Metals/bisulfite system involved generation of 24-sulfonic-25-ene ginsenoside Rg1, a potential quality control marker for sulfur-fumigated ginseng

Ginseng is a most popular health-promoting food with ginsenosides as its main bioactive ingredients. Illegal sulfur-fumigation causes ginsenosides convert to toxic sulfur-containing derivatives, and reduced the efficacy/safety of ginseng. 24-sulfo-25-ene ginsenoside Rg1 (25-ene SRg1), one of the sulfur-containing derivatives, is a potential quality control marker of fumigated ginseng, but with low accessibility owing to its unknown generation mechanism. In this study, metals/bisulfite system involved generation mechanism was investigated and verified. The generation of 25-ene SRg1 in sulfur-fumigated ginseng is that SO2, formed during sulfur-fumigation, reacted with water and ionized into HSO3-. On the one hand, under the metals/bisulfite system, HSO3- generates HSO5- and free radicals which converted ginsenoside Rg1 to 24,25-epoxide Rg1; on the other hand, as a nucleophilic group, HSO3- reacted with 24,25-epoxide Rg1 and further dehydrated to 25-ene SRg1. This study provided a technical support for the promotion of 25-ene SRg1 as the characteristic quality control marker of sulfur-fumigated ginseng.

Novel fluorescent probes based on sulfur and nitrogen co-doped carbon dots for determination of three N-substituted phenothiazine derivatives in dosage forms

In the current work, sulfur and nitrogen co-doped carbon dots (S,N-CDs) as simple, sensitive, and selective turn-off fluorescent nanosensors were utilized for analysis of three phenothiazine derivatives, including acetophenazine (APZ), chlorpromazine (CPH), and promethazine (PZH). S,N-CDs were synthesized through a green one-pot microwave-assisted technique using widely available precursors (thiourea and ascorbic acid). HRTEM, EDX, FTIR spectroscopy, UV-Vis absorption spectroscopy, and fluorescence spectroscopy were used to characterize the as-synthesized CDs. When excited at 330 nm, the carbon dots produced a maximum emission peak at 410 nm. The cited drugs statically quenched the S,N-CDs fluorescence as revealed by the Stern-Volmer equation. The current method represents the first spectrofluorimetric approach for the determination of the studied drugs without the need for chemical derivatization or harsh reaction conditions. The importance of the proposed work is magnified as the cited drugs do not have any fluorescent properties. The fluorescence of the developed sensor exhibited a linear response to APZ, CPH, and PZH in the concentration ranges of 5.0-100.0, 10.0-100.0, and 10.0-200.0 μM with detection limits of 1.53, 1.66, and 2.47 μM, respectively. The developed fluorescent probes have the advantages of rapidity and selectivity for APZ, CPH, and PZH analysis in tablets with acceptable % recoveries of (98.06-101.66 %). Evaluation of the method's greenness was performed using the Complementary Green Analytical Procedure Index (ComplexGAPI) and Analytical GREEnness metric (AGREE) metrics, indicating that the method is environmentally friendly. Validation of the proposed method was performed according to ICHQ2 (R1) guidelines.

Surface enhanced Raman spectroscopy for the characterization of the metabolites of the biodesulfurization of dibenzothiophene carried out by Tsukamurella paurometabola

Large amount of sulphur is released by the combustion of fossil fuels in the form of SoX which affects human health and leads to acid rain. To overcome this issue, it is essential to eliminate sulphur moieties from heterocyclic organo-sulphur compounds like Dibenzothiophene (DBT) present in the petrol. In this study Surface enhanced Raman scattering (SERS) spectroscopy is used to analyze the desulfurizing activity of Tsukamurella paurometabola bacterial strain. The most prominent SERS peaks observed at 791, 837, 944 and 1032 cm-1, associated to C-S stretching, are solely observed in dibenzothiophene and its metabolite-I (DBTS) but absent in 2-Hydroxybiphenyl (metabolite-II) and extraction sample of supernatant as a result of biodesulfurization. Moreover, the SERS peaks observed at 974 (characteristic peak of benzene ring) and 1015 cm-1 is associated to C-C ring breathing while 1642 and 1655 cm-1 assigned to CC bonds of aromatic ring. These peaks are only observed in 2-Hydroxybiphenyl (metabolite-II) and extraction sample of supernatant as a result of biodesulfurization. Notably, these peaks are absent in the Dibenzothiophene and its metabolite-I which indicate that aromatic ring is carrying sulfur in this fraction. Moreover, multivariate data analytical tools like principal component analysis (PCA) and PCA-loadings are applied to further differentiate between dibenzothiophene and its metabolites that are Dibenzothiophene sulphone (metabolite-I) and 2-Hydroxybiphenyl (metabolite-II).

In Solution Identification of the Lysine-Cysteine Redox Switch with a NOS Bridge in Transaldolase by Sulfur K-Edge X-ray Absorption Spectroscopy

A novel covalent post-translational modification (lysine-NOS-cysteine) was discovered in proteins, initially in the enzyme transaldolase of Neisseria gonorrhoeae (NgTAL) [Nature 2021, 593, 460-464], acting as a redox switch. The identification of this novel linkage in solution was unprecedented until now. We present detection of the NOS redox switch in solution using sulfur K-edge X-ray absorption spectroscopy (XAS). The oxidized NgTAL spectrum shows a distinct shoulder on the low-energy side of the rising edge, corresponding to a dipole-allowed transition from the sulfur 1s core to the unoccupied σ* orbital of the S-O group in the NOS bridge. This feature is absent in the XAS spectrum of reduced NgTAL, where Lys-NOS-Cys is absent. Our experimental and calculated XAS data support the presence of a NOS bridge in solution, thus potentially facilitating future studies on enzyme activity regulation mediated by the NOS redox switches, drug discovery, biocatalytic applications, and protein design.

High-Throughput Interactome Determination via Sulfur Anomalous Scattering

We propose a novel approach for detecting the binding between proteins making use of the anomalous diffraction of natively present heavy elements, e.g., sulfurs, inside molecular three-dimensional structures. In particular, we analytically and numerically show that the diffraction patterns produced by the anomalous scattering of the sulfur atoms in a given direction depend additively on the relative distances between all couples of sulfur atoms. Thus, the differences in the patterns produced by bound proteins with respect to their nonbonded states can be exploited to rapidly assess protein complex formation. On the basis of our results, we suggest a possible experimental procedure for detecting protein-protein binding. Overall, the completely label-free and rapid method we propose may be readily extended to probe interactions on a large scale, thus paving the way for the development of a novel field of research based on a synchrotron light source.

Analysis and characterization of sulfane sulfur

In the late 1970s, sulfane sulfur was defined as sulfur atoms covalently bound only to sulfur atoms. However, this definition was not generally accepted, as it was slightly vague and difficult to comprehend. Thus, in the early 1990s, it was defined as "bound sulfur," which easily converts to hydrogen sulfide upon reduction with a thiol-reducing agent. H2S-related bound sulfur species include persulfides (R-SSH), polysulfides (H2Sn, n ≥ 2 or R-S(S)nS-R, n ≥ 1), and protein-bound elemental sulfur (S0). Many of the biological effects currently associated with H2S may be attributed to persulfides and polysulfides. In the 20th century, quantitative determination of "sulfane sulfur" was conventionally performed using a reaction called cyanolysis. Several methods have been developed over the past 30 years. Current methods used for the detection of H2S and polysulfides include colorimetric assays for methylene blue formation, sulfide ion-selective or polarographic electrodes, gas chromatography with flame photometric or sulfur chemiluminescence detection, high-performance liquid chromatography analysis with fluorescent derivatization of sulfides, liquid chromatography with tandem mass spectrometry, the biotin switch technique, and the use of sulfide or polysulfide-sensitive fluorescent probes. In this review, we discuss the methods reported to date for measuring sulfane sulfur and the results obtained using these methods.

Redox potentials elucidate the electron transfer pathway of NAD+-dependent formate dehydrogenases

Metal-dependent, nicotine adenine dinucleotide (NAD+)-dependent formate dehydrogenases (FDHs) are complex metalloenzymes coupling biochemical transformations through intricate electron transfer pathways. Rhodobacter capsulatus FDH is a model enzyme for understanding coupled catalysis, in that reversible CO2 reduction and formate oxidation are linked to a flavin mononuclotide (FMN)-bound diaphorase module via seven iron-sulfur (FeS) clusters as a dimer of heterotetramers. Catalysis occurs at a bis-metal-binding pterin (Mo) binding two molybdopterin guanine dinucleotides (bis-MGD), a protein-based Cys residue and a participatory sulfido ligand. Insights regarding the proposed electron transfer mechanism between the bis-MGD and the FMN have been complicated by the discovery that an alternative pathway might occur via intersubunit electron transfer between two [4Fe4S] clusters within electron transfer distance. To clarify this difference, the redox potentials of the bis-MGD and the FeS clusters were determined via redox titration by EPR spectroscopy. Redox potentials for the bis-MGD cofactor and five of the seven FeS clusters could be assigned. Furthermore, substitution of the active site residue Lys295 with Ala resulted in altered enzyme kinetics, primarily due to a more negative redox potential of the A1 [4Fe4S] cluster. Finally, characterization of the monomeric FdsGBAD heterotetramer exhibited slightly decreased formate oxidation activity and similar iron-sulfur clusters reduced relative to the dimeric heterotetramer. Comparison of the measured redox potentials relative to structurally defined FeS clusters support a mechanism by which electron transfer occurs within a heterotetrameric unit, with the interfacial [4Fe4S] cluster serving as a structural component toward the integrity of the heterodimeric structure to drive efficient catalysis.

Biochemical engineering for elemental sulfur from flue gases through multi-enzymatic based approaches - A review

Flue gases are the gases which are produced from industries related to chemical manufacturing, petrol refineries, power plants and ore processing plants. Along with other pollutants, sulfur present in the flue gas is detrimental to the environment. Therefore, environmentalists are concerned about its removal and recovery of resources from flue gases due to its activation ability in the atmosphere to transform into toxic substances. This review is aimed at a critical assessment of the techniques developed for resource recovery from flue gases. The manuscript discusses various bioreactors used in resource recovery such as hollow fibre membrane reactor, rotating biological contractor, sequential batch reactor, fluidized bed reactor, entrapped cell bioreactor and hybrid reactors. In conclusion, this manuscript provides a comprehensive analysis of the potential of thermotolerant and thermophilic microbes in sulfur removal. Additionally, it evaluates the efficacy of a multi-enzyme engineered bioreactor in this process. Furthermore, the study introduces a groundbreaking sustainable model for elemental sulfur recovery, offering promising prospects for environmentally-friendly and economically viable sulfur removal techniques in various industrial applications.

Selection and application of aptamers for p-hydroxybenzyl hydrogen sulfite after Gastrodia elata Bl. fumigated with sulfur

Gastrodia elata Bl. is a widely used traditional Chinese medicine known for its medicinal properties. However, during the drying process, G. elata is often fumigated with sulfur to prevent corrosion and improve its appearance. Sulfur-fumigation can result in a reduction in the effective components of the herb and can also be hazardous to human health due to the remaining sulfur dioxide. Sulfur-fumigation of G. elata poses a significant challenge to both end-users and researchers. The detection of p-hydroxybenzyl hydrogen sulfite (p-HS) is a useful tool in determining whether G. elata has been fumigated with sulfur. Unfortunately, the current method for detecting p-HS is costly and requires sophisticated instruments. Therefore, there is a need to develop a more cost-effective and user-friendly method for the detection of p-HS. This study utilized the Capture-SELEX technique to screen high-affinity aptamers for p-HS, which were subsequently characterized by isothermal titration calorimetry (ITC). An aptamer sequence (seq 6) with a high affinity of Kd = 26.5 μM was obtained following 8 rounds of selection against p-HS. With the aptamer serving as the recognition element and gold nanoparticles as the colorimetric indicator, a simple and efficient colorimetric sensor was developed for the specific detection of p-HS. This detection method exhibited a limit of detection of 1 μg/ml, while the p-HS recoveries demonstrated a range of between 88.5 % and 105 % for samples of G. elata obtained in the market. In summary, the aptamer exhibited a high affinity for p-HS, and the sensor developed through the use of a colloidal gold detector based on nucleic acid aptamer can be utilized for rapid detection of sulfur-fumigated G. elata. With these findings, this research paper provides valuable scientific insights and highlights significant potential for future studies in this area.

Research on the inhibitory properties and mechanism of carboxymethyl cellulose-modified sulfur quantum dots towards calcium sulfate and calcium carbonate

An eco-friendly antimicrobial sulfur quantum dot scale inhibitor (CMC-SQDs) synthesized using carboxymethyl cellulose (CMC) showed strong inhibition of calcium sulfate (CaSO4) at a concentration just below 1 mg/L, with an inhibition efficiency exceeding 99 %. However, the precise interaction process between CMC-SQDs and CaSO4 remains unclear. This article investigates the effectiveness of SQDs in inhibiting the formation of CaSO4 and calcium carbonate (CaCO3) scales. Through static scale inhibition tests, molecular dynamics simulations, and quantum chemical calculations, the study aims to elucidate the different impacts of CMC-SQDs on CaSO4 and CaCO3 scale formation. The research focuses on understanding the relationship between the structural activity of CMC-SQDs and their scale-inhibiting performance and delving into the underlying mechanisms of scale inhibition. The findings describe the role of SQDs in a water-based solution, acting as persistent "nanodusts" that interact with calcium (Ca2+) ions and sulfate ions. CMC forms complexes with Ca2+ ions, and the presence of SQDs enhances the van der Waals force, indirectly increasing the resistance of associated ions and the binding energy on the surface of precipitated gypsum. Conversely, SQDs exhibit weak surface stability and have minimal binding energy when interacting with calcite, leading to limited occupation of available adsorption sites.

Advanced electrolysis sulfur-based biofiltration for simultaneous total nitrogen removal and estrogen toxicity reduction from low carbon-to-nitrogen ratio wastewater

A sulfur-based biofilter enhanced by phosphate modified activated carbon as particle electrodes was constructed to simultaneously remove total nitrogen (TN) and estrogen from low carbon-to-nitrogen ratio (C/N) wastewater containing 1 mg/L 17-alpha-ethinylestradiol (EE2). Results showed that the enhanced biofilter achieved outstanding performance in EE2 removal (93.2 %) and TN reduction (effluent < 5 mg/L), demonstrating robustness against C/N fluctuations. It was noteworthy that it successfully reduced both acute toxicity (59.5 %) and estrogenic activity (88.6 %). Comprehensive characterization investigations and microbial community structure analysis revealed that enhanced electron transfer and increased microbial abundance likely contributed to improved biofilter performance. Core microorganisms, such as Pseudomonas and Chryseobacterium were identified as key contributors to synergistic estrogen degradation and denitrification. This study presented a feasible and promising strategy of combined process with three-dimensional electrodes and sulfur-based biofilter, highlighting substantial potential for advanced purification and safe reuse of wastewater.

Sulfur vacancy-enhanced In2S3-x hollow microtubes for photocatalytic Cr (VI) and tetracycline removal

Morphological regulation and defect engineering are efficient methods for photocatalytic technology by improving photon absorption and electron dissociation. Herein, In2S3-x hollow microtubes with S-vacancies (MIS) were fabricated via a simple solvothermal reaction using In-based metal-organic frameworks (In-MOFs) as a precursor. Experimental results demonstrate that the hollow structure and optimal S-vacancies can jointly accelerate the photocatalytic reaction, attributed to a larger specific surface area, more active sites, and faster electron transfer efficiency. The champion MIS(2) displayed significantly better photocatalytic activity for Cr(VI) reduction and tetracycline (TC) degradation. The Cr(VI) reduction rate by MIS(2) is 3.67 and 2.82 times higher than those of optimal In2S3 template-free (HIS(2)) and MIS(1) with poor S-vacancies, respectively. The removal efficiency of TC by MIS(2) is 1.37 and 1.15 times higher than those of HIS(2) and MIS(1). Further integration of MIS(2) with aerogel simplifies the recovery process significantly.

A steady-state pH-control model for the biological production of elemental sulfur from sulfate in mining-influenced water

We developed a model to predict pH, alkalinity, and the Langelier Saturation Index (LSI) in coupled systems of hydrogen-based autotrophic sulfate reduction and aerobic oxidation of sulfide to elemental sulfur. To neutralize the biologically generated base, the model allows for the addition of CO2 as part of the gas mixture, the independent addition of HCl or CO2, or a combination of the alternatives. The model was evaluated against the results from a laboratory system for the production of elemental sulfur from sulfate present in mine-tailings water, which is characterized by the presence of elevated sulfate and calcium concentrations. Model results were consistent with measurements of pH, alkalinity, and LSI. The model showed how the acid demands of the coupled reactors vary with pH, being approximately equivalent at pH over 8, when ionized sulfide predominates. Also, while the sulfidogenic reactor was well buffered due to the production of ionized sulfide, the sulfidotrophic reactor in the absence of sulfide and carbonate alkalinity was prone to pH declines. Considering that both reactors operated in the positive range of LSI, the model also indicated that addition of CO2 should be minimized due to increase in the bicarbonate concentration and its effect on increasing the LSI. Furthermore, the model also showed that exclusive reliance on HCl for pH control can be incompatible with Cl- effluent standards, which means that a compromise must be reached between CO2 and HCl additions.

Unveiling the Chemical Composition of Sulfur-Fumigated Herbs: A Triple Synthesis Approach Using UHPLC-LTQ-Orbitrap MS-A Case Study on Steroidal Saponins in Ophiopogonis Radix

Ophiopogonis Radix (OR) is a traditional Chinese medicine. In recent years, in order to achieve the purpose of drying, bleaching, sterilizing and being antiseptic, improving appearance, and easy storage, people often use sulfur fumigation for its processing. However, changes in the chemical composition of medicinal herbs caused by sulfur fumigation can lead to the transformation and loss of potent substances. Therefore, the development of methods to rapidly reveal the chemical transformation of medicinal herbs induced by sulfur fumigation can guarantee the safe clinical use of medicines. In this study, a combined full scan-parent ions list-dynamic exclusion acquisition-diagnostic product ions analysis strategy based on UHPLC-LTQ-Orbitrap MS was proposed for the analysis of steroidal saponins and their transformed components in sulfur-fumigated Ophiopogonis Radix (SF-OR). Based on precise mass measurements, chromatographic behavior, neutral loss ions, and diagnostic product ions, 286 constituents were screened and identified from SF-OR, including 191 steroidal saponins and 95 sulfur-containing derivatives (sulfates or sulfites). The results indicated that the established strategy was a valuable and effective analytical tool for comprehensively characterizing the material basis of SF-OR, and also provided a basis for potential chemical changes in other sulfur-fumigated herbs.

Adaptability of sulfur-disproportionating bacteria for mine water remediation under the pressures of heavy metal ions and high sulfate content

Biological sulfide production processes mediated by sulfate/sulfur reduction have gained attention for metal removal from industrial wastewater (e.g., mine water (MW) and metallurgical wastewater) via forming insoluble metal sulfides. However, these processes often necessitate the addition of external organic compounds as electron donors, which poses a constraint on the broad application of this technology. A recent proof of concept study reported that microbial sulfur disproportionation (SD) produced sulfide with no demand for organics, which could achieve more cost-benefit MW treatment against the above-mentioned processes. However, the resistance of SD bioprocess to different metals and high sulfate content in MW remains mysterious, which may substantially affect the practical applicability of such process. In this study, the sulfur-disproportionating bacteria (SDB)-dominated consortium was enriched from a previously established SD-driven bioreactor, in which Dissulfurimicrobium sp. with a relative abundance of 39.9 % was the predominated SDB. When exposed to the real pretreated acidic MW after the pretreatment process of pH amelioration, the sulfur-disproportionating activity remained active, and metals were effectively removed from the MW. Metal tolerance assays further demonstrated that the consortium had a good tolerance to different metal ions (i.e., Pb2+, Cu2+, Ni2+, Mn2+, Zn2+), especially for Mn2+ with a concentration of approximately 20 mg/L. It suggested the robustness of Dissulfurimicrobium sp. likely due to the presence of genes encoding for the enzymes associated with metal(loid) resistance/uptake. Additionally, although high sulfate content resulted in a slight inhibition on the sulfur-disproportionating activity, the consortium still achieved sulfide production rates of 27.3 mg S/g VSS-d on average under an environmentally relevant sulfate level (i.e., 1100 mg S/L), which is comparable to those reported in sulfate reduction. Taken together, these findings imply that SDB could ensure sustainable MW treatment in a more cost-effective and organic-free way.

Structure-based insights into the mechanism of [4Fe-4S]-dependent sulfur insertase LarE

Several essential cellular metabolites, such as enzyme cofactors, contain sulfur atoms and their biosynthesis requires specific thiolation enzymes. LarE is an ATP-dependent sulfur insertase, which catalyzes the sequential conversion of the two carboxylate groups of the precursor of the lactate racemase cofactor into thiocarboxylates. Two types of LarE enzymes are known, one that uses a catalytic cysteine as a sacrificial sulfur donor, and the other one that uses a [4Fe-4S] cluster as a cofactor. Only the crystal structure of LarE from Lactobacillus plantarum (LpLarE) from the first class has been solved. We report here the crystal structure of LarE from Methanococcus maripaludis (MmLarE), belonging to the second class, in the cluster-free (apo-) and cluster-bound (holo-) forms. The structure of holo-MmLarE shows that the [4Fe-4S] cluster is chelated by three cysteines only, leaving an open coordination site on one Fe atom. Moreover, the fourth nonprotein-bonded iron atom was able to bind an anionic ligand such as a phosphate group or a chloride ion. Together with the spectroscopic analysis of holo-MmLarE and the previously reported biochemical investigations of holo-LarE from Thermotoga maritima, these crystal structures support the hypothesis of a reaction mechanism, in which the [4Fe-4S] cluster binds a hydrogenosulfide ligand in place of the chloride anion, thus generating a [4Fe-5S] intermediate, and transfers it to the substrate, as in the case of [4Fe-4S]-dependent tRNA thiolation enzymes.

An XAS study of Hg(II) sorption to Al-based drinking water treatment residuals

Drinking water treatment residuals (DWTRs) are produced from the coagulation and flocculation processes in conventional drinking water treatment. The abundant metal oxide content of these materials resulting from the use of coagulants, like alum and ferric chloride, has driven strong research interest into the reuse of DWTRs as sorptive materials. Using a suite of aluminum-based DWTRs, we provide new insights into Hg(II) sorption mechanisms. Experiments performed at circum-neutral pH show that sorption capacities are related to the amount of organic carbon/matter present in DWTRs. We found that carbon rich samples can scavenge about 9000 mg/kg of Hg, in contrast to 2000 mg/kg for lime based DWTRs. X-ray absorption spectroscopy (XAS) at the Hg L3 edge further characterizes mercury coordination. X-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) results point to a partial association of mercury with sulfur at low mass loadings, transitioning to a full association with oxygen/carbon at higher concentrations of sorbed Hg(II) and in DWTRs with limited sulfur content. These results suggest that sorption of Hg(II) is primarily controlled by the carbon/organic matter fraction of DWTRs, but not by the coagulants.

NCOA4 requires a [3Fe-4S] to sense and maintain the iron homeostasis

NCOA4 is a selective cargo receptor for ferritinophagy, the autophagic turnover of ferritin (FTH), a process critical for regulating intracellular iron bioavailability. However, how ferritinophagy flux is controlled through NCOA4 in iron-dependent processes needs to be better understood. Here, we show that the C-terminal FTH-binding domain of NCOA4 harbors a [3Fe-4S]-binding site with a stoichiometry of approximately one labile [3Fe-4S] cluster per NCOA4 monomer. By analyzing the interaction between NCOA4 and HERC2 ubiquitin ligase or NCOA4 and FTH, we demonstrate that NCOA4 regulates ferritinophagy by sensing the intracellular iron-sulfur cluster levels. Under iron-repletion conditions, HERC2 recognizes and recruits holo-NCOA4 as a substrate for polyubiquitination and degradation, favoring ferritin iron storage. Under iron-depletion conditions, NCOA4 exists in the form of apo-protein and binds ferritin to promote the occurrence of ferritinophagy and release iron. Thus, we identify an iron-sulfur cluster [3Fe-4S] as a critical cofactor in determining the fate of NCOA4 in favoring iron storage in ferritin or iron release via ferritinophagy and provide a dual mechanism for selective interaction between HERC2 and [3Fe-4S]-NCOA4 for proteasomal degradation or between ferritin and apo-NCOA4 for ferritinophagy in the control of iron homeostasis.

Recent Studies of Nitrogen and Sulfur Containing Heterocyclic Analogues as Novel Antidiabetic Agents: A Review

The prevalence of diabetes mellitus is on the rise, which demands the identification of novel antidiabetic drugs. There is a need for safer and more effective alternatives because the therapy methods now available to manage diabetes have limits. Due to their diverse pharmacological characteristics, heterocyclic molecules with nitrogen and Sulfur atoms have become intriguing candidates in medicinal chemistry. These substances have a wide variety of structures that can be customized to target different pathways associated with diabetes and can affect important biological targets involved in glucose homeostasis. This review provides a thorough summary of the most recent studies on heterocyclic analogues of nitrogen and Sulfur as prospective antidiabetic agents. This review examines the variety of their structural forms, their methods of action, and assesses the results of preclinical and clinical investigations on their effectiveness and safety. Additionally, further optimization and development of innovative antidiabetic medications are highlighted, as well as the difficulties and prospects for the future in utilizing the therapeutic potential of these analogues. This study seeks to stimulate additional investigation and cooperation between researchers and medicinal chemists, promoting improvements in the creation of efficient and secure antidiabetic medicines to fulfill the needs in the management of diabetes.

Discovery of a Biotin Synthase That Utilizes an Auxiliary 4Fe-5S Cluster for Sulfur Insertion

Biotin synthase (BioB) is a member of the Radical SAM superfamily of enzymes that catalyzes the terminal step of biotin (vitamin B7) biosynthesis, in which it inserts a sulfur atom in desthiobiotin to form a thiolane ring. How BioB accomplishes this difficult reaction has been the subject of much controversy, mainly around the source of the sulfur atom. However, it is now widely accepted that the sulfur atom inserted to form biotin stems from the sacrifice of the auxiliary 2Fe-2S cluster of BioB. Here, we bioinformatically explore the diversity of BioBs available in sequence databases and find an unexpected variation in the coordination of the auxiliary iron-sulfur cluster. After in vitro characterization, including the determination of biotin formation and representative crystal structures, we report a new type of BioB utilized by virtually all obligate anaerobic organisms. Instead of a 2Fe-2S cluster, this novel type of BioB utilizes an auxiliary 4Fe-5S cluster. Interestingly, this auxiliary 4Fe-5S cluster contains a ligated sulfide that we propose is used for biotin formation. We have termed this novel type of BioB, Type II BioB, with the E. coli 2Fe-2S cluster sacrificial BioB representing Type I. This surprisingly ubiquitous Type II BioB has implications for our understanding of the function and evolution of Fe-S clusters in enzyme catalysis, highlighting the difference in strategies between the anaerobic and aerobic world.

Roles of the Comproportionation Reaction in SO2 Reduction Using Methane for the Flexible Recovery of Elemental Sulfur or Sulfides

SO2 reduction with CH4 to produce elemental sulfur (S8) or other sulfides is typically challenging due to high energy barriers and catalyst poisoning by SO2. Herein, we report that a comproportionation reaction (CR) induced by H2S recirculating significantly accelerates the reactions, altering reaction pathways and enabling flexible adjustment of the products from S8 to sulfides. Results show that SO2 can be fully reduced to H2S at a lower temperature of 650 °C, compared to the 800 °C required for the direct reduction (DR), effectively eliminating catalyst poisoning. The kinetic rate constant is significantly improved, with CR at 650 °C exhibiting about 3-fold higher value than DR at 750 °C. Additionally, the apparent activation energy decreases from 128 to 37 kJ/mol with H2S, altering the reaction route. This CR resolves the challenges related to robust sulfur-oxygen bond activation and enhances CH4 dissociation. During the process, the well-dispersed lamellar MoS2 crystallites with Co promoters (CoMoS) act as active species. H2S facilitates the comproportionation reaction, reducing SO2 to a nascent sulfur (Sx*). Subsequently, CH4 efficiently activates CoMoS in the absence of SO2, forming H2S. This shifts the mechanism from Mars-van Krevelen (MvK) in DR to sequential Langmuir-Hinshelwood (L-H) and MvK in CR. Additionally, it mitigates sulfation poisoning through this rapid activation reaction pathway. This unique comproportionation reaction provides a novel strategy for efficient sulfur resource utilization.

Predicting Autoxidation of Sulfides in Drug-like Molecules Using Quantum Mechanical/Density Functional Theory Methods

Autoxidation of drugs and drug-like molecules is a major concern in the development of safe and effective therapeutics. Because active pharmaceutical ingredients (APIs) that contain sulfur atoms can form sulfoxides under oxidative stress, predicting oxidative susceptibilities within an organic molecule can have a major impact in accelerating the compound's stability assessment. For investigation of a sulfur atom's oxidative stability, density functional theory (DFT) methods were applied to accurately predict S-O estimated bond dissociation enthalpies (BDEs) of sulfoxides. Our process employed B3LYP/6-31+G(d) for geometry optimization and frequency calculation, and we employed B3P86/6-311++G(2df,2p) to obtain electronic energies from single-point energy calculations. A total of 84 drug-like molecules containing 50 different sulfide scaffolds were used to develop a risk scale. Our results showed that when S-O BDE is less than 69 kcal/mol, the sulfur atom has low oxidative susceptibility. High oxidation risk occurs when the S-O BDE is greater than 75 kcal/mol. The risk scale was successful in predicting the relative propensities of sulfide oxidation among the small organic molecules and commercial drugs examined.

Exploring the impact of competitive compounds and catalyst synthesis method in DBT oxidative desulfurization using MoO3-V2O5/Al2O3 catalyst

This research endeavors to address the pressing challenge of reducing sulfur content in fuels, an environmental imperative. It does so by employing bimetallic catalysts to enhance the efficiency of oxidative desulfurization (ODS) processes. This involves utilizing successive impregnation and co-impregnation methods to prepare a MoO3-V2O5/Al2O3. The catalysts underwent characterization using various techniques including X-ray diffraction (XRD), N2 adsorption-desorption, UV-vis (DRS), temperature-programmed desorption (NH3-TPD), Raman, Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and energy dispersive spectrum (EDS). The catalyst was utilized for the evaluation of the ODS process of dibenzothiophene (DBT). The effects of oxidants, namely H2O2 and t-butyl hydroperoxide (TBHP), were studied in the ODS. The catalyst prepared using the co-impregnation method (5M-15V-co) demonstrated significant acidic sites and exhibited remarkable efficiency in oxidative desulfurization. Remarkably, this catalyst achieved 100% oxidation of sulfur components within 30 min (min). To assess the catalyst's performance further, competitive compounds including nitrogen-containing compounds (NCCs) and saturated and unsaturated hydrocarbon compounds (HCs) were employed in the ODS. Initially, the introduction of NCCs led to a decrease in the sulfur removal rate; however, the catalyst successfully oxidized DBT completely within 60 min. When cyclohexene was present as an olefinic hydrocarbon compound, the catalyst oxidized DBT by approximately 75%, whereas DBT oxidation reached 100% within 20 min when p-xylene was introduced to the catalytic reactor. Additionally, as the O/S ratio increased from 2/5 to 10, the sulfur removal rate improved from 30 to 90%, indicating that HCs and NCCs compete with sulfur in terms of oxidant consumption.

Microbial community structure and functional prediction in five full-scale industrial park wastewater treatment plants

The development of industrial parks has become an important global trend contributing significantly to economic and industrial growth. However, this growth comes at a cost, as the treatment of multisource industrial wastewater generated in these parks can be difficult owing to its complex composition. Microorganisms play a critical role in pollutant removal during industrial park wastewater treatment. Therefore, our study focused on the microbial communities in five full-scale industrial park wastewater treatment plants (WWTPs) with similar treatment processes and capacities. The results showed that denitrifying bacteria were dominant in almost every process section of all the plants, with heterotrophic denitrification being the main pathway. Moreover, autotrophic sulfur denitrification and methane oxidation denitrification may contribute to total nitrogen (TN) removal. In plants where the influent had low levels of COD and TN, dominant bacteria included oligotrophic microorganisms like Prosthecobacter (2.88 % ~ 10.02 %) and hgcI_clade (2.05 % ~ 9.49 %). Heavy metal metabolizing microorganisms, such as Norank_f__PHOS-HE36 (3.96 % ~ 5.36 %) and Sediminibacterium (1.86 % ~ 5.34 %), were prevalent in oxidation ditch and secondary settling tanks in certain plants. Functional Annotation of Prokaryotic Taxa (FAPROTAX) revealed that microbial communities in the regulation and hydrolysis tanks exhibited higher potential activity in the nitrogen (N) and sulfur (S) cycles than those in the oxidation ditch. Sulfate/sulfite reduction was common in most plants, whereas the potential occurrence of sulfide compounds and thiosulfate oxidation tended to be higher in plants with a relatively high sulfate concentration and low COD content in their influent. Our study provides a new understanding of the microbial community in full-scale industrial park WWTPs and highlights the critical role of microorganisms in the treatment of industrial wastewater.

Effect of ibuprofen (IBU) on the sulfur-based and calcined pyrite-based autotrophic denitrification (SCPAD) systems with two filling modes: Performance and toxic response mechanism

To investigate the effect of ibuprofen (IBU) on the sulfur-based and calcined pyrite-based autotrophic denitrification (SCPAD) systems, two individual reactors with the layered filling (L-SCPAD) and mixed filling (M-SCPAD) systems were established via sulfur and calcined pyrite. Effluent NO3--N concentration of the L-SCPAD and M-SCPAD systems was first increased to 6.44, 0.93 mg/L under 0.5 mg/L IBU exposure and gradually decreased to 1.66 mg/L, 0 mg/L under 4.0 mg/L IBU exposure, indicating that NO3--N removal performance of the M-SCPAD system was better than that of the L-SCPAD system. The variation of extracellular polymeric substances (EPS) characteristics demonstrated that more EPS was secreted in the M-SCPAD system compared to the L-SCPAD system, which contributed to forming a more stable biofilm structure and protecting microorganisms against the toxicity of IBU in the M-SCPAD system. Moreover, the increased electron transfer impedance and decreased cytochrome c implied that IBU inhibited the electron transfer efficiency of the L-SCPAD and M-SCPAD systems. The decreased adenosine triphosphate (ATP) and electron transfer system activity (ETSA) content showed that IBU inhibited metabolic activity, but the M-SCPAD system exhibited higher metabolic activity compared to the L-SCPAD system. In addition, the analysis of the bacterial community indicated a more stable abundance of nitrogen removal function bacteria (Bacillus) in the M-SCPAD system compared to the L-SCPAD system, which was conducive to maintaining a stable denitrification performance. The toxic response mechanism based on the biogeobattery effect was proposed in the SCPAD systems under IBU exposure. This study provided an important reference for the long-term toxic effect of IBU on the SCPAD systems.

Investigating the oxidation mechanism of facet-dependent pyrite: implications for the environment and sulfur evolution

The oxidation of pyrite (FeS2) not only adversely affects the environment, but also plays a critical role in the geochemical evolution of Fe and S elements. However, the oxidation rate of FeS2 is often controlled by its exposed crystal facets. Herein, the oxidation behaviors and mechanisms of naturally existing FeS2(100) and FeS2(210) crystals are investigated. The adsorption models of O2 on FeS2(100) and FeS2(210) facets are established, additionally, their corresponding surface energies, O2 adsorption sites and energies are also obtained using Density Functional Theory (DFT) calculations. These results suggest that the FeS2(210) facet more readily reacts with O2 because it has more unsaturated coordination of Fe atoms compared with the FeS2(100) facet. Moreover, electrochemical results such as EIS, Tafel and CV curves further prove that FeS2(210) possesses a higher oxidation rate than that of FeS2(100). The results of chemical oxidation experiments and XPS analyses show that FeS2(210) can produce more total Fe, SO42- and H+ than FeS2(100). Furthermore, various intermediate S species such as SO32-, S2O32-, S3O62-, S4O62- and S5O62- are also detected. This work can provide a basis for understanding the oxidation mechanism of facet-dependent FeS2 and the geochemical evolution of Fe and S elements.

Sustainable synthesis of lignin-derived carbon dots with visible pH response for Fe3+ detection and bioimaging

Synthesis of lignin-based carbon dots (LCDs) with high quantum yield (QY), stable fluorescence properties and biocompatibility has been a challenge. Here, we propose an improved two-step strategy for producing high-quality LCDs from enzymatic hydrolysis lignin (EHL). The p-aminobenzenesulfonic acid used in the strategy not only provides nitrogen and sulfur elements, but also tailors the disordered three-dimensional structure of EHL. The successful co-doping of N and S elements favors the reduction of the optical energy bandgap (Eg), resulting in a high QY of 45.05% for LCDs. The LCDs exhibited superior selectivity and sensitivity for Fe3+ with a limit of detection (LOD) of 0.15 μM when Fe3+ concentration was 50-500 μM. In addition, LCDs demonstrated significant fluorescence in HepG2 cells and HepG2 cells loaded with LCDs at a concentration of 80 μg/mL showed good viability, suggesting that they are suitable for in vivo applications. The luminescent centers of LCDs change during pH regulation and thus show a special visual response to pH changes, making them have great potential for detecting metabolism in living cells. This work provides a novel and low-cost method for fabricating sustainable fluorescent probes for chemical sensing and bioimaging.

Multicolor emission-based nitrogen, sulfur and boron co-doped photoluminescent carbon dots for sequential sensing of Fe3+ and cysteine: RGB color sensor and live cell imaging

Herein, a simple hydrothermal synthesis is used to prepare multiple heteroatom-doped photoluminescent carbon dots (CDs) from thiourea (N and S source) and boric acid (B source) as precursors. The optical and physicochemical properties of the as-synthesized NSB-CDs were studied using UV-Vis, photoluminescence, TEM, FT-IR, XRD, Raman, and XPS analyses. The NSB-CDs exhibited excellent stability, high photostability, pH, and ionic strength tolerance; they retained their excellent stability independent of excitation. The NSB-CDs featured small sizes of approximately 3.2 ± 0.4 nm (range: 2.0-5.0 nm) as evidenced using TEM measurements. The NSB-CDs were used as a photoluminescent sensing platform to detect Fe3+ as well as cysteine (Cys) molecules. The competitive binding of Cys to Fe3+ resulted in NSB-CDs that retained their photoluminescence. For the rapid identification and quantification of Fe3+ and Cys, NSB-CDs were developed as a "switch-on" dual-function sensing platform. The linear detection range of Fe3+ was 0-20 μM (limit of detection [LOD]: 54.4 nM) and that of Cys was 0-50 μM (LOD: 4.9 nM). We also introduced a smartphone RGB analysis method for detecting low-concentration solutions based on digital images. The NSB-CDs showed no toxicity at 100 μg/mL. Photoluminescent probes for multicolor live-cell imaging can be used with NSB-CDs at this concentration, suggesting that NSB-CDs may be promising photoluminescent probes.

Nitrogenase beyond the Resting State: A Structural Perspective

Nitrogenases have the remarkable ability to catalyze the reduction of dinitrogen to ammonia under physiological conditions. How does this happen? The current view of the nitrogenase mechanism focuses on the role of hydrides, the binding of dinitrogen in a reductive elimination process coupled to loss of dihydrogen, and the binding of substrates to a binuclear site on the active site cofactor. This review focuses on recent experimental characterizations of turnover relevant forms of the enzyme determined by cryo-electron microscopy and other approaches, and comparison of these forms to the resting state enzyme and the broader family of iron sulfur clusters. Emerging themes include the following: (i) The obligatory coupling of protein and electron transfers does not occur in synthetic and small-molecule iron-sulfur clusters. The coupling of these processes in nitrogenase suggests that they may involve unique features of the cofactor, such as hydride formation on the trigonal prismatic arrangement of irons, protonation of belt sulfurs, and/or protonation of the interstitial carbon. (ii) Both the active site cofactor and protein are dynamic under turnover conditions; the changes are such that more highly reduced forms may differ in key ways from the resting-state structure. Homocitrate appears to play a key role in coupling cofactor and protein dynamics. (iii) Structural asymmetries are observed in nitrogenase under turnover-relevant conditions by cryo-electron microscopy, although the mechanistic relevance of these states (such as half-of-sites reactivity) remains to be established.

Discovering covalent inhibitors of protein-protein interactions from trillions of sulfur(VI) fluoride exchange-modified oligonucleotides

Molecules that covalently engage target proteins are widely used as activity-based probes and covalent drugs. The performance of these covalent inhibitors is, however, often compromised by the paradox of efficacy and risk, which demands a balance between reactivity and selectivity. The challenge is more evident when targeting protein-protein interactions owing to their low ligandability and undefined reactivity. Here we report sulfur(VI) fluoride exchange (SuFEx) in vitro selection, a general platform for high-throughput discovery of covalent inhibitors from trillions of SuFEx-modified oligonucleotides. With SuFEx in vitro selection, we identified covalent inhibitors that cross-link distinct residues of the SARS-CoV-2 spike protein at its protein-protein interaction interface with the human angiotensin-converting enzyme 2. A separate suite of covalent inhibitors was isolated for the human complement C5 protein. In both cases, we observed a clear disconnection between binding affinity and cross-linking reactivity, indicating that direct search for the aimed reactivity-as enabled by SuFEx in vitro selection-is vital for discovering covalent inhibitors of high selectivity and potency.

Chalcogen bonds formed by protein sulfur atoms in proteins. A survey of high-resolution structures deposited in the protein data bank

The presence of chalcogen bonds in native proteins was investigated on a non-redundant and high-resolution (≤ 1 Angstrom) set of protein crystal structures deposited in the Protein Data Bank. It was observed that about one half of the sulfur atoms of methionines and disulfide bridges from chalcogen bonds with nucleophiles (oxygen and sulfur atoms, and aromatic rings). This suggests that chalcogen bonds are a non-bonding interaction important for protein stability. Quite numerous chalcogen bonds involve water molecules. Interestingly, in the case of disulfide bridges, chalcogen bonds have a marked tendency to occur along the S-S bond extension rather than along the C-S bond extension. Additionally, it has been observed that closer residues have a higher probability of being connected by a chalcogen bonds, while the secondary structure of the two residues connected by a chalcogen bond do not correlate with its formation.Communicated by Ramaswamy H. Sarma.

Characterization of a promiscuous DNA sulfur binding domain and application in site-directed RNA base editing

Phosphorothioate (PT)-modification was discovered in prokaryotes and is involved in many biological functions such as restriction-modification systems. PT-modification can be recognized by the sulfur binding domains (SBDs) of PT-dependent restriction endonucleases, through coordination with the sulfur atom, accompanied by interactions with the DNA backbone and bases. The unique characteristics of PT recognition endow SBDs with the potential to be developed into gene-targeting tools, but previously reported SBDs display sequence-specificity for PT-DNA, which limits their applications. In this work, we identified a novel sequence-promiscuous SBDHga from Hahella ganghwensis. We solved the crystal structure of SBDHga complexed with PT-DNA substrate to 1.8 Å resolution and revealed the recognition mechanism. A shorter L4 loop of SBDHga interacts with the DNA backbone, in contrast with previously reported SBDs, which interact with DNA bases. Furthermore, we explored the feasibility of using SBDHga and a PT-oligonucleotide as targeting tools for site-directed adenosine-to-inosine (A-to-I) RNA editing. A GFP non-sense mutant RNA was repaired at about 60% by harnessing a chimeric SBD-hADAR2DD (deaminase domain of human adenosine deaminase acting on RNA), comparable with currently available RNA editing techniques. This work provides insights into understanding the mechanism of sequence-specificity for SBDs and for developing new tools for gene therapy.

Sulfur dots and iron co-doped nickel-based metal-organic frameworks with high nanozyme activity for the colorimetric determination of α-glucosidase activity

Alpha-glucosidase (α-Glu) plays a crucial role in regulating the normal physiological function of the body; therefore, α-Glu activity detection is crucial in clinical studies. In this study, a nickel-based metal-organic framework (Ni-MOF) co-doped with sulfur dots (SDs) and iron (Fe) was designed and constructed for the colorimetric detection of α-Glu. The SDs/Fe/Ni-MOF shows a very low Michaelis-Menten constant (0.0466 mM) for H2O2, suggesting a very high affinity for H2O2. Additionally, the free radicals generated by the nanozyme-catalyzed reaction were analyzed, and the feasibility of the nanozyme-catalyzed process was further verified using density functional theory. The bimetallic (Fe and Ni) can improve the catalytic activity of the material, and sulfur can improve the affinity with the substrate to further enhance the catalytic performance. Notably, hydroquinone (HQ) inhibits nanozyme activity, whereas α-Glu hydrolyzes alpha-arbutin (α-Arb) and subsequently produces HQ. Therefore, this study developed a method for detecting α-Glu activity using α-Arb as a substrate. This method has high selectivity, a wide detection range (1.00-100 U L-1), and a low detection limit (0.525 U L-1). Finally, the method was used to α-Glu activity detected in serum samples with good accuracy. This study provides a new method for the detection of α-Glu.

Controlled delivery of sildenafil by β-Cyclodextrin-decorated sulfur-doped carbon nanodots: a synergistic activation of ROS signaling in tumors overexpressing PDE-5

Fluorescent sulfur- and nitrogen-doped carbon nanodots (CDs) are zero-dimensional nanoparticles that mediate ROS production in cancer cells, displaying inherent anticancer properties. Thus, they have been proposed as nanotheranostic tools useful in image-guided cancer therapy. Here, we try to show that cancerous cells (high PDE-5 expression) receiving sildenafil delivered by CDs-based nanostructures promote positive reinforcement of PDE-5-mediated cell death via the overexpression of genes involved in the production of ROS. We explored the regioselective Huisgen cycloaddition between azide-β-cyclodextrin and CDs-alkyne to synthetize homogeneous nanostructures, named CDs-PEG4-β-Cdx, consisting of CDs functionalized at the surface with β-cyclodextrins capable of including high amount drugs such as sildenafil (>20 % w/w), and releasing them in a controlled manner. We investigated how CDs-PEG4-β-Cdx bearing sildenafil enter cells, enhancing ROS production and cell death specifically in cancer cells overexpressing PDE-5. These nanoplatforms go beyond the bounds of EPR-based nanomedicines in which carriers are conceived as inert vehicles of toxic drugs. Our findings enable the development of clever anticancer nanoplatforms that synergistically combine nanomedicines that perturb the mitochondrial electron transport chain (ROS production) with PDE-5 inhibitors which trigger oxidative stress specifically in cancer cells regardless of their location.

Sensing and regulation of reactive sulfur species (RSS) in bacteria

The infected host deploys generalized oxidative stress caused by small inorganic reactive molecules as antibacterial weapons. An emerging consensus is that hydrogen sulfide (H2S) and forms of sulfur with sulfur-sulfur bonds termed reactive sulfur species (RSS) provide protection against oxidative stressors and antibiotics, as antioxidants. Here, we review our current understanding of RSS chemistry and its impact on bacterial physiology. We start by describing the basic chemistry of these reactive species and the experimental approaches developed to detect them in cells. We highlight the role of thiol persulfides in H2S-signaling and discuss three structural classes of ubiquitous RSS sensors that tightly regulate cellular H2S/RSS levels in bacteria, with a specific focus on the chemical specificity of these sensors.

The influence of alkylating agents on sulfur-sulfur bonds in per- and polysulfides

Per- and polysulfides are sulfane sulfur species produced inside living cells, in organisms as diverse as bacteria, plants and humans, but their biological roles remain to be fully understood. Unfortunately, due to their reactivity, per- and polysulfides are easily altered, interconverted or lost during the processing and analysis of biological material. Thus, all current analytical methods make use of alkylating agents, to quench reactivity of hydropersulfides and hydropolysulfides and also to prevent free thiols from attacking sulfur chains in hydropolysulfides and dialkyl polysulfides. However, recent findings reveal that alkylating agents can also destroy per- and polysulfides, to varying degrees, depending on the choice of alkylating agent. Here, we discuss the challenges associated with the alkylation of per- and polysulfides, the single most important step for their preservation and detection in biological samples.

Impacts of sulfur fumigation on the chemistry and immunomodulatory activity of polysaccharides in ginseng

Ginseng is widely regarded as a panacea in Oriental medicine mainly due to its immunomodulatory activity. We previously found that sulfur fumigation, a commonly used pesticidal and anti-bacterial processing practice, weakened the immunomodulatory activity of ginseng. However, if and how sulfur fumigation affects the polysaccharides in ginseng, the crucial components contributing to the immunomodulatory function, remain unknown. Here we report that polysaccharides extracted from sulfur-fumigated ginseng (SGP) presented different chemical properties with polysaccharides extracted with non-fumigated ginseng (NGP), particularly increased water extraction yield and decreased branching degree. SGP had weaker immunomodulatory activity than NGP in immunocompromised mice, as evidenced by less improved immunophenotypes involving body weight, immune organ indexes, white blood cells, lymphocyte cell populations and inflammation. The different immunomodulatory activities were accompanied by changes in the interaction between the polysaccharides and gut microbiota, in which SGP stimulated the growth of different bacteria but produced less SCFAs as compared to NGP. Fecal microbiota transplantation experiment suggested that gut microbiota played a central role in causing the weakened immunomodulatory activity in vivo. This study provides definite evidence that sulfur fumigation affects the chemistry and bioactivity of ginseng polysaccharides, thereby contributing to understanding how sulfur fumigation weakens the immunomodulatory activity of ginseng.

Identification and Detection of Intracellular Reactive Sulfur Species Using a Reaction-Mediated Dual-Recognition Strategy

Reactive sulfur species (RSS) are emerging as a potential key gasotransmitter in diverse physiological processes linking two signaling molecules H2S and SO2. However, the exact roles of H2S and SO2 remain unclear. A major hurdle is the shortage of accurate and robust approaches for sensing of H2S and SO2 in biological systems. Herein, we report a reaction-mediated dual-recognition strategy-based nanosensor, silver nanoparticles (AgNPs)-loaded MIL-101 (Fe) (ALM) hybrids, for the simultaneous detection of H2S and SO2 in a living cell. Upon exposure to H2S, AgNPs can be oxidized to form Ag2S, causing a decrease of surface enhanced Raman spectroscopy (SERS) signals of p,p'-dimercaptoazobenzene. Moreover, SO2 reacts with the amino moiety of MIL-101 to form charge-transfer complexes, resulting in an increment of fluorescent (FL) intensity. The ALM with dual-modal signals can simultaneously analyze H2S and SO2 at a concentration as low as 2.8 × 10-6 and 0.003 μM, respectively. Most importantly, the ALM sensing platform enables targeting mitochondria and detection multiple RSS simultaneously in living cells under external stimulation, as well as displays indiscernible crosstalk between SERS and FL signals, which is very beneficial for the comprehension of physiological issues related with RSS.

Construction and optimization of macromolecular structure model of Tiebei lignite

Mastering the molecular structure of coal is important for the effective utilization of coal. For a detailed study of the microstructural characteristics of Tiebei lignite, its molecular structure was characterized by elemental analysis, solid 13C nuclear magnetic resonance (13C NMR), Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results showed that the aromatic carbon content of Tiebei lignite was 51.98%, the aromatic carbon structure was mainly composed of benzene and naphthalene, and the ratio of aromatic bridgehead carbon to surrounding carbon Xbp was 0.14. Oxygen existed in phenol, ether, carbonyl, and carboxyl; nitrogen-containing structures mainly existed in the form of pyrrole and pyridine; sulfur mainly existed in thiophene sulfur; and aromatic substitution was mainly in the form of trisubstitution. The molecular formula of the macromolecular structure model of Tiebei lignite was C190H161O57N2, and the 13C NMR spectrum of the model was in good agreement with the experimental results, which fully verified the accuracy of the macromolecular structure model of Tiebei lignite. The construction of a macromolecular structure model of Tiebei lignite is essential to intuitively understand the molecular structure characteristics of Tiebei lignite and to provide theoretical support and guidance for the micromechanism research and prevention of lignite spontaneous combustion and other disasters.

Direct Cysteine Desulfurase Activity Determination by NMR and the Study of the Functional Role of Key Structural Elements of Human NFS1

The mitochondrial cysteine desulfurase NFS1 is an essential PLP-dependent enzyme involved in iron-sulfur cluster assembly. The enzyme catalyzes the desulfurization of the l-Cys substrate, producing a persulfide and l-Ala as products. In this study, we set the measurement of the product l-Ala by NMR in vitro by means of 1H NMR spectra acquisition. This methodology provided us with the possibility of monitoring the reaction in both fixed-time and real-time experiments, with high sensitivity and accuracy. By studying I452A, W454A, Q456A, and H457A NFS1 variants, we found that the C-terminal stretch (CTS) of the enzyme is critical for function. Specifically, mutation of the extremely conserved position W454 resulted in highly decreased activity. Additionally, we worked on two singular variants: "GGG" and C158A. In the former, the catalytic Cys-loop was altered by including two Gly residues to increase the flexibility of this loop. This variant had significantly impaired activity, indicating that the Cys-loop motions are fine-tuned in the wild-type enzyme. In turn, for C158A, we found an unanticipated increase in l-Cys desulfurase activity. Furthermore, we carried out molecular dynamics simulations of the supercomplex dedicated to iron-sulfur cluster biosynthesis, which includes NFS1, ACP, ISD11, ISCU2, and FXN subunits. We identified CTS as a key element that established interactions with ISCU2 and FXN concurrently; we found specific interactions that are established when FXN is present, reinforcing the idea that FXN not only forms part of the iron-sulfur cluster assembly site but also modulates the internal motions of ISCU2.

Rapid, inexpensive, sequence-independent fluorescent labeling of phosphorothioate DNA

Fluorescently labeled oligonucleotides are powerful tools for characterizing DNA processes; however, their use is limited by the cost and sequence requirements of current labeling technologies. Here, we develop an easy, inexpensive, and sequence-independent method for site-specifically labeling DNA oligonucleotides. We utilize commercially synthesized oligonucleotides containing phosphorothioate diester(s) in which a nonbridging oxygen is replaced with a sulfur (PS-DNA). The increased nucleophilicity of the thiophosphoryl sulfur relative to the phosphoryl oxygen permits selective reactivity with iodoacetamide compounds. As such, we leverage a long-existing bifunctional linker, N,N'-bis(α-iodoacetyl)-2-2'-dithiobis(ethylamine) (BIDBE), that reacts with PS-DNAs to leave a free thiol, allowing conjugation of the wide variety of commercial maleimide-functionalized compounds. We optimized BIDBE synthesis and its attachment to PS-DNA and then fluorescently labeled the BIDBE-PS-DNA using standard protocols for labeling cysteines. We purified the individual epimers, and using single-molecule Förster resonance energy transfer (FRET), we show that the FRET efficiency is independent of the epimeric attachment. Subsequently, we demonstrate that an epimeric mixture of double-labeled Holliday junctions (HJs) can be used to characterize their conformational properties in the absence and presence of the structure-specific endonuclease Drosophila melanogaster Gen. Finally, we use a biochemical activity assay to show that this double-labeled HJ is functional for cleavage by Gen and that the double-labeled HJ allows multiple DNA species to be identified in a single experiment. In conclusion, our results indicate that dye-labeled BIDBE-PS-DNAs are comparable to commercially labeled DNAs at a significantly reduced cost. Notably, this technology could be applied to other maleimide-functionalized compounds, such as spin labels, biotin, and proteins. The sequence independence of labeling, coupled with its ease and low cost, enables unrestricted exploration of dye placement and choice, providing the potential for creation of differentially labeled DNA libraries and opening previously inaccessible experimental avenues.

Recovery of zinc and extraction of calcium and sulfur from zinc-rich gypsum residue by selective reduction roasting combined with hydrolysis

A novel process that includes selective reduction roasting followed by hydrolysis was proposed in this work to recover zinc, and efficiently extract calcium and sulfur from hazardous zinc-rich gypsum residue (ZGR) waste for high-purity of CaCO₃ and sulfur production. The selective reduction behaviors of ZGR during the reduction roasting were investigated in detail based on thermodynamic analysis and roasting experiments. The effect of roasting temperature, carbon dosage and time on the selective reduction of ZGR was comprehensively investigated, and the results indicated that ZnO and CaSO₄ in the ZGR can be selectively reduced to Zn(g) and CaS, respectively. The volatile Zn(g) was oxidized to ZnO and enriched in the dust, which can be used as a secondary zinc resource. Moreover, the hydrolysis behaviors and leaching kinetic of CaS during hydrolysis were studied intensively. Results depicted that in the H₂S-H₂O system, the CaS in the roasted product can be selectively and efficiently dissolved into the leachate. Furthermore, the kinetic analysis revealed that the hydrolysis of CaS conformed to the internal diffusion reaction control model in the shrinking core model and the apparent activation energy Ea = -12.02 kJ/mol. The obtained hydrolysate with low impurities could be used to capture CO₂ for the production of high-purity sulfur and CaCO₃. Iron and other impurities in the roasted product were concentrated into the leaching slag in the form of metallic iron and akermanite. The whole process realized the recovery of zinc, and the selective and effective extraction of calcium and sulfur, which could provide an alternative process for the large-scale treatment of these hazardous wastes.

Solvent‐Free Synthesis of S,N‐Doped Carbon Dots for Extended Visible‐Light‐Induced Oxidase‐Mimicking Activities and Antimicrobial Applications

Photo-oxidase nanozymes are emerging enzyme-mimicking materials that produce reactive oxygen species (ROS) upon light illumination and subsequently catalyze the oxidation of the substrate. Carbon dots are promising photo-oxidase nanozymes due to their biocompatibility and straightforward synthesis. Carbon dot-based photo-oxidase nanozymes become active for ROS generation under UV or blue light illumination. In this work, sulfur and nitrogen doped carbon dots (S,N-CDs) were synthesized by solvent-free, microwave assisted technique. We demonstrated that sulfur, nitrogen doping of carbon dots (band gap of 2.11 eV) has enabled photo-oxidation of 3,3,5,5'-tetramethylbenzidine (TMB) with extended visible light (up to 525 nm) excitation at pH 4. The photo-oxidase activities by S,N-CDs produce Michaelis-Menten constant (K_m ) of 1.18 mM and the maximum initial velocity (V_max ) as 4.66×10^-8  Ms^-1 , under 525 nm illumination. Furthermore, visible light illumination can also induce bactericidal activities with growth inhibition of Escherichia coli (E. coli). These results demonstrate that S,N-CDs can increase intracellular ROS in the presence of LED light illumination.

Turn-off fluorescence of S,N-doped carbon dots for determination of two nitro-containing drugs in dosage forms and human plasma

This study describes the development of an environmentally-friend optical nanosensor for the rapid spectrofluorimetric assessment of two nitro-compounds, namely nitrofurantoin and dantrolene in their dosage forms and plasma samples. A one-step synthetic technique successfully created very bright water-soluble carbon quantum dots doped with sulfur and nitrogen (S,N-CQDs). Carbon was derived from citric acid, while nitrogen and sulfur were obtained from thiosemicarbazide. The dimensions of the synthesized dots were measured using a high-resolution transmission electron microscope. FT-IR spectroscopy was used to determine which functional groups were located on their surfaces. The nanosensor's fluorescence emission peaked intensely at 415 nm after excitation at 345 nm with a quantum yield of about 0.52. The inherent fluorescence of the nanosensors gradually decreased upon addition of the studied analytes in increasing concentrations. The fluorescence reduction of nanosensor with the concentrations of the investigated drugs demonstrated linear correlation within the ranges of 0.5-8.0 μg/mL and 1.0-10.0 μg/mL with limits of detection of 0.14 μg/mL (0.59 μM) and 0.23 μg/mL (0.73 μM) for nitrofurantoin and dantrolene, respectively. The recommended method was used to determine the concentrations of the investigated drugs in their commercial capsules, with recoveries ranging from 97.90 % to 101.57 % and low percent RSD values less than 2 %. Moreover, the method was adapted for the in-vitro analysis of the two analytes in spiked human plasma samples with % recoveries from 95.20 % to 102.20 %. The mechanism of interaction between each analyte and the dots was also investigated. The selectivity of the approach for measuring analytes concentration in the presence of excipients, co-formulated medications, or co-administered pharmaceuticals was further evaluated through an interference study. The suggested method's validity was evaluated in accordance with ICH criteria.

Exploring key physicochemical sediment properties influencing bioleaching of heavy metals

Bioleaching is a promising technology to remediate sediments contaminated by heavy metals. However, the complex heterogeneities of the sediments can reduce the acidification efficiency and the heavy metal removal rate, thus hindering the practical application of sediment bioleaching. This experiment conducted comparative bioleaching experiments between the inoculated group (average leaching percentages: Cu 67.64%; Zn 54.44%; Ni 29.59%) and the non-inoculated control group (Cu 37.10%; Zn 41.04%; Ni 19.89%) on 28 sediments characterized by different physicochemical properties to explore the key factors influencing bioleaching. The results indicated that the bioleaching process was predominated by the indigenous bioleaching bacteria and the bioleaching inoculum, respectively. The ACC_pH=4 (acid-consuming capacity), TOC (total organic carbon), and TN (total nitrogen) of the sediments played an essential role in influencing the microbial community structure and bioleaching performance: the ACC_pH=4, as the inhibitive factor, could influence the succession growth of the indigenous bioleaching bacteria and the inoculum during the bioleaching process, while the TOC and TN, as the contributing factor, could influence the metabolism of the indigenous bioleaching bacteria. Based on these results, the bioleaching process was improved with the classification and pretreatments of sediment to realize successful bioleaching of all types of the sediments examined in this research.

Experimental study on the effect of cold soaking with liquid nitrogen on the coal chemical and microstructural characteristics

In this paper, the chemical microstructure of coal samples is quantitatively analyzed experimentally before and after liquid nitrogen cold soaking, by using elemental analyzer, X-ray diffractometer, and Fourier infrared spectrometer, including the reverse side of chemical composition of elements, organic matter, and functional groups. It was found that with the increase of coal metamorphism, the contents of carbon, nitrogen, and sulfur elements gradually increase, while those of hydrogen and oxygen elements gradually decrease. In addition, as the degree of metamorphism increases, the graphitization phenomenon of coal becomes weaker, the interlayer spacing of aromatic rings (d₀₀₂) increases, the structure of coal crystal nucleus is loose, its order is weakened, the crystal volume becomes smaller, and the void structure unit increases. The FTIR spectra of each coal sample could be divided into four absorption bands, i.e., the aromatic structure, oxygen-containing functional group, aliphatic group, and hydroxyl absorption band. After cold soaking of liquid nitrogen, the peak intensity areas of aromatic and aliphatic structures decrease, while those of oxygenated functional groups and hydroxyl groups increase, and the values of A(C = O)/A(C-O) increase and those of A(CH₃)/A(CH₂) decrease, mainly due to the gradual decrease of methylene side chains and increase of methylene straight chains. The present results are helpful to further reveal the mechanism of adsorption-resolution deformation of coal body due to cold immersion of liquid nitrogen.

Desulfurization of hydrophilic and hydrophobic volatile reduced sulfur with elemental sulfur production in denitrifying bioscrubber

Volatile reduced sulfur compounds were odor and irritating toxic gas, which were commonly produced during waste and wastewater treatment. The autotrophic sulfide denitrifiers converted sulfide as alternative electron acceptor to reduce nitrate, which achieved simultaneous denitrification and sulfur oxidation. In this study, to investigate the effect of sulfur compounds solubility, S/N and oxygen on sulfur and nitrogen removal, a bioscrubber was studied for treatment of hydrophilic H₂S and hydrophobic CS₂. Both H₂S and CS₂ could be efficiently removed (99%), with the highest sulfide loading of 46.9 gS/m³·d. The elemental sulfur production was strongly correlated to S/N ratio (r = 0.969, p = 0.03), the highest elemental sulfur production efficiency achieved 92.0% under S/N ratio of 2.0 for treatment of H₂S. Thiobacillus sp. bacteria was the pre-dominated sulfide-dependent denitrifiers (78.2%) before exposing to oxygen, while abundance of Cryseobacterium and unclassified Xanthomonadaceae aerobic sulfide oxidizer dramatically increased up to 40% and 7.3% after aeration. Remarkably increasing production of extracellular polymeric substance (197%) was observed after treatment of CS₂, which might promote the hydrolysis of CS₂ and stabilization of elemental sulfur. This study demonstrated the possibility to apply sulfide-dependent denitrification process for treatment of both hydrophilic and hydrophobic volatile reduced sulfur waste gas with elemental sulfur recovery.

Sulfur(VI) fluorides as tools in biomolecular and medicinal chemistry

Recent advances in the synthesis of sulfur(VI)-fluorides has enabled incredible growth in their application in biomolecular chemistry. This review aims to serve as a primer highlighting synthetic strategies toward a diversity of S(VI) fluorides and their application in chemical biology, bioconjugation, and medicinal chemistry.

Nitrogen, sulfur, and phosphorus Co-doped carbon dots-based ratiometric chemosensor for highly selective sequential detection of Al3+ and Fe3+ ions in logic gate, cell imaging, and real sample analysis

Heteroatom-doped photoluminescent (PL) carbon dots (CDs) have recently gained attention as optical sensors due to their excellent tunable properties. In this work, we propose a one-pot hydrothermal synthesis of PL nitrogen (N), sulfur (S), and phosphorus (P) co-doped carbon dots (NSP-CDs) using glutathione and phosphoric acid (H₃PO₄) as precursors. The synthesized NSP-CDs were characterized using different spectroscopic and microscopic techniques, including ultraviolet-visible (UV-Vis) spectroscopy, fluorescence spectroscopy, Fourier-transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. The NSP-CDs exhibited excellent PL properties with green emission at 492 nm upon excitation at 417 nm, a high quantum yield of 26.7%, and dependent emission behavior. The as-prepared NSP-CDs were spherical with a well-monodispersed average particle size of 5.2 nm. Moreover, NSP-CDs demonstrate high PL stability toward a wider pH, high salt ionic strength, and various solvents. Furthermore, the NSP-CDs showed a three-state "off-on-off" PL response upon the sequential addition of Al³⁺ and Fe³⁺ ions, with a low limit of detection (LOD) of 10.8 nM for Al³⁺ and 50.7 nM for Fe³⁺. The NSP-CD sensor can construct an INHIBIT logic gate with Al³⁺ and Fe³⁺ ions as the chemical inputs and emissions as the output mode. Owing to an excellent tunable PL property and biocompatibility, the NSP-CDs were applied for sensing Al³⁺ and Fe³⁺ ions as well as live cell imaging. Furthermore, NSP-CDs were designed as PL sensors for detecting Al³⁺ and Fe³⁺ ions in real water show their potential application.

Investigations of the ODS process utilizing CNT- and CNF-based WO3 catalysts for environmental depollution: experimental and theoretical aspects

In this contribution, CoW/X materials (X = CNT or CNF) were utilized as oxidative desulfurization (ODS) catalysts for the removal of dibenzothiophene (DBT) from a model fuel (n-decane), incorporating the H₂O₂ as an efficient oxidant. Different operating conditions were investigated. Both compounds revealed high desulfurization efficiency using milder operating conditions leading to low levels of the DBT compound since only 1 h while using a low ratio of H₂O₂/S = 6. Among synthesized compounds, the CoW (15)/CNT showed superior DBT conversion through the ODS process. In other words, the highest sulfur removal efficiency of 100% for a feed sulfur content of 500 ppm was determined in a 40-min duration under optimum conditions. This was satisfyingly more effective than a recently reported CoW (20)/rGO catalyst. The characterization of synthesized catalysts was performed in order to evaluate their physicochemical properties. Moreover, product identification of the oxidation desulfurization process was performed using the GC-Mass, FTIR, and NMR techniques where it was found that this process was that of a single product. These experimental studies were complemented with density functional theory (DFT) investigations, which indeed shed important light on understanding the adsorption mechanisms as well as electronic properties of the system undertaken.