Effect of Cu/HZSM-5 sorbents with different Si/Al ratios on the adsorption and oxidation performance of H2S.

This study employed a wet impregnation method to synthesize five types of Cu/HZSM-5 adsorbents with Si/Al ratios of 25, 50, 85, 200, and 300, used for the removal of H2S in low-temperature, low-oxygen environments. The impact of different Si/Al ratios on the adsorption oxidative performance of Cu30/HZSM-5-85 adsorbents was investigated. According to the performance test results, Cu30/HZSM-5-85 exhibited the highest breakthrough capacity, reaching 231.75 mg H2S/gsorbent. Cu/HZSM-5 sorbent maintains a strong ability to remove H2S even under humid conditions and shows excellent water resistance. XRD, BET, and XPS results revealed that CuO is the primary active species, with Cu30/HZSM-5-85 having the largest surface area and highest CuO content, providing more active sites for H2S adsorption. H2-TPR and O2-TPD results confirmed that Cu30/HZSM-5-85 sorbent exhibits outstanding redox properties and oxygen storage capacity, contributing to excellent oxygen transferability in the molecular sieve adsorption-oxidation process. With notable characteristics such as a large surface area, high desulfurization efficiency, and water resistance, Cu30/HZSM-5-85 sorbents hold significant importance for industrial applications.

Cu/TiO2 adsorbents modified by air plasma for adsorption-oxidation of H2S.

In this study, non-thermal plasma (NTP) was employed to modify the Cu/TiO2 adsorbent to efficiently purify H2S in low-temperature and micro-oxygen environments. The effects of Cu loading amounts and atmospheres of NTP treatment on the adsorption-oxidation performance of the adsorbents were investigated. The NTP modification successfully boosted the H2S removal capacity to varying degrees, and the optimized adsorbent treated by air plasma (Cu/TiO2-Air) attained the best H2S breakthrough capacity of 113.29 mg H2S/gadsorbent, which was almost 5 times higher than that of the adsorbent without NTP modification. Further studies demonstrated that the superior performance of Cu/TiO2-Air was attributed to increased mesoporous volume, more exposure of active sites (CuO) and functional groups (amino groups and hydroxyl groups), enhanced Ti-O-Cu interaction, and the favorable ratio of active oxygen species. Additionally, the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated the main reason for the deactivation was the consumption of the active components (CuO) and the agglomeration of reaction products (CuS and SO42-) occupying the active sites on the surface and the inner pores of the adsorbents.

The role of sulfur cycle in new particle formation: Cycloaddition reaction of SO3 to H2S.

The chemistry of sulfur cycle contributes significantly to the atmospheric nucleation process, which is the first step of new particle formation (NPF). In the present study, cycloaddition reaction mechanism of sulfur trioxide (SO3) to hydrogen sulfide (H2S) which is a typical air pollutant and toxic gas detrimental to the environment were comprehensively investigate through theoretical calculations and Atmospheric Cluster Dynamic Code simulations. Gas-phase stability and nucleation potential of the product thiosulfuric acid (H2S2O3, TSA) were further analyzed to evaluate its atmospheric impact. Without any catalysts, the H2S + SO3 reaction is infeasible with a barrier of 24.2 kcal/mol. Atmospheric nucleation precursors formic acid (FA), sulfuric acid (SA), and water (H2O) could effectively lower the reaction barriers as catalysts, even to a barrierless reaction with the efficiency of cis-SA > trans-FA > trans-SA > H2O. Subsequently, the gas-phase stability of TSA was investigated. A hydrolysis reaction barrier of up to 61.4 kcal/mol alone with an endothermic isomerization reaction barrier of 5.1 kcal/mol under the catalytic effect of SA demonstrates the sufficient stability of TSA. Furthermore, topological and kinetic analysis were conducted to determine the nucleation potential of TSA. Atmospheric clusters formed by TSA and atmospheric nucleation precursors (SA, ammonia NH3, and dimethylamine DMA) were thermodynamically stable. Moreover, the gradually decreasing evaporation coefficients for TSA-base clusters, particularly for TSA-DMA, suggests that TSA may participate in NPF where the concentration of base molecules are relatively higher. The present new reaction mechanism may contributes to a better understanding of atmospheric sulfur cycle and NPF.

A novel structurally modified isophorone fluorescent probe for H2S detection.

Hydrogen sulfide (H2S) has a comprehensive contribution to the normal operation and stability of organisms and is also present in environmental water samples and food deterioration. Thus, it is exceedingly promising and significant to develop a highly sensitive detection technique for tracing H2S. Inspired by this, we designed and synthesized a new fluorescent probe 2-[3-[2-[3-bromo-4-(2,4- dinitrobenzenesulfonate)] ethenyl]-5,5-dimethyl-2-cyclohexen-1-ylidene]propanedinitrile (SP-Br) for hydrosulfide ion detection by introducing bromine atom. Compared with reported H2S probes based on the same fluorescent parent, SP-Br has longer fluorescence emission (λem = 670 nm), shorter response time (3 min), lower detection limit (149 nM), and wider detection range (0-30 nM). SP-Br can emit weak yellow fluorescence, and the emission intensity at 670 nm is considerably enhanced in the presence of hydrosulfide ions. The identification mechanism of hydrosulfide ion by SP-Br was verified by high-resolution mass spectrometry, fluorescence, and UV-vis absorption spectroscopy. In addition, SP-Br has been successfully applied to the monitoring of actual water samples and beer samples and has certain development prospects and value in the fields of environmental pollution and food quality analysis.

H2S protects rat cerebral ischemia-reperfusion injury by inhibiting expression and activation of hippocampal ROCK2 at the Thr436 and Ser575 sites.

BACKGROUND: H2S is an endogenous gas signal molecule, which protects cerebral ischemia/reperfusion (I/R) injury by phosphorylating rho-associated coiled coil-containing protein kinase 2 (ROCK2) at Tyr722, and inhibiting ROCK2 protein expression and activities. We previously reported that H2S protected rat neurons from hypoxia/reoxygenation injury in vitro through inhibiting phosphorylation of ROCK2 at Thr436 and Ser575, but it is unclear whether these two sites are involved in protection of H2S against cerebral I/R injury. METHOD: Rats transfected with wild-type and mutant eukaryotic plasmids of ROCK2 in hippocampus were used to establish I/R model by ligating bilateral common carotid artery. Rat behavioral deficit was detected by water maze assay, and ROCK2, lactate dehydrogenase (LDH), nerve-specific enolase (NSE) and reactive oxygen species (ROS) were determined by ELISA. ROCK2 expressions was examined by western-blot assay, and bcl-2 and Bax mRNAs were examined by RT-qPCR. RESULTS: NaHS (4.8mg/kg) significantly inhibited the I/R-increased serum LDH, NSE and ROS in the ROCK2wild-pEGFP-N1-transfected rats, but had no obvious effect in the ROCK2T436A-pEGFP-N1- or the ROCK2S575F-pEGFP-N1-transfected rats; inhibitions of NaHS on the I/R-increased escape latency and the I/R-decreased percentage of target quadrant distance to total distance were markedly attenuated or abolished in the ROCK2T436A-pEGFP-N1- or the ROCK2S575F-pEGFP-N1-transfected rats compared with those in the ROCK2wild-pEGFP-N1-transfected rats; NaHS obviously inhibited the I/R-increased hippocampal ROCK2 and GFP-ROCK2 proteins, Bax mRNA, and ROCK2 activity, as well as the I/R-decreased hippocampal bcl-2 mRNA in the hippocampus of the ROCK2wild-pEGFP-N1-transfected rats, but had no significant effect in the ROCK2T436A-pEGFP-N1- or the ROCK2S575F-pEGFP-N1-transfected rats. CONCLUSION: H2S protects cerebral I/R injury in rats by inhibiting expression and activation of hippocampal ROCK2 via the Thr436 and Ser575 sites.

Molecular regulation by H2S of antioxidant and glucose metabolism in cold-sensitive Capsicum.

BACKGROUND: Cold is an important environmental limiting factor affecting plant yield and quality. Capsicum (chili pepper), a tropical and subtropical vegetable crop, is extremely sensitive to cold. Although H2S is an important signaling regulator in the responses of plant growth and development to abiotic stress, few studies have examined its effects on cold-sensitive capsicum varieties. Through biotechnology methods to enhance the cold resistance of peppers, to provide some reference for pepper breeding, investigated molecular regulation by H2S of responses to cold stress in cold-sensitive capsicum plants, via physiological and transcriptomic analyses. RESULTS: In capsicum seedlings, exogenous H2S enhanced relative electrical conductivity (REC) and levels of malondialdehyde (MDA) under cold stress, maintained membrane integrity, increased the activity of enzymatic and non-enzymatic antioxidants, balanced reactive oxygen species levels (O2·- and H2O2), and improved photosynthesis, mitigating the damage caused by cold. In addition, 416 differentially expressed genes (DEGs) were involved in the response to cold stress after H2S treatment. These DEGs were mainly enriched in the ascorbate-glutathione and starch-sucrose metabolic pathways and plant hormone signal-transduction pathways. Exogenous H2S altered the expression of key enzyme-encoding genes such as GST, APX, and MDHAR in the ascorbate-glutathione metabolism pathway, as well as that of regulatory genes for stimulatory hormones (auxin, cytokinins, and gibberellins) and inhibitory hormones (including jasmonate and salicylic acid) in the plant hormone signal-transduction pathway, helping to maintain the energy supply and intracellular metabolic stability under cold stress. CONCLUSIONS: These findings reveal that exogenous H2S improves cold tolerance in cold-sensitive capsicum plants, elucidating the molecular mechanisms underlying its responses to cold stress. This study provides a theoretical basis for exploring and improving cold tolerance in capsicum plants.

Elucidating the downstream pathways triggered by H2S signaling in Arabidopsis thaliana under drought stress via transcriptome analysis.

Hydrogen sulfide (H2S) is a crucial signaling molecule in plants. Recent studies have shown that H2S plays an equally important role as nitric oxide (NO) and hydrogen peroxide (H2O2) in plant signaling. Previous studies have demonstrated the involvement of H2S in regulating drought and other stressful environmental conditions, but the exact downstream molecular mechanisms activated by the H2S signaling molecule remain unclear. In this study, we conducted a comprehensive genome-wide transcriptomic analysis of both wild type (WT) and double mutant (lcd/des1). Arabidopsis thaliana plants were exposed to 40% polyethylene glycol (PEG) to induce drought stress and 20 µM sodium hydrosulfide (NaHS). The resulting transcriptome data were analyzed for differentially significant genes and their statistical enrichments in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The results indicated significant upregulation of genes related to photosynthesis, carbon fixation, plant secondary metabolite biosynthesis, inositol and phosphatidylinositol signaling pathways, and stress-responsive pathways in mutant plants under drought stress. Mutant plants with impaired H2S signaling mechanisms displayed greater susceptibility to drought stress compared to wild-type plants. In summary, all findings highlight the pivotal role of H2S signaling in stimulating other drought-responsive signaling pathways.

Ultrasensitive detection of hazardous gas at room temperature enabled by MOF@MXene 0D-2D heterostructure.

Achieving high sensitivity in detecting trace concentrations of toxic gases, particularly under room temperature (RT) conditions, remains a significant challenge. Herein, a 0D-2D heterostructure that can detect ppb-level H2S at RT is proposed by self-assembling cobalt-based metal-organic framework (Co-MOF) on Ti3C2Tx MXene. Co-MOFs with high specific surface areas can capture and concentrate target gas molecules, enhancing host-guest interactions and thereby boosting the selectivity and sensitivity. MXene nanosheets with high conductivity enable rapid electron transport at heterointerface, hence efficiently accelerating the reaction kinetics. Thereby, the as-prepared chemiresistive gas sensor based on Co-MOF@MXene 0D-2D heterostructure possessed excellent sensitivity against interfering gases and delivered an excellent response value of 11.1 to 400 ppb H2S at RT. The judicious design of MOF@MXene heterostructure may spur advanced hybrid material systems for superior sensing applications.

Increased hydrogen sulfide turnover serves a cytoprotective role during the development of replicative senescence.

The mammalian gasotransmitter hydrogen sulfide (H2S) is produced by enzymes such as cystathionine ß-synthase (CBS), cystathionine γ-lyase (CSE), 3-mercaptopyruvate sulfurtransferase (3-MST). Prior studies suggest that H2S may have cytoprotective and anti-aging effects. This project explores the regulation and role of endogenous H2S in a murine model of replicative senescence. H2S and polysulfide levels in RAW 264.7 murine macrophages (control cells: passage 5-10; senescent cells: passage 30-40) were measured using fluorescent probes. The expression of H2S-related enzymes and the activity of senescence marker beta-galactosidase (SA-ß-Gal) were also analyzed. CBS, CSE, and 3-MST were inhibited using selective pharmacological inhibitors. Senescence led to a moderate upregulation of CBS and in a significant increase in CSE and 3-MST. H2S degradation enzymes were also elevated in senescence. Inhibition of H2S-producing enzymes reduced H2S levels but increased polysulfides. Inhibition of H2S production during senescence suppressed cell proliferation, and elevated SA-ß-Gal and p21 levels. Comparing young and old mice spleens revealed downregulation of CBS and ETHE1 and upregulation of rhodanese and SUOX in older mice. The results demonstrate that increased reactive sulfur turnover occurs in senescent macrophages and that reactive sulfur species support cell proliferation and regulate cellular senescence.

Room-Temperature Flexible CNT/Fe2O3 Film Sensor for ppb-Level H2S Detection.

Carbon nanotubes (CNTs) had room temperature response, large surface area, and excellent mechanical properties, making them favorable for the design of flexible, wearable, and portable gas sensors. However, CNTs were lacking in response and selective response to different gases, such as H2S. Here, we demonstrated a flexible H2S ppb-level gas sensor based on a carbon nanotube/amorphous Fe2O3 (CNT/Fe2O3) film at room temperature, which was fabricated via a simple one-step solvent-thermal method. The CNT/Fe2O3 film gas sensor exhibited a high selective response to H2S (with a response of 55.1% to 100 ppb H2S), rapid reversible response at room temperature (with a response time of ∼127 s to 100 ppb H2S), and low limit of detection to about 2 ppb. Additionally, the CNT/Fe2O3 film maintained good sensing performance under various bending conditions and could be further fabricated into the fiber gas sensor device via wet stretching, retaining response at the ppb level (with a response of 18.6% to 100 ppb H2S). This research on a flexible gas sensor device based on the CNT film/fiber opened up new possibilities for wearable portable electronic device applications.

Enhanced Regulation of Selectivity by the Coupling Effects of Surface Acidity and Strain Effects via Precisely Controlling the Location of Pt.

Loading a sensitizer and constructing a rational nanostructure have been reported to be effective approaches for enhancing the catalytic/sensing performance. However, the impact of the precise loading position on the catalytic/sensing performance is always overlooked. Here, we discovered that precisely changing the location of Pt clusters from the outside of Al2O3-ZnO nanocoils (O-PtAlZnNCs) to the inner side of the nanocoils (I-PtAlZnNCs) could change the sensing performance of the sensor from H2S to acetone. Furthermore, precisely loading Pt inside of the confined space led to a high sensing performance and reduced the limit of detection (LOD) of acetone by a factor of 50 times (from 100 to 2 ppb). Combining X-ray photoelectron spectroscopy (XPS), NH3-diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), in situ X-ray absorption spectroscopy (XAS), and density functional theory (DFT) simulations, the enhancement of sensitivity and regulation of sensing selectivity are attributed to the coupling effects from enrichment of confined space and Al2O3 acid-base active sites as well as the regulation of electronic structure by location-dominated strain effects. This work not only provides a novel sight to precisely regulate the selectivity and obtain ultrasensitive materials but also serves as a useful instruction for further understanding and precisely designing specific sensors and catalysts with high performance.

In Situ Generatable and Recyclable Oxygen Vacancy-Modified Fe2O3-Decorated WO3 Nanowires with Super Stability for ppb-Level H2S Sensing.

Detecting hydrogen sulfide (H2S) odor gas in the environment at parts-per-billion-level concentrations is crucial. However, a significant challenge is the rapid deactivation caused by SO42- deposition. To address this issue, we developed a sensing material comprising Fe2O3-decorated WO3 nanowires (FWO) with strong interfacial interaction. During the H2S sensing process, important oxygen vacancies (OVs) are generated in situ and are recyclable on the surface of the Fe2O3 cluster. This sensor achieves a response of 140 (Ra/Rg) toward 50 ppm of H2S at 250 °C, with an experimentally measured detection limit of 1 ppb. It also exhibits remarkable stability, with no significant change observed over a long period of 150 days. Based on a combination of in situ DRIFT and DFT calculations, we have identified that the overactivation of O2 is the key step in the formation of SO42-. This overactivation can be partially modulated by the synergistic effect of Fe2O3 decoration and the in situ generated OVs, regulating the oxidation product to SO2 rather than the toxic SO42-. Furthermore, the continuous generation of OVs compensates for the loss of active sites pertaining to SO42- deposition, thereby contributing to the excellent stability of the sensor. This study underscores the beneficial impact of in situ OV generation in FWO for H2S sensing, offering a dynamic strategy to enhance sensor performance, particularly in terms of stability.

Multifunctional Au-Ag NCs for luminescence and colorimetric double signal sensing of H2S and catalytic reduction of nitrophenol.

In this study, the N-Acetyl-l-Cysteine (NAC)-capped gold and silver bimetallic nanoclusters (NAC@Au-Ag NCs) was synthesized by reflux method. Due to the silver effect, the NAC@Au-Ag NCs exhibited strong photoluminescence at far-red/near-infrared regions and better catalytic performance than Au or Ag NCs. Upon addition of H2S, the Au-Ag NCs exhibited obvious fluorescence quench and color changes through the generation of metal sulfides and a static quenching process. The Au-Ag NCs displayed a wide linear luminescence response for H2S (18.5-217 µmol/L) with a detection limit of 0.269 µmol/L. Moreover, the visible color of Au-Ag NCs changed from white to brown-yellow along with increased H2S, the corresponding RGB values also displayed good linearity with the concentration of H2S (90.1-678 µmol/L). Notably, the fabrication of test strips provided a convenient and intuitive tool to screen the freshness of eggs by the color change of test strips. Au-Ag NCs could be used for living HeLa cells bioimaging and recognition of H2S abnormalities. Furthermore, it can be used as a catalyst to reduction of nitrophenols (NPhs), specific included 2NP, 3NP and 4NP. The reaction was regarded as a pseudo-first-order kinetic reaction due to the presence of excess NaBH4. At 298K, the catalytic rate constants(k) of 2NP, 3NP and 4NP were 0.1754 min-1, 0.1734 min-1 and 0.2782 min-1, respectively. The NAC@Au-Ag NCs catalyst still showed good catalytic activity and reusability after five cycles. Therefore, this study developed a H2S sensor for food samples and biological systems. And this nanocatalyst had great application potential for removed the nitrophenol pollutants in water.

Microbiota and detrimental protein derived metabolites in colorectal cancer.

Colorectal cancer (CRC) is the third leading cancer in incidence and the second leading cancer in mortality worldwide. There is growing scientific evidence to support the crucial role of the gut microbiota in the development of CRC. The gut microbiota is the complex community of microorganisms that inhabit the host gut in a symbiotic relationship. Diet plays a crucial role in modulating the risk of CRC, with a high intake of red and processed meat being a risk factor for the development of CRC. The production of metabolites derived from protein fermentation by the gut microbiota is considered a crucial element in the interaction between red and processed meat consumption and the development of CRC. This paper examines several metabolites derived from the bacterial fermentation of proteins associated with an increased risk of CRC. These metabolites include ammonia, polyamines, trimethylamine N-oxide (TMAO), N-nitroso compounds (NOC), hydrogen sulphide (H2S), phenolic compounds (p-cresol) and indole compounds (indolimines). These compounds are depicted and reviewed for their association with CRC risk, possible mechanisms promoting carcinogenesis and their relationship with the gut microbiota. Additionally, this paper analyses the evidence related to the role of red and processed meat intake and CRC risk and the factors and pathways involved in bacterial proteolytic fermentation in the large intestine.

Chitosan-naphthalimide probes for dual channel recognition of HClO and H2S in cells and their application in photodynamic therapy.

The combination of bio-imaging with photodynamic therapy (PDT) to accomplish theranostics is promising in cancer treatment. Three chitosan-naphthalimide probes were studied in this work. 4-(5-Bromothiophen-2-yl)-1,8-naphthalic anhydride was first synthesized, and then reacted with chitosan to obtain the macromolecules (CS-N-Br). The recognition group thiomorpholine or its derivatives were introduced into CS-N-Br to obtain nano-probes (CS-N-ML, CS-N-BSZ, CS-N-FSQ) eventually. The studies revealed that CS-N-ML and CS-N-FSQ exhibit high selectivity and can specifically recognize HClO and H2S. CS-N-ML and CS-N-FSQ can perform exogenous and endogenous confocal imaging of HClO and H2S in cells also. CS-N-ML's ability to target lysosomes positions indicated it could act as a lysosome-specific probe. It was discovered that the probes generate superoxide anions (O2•-) via a Type I mechanism. This discovery endows the probes with high photosensitizing activity even under hypoxic conditions. There is a positive correlation between the extent of the conjugated system and the photosensitivity of the probes, indicating that an enhanced conjugation leads to increased photosensitivity. Upon light irradiation, the probes generate ROS within HeLa cells. These results suggested that these probes can achieve theranostics for diseases associated with abnormal levels of HClO and H2S.

Two-pronged strategy: A mitochondria targeting AIE photosensitizer for hydrogen sulfide detection and type I and type II photodynamic therapy.

Multifunctional type-I photosensitizers (PSs) for hydrogen sulfide (H2S) detection and photodynamic therapy (PDT) of hypoxia tumors exhibits attractive curative effect but remains a challenging task. Herein, a mitochondria targeted aggregation-induced emission (AIE) photosensitizer TSPy-SS-P was designed and synthesized, which could be used for H2S detection and simultaneously type I and type II PDT. TSPy-SS-P had excellent selectivity and anti-interference abilities for endogenous and exogenous H2S detection in tumor cells. TSPy-SS-P was able to distinguish tumor cells with high level of H2S from normal cells by fluorescence "turn off" response to H2S. In addition, TSPy-SS-P showed type Ⅰ and type Ⅱ reactive oxygen species (ROS) generation ability to effectively ablate hypoxic tumor cells. TSPy-SS-P showed mitochondria targeting capacity which could produce ROS in situ to disrupt mitochondria and promote cell apoptosis. In vivo PDT experiments showcased that TSPy-SS-P had excellent tumor retention capability, effective tumor ablation ability and good biocompatibility. This work provided a two-pronged strategy to design organelles targeted photosensitizers for H2S detection and effective PDT of tumors.

Engineering of in-plane SnS2-SnO2 nanosheets heterostructures for enhanced H2S sensing.

In-plane heterostructures has attracted considerable interest due to exceptional electron transport properties, high specific surface area, and abundant active sites. However, synthesis of in-plane SnS2-SnO2 heterostructures are rarely reported, and the deep investigation of the fine structure on reactivity is of great significance. Here, we propose partial in-situ oxidation strategy to construct the in-plane SnS2-SnO2 heterostructures and the surface properties, the ratio of two components can be finely tuned by precisely adjusting the treatment temperature. In particular, the SnS2-SnO2 heterostructures formed after annealing of SnS2 nanosheets at 350 °C exhibits a unique electronic structure and surface properties due to rich grain boundaries, which exhibits excellent gas sensing performance to H2S (Ra/Rg = 169.81 for 5 ppm H2S at 160 °C, fast response and recovery dynamic (41/101 s), excellent reliability (σ = 0.01) and sensing stability (φ = 0.11 %)). Notably, the in-plane heterostructures endow the material with abundant grain boundaries and effectively regulates the electronic structure of the Sn p-orbital, which facilitate the formation of active oxygen species (O-(ad)), thus contributing to the sensing performance. Our work provides a promising platform to design in-plane heterostructures for various advanced applications.

Photoelectric H2S Sensing Based on Electrospun Hollow CuO-SnO2 Nanotubes at Room Temperature.

Pure tin oxide (SnO2) as a typical conductometric hydrogen sulfide (H2S) gas-sensing material always suffers from limited sensitivity, elevated operation temperature, and poor selectivity. To overcome these hindrances, in this work, hollow CuO-SnO2 nanotubes were successfully electrospun for room-temperature (25 °C) trace H2S detection under blue light activation. Among all SnO2-based candidates, a pure SnO2 sensor showed no signal, even toward 10 ppm, while the 1% CuO-SnO2 sensor achieved a limit of detection (LoD) value of 2.5 ppm, a large response of 4.7, and a short response/recovery time of 21/61 s toward 10 ppm H2S, as well as nice repeatability, long-term stability, and selectivity. This excellent performance could be ascribed to the one-dimensional (1D) hollow nanostructure, abundant p-n heterojunctions, and the photoelectric effect of the CuO-SnO2 nanotubes. The proposed design strategies cater to the demanding requirements of high sensitivity and low power consumption in future application scenarios such as Internet of Things and smart optoelectronic systems.

Regulatory mechanism of cysteine-dependent methionine biosynthesis in Bifidobacterium longum: insights into sulfur metabolism in gut microbiota.

Sulfur, a critical element for bacterial growth, is not directly utilized by bifidobacteria, rendering the sulfur-containing amino acid biosynthesis pathway, particularly for cysteine and methionine, poorly understood. This research identifies six genes involved in this pathway through re-annotation of the Bifidobacterium longum DJO10A genome. These genes play crucial roles in bioconversion processes essential for cysteine utilization, highlighting its significance in sulfur metabolism. Our study uncovers a novel regulatory mechanism of these pathways under varying cysteine concentrations. We demonstrate a dual-pathway mechanism for methionine biosynthesis: one directly utilizing cysteine (trans-sulfurylation pathway) and another utilizing H2S derived from cysteine degradation (direct sulfurylation pathway). This regulatory dual-pathway mechanism is contingent on environmental cysteine levels, with both pathways activated at low cysteine levels, while higher levels predominantly engage the H2S-utilizing pathway. This investigation not only advances our understanding of DJO10A's metabolic capabilities but also underscores the bacterium's adaptability through sophisticated regulatory mechanisms for sulfur-containing amino acid biosynthesis. The elucidation of these pathways provides valuable insights into the survival strategies of bifidobacteria in the gut environment, where sulfur sources can vary greatly. Through detailed genomic, transcriptional, and enzymatic analyses, this study significantly contributes to the field of microbiology, offering a foundation for future research on gut microbiota metabolic pathways and their implications for host health.

Signaling Paradigms of H2S-Induced Vasodilation: A Comprehensive Review.

Hydrogen sulfide (H2S), a gas traditionally considered toxic, is now recognized as a vital endogenous signaling molecule with a complex physiology. This comprehensive study encompasses a systematic literature review that explores the intricate mechanisms underlying H2S-induced vasodilation. The vasodilatory effects of H2S are primarily mediated by activating ATP-sensitive potassium (K_ATP) channels, leading to membrane hyperpolarization and subsequent relaxation of vascular smooth muscle cells (VSMCs). Additionally, H2S inhibits L-type calcium channels, reducing calcium influx and diminishing VSMC contraction. Beyond ion channel modulation, H2S profoundly impacts cyclic nucleotide signaling pathways. It stimulates soluble guanylyl cyclase (sGC), increasing the production of cyclic guanosine monophosphate (cGMP). Elevated cGMP levels activate protein kinase G (PKG), which phosphorylates downstream targets like vasodilator-stimulated phosphoprotein (VASP) and promotes smooth muscle relaxation. The synergy between H2S and nitric oxide (NO) signaling further amplifies vasodilation. H2S enhances NO bioavailability by inhibiting its degradation and stimulating endothelial nitric oxide synthase (eNOS) activity, increasing cGMP levels and potent vasodilatory responses. Protein sulfhydration, a post-translational modification, plays a crucial role in cell signaling. H2S S-sulfurates oxidized cysteine residues, while polysulfides (H2Sn) are responsible for S-sulfurating reduced cysteine residues. Sulfhydration of key proteins like K_ATP channels and sGC enhances their activity, contributing to the overall vasodilatory effect. Furthermore, H2S interaction with endothelium-derived hyperpolarizing factor (EDHF) pathways adds another layer to its vasodilatory mechanism. By enhancing EDHF activity, H2S facilitates the hyperpolarization and relaxation of VSMCs through gap junctions between endothelial cells and VSMCs. Recent findings suggest that H2S can also modulate transient receptor potential (TRP) channels, particularly TRPV4 channels, in endothelial cells. Activating these channels by H2S promotes calcium entry, stimulating the production of vasodilatory agents like NO and prostacyclin, thereby regulating vascular tone. The comprehensive understanding of H2S-induced vasodilation mechanisms highlights its therapeutic potential. The multifaceted approach of H2S in modulating vascular tone presents a promising strategy for developing novel treatments for hypertension, ischemic conditions, and other vascular disorders. The interaction of H2S with ion channels, cyclic nucleotide signaling, NO pathways, ROS (Reactive Oxygen Species) scavenging, protein sulfhydration, and EDHF underscores its complexity and therapeutic relevance. In conclusion, the intricate signaling paradigms of H2S-induced vasodilation offer valuable insights into its physiological role and therapeutic potential, promising innovative approaches for managing various vascular diseases through the modulation of vascular tone.