molecule with important roles in regulating organelle function and stress. Because of its high reactivity, targeted delivery of H2S using small molecule H2S donors has garnered significant interest to minimize off-target effects. Although mitochondrially targeted H2S donors, such as AP39, have been reported previously and exhibit significantly higher potency than nontargeted donors, the expansion of targeted H2S delivery to other subcellular organelles remains largely absent. To fill this key unmet need, we report a library of organelle targeted H2S donors that localize H2S delivery to specific subcellular organelles, including the Golgi apparatus, lysosome, endoplasmic reticulum, and mitochondria. We measured H2S production in vitro from each donor, confirmed the localization of H2S delivery using organelle-specific H2S responsive fluorescent probes, and demonstrated enhanced potency of these targeted H2S donors in providing protection against organelle-specific stress. We anticipate this class of targeted H2S donors will enable future studies of subcellular roles of H2S and the pathways by which H2S alleviates subcellular organelle stress.

Recent efforts have expanded the development of small molecule donors that release the important biological signaling molecule hydrogen sulfide (H2S). Previous work on 1,2,4-thiadiazolidin-3,5-diones (TDZNs) reported that these compounds release H2S directly, albeit inefficiently. However, TDZNs showed promising efficacy in H2S-mediated relaxation in ex vivo aortic ring relaxation models. Here, we show that TDZNs release carbonyl sulfide (COS) efficiently, which can be converted to H2S by the enzyme carbonic anhydrase (CA) rather than releasing H2S directly as previously reported.

Hydrogen sulfide is a biologically important molecule and developing chemical tools that enable further investigations into the functions of H2S is essential. Fluorescent turn-on H2S probes have been developed for use in cellulo and in vivo, but the membrane permeability of these probes can lead to probe leakage and signal attenuation over time. Here we report a cell trappable fluorescent probe for H2S, CT-MeRhoAz, which is based on a methylrhodolazide scaffold derivatized with an acetoxymethyl ester group. Prior to ester cleavage, the CT-MeRhoAz probe generates a 2500-fold turn-on response to H2S, which is enhanced to a 3000-fold response for the carboxylic acid form of the probe. Additionally, the probe is highly selective for H2S over other biologically relevant sulfur, oxygen, and nitrogen-based analytes. Live cell imaging experiments confirmed the biocompatibility of CT-MeRhoAz and also that it is cell trappable, unlike the parent MeRhoAz scaffold.

Fluorophores are powerful tools for interrogating biological systems. Carbon nanotubes (CNTs) have long been attractive materials for biological imaging due to their near-infrared excitation and bright, tunable optical properties. The difficulty in synthesizing and functionalizing these materials with precision, however, has hampered progress in this area. Carbon nanohoops, which are macrocyclic CNT substructures, are carbon nanostructures that possess ideal photophysical characteristics of nanomaterials, while maintaining the precise synthesis of small molecules. However, much work remains to advance the nanohoop class of fluorophores as biological imaging agents. Herein, we report an intracellular targeted nanohoop. This fluorescent nanostructure is noncytotoxic at concentrations up to 50 mu M, and cellular uptake investigations indicate internalization through endocytic pathways. Additionally, we employ this nanohoop for two-photon fluorescence imaging, demonstrating a high two-photon absorption cross-section (65 GM) and photostability comparable to a commercial probe. This work further motivates continued investigations into carbon nanohoop photophysics and their biological imaging applications.

Mechanical interlocking of a nanohoop fluorophore and a reactive thread couples the benefits of a reaction-based probe with a sterically congested active site for enhanced selectivity. Advantageously, the thread design uses dual function stoppers that act as both a quencher and a trigger for sensing. In progress toward expanding this approach to biologically relevant analytes, this system is used to demonstrate steric differentiation and provide a selective turn-on fluorescent response with size selectivity for HS- rather than larger thiolates.

Hydrogen sulfide (H2S) is an important biomolecule, and selfimmolative thiocarbamates have shown great promise as triggerable H2S donors with suitable analogous control compounds; however, thiocarbamates with electron-deficient payloads are less efficient H2S donors. We report here the synthesis and study of a series of N-methylated esterase-triggered thiocarbamates that block the postulated unproductive deprotonation-based pathway for these compounds. The relative reaction profiles for H2S release across a series of electron-rich and electron-poor N-Me aniline payloads are examined experimentally and computationally. We show that thiocarbamate N-methylation does block some side reactivity and increases the H2S release profiles for electron-poor donors. Additionally, we show that isothiocyanate release is not a competitive pathway, and rather that the reduced efficiency of electron-poor donors is likely due to other side reactions.

Hydrogen sulfide (H2S) is an important biomolecule that plays key signaling and protective roles in different physiological processes. With goals of advancing both the available research tools and the associated therapeutic potential of H2S, researchers have developed different methods to deliver H2S on demand in different biological contexts. A recent approach to develop such donors has been to design compounds that release carbonyl sulfide (COS), which is quickly converted to H2S in biological systems by the ubiquitous enzyme carbonic anhydrase (CA). Although highly diversifiable, many approaches using this general platform release quinone methides or related electrophiles after donor activation. Many such electrophiles are likely scavenged by water, but recent efforts have also expanded alternative approaches that minimize the formation of electrophilic byproducts generated after COS release. This mini-review focuses specifically on recent examples of COS-based H2S donors that do no generate quinone methide byproducts after donor activation. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.

Hydrogen sulfide (H2S) is an important biomolecule and significant efforts have focused on developing chemical tools to aid different biological investigations. Of such tools, there are relatively few chemiluminescent or bioluminescent methods for H2S detection. Here we report two dioxetane-based chemiluminescent probes for H2S detection. With these probes, we directly compare the probe response to H2S-mediated azide reduction and nucleophilic displacement of 2,4-dinitrophenyl (DNP) motifs and demonstrate that the SNAr cleavage of the DNP group results in a larger response and greater stability in water.