Hydrogen sulfide (H2S) is a biologically important small gaseous molecule that exhibits promising protective effects against a variety of physiological and pathological processes. To investigate the expanding roles of H2S in biology, researchers often use H2S donors to mimic enzymatic H2S synthesis or to provide increased H2S levels under specific circumstances. Aligned with the need for new broad and easily modifiable platforms for H2S donation, we report here the preparation and H2S release kinetics from a series of isomeric caged-carbonyl sulfide (COS) compounds, including thiocarbamates, thiocarbonates, and dithiocarbonates, all of which release COS that is quickly converted to H2S by the ubiquitous enzyme carbonic anhydrase. Each donor is designed to release COS/H2S after the activation of a trigger by activation by hydrogen peroxide (H2O2). In addition to providing a broad palette of new, H2O2-responsive donor motifs, we also demonstrate the H2O2 dose-dependent COS/H2S release from each donor core, establish that release profiles can be modified by structural modifications, and compare COS/H2S release rates and efficiencies from isomeric core structures. Supporting our experimental investigations, we also provide computational insights into the potential energy surfaces for COS/H2S release from each platform. In addition, we also report initial investigations into dithiocarbamate cores, which release H2S directly upon H2O2-mediated activation. As a whole, the insights on COS/H2S release gained from these investigations provide a foundation for the expansion of the emerging area of responsive COS/H2S donor systems.

In an effort to expand the availability of simple polysulfides for H2S donation, we report here the synthesis and H2S release profiles of bis(aryl) and bis(alkyl) tetrasulfides. The tetrasulfide donors release H2S in a first-order dependence on reduced glutathione (GSH) and release more H2S than the commonly used trisulfide DATS.

Hydrogen sulfide (H2S) is an important biomolecule, and responsive chemical tools for its delivery are needed. Here, we utilize the photocleavable o-nitrobenzyl group to unmask caged thiocarbamates and to access photoactivated H2S releasing molecules. These donors function by the initial release of carbonyl sulfide (COS), which is quickly hydrolyzed to H2S by carbonic anhydrase (CA). Our investigations demonstrate that o-nitrobenzyl-caged thiocarbamates can serve as a donor platform for the bio-orthogonal stimulated release of COS/H2S.

There is constant demand for new ligand archictectures on which inorganic and organometallic structures can be leveraged. An important, but often synthetically challenging, class of ligands is bidentate phosphines. Here we report self-assembling, supramolecular bidentate ligand scaffolds based on deconstructed Hamilton receptors with binding affinities up to 800 ± 100 M−1.

Hydrogen sulfide (H2S) is an important biomolecule with high therapeutic potential. Here we leverage the inverse-electron demand Diels–Alder (IEDDA) click reaction between a thiocarbamate-functionalized trans-cyclooctene and a tetrazine to deliver carbonyl sulfide (COS), which is quickly converted to H2S by the uniquitous enzyme carbonic anhydrase (CA), thus providing a new strategy for bio-orthogonal COS/H2S donation.

•The interaction of hydrogen sulfide with various metal protoporphyrins is reported.•Protoporphyrins provide a bio-relevant and consistent scaffold for investigation.•The differential reactivity of H2S/HS− is investigated in organic solution.•Observed H2S/HS− interactions include binding and redox chemistry.Hydrogen sulfide (H2S) is the most recently discovered gasotransmitter molecule joining nitric oxide and carbon monoxide. In addition to being biologically important gases, these gasotransmitters also provide distinct modes of reactivity with biomimetic metal complexes. The majority of previous investigations on the reactivity of H2S with bioinorganic models have focused on Fe-based porphyrin systems, whereas investigations with other metals remains underinvestigated. To address this gap, we report here an examination of the reactions of H2S, HS−, and S8 with MgII, CuII, CoII, ZnII, CrII, SnIV, and MnII/III protoporphyrins.The reaction chemistry between hydrogen sulfide (H2S) and non-iron base porphyrins remains widely under-investigated. We investigate the reaction of H2S/HS− with a series of metal protoporphyrin derivatives.Download high-res image (154KB)Download full-size image

Hydrogen sulfide (H2S) is an important biological signaling molecule, and chemical tools for H2S delivery and detection have emerged as important investigative methods. Key challenges in these fields include developing donors that are triggered to release H2S in response to stimuli and developing probes that do not irreversibly consume H2S. Here we report a new strategy for H2S donation based on self-immolation of benzyl thiocarbamates to release carbonyl sulfide, which is rapidly converted to H2S by carbonic anhydrase. We leverage this chemistry to develop easily modifiable donors that can be triggered to release H2S. We also demonstrate that this approach can be coupled with common H2S-sensing motifs to generate scaffolds which, upon reaction with H2S, generate a fluorescence response and also release caged H2S, thus addressing challenges of analyte homeostasis in reaction-based probes.

Hydrogen sulfide (H2S) has gained recent attention as an important biological analyte that interacts with bioinorganic targets. Despite this importance, stable H2S or HS− adducts of bioinorganic metal complexes remain rare due to the redox activity of sulfide and its propensity to form insoluble metal sulfides. We report here reversible coordination of HS− to Zn(didpa)Cl2, which is enabled by an intramolecular hydrogen bond between the zinc hydrosulfido product and the pendant tertiary amine of the didpa ligand.

Hydrogen sulfide (H2S) is an essential biological signaling molecule in diverse biological regulatory pathways. To provide new chemical tools for H2S imaging, we report here a fluorescent H2S detection platform (HSN2-BG) that is compatible with subcellular localization SNAP-tag fusion protein methodologies and use appropriate fusion protein constructs to demonstrate mitochondrial and lysosomal localization. We also demonstrate the efficacy of this detection platform to image endogenous H2S in Chinese hamster ovary (CHO) cells and use the developed constructs to report on the subcellular H2S distributions provided by common H2S donor molecules AP39, ADT–OH, GYY4137, and diallyltrisulfide (DATS). The developed constructs provide a platform poised to provide new insights into the subcellular distribution of common H2S donors and a useful tool for investigating H2S biochemistry.

Hydrogen sulfide (H2S) and nitric oxide (NO) are important biosignaling molecules, and their biochemistries are increasingly recognized to be intertwined. Persulfides are an oxidized product of biological H2S and have emerged as important species involved in the biological action of reactive sulfur species. Using isolated persulfides, we employed a combination of experimental and computational methods to investigate the contribution of persulfides to H2S/NO crosstalk. Our studies demonstrate that isolated persulfides react with nitrite to produce NO via polysulfide and perthionitrite intermediates. These results highlight the importance of persulfides, polysulfides, and perthionitrite as intertwined reactive nitrogen and sulfur species.

The reversible binding of hydrogen sulfide (H2S) to hemeprotein sites has been attributed to several factors, likely working in concert, including the protected binding pocket environment, proximal hydrogen bond interactions, and iron ligation environment. To investigate the importance of a sterically-constrained, protected environment on sulfide reactivity with heme centers, we report here the reactivity of H2S and HS− with the picket-fence porphyrin system. Our results indicate that the picket-fence porphyrin does not bind H2S in the ferric or ferrous state. By contrast, reaction of the ferric scaffold with HS− results in reduction to the ferrous species, followed by ligation of one equivalent of HS−, as evidenced by UV-vis, NMR spectroscopy and mass spectrometry studies. Measurement of the HS− binding affinities in the picket-fence or tetraphenyl porphyrin systems revealed identical binding. Taken together, these results suggest that the protected, sterically-constrained binding pocket alone is not the primary contributor for stabilization of ferric H2S/HS− species in model systems, but that other interactions, such as hydrogen bonding, must play a critical role in facilitation of reversible interactions in ferric hemes.

Hydrogen sulfide (H2S) is an important biological mediator and has been at the center of a rapidly expanding field focused on understanding the biogenesis and action of H2S as well as other sulfur-related species. Concomitant with this expansion has been the development of new chemical tools for H2S research. The use of H2S-selective fluorescent probes that function by H2S-mediated reduction of fluorogenic aryl azides has emerged as one of the most common methods for H2S detection. Despite this prevalence, the mechanism of this important reaction remains under-scrutinized. Here we present a combined experimental and computational investigation of this mechanism. We establish that HS–, rather than diprotic H2S, is the active species required for aryl azide reduction. The hydrosulfide anion functions as a one-electron reductant, resulting in the formation of polysulfide anions, such as HS2–, which were confirmed and trapped as organic polysulfides by benzyl chloride. The overall reaction is first-order in both azide and HS– under the investigated experimental conditions with ΔS⧧ = −14(2) eu and ΔH⧧ = 13.8(5) kcal/mol in buffered aqueous solution. By using NBu4SH as the sulfide source, we were able to observe a reaction intermediate (λmax = 473 nm), which we attribute to formation of an anionic azidothiol intermediate. Our mechanistic investigations support that this intermediate is attacked by HS– in the rate-limiting step of the reduction reaction. Complementing our experimental mechanistic investigations, we also performed DFT calculations at the B3LYP/6-31G(d,p), B3LYP/6-311++G(d,p), M06/TZVP, and M06/def2-TZVPD levels of theory applying the IEF-PCM water and MeCN solvation models, all of which support the experimentally determined reaction mechanism and provide cohesive mechanistic insights into H2S-mediated aryl azide reduction.

Hydrogen sulfide (H2S) is a critical gaseous signaling molecule emerging at the center of a rich field of chemical and biological research. As our understanding of the complexity of physiological H2S in signaling pathways evolves, advanced chemical and technological investigative tools are required to make sense of this interconnectivity. Toward this goal, we have developed an azide-functionalized O-methylrhodol fluorophore, MeRho-Az, which exhibits a rapid >1000-fold fluorescence response when treated with H2S, is selective for H2S over other biological analytes, and has a detection limit of 86 nM. Additionally, the MeRho-Az scaffold is less susceptible to photoactivation than other commonly used azide-based systems, increasing its potential application in imaging experiments. To demonstrate the efficacy of this probe for H2S detection, we demonstrate the ability of MeRho-Az to detect differences in H2S levels in C6 cells and those treated with AOAA, a common inhibitor of enzymatic H2S synthesis. Expanding the use of MeRho-Az to complex and heterogeneous biological settings, we used MeRho-Az in combination with light sheet fluorescence microscopy (LSFM) to visualize H2S in the intestinal tract of live zebrafish. This application provides the first demonstration of analyte-responsive 3D imaging with LSFM, highlighting the utility of combining new probes and live imaging methods for investigating chemical signaling in complex multicellular systems.

Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule in the last decade. During the growth of this field, significant controversy has arisen centered on the physiological concentrations of H2S. Recently, a monobromobimane (mBB) method has been developed for the quantification of different biologically-relevant sulfide pools. Based on the prevalence of the mBB method for sulfide quantification, we expand on this method to report the use of dibromobimane (dBB) for sulfide quantification. Reaction of H2S with dBB results in formation of highly-fluorescent bimane thioether (BTE), which is readily quantifiable by HPLC. Additionally, the reaction of sulfide with dBB to form BTE is significantly faster than the reaction of sulfide with mBB to form sulfide dibimane. Using the dBB method, BTE levels as low as 0.6 pM can be detected. Upon use of the dBB method in wild-type and CSE−/− mice, however, dBB reports significantly higher sulfide levels than those measured using mBB. Further investigation revealed that dBB is able to extract sulfur from other sulfhydryl sources including thiols. Based on mechanistic studies, we demonstrate that dBB extracts sulfur from thiols with α- or β-hydrogens, thus leading to higher BTE formation than from sulfide alone. Taken together, the dBB method is a highly sensitive method for H2S but is not compatible for use in studies in which other thiols are present.

D-Amino acid oxidase (DAO) plays important roles in regulating D-amino acid neurotransmitters and was recently identified as a key enzyme integral to hydrogen sulfide production from D-Cys. We report here the development of a simple biocompatible, bioluminescent method for measuring DAO activity based on the highly selective condensation of D-Cys with 6-hydroxy-2-cyanobenzothiazole (CBT-OH) to form D-luciferin.

Despite the prevalence of supramolecular architectures derived from metal–ligand or hydrogen-bonding interactions, few studies have focused on the simultaneous use of these two strategies to form discrete assemblies. Here we report the use of a supramolecular tecton containing both metal-binding and self-complementary hydrogen-bonding interactions that upon treatment with metal precursors assembles into discrete hybrid metal–ligand hydrogen-bonded assemblies with closed topology. 1H NMR DOSY experiments established the stability of the structures in solution, and the measured hydrodynamic radii match those determined crystallographically, suggesting that the closed topology is maintained both in solution and in the solid state. Taken together, these results demonstrate the validity of using both hydrogen-bonding and metal–ligand interactions to form stable supramolecular architectures.

To expand the interface between self-assembled metal–ligand and hydrogen-bonded architectures, here we report the preparation, self-assembly, and metal–ligand binding of a pyridyl quinolone ligand (5-PYQ). The 5-PYQ ligand self-associates through quinolone hydrogen bonding, and it binds to metal centers through the pyridine ligand component. As a first step toward investigating more-complex hybrid metal–ligand hydrogen-bonded (MLHB) architectures, we report investigations of 5-PYQ with mono- and bis-platinated anthracene precursors. These results demonstrate that the 5-PYQ ligand maintains hydrogen bonding interactions while binding to square-planar platinum centers, but that generation of coordination compounds with closed topology erodes the hydrogen bonding fidelity to favor ambidentate coordination modes of the 5-PYQ ligand.

Hydrogen sulfide (H2S) has gained significant interest within the scientific community due to its expanding roles in different (patho)physiological processes. Despite this importance, the chemical mechanisms by which H2S exerts its action remain under-scrutinized. Biomimetic investigations in organic solution offer the potential to clarify these mechanisms and to delineate the differential reactivity between H2S and HS−. However, such studies are hampered by the lack of readily-available sources of HS− that are soluble in organic solution. Here we present a simple method for preparing analytically pure tetrabutylammonium hydrosulfide (NBu4SH), which we anticipate will be of significant utility to researchers in the H2S and anion-binding communities.

Decreased funding for middle and high school education has resulted in reduced classroom time, which, when coupled with an increased focus on standardized testing, has decreased the exposure of many middle school students to hands-on science education. To help address these challenges, we developed an integrated outreach program, spanning grades 6–12, designed to engage students by bringing students to the University of Oregon to perform hands-on laboratory experiments. Initially developed to supplement science education lost to state-mandated furlough days, the programmatic design can be applied readily in other contexts including afterschool, weekend, or summer programs. The outreach activities and scaffolding rely heavily on near-peer mentoring, which provides a visible pathway for younger students to envision themselves as future scientists while also providing mentoring and leadership opportunities for high school, undergraduate, and graduate students. The use of near-peer mentoring is also critically important for the program’s sustainability because it enables a more efficient allocation of graduate student and faculty time. In the first 2.5 years, over 450 middle school students have participated in the program and student feedback shows that students are engaged and excited about the outreach activities.

Hydrogen sulfide (H2S) is an important biological signaling agent that exerts action on numerous (patho)physiological processes. Once generated, H2S can be oxidized to generate reductant-labile sulfane sulfur pools, which include hydrodisulfides/persulfides. Despite the importance of hydrodisulfides in H2S storage and signaling, little is known about the physical properties or chemical reactivity of these compounds. We report here the synthesis, isolation, and characterization (NMR, IR, Raman, HRMS, X-ray) of a small-molecule hydrodisulfide and highlight its reactivity with reductants, nucleophiles, electrophiles, acids, and bases. Our experimental results establish that hydrodisulfides release H2S upon reduction and that deprotonation results in disproportionation to the parent thiol and S0, thus providing a mechanism for transsulfuration in the sulfane sulfur pool.

Sulfhydryl-containing compounds, including thiols and hydrogen sulfide (H2S), play important but differential roles in biological structure and function. One major challenge in separating the biological roles of thiols and H2S is developing tools to effectively separate the reactivity of these sulfhydryl-containing compounds. To address this challenge, we report the differential responses of common electrophilic fluorescent thiol labeling reagents, including nitrobenzofurazan-based scaffolds, maleimides, alkylating agents, and electrophilic aldehydes, toward cysteine and H2S. Although H2S reacted with all of the investigated scaffolds, the photophysical response to each scaffold was significantly different. Maleimide-based, alkylating, and aldehydic thiol labeling reagents provided a diminished fluorescence response when treated with H2S. By contrast, nitrobenzofurazan-based labeling reagents were deactivated by H2S addition. Furthermore, the addition of H2S to thiol-activated nitrobenzofurazan-based reagents reduced the fluorescence signal, thus establishing the incompatibility of nitrobenzofurazan-based thiol labeling reagents in the presence of H2S. Taken together, these studies highlight the differential reactivity of thiols and H2S toward common thiol-labeling reagents and suggest that sufficient care must be taken when labeling or measuring thiols in cellular environments that produce H2S due to the potential for both false-positive and eroded responses.

Hydrogen sulfide (H2S) is an integral signaling molecule in biology with complex generation, translocation, and metabolism processes that are intertwined with cellular thiols. Differentiating the complex interplay between H2S and biological thiols, however, remains challenging due to the difficulty of monitoring H2S and thiol levels simultaneously in complex redox environments. As a step toward unraveling the complexities of H2S and thiols in sulfur redox homeostasis, we present a dual-fluorophore fragmentation strategy that allows for the ratiometric determination of relative H2S and cysteine (Cys) or homocysteine (Hcy) concentrations, two important metabolites in H2S biosynthesis. The key design principle is based on a nitrobenzofurazan-coumarin (NBD-Coum) construct, which fragments into spectroscopically differentiable products upon nucleophilic aromatic substitution with either H2S or Cys/Hcy. Measurement of the ratio of fluorescence intensities from coumarin and the NBD-Cys or NBD-Hcy adducts generates a sigmoidal response with a dynamic range of 3 orders of magnitude. The developed scaffold displays a rapid response (<1 min) and is selective for sulfhydryl-containing nucleophiles over other reactive sulfur, oxygen, and nitrogen species, including alcohol- and amine-functionalized amino acids, polyatomic anionic sulfur species, NO, and HNO. Additionally, NBD-Coum is demonstrated to differentiate and report on different oxidative stress stimuli in simulated sulfur pools containing H2S, Cys, and cystine.

Hydrogen sulfide (H2S) is an important signaling molecule that exerts action on various bioinorganic targets. Despite this importance, few studies have investigated the differential reactivity of the physiologically relevant H2S and HS– protonation states with metal complexes. Here we report the distinct reactivity of H2S and HS– with zinc(II) and cobalt(II) phthalocyanine (Pc) complexes and highlight the chemical reversibility and cyclability of each metal. ZnPc reacts with HS–, but not H2S, to generate [ZnPc-SH]−, which can be converted back to ZnPc by protonation. CoPc reacts with HS–, but not H2S, to form [CoIPc]−, which can be reoxidized to CoPc by air. Taken together, these results demonstrate the chemically reversible reaction of HS– with metal phthalocyanine complexes and highlight the importance of H2S protonation state in understanding the reactivity profile of H2S with biologically relevant metal scaffolds.

Synthetic barbiturate receptors have been utilized for many applications due to their high binding affinities for complementary guests. Although interest in this class of receptors spans from supramolecular to materials chemistry, the effects of receptor steric bulk and preorganization on guest binding affinity has not been studied systematically. To investigate the roles that steric bulk and preorganization play in guest binding, we prepared a series of 12 deconstructed Hamilton receptors with varying degrees of steric bulk and preorganization. Both diethylbarbital and 3-methyl-7-propylxanthine were investigated as guests for the synthetic receptors. The stoichiometry of guest binding was investigated using Job plots for each host–guest pair, and 1H NMR titrations were performed to measure the guest binding affinities. To complement the solution-state studies, DFT calculations at the B3LYP/6-31+G(d,p) level of theory employing the IEF-PCM CHCl3 solvation model were also performed. Calculated guest binding energies correlated well with the experimental findings and provided additional insight into the factors influencing guest binding. Taken together, the results presented highlight the interplay between preorganization and steric interactions in establishing favorable interactions for self-assembled hydrogen-bonded systems.

Hydrogen bond strength in host–guest systems is modulated by many factors including preorganization, steric effects, and electronic effects. To investigate how electronic effects impact barbiturate binding in bifurcated Hamilton receptors, a library of receptors with differing electronic substituents was synthesized and 1H NMR titrations were performed with diethyl barbital. The Hammett plot revealed a clear break between the different electronic substituents suggesting a change in binding conformation. The titration data were complimented with computational studies confirming the change in structure.

Hydrogen sulfide (H2S) is now recognized as an important biological regulator and signaling agent that is active in many physiological processes and diseases. Understanding the important roles of this emerging signaling molecule has remained challenging, in part due to the limited methods available for detecting endogenous H2S. Here we report two reaction-based ChemiLuminescent Sulfide Sensors, CLSS-1 and CLSS-2, with strong luminescence responses toward H2S (128- and 48-fold, respectively) and H2S detection limits (0.7 ± 0.3, 4.6 ± 2.0 μM, respectively) compatible with biological H2S levels. CLSS-2 is highly selective for H2S over other reactive sulfur, nitrogen, and oxygen species (RSONS) including GSH, Cys, Hcy, S2O32–, NO2–, HNO, ONOO–, and NO. Despite its similar chemical structure, CLSS-1 displays lower selectivity toward amino acid-derived thiols than CLSS-2. The origin of this differential selectivity was investigated using both computational DFT studies and NMR experiments. Our results suggest a model in which amino acid binding to the hydrazide moiety of the luminol-derived probes provides differential access to the reactive azide in CLSS-1 and CLSS-2, thus eroding the selectivity of CLSS-1 for H2S over Cys and GSH. On the basis of its high selectivity for H2S, we used CLSS-2 to detect enzymatically produced H2S from isolated cystathionine γ-lyase (CSE) enzymes (p < 0.001) and also from C6 cells expressing CSE (p < 0.001). CLSS-2 can readily differentiate between H2S production in active CSE and CSE inhibited with β-cyanoalanine (BCA) in both isolated CSE enzymes (p < 0.005) and in C6 cells (p < 0.005). In addition to providing a highly sensitive and selective reaction-based tool for chemiluminescent H2S detection and quantification, the insights into substrate–probe interactions controlling the selectivity for H2S over biologically relevant thiols may guide the design of other selective H2S detection scaffolds.

Hydrogen sulfide is an important biological signaling molecule and an important environmental target for detection. A major challenge in developing H2S detection methods is separating the often similar reactivity of thiols and other nucleophiles from H2S. To address this need, the nucleophilic aromatic substitution (SNAr) reaction of H2S with electron-poor aromatic electrophiles was developed as a strategy to separate H2S and thiol reactivity. Treatment of aqueous solutions of nitrobenzofurazan (7-nitro-1,2,3-benzoxadiazole, NBD) thioethers with H2S resulted in thiol extrusion and formation of nitrobenzofurazan thiol (λmax = 534 nm). This reactivity allows for unwanted thioether products to be converted to the desired nitrobenzofurazan thiol upon reaction with H2S. The scope of the reaction was investigated using a Hammett linear free energy relationship study, and the determined ρ = +0.34 is consistent with the proposed SN2Ar reaction mechanism. The efficacy of the developed probes was demonstrated in buffer and in serum with associated submicromolar detection limits as low as 190 nM (buffer) and 380 nM (serum). Furthermore, the sigmoidal response of nitrobenzofurazan electrophiles with H2S can be fit to accurately quantify H2S. The developed detection strategy offers a manifold for H2S detection that we foresee being applied in various future applications.

Hydrogen sulfide (H2S) is an important biological messenger but few biologically-compatible methods are available for its detection. Here we report two bright fluorescent probes that are selective for H2S over cysteine, glutathione and other reactive sulfur, nitrogen, and oxygen species. Both probes are demonstrated to detect H2S in live cells.

•Levels of hydrogen sulfide (H2S) are elevated in renal cell carcinoma (RCC).•Inhibiting endogenous H2S production is cytotoxic for RCC cell lines in vitro.•Inhibiting endogenous H2S production hinders metabolism in VHL-mutant RCC cell lines.•Inhibiting endogenous H2S production hinders neovascularization of RCC xenografts.Clear cell renal cell carcinoma (ccRCC) is characterized by Von Hippel–Lindau (VHL)-deficiency, resulting in pseudohypoxic, angiogenic and glycolytic tumours. Hydrogen sulfide (H2S) is an endogenously-produced gasotransmitter that accumulates under hypoxia and has been shown to be pro-angiogenic and cytoprotective in cancer. It was hypothesized that H2S levels are elevated in VHL-deficient ccRCC, contributing to survival, metabolism and angiogenesis. Using the H2S-specific probe MeRhoAz, it was found that H2S levels were higher in VHL-deficient ccRCC cell lines compared to cells with wild-type VHL. Inhibition of H2S-producing enzymes could reduce the proliferation, metabolism and survival of ccRCC cell lines, as determined by live-cell imaging, XTT/ATP assay, and flow cytometry respectively. Using the chorioallantoic membrane angiogenesis model, it was found that systemic inhibition of endogenous H2S production was able to decrease vascularization of VHL-deficient ccRCC xenografts. Endogenous H2S production is an attractive new target in ccRCC due to its involvement in multiple aspects of disease.

Hydrogen sulfide (H2S) has gained significant interest within the scientific community due to its expanding roles in different (patho)physiological processes. Despite this importance, the chemical mechanisms by which H2S exerts its action remain under-scrutinized. Biomimetic investigations in organic solution offer the potential to clarify these mechanisms and to delineate the differential reactivity between H2S and HS−. However, such studies are hampered by the lack of readily-available sources of HS− that are soluble in organic solution. Here we present a simple method for preparing analytically pure tetrabutylammonium hydrosulfide (NBu4SH), which we anticipate will be of significant utility to researchers in the H2S and anion-binding communities.

Hydrogen sulfide (H2S) is the most recently accepted endogenously produced gasotransmitter and is now implicated in a variety of physiological functions. In this tutorial review, our goal is to provide researchers new to the field of H2S chemical biology with practical considerations, pitfalls, and best practices to enable smooth entry into investigations focused on biological H2S. We present practical handling and safety considerations for working with this reactive biomolecule, and cover basic roles of H2S biogenesis and action. Experimental methods for modulating H2S levels, including enzymatic knockout, RNA silencing, enzymatic inhibition, and use of small molecule H2S donors are highlighted. Complementing H2S modulation techniques, we also highlight current strategies for H2S detection and quantification.

Hydrogen sulfide (H2S) is an important biomolecule with high therapeutic potential. Here we leverage the inverse-electron demand Diels–Alder (IEDDA) click reaction between a thiocarbamate-functionalized trans-cyclooctene and a tetrazine to deliver carbonyl sulfide (COS), which is quickly converted to H2S by the uniquitous enzyme carbonic anhydrase (CA), thus providing a new strategy for bio-orthogonal COS/H2S donation.

Hydrogen sulfide (H2S) is an important biological messenger but few biologically-compatible methods are available for its detection. Here we report two bright fluorescent probes that are selective for H2S over cysteine, glutathione and other reactive sulfur, nitrogen, and oxygen species. Both probes are demonstrated to detect H2S in live cells.

D-Amino acid oxidase (DAO) plays important roles in regulating D-amino acid neurotransmitters and was recently identified as a key enzyme integral to hydrogen sulfide production from D-Cys. We report here the development of a simple biocompatible, bioluminescent method for measuring DAO activity based on the highly selective condensation of D-Cys with 6-hydroxy-2-cyanobenzothiazole (CBT-OH) to form D-luciferin.

There is constant demand for new ligand archictectures on which inorganic and organometallic structures can be leveraged. An important, but often synthetically challenging, class of ligands is bidentate phosphines. Here we report self-assembling, supramolecular bidentate ligand scaffolds based on deconstructed Hamilton receptors with binding affinities up to 800 ± 100 M−1.

Hydrogen sulfide (H2S) has gained recent attention as an important biological analyte that interacts with bioinorganic targets. Despite this importance, stable H2S or HS− adducts of bioinorganic metal complexes remain rare due to the redox activity of sulfide and its propensity to form insoluble metal sulfides. We report here reversible coordination of HS− to Zn(didpa)Cl2, which is enabled by an intramolecular hydrogen bond between the zinc hydrosulfido product and the pendant tertiary amine of the didpa ligand.

Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule in the last decade. During the growth of this field, significant controversy has arisen centered on the physiological concentrations of H2S. Recently, a monobromobimane (mBB) method has been developed for the quantification of different biologically-relevant sulfide pools. Based on the prevalence of the mBB method for sulfide quantification, we expand on this method to report the use of dibromobimane (dBB) for sulfide quantification. Reaction of H2S with dBB results in formation of highly-fluorescent bimane thioether (BTE), which is readily quantifiable by HPLC. Additionally, the reaction of sulfide with dBB to form BTE is significantly faster than the reaction of sulfide with mBB to form sulfide dibimane. Using the dBB method, BTE levels as low as 0.6 pM can be detected. Upon use of the dBB method in wild-type and CSE−/− mice, however, dBB reports significantly higher sulfide levels than those measured using mBB. Further investigation revealed that dBB is able to extract sulfur from other sulfhydryl sources including thiols. Based on mechanistic studies, we demonstrate that dBB extracts sulfur from thiols with α- or β-hydrogens, thus leading to higher BTE formation than from sulfide alone. Taken together, the dBB method is a highly sensitive method for H2S but is not compatible for use in studies in which other thiols are present.

The reversible binding of hydrogen sulfide (H2S) to hemeprotein sites has been attributed to several factors, likely working in concert, including the protected binding pocket environment, proximal hydrogen bond interactions, and iron ligation environment. To investigate the importance of a sterically-constrained, protected environment on sulfide reactivity with heme centers, we report here the reactivity of H2S and HS− with the picket-fence porphyrin system. Our results indicate that the picket-fence porphyrin does not bind H2S in the ferric or ferrous state. By contrast, reaction of the ferric scaffold with HS− results in reduction to the ferrous species, followed by ligation of one equivalent of HS−, as evidenced by UV-vis, NMR spectroscopy and mass spectrometry studies. Measurement of the HS− binding affinities in the picket-fence or tetraphenyl porphyrin systems revealed identical binding. Taken together, these results suggest that the protected, sterically-constrained binding pocket alone is not the primary contributor for stabilization of ferric H2S/HS− species in model systems, but that other interactions, such as hydrogen bonding, must play a critical role in facilitation of reversible interactions in ferric hemes.