Addition Of H2S Research Articles

Hydrogen Sulfide Inhibits High Glucose-Induced sFlt-1 Production via Decreasing ADAM17 Expression in 3T3-L1 Adipocytes.

Hydrogen sulfide (H2S) has recently been identified as an endogenous gaseous signaling molecule. The aim of the present study was to investigate the effect of H2S on high glucose- (HG-) induced ADAM17 expression and sFlt-1 production in 3T3-L1 adipocytes. Firstly, we found that HG DMEM upregulated the expression of ADAM17 and production of sFlt-1 in 3T3-L1 adipocytes. Knocking down ADAM17 attenuated the effect of high glucose on sFlt-1 production in adipocytes. HG decreased the expression of CSE and 3-MST, as well as the endogenous H2S production. Furthermore, knocking down CSE and 3-MST significantly increased ADAM17 expression and sFlt-1 production. The addition of exogenous H2S through the administration of sodium hydrosulfide (NaHS) inhibited HG-induced upregulation of ADAM17 expression and sFlt-1 production. In conclusion, decreased expression of CSE and 3-MST and the subsequent decrease in H2S production contribute to high glucose-induced sFlt-1 production via activating ADAM17 in adipocytes. Exogenous H2S donor NaHS has a potential therapeutic value for diabetic vascular complications.

A highly selective fluorescent probe based on Michael addition for fast detection of hydrogen sulfide

A new 4-hydroxy-1,8-naphthalimide-based compound (probe 1) has been designed and synthesized. The colorimetric and fluorescent properties of probe 1 towards hydrogen sulfide (H2S) were investigated in detail. The results show that the probe 1 could selectively and sensitively recognize H2S rather than other reactive sulfur species. The reaction mechanism of this probe is an intramolecular cyclization caused by the Michael addition of H2S to give 4-hydroxy-1,8-naphthalimide. The intramolecular charge transfer of 4-hydroxy-1,8-naphthalimide is significant. Probe 1 quickly responded to H2S and showed a 75-fold fluorescence enhancement in 5min. Moreover, probe 1 could detect H2S quantitatively with a detection limit as low as 0.23μM.

Enhanced response speed and selectivity of fluorescein-based H2S probe via the cleavage of nitrobenzene sulfonyl ester assisted by ortho aldehyde groups

In this work, we developed three fluorescent probes (F-1, F-2, and F-3) based on fluorescein, mono-formylated fluorescein, and bis-formylated fluorescein for hydrogen sulfide (H2S) detection. The probe F-3, which bears two aldehyde groups, exhibited the fastest response. This fast response is attributed to the ortho effect of the aldehyde group, which enables fast nucleophilic addition of H2S to an aldehyde group and subsequent intramolecular thiolysis of dinitrophenyl ether. In addition, the aldehyde groups on F-3 react with biothiols (e.g., cysteine, homocysteine) to form thiazolidine diastereomers, which suppress the fluorescence of fluorescein. The introduction of two aldehyde groups also resulted in high selectivity of F-3 towards H2S. Furthermore, good linearity was observed between F-3 fluorescence intensity at 510nm and H2S concentration in the range of 0–10µM. F-3 exhibited a detection limit as low as 0.024μM. Confocal laser scanning micrographs of HeLa cells incubated with F-3 confirmed that F-3 is cell-permeable and can successfully detect H2S in living cells.

Colorimetric detection of hydrogen sulfide based on terbium-G-quadruplex-hemin DNAzyme

It is of great importance to simply and sensitively detect hydrogen sulfide (H2S) because of its role in various physiological processes as well as its inherent toxicity. In this work, a colorimetric method for H2S detection was developed by employing terbium-G-quadruplex-hemin (Tb/G4-hemin) DNAzyme as a peroxidase mimic, which can catalyze H2O2-mediated oxidation of 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) to produce radical cation (ABTS+). Compared with the G4-hemin DNAzyme promoted by K+ and Na+, Tb/G4-hemin DNAzyme exhibits a higher catalytic activity. In the presence of Ag+, the peroxidase-like activity of Tb/G4-hemin DNAzyme can be inhibited significantly owing to the disruption of G-quadruplex structure. However, the addition of H2S can effectively suppress such negative behavior by competitive binding with Ag+, leading to the recovery of the peroxidase-like activity of Tb/G4-hemin DNAzyme, which can be reflected by an increase in absorbance signal of ABTS+. The absorbance of ABTS+ was enhanced linearly with increasing H2S concentration from 20nM to 2μM. The detection limit for H2S is 13nM, which is much lower than most of previous methods. Moreover, the proposed method possesses the features of simple preparation, easy reproducibility and good biocompatibility. Given the fine performances and striking properties, we believe that the Tb/G4-hemin DNAzyme would have a great promise for analytical applications.

A highly selective and sensitive 3-hydroxyflavone-based colorimetric and fluorescent probe for hydrogen sulfide with a large Stokes shift

A 3-hydroxyflavone-based colorimetric and fluorescence probe for hydrogen sulfide (H2S) has been developed with high sensitivity and excellent selectivity. This probe was designed based on the mechanism that H2S selectively cleaved the NBD (7-nitro-2,1,3-benzoxadiazole) ether moiety in this probe and therefore release the fluorophore, 3-hydroxyflavone. The addition of H2S to the solution of probe 1 resulted in a green fluorescence and an obvious color change from colorless to pink, indicating that this probe can serve as a colorimetric and fluorescent dual probe for H2S. Furthermore, this probe displays a rapid response and reaches to a plateau within 5 min. It also exhibits a 146 nm Stokes shift and a low detection limit (20 nM, based on S/N=3) in detecting H2S. Importantly, practical utility of this probe for the selective detection of H2S in living cells has been successfully demonstrated.

Effect of H2S in Syngas on the Fischer–Tropsch Synthesis Performance of a 0.5%Pt–25%Co–Al2O3 Catalyst

The effect of 1.0 ppm H2S in the syngas feed on initial activity and selectivity of a 0.5%Pt–25%Co/Al2O3 catalyst was studied by comparing the catalyst performance under H2S and sulfur free conditions. The reaction tests were performed using a 1-L slurry phase reactor for 141–212 h under constant reaction conditions: 220 °C, 2.0 MPa, H2/CO = 2.0 and 6.0 Nl/g-cat/h. In the H2S poisoning test, an H2S in N2 gas mixture was added to the syngas feed (1.0 ppm) after running the Fischer–Tropsch synthesis (FTS) reaction for ca. 6.0 h; as such, the impact of H2S on the initial deactivation of the cobalt catalyst (unsteady state) was successfully assessed. The used catalysts were characterized by XANES to investigate if Co–S surface species were formed during the deactivation. The initial deactivation under 1.0 ppm H2S condition was significantly higher (by 2.0–2.4 times) than that under clean conditions. CH4 selectivity increased substantially and C5+ selectivity decreased greatly with time regardless of whether H2S was added or not; however, the addition of H2S accelerated the changes in the hydrocarbon selectivities, which were likely caused by the sharp deactivation of the catalyst in the presence of H2S. After co-feeding the sulfur for 141 h, a comparison was made at similar conversions by adjusting space velocity; the sulfur pretreated cobalt catalysts favored heavier hydrocarbons (C5+) formation and suppressed lower hydrocarbon formation. The addition of H2S to the feed increased CO2 selectivity and the secondary reaction of 1-olefins. The XANES results revealed that surface species involving Co–S bonding formed on the cobalt catalyst after exposure to H2S during FTS. This was likely the primary reason for the abnormal selectivity trends observed during and after the deactivation of the catalyst by sulfur. This study points out a possible approach to increase the selectivity to heavy hydrocarbons by properly sulfiding the cobalt catalyst prior to the FTS reaction.

Effect of H2S in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst

The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270°C, 1.3MPa, H2/CO=0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase reactor. The used Fe catalysts were characterized by XRD, Mössbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1ppm H2S in the feed. Co-feeding of 0.1ppm H2S in syngas for 70h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270°C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260°C and increased further to 13.5 at 230°C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mössbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230°C), and similar M/S ratios (13.5–15.0) were obtained.

H<sub>2</sub>S interference on CO<sub>2</sub> isotopic measurements using a Picarro G1101-i cavity ring-down spectrometer

Abstract. Cavity ring-down spectrometers (CRDSs) have the capacity to make isotopic measurements of CO2 where concentrations range from atmospheric (~ 400 ppm) to 6000 ppm. Following field trials, it has come to light that the spectrographic lines used for CO2 have an interference with elevated (higher than ambient) amounts of hydrogen sulfide (H2S), which causes significant depletions in the δ13C measurement by the CRDSs. In order to deploy this instrument in environments with elevated H2S concentrations (i.e., active volcanoes), we require a robust method for eliminating this interference. Controlled experiments using a Picarro G1101-i optical spectrometer were done to characterize the H2S interference at varying CO2 and H2S concentrations. The addition of H2S to a CO2 standard gas reveals an increase in the 12CO2 concentration and a more significant decrease in the 13CO2 concentration, resulting in a depleted δ13C value. Reacting gas samples containing H2S with copper prior to analysis can eliminate this effect. Models post-dating the G1101-i carbon isotope analyzer have maintained the same spectral lines for CO2 and are likely to have a similar H2S response at elevated H2S concentrations. It is important for future work with CRDS, particularly in volcanic regions where H2S is abundant, to be aware of the H2S interference on the CO2 spectroscopic lines and to remove all H2S prior to analysis. We suggest employing a scrub composed of copper to remove H2S from all gas samples that have concentrations in excess of 1 ppb.

A Matter of Timing: Contrasting Effects of Hydrogen Sulfide on Oxidative Stress Response in Shewanella oneidensis.

Hydrogen sulfide (H2S), well known for its toxic properties, has recently become a research focus in bacteria, in part because it has been found to prevent oxidative stress caused by treatment with some antibiotics. H2S has the ability to scavenge reactive oxygen species (ROS), thus preventing oxidative stress, but it is also toxic, leading to conflicting reports of its effects in different organisms. Here, with Shewanella oneidensis as a model, we report that the effects of H2S on the response to oxidative stress are time dependent. When added simultaneously with H2O2, H2S promoted H2O2 toxicity by inactivating catalase, KatB, a heme-containing enzyme involved in H2O2 degradation. Such an inhibitory effect may apply to other heme-containing proteins, such as cytochrome cbb3 oxidase. When H2O2 was supplied 20 min or later after the addition of H2S, the oxidative-stress-responding regulator OxyR was activated, resulting in increased resistance to H2O2. The activation of OxyR was likely triggered by the influx of iron, a response to lowered intracellular iron due to the iron-sequestering property of H2S. Given that Shewanella bacteria thrive in redox-stratified environments that have abundant sulfur and iron species, our results imply that H2S is more important for bacterial survival in such environmental niches than previously believed. Previous studies have demonstrated that H2S is either detrimental or beneficial to bacterial cells. While it can act as a growth-inhibiting molecule by damaging DNA and denaturing proteins, it helps cells to combat oxidative stress. Here we report that H2S indeed has these contrasting biological functions and that its effects are time dependent. Immediately after H2S treatment, there is growth inhibition due to damage of heme-containing proteins, at least to catalase and cytochrome c oxidase. In contrast, when added a certain time later, H2S confers an enhanced ability to combat oxidative stress by activating the H2O2-responding regulator OxyR. Our data reconcile conflicting observations about the functions of H2S.

Role of cystathionine β-synthase in human breast Cancer

Cystathionine β-synthase (CBS) is an enzyme in the transulfuration pathway that can catalyze the condensation of homocysteine (Hcy) and cysteine (Cys) to hydrogen sulfide (H2S) and cystathionine (CTH). CBS-derived H2S is important in angiogenesis and drug resistance in colon and ovarian cancers, respectively. However, the mechanisms by which cancer cell-derived H2S is utilized by cancer cells as a protective agent against host-derived activated macrophages are not yet investigated. This study investigated the mechanistic role of CBS-derived H2S in the protection of human breast cancer (HBC) cells against activated macrophages. HBC patient-derived tissue arrays and immunoblot analysis of HBC cells exhibited significantly increased levels of CBS when compared with their normal counterparts. This was associated with increased levels of H2S and CTH. Silencing of CBS in HBC cells caused a significant decrease in the levels of H2S and CTH but did not affect the growth of these cells per se, in in vitro cultures. However CBS-silenced cells exhibited significantly reduced growth in the presence of activated macrophages and in xenograft models. This was associated with an increase in the steady state levels of reactive aldehyde-derived protein adducts. Exogenous addition of H2S countered the effects of CBS silencing in the presence of macrophages. Conversely overexpression of CBS in human breast epithelial (HBE) cells (which do not naturally express CBS) protected them from activated macrophages, which were otherwise susceptible to the latter.

Sulfur Tolerance of La0.3M0.7Fe0.7Cr0.3O3 -δ (M= Sr, Ca) Solid Oxide Fuel Cell Anodes

Solid oxide fuel cells (SOFCs) are highly efficient electrochemical devices that also demonstrate excellent fuel flexibility, functioning on fuels such as H2, CO, methane. Traditionally, SOFCs are based on a Ni-YSZ (yttria stabilized zirconia) cermet anode, a YSZ electrolyte, and a lanthanum strontium manganite (LSM) cathode. Although Ni-YSZ cermets are excellent SOFC anodes, largely because of their excellent catalytic activity towards fuel oxidation, work in our group and by others has shown that Ni is susceptible to poisoning in low levels (1-100 ppm) of H2S exposure at SOFC operating temperatures (700-1000 oC) [1-4]. It has been suggested that H2S inhibits the H2 oxidation reaction (HOR) rates because it readily dissociates to form a surface adsorbed Ni-S layer (Sads) on catalytic sites normally involved in H2 dissociation and subsequent oxidation [4], thereby decreasing the performance of the SOFC. As a result, extensive research has been carried out to develop sulfur tolerant SOFC anode materials based on Ni-free conducting metal oxides, such as perovskites. Previous and current studies in our group employing La0.3M0.7Fe0.7Cr0.3O3-δ (M= Sr, Ca) perovskite oxides as both the anode and cathode electrode material, screen printed onto both sides of a YSZ electrolyte with a Gd0.9Ce0.1O2-δ (GDC) buffer layer separating the electrodes and the YSZ, showed very good electrochemical performance in both H2 and CO/CO2 atmospheres in the absence of H2S [5-6]. Therefore, in this work, extensive electrochemical studies, focusing on the performance of La0.3M0.7Fe0.7Cr0.3O3-δ (M= Sr, Ca) in a symmetrical SOFC configuration and operating on H2 and/or CO/CO2 fuels containing varying concentrations of H2S (5- 30 ppm), were carried out at 500 - 800 oC. Also, the effect of the dc bias on the sulfur tolerance of these materials has been examined. Our preliminary results have shown that La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr) electrodes, operated as an anode in humidified H2 plus up to 9 ppm H2S (balance in H2) at 800 oC showed no H2S poisoning. The polarization resistance (Rp) observed for the cell in 30% humidified H2 was 1.20 Ω.cm2 at 800 oC and, with the addition of 9 ppm H2S, there was no observed change in Rp. However, in dry CO/CO2, the addition of H2S showed a ca. 3% increase in Rp, but without any further degradation after longer term exposures to H2S. Importantly, when the H2S was removed from this gas mixture, the performance recovered fully. Acknowledgements – We are very grateful to the SOFC Canada NSERC Strategic Research Network, as well as Carbon Management Canada, for the support of this work. References Y. Matsuzaki and I. Yasuda, Solid State Ionics 132, 261 (2000).Z. Cheng, S. Zha and M. Liu, J. Power Sources, 172,688 (2007).L. Debeeleeck et al, Phys.Chem.Chem.Phys., 16, 9383(2014).J. B. Hansen, Electrochem. Solid-State Lett., 11, B178 (2008).M. Chen, S. Paulson, V. Thangadurai and V. Birss, J. Power Sources, 236, 68 (2013).P. Addo, B. Molero-Sánchez, M. Chen, S. Paulson and V. Birss, 11th European SOFC and SOE Forum, Luzerne, Switzerland, 2014.

Electrochemical oxidation of sour natural gas over La0.4Ce0.6O1.8–La0.4Sr0.6TiO3±δ anode in SOFC: A mechanism study of H2S effects

For solid oxide fuel cell with La0.4Ce0.6O1.8–La0.4Sr0.6TiO3±δ (LDC-L4ST) impregnated anodes, the electrochemical oxidation rates of H2 and CH4 were significantly improved when H2S (0.5%) was present in the feeds as evidenced by the substantially decreased polarization resistance and the improved power density of the cell although H2S did not predominantly function as a fuel. Conductivity measurements of various anode component materials implied that the addition of H2S into the feeds increased their conductivities. More importantly, from the mass spectroscopic analysis of the anode gas effluents and the thermodynamic calculations, direct evidences of H2S caused SOFC performance improvement have been confirmed, three distinct regions for the electrochemical oxidation pathways of 0.5% H2S–CH4 vs. overpotential (η) were proposed to explain the effect. The chemisorbed S species, together with LDC-L4ST, behaved as an effective catalyst promoting CH4 oxidations via COS and CS2 intermediates. The addition of LDC in the anode enhanced this synergic effect and further increased CH4 electrochemical conversion as well as coking resistance in comparison of the L4ST anode.

Evidence for the presence of strong Mn(III)-binding ligands in the water column of the Chesapeake Bay

Soluble manganese speciation was determined in suboxic and anoxic waters of the Chesapeake Bay using a water soluble porphyrin ligand as spectrophotometric reagent. Initial addition of the reagent detected only Mn(II); on addition of 100μM H2S (excess of the expected total dissolved Mn concentration) an increase in Mn occurred, indicating a reduction of Mn(III). Mn(III) comprised up to 54.21±2.71% of the total dissolved Mn pool. Samples with low H2S (4.82±0.80μM) had high Mn(III) (6.98±0.63μM) whereas those with high H2S (38.37±1.70μM) had low Mn(III) (1.12±0.17μM) indicating that Mn(III) is kinetically stabilized in situ by strong ligands so reduction to Mn(II) is not complete. Assays for MnOx particles showed that these were negligible or not detected except near the oxic–anoxic interface, and Mn(III) depth profiles showed peaks below the oxic–anoxic interface. Sulfidic sediments were not a source of Mn(III) to overlying waters as no Mn(III) was detected in overlying waters. These Mn(III) profiles likely result from the one electron reductive dissolution of solid MnO2 particles formed at the oxic–anoxic interface, which then fall into the anoxic hydrogen sulfide rich zone. Laboratory experiments with known ligands bound to Mn(III) confirm that Mn(III)-L complexes do not completely react with H2S as these are concentration dependent reactions under kinetic control.

Hydrogen sulfide inhibits amyloid formation.

Amyloid fibrils are large aggregates of misfolded proteins, which are often associated with various neurodegenerative diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and vascular dementia. The amount of hydrogen sulfide (H2S) is known to be significantly reduced in the brain tissue of people diagnosed with Alzheimer’s disease relative to that of healthy individuals. These findings prompted us to investigate the effects of H2S on the formation of amyloids in vitro using a model fibrillogenic protein hen egg white lysozyme (HEWL). HEWL forms typical β-sheet rich fibrils during the course of 70 min at low pH and high temperatures. The addition of H2S completely inhibits the formation of β-sheet and amyloid fibrils, as revealed by deep UV resonance Raman (DUVRR) spectroscopy and ThT fluorescence. Nonresonance Raman spectroscopy shows that disulfide bonds undergo significant rearrangements in the presence of H2S. Raman bands corresponding to disulfide (RSSR) vibrational modes in the 550–500 cm–1 spectral range decrease in intensity and are accompanied by the appearance of a new 490 cm–1 band assigned to the trisulfide group (RSSSR) based on the comparison with model compounds. The formation of RSSSR was proven further using a reaction with TCEP reduction agent and LC-MS analysis of the products. Intrinsic tryptophan fluorescence study shows a strong denaturation of HEWL containing trisulfide bonds. The presented evidence indicates that H2S causes the formation of trisulfide bridges, which destabilizes HEWL structure, preventing protein fibrillation. As a result, small spherical aggregates of unordered protein form, which exhibit no cytotoxicity by contrast with HEWL fibrils.

Temporal dynamics of nitrogen loss in the coastal upwelling ecosystem off central Chile: Evidence of autotrophic denitrification through sulfide oxidation

Coastal upwelling areas are highly productive marine systems in which the development of oxygen‐depleted conditions and the availability of diverse electron donors (e.g., organic matter, , H2S) favor the processes involved in nitrogen (N) loss. We characterize the temporal and vertical variability of anammox and denitrification over the continental shelf off central Chile (36.5°S), through 15N and 13C tracer experiments, including amendments with H2S and along with measurements of 15N2 and 15N2O production and oceanographic variables during a year (2009 to 2010). Restricted to the bottom waters, both anammox and denitrification contributed similarly (∼ 500 nmol N2 L−1 d−1) to N loss during spring, while a marked decrease in the activity of these processes occurred in summer (103 and 14 nmol N2 L−1 d−1 for anammox and denitrification, respectively). During fall, denitrification was the only contributor to the observed nitrogen deficit (894 nmol N2 L−1 d−1). Interestingly, a substantial increase in the rates of denitrification (∼ 1200 nmol N2 L−1 d−1) and dark 13C assimilation were observed after the addition of H2S, indicating an autotrophic contribution to denitrification, which could be fueled in situ by H2S emitted from sediments or produced in the water column. The observed patterns seem to be controlled (stimulated or inhibited) by the availability of oxygen, organic matter, and H2S. This study establishes the magnitude and co‐occurrence of the different processes responsible for N removal in the coastal upwelling system of central Chile. This linkage of the nitrogen, carbon, and sulfur cycles is relevant to a global climate change scenario.

Effects of Hydrogen Sulfide on the Corrosion Behavior of High Strength Steel in Alkaline Solutions

In-situ electrochemical corrosion measurements were performed for high-strength low-alloy steels in 5 %wt. NaCl solutions of pH 7.5, 10.6, and 12.3 at 85 °C. It was observed that the corrosion typically reached a steady state by 60 hours. The corrosion rate at steady state was slower at higher pH, regardless of H2S concentration. The addition of H2S accelerated the corrosion rates of UD-165 at pH 7.5 and 12.3, but decreased the corrosion rate at pH 10.6. This could have been related to the autocatalytic effect of H2S and the nature of the corrosion product film on the surface. Both the Pourbaix diagrams and the surface analyses suggested that the corrosion products shifted from iron sulfides to iron oxides as the solution pH was increased.

Hydrogen sulfide alleviates the aluminum-induced changes in Brassica napus as revealed by physiochemical and ultrastructural study of plant.

In the present study, ameliorating role of hydrogen sulfide (H2S) in oilseed rape (Brassica napus L.) was studied with or without application of H2S donor sodium hydrosulfide (NaHS) (0.3 mM) in hydroponic conditions under three levels (0, 0.1 and 0.3 mM) of aluminum (Al). Results showed that addition of H2S significantly improved the plant growth, photosynthetic gas exchange, and nutrients concentration in the leaves and roots of B. napus plants under Al stress. Exogenously applied H2S significantly lowered the Al concentration in different plant parts, and reduced the production of malondialdehyde and reactive oxygen species by improving antioxidant enzyme activities in the leaves and roots under Al stress. Moreover, the present study indicated that exogenously applied H2S improved the cell structure and displayed clean mesophyll and root tip cells. The chloroplast with well-developed thylakoid membranes could be observed in the micrographs. Under the combined application of H2S and Al, a number of modifications could be observed in root tip cell, such as mitochondria, endoplasmic reticulum, and golgi bodies. Thus, it can be concluded that exogenous application of H2S under Al stress improved the plant growth, photosynthetic parameters, elements concentration, and biochemical and ultrastructural changes in leaves and roots of B. napus.

Carbon formation on stainless steel 304H in convection section of ethane cracking plant

The coking of stainless steel 304H alloy (SS304H) has been investigated in ethane–steam mixtures in the presence/absence of a few ppm of H2S at 700°C. In this, first detailed study of the influence of H2S on carbon morphology on SS304H, we show that the addition of H2S greatly altered the carbon morphology, in the long-term experiments (90 h). For shorter exposure times (4 h), carbon formation decreased as H2S concentration was increased. This improved carbon tolerance of SS304H is likely due to adsorption of sulphfur on its surface. Addition of H2S did not change the ethane cracking initiation temperature or the product distribution.

A ratiometric colorimetric and fluorescent chemosensor for rapid detection hydrogen sulfide and its bioimaging

A new selective colorimetric and fluorescent sensor for H2S, diethylaminocoumarin–hemicyanine dye has been designed, synthesized and evaluated. In CH3OH-HEPES (10mM, pH 7.4) buffer solution containing the sensor, the addition of H2S made the UV–vis absorption of the sensor taking place blue-shift from red to yellow, and the fluorescence of the sensor also changed from red to green. Other analytes did not disturb the determination of H2S. The mechanism is based on the nucleophilic attack toward the polarized CN and an electron-poor CC bond of the sensor. Moreover, its adduct was proved by ESI-MS and NMR. The system was used to react with H2S in the cell, which can provide a potentially powerful approach for probing H2S chemistry in biological system.

Hydrogen sulfide deactivates common nitrobenzofurazan-based fluorescent thiol labeling reagents.

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.