Sulfur-containing Precursor Research Articles

Sulfur-functionalized graphene obtained by a non-thermal plasma process for simultaneous electrochemical determination of tert-butylhydroquinone and bisphenol A

Electrochemical sensors based on graphene have proven to be powerful tools for detecting bisphenol A (BPA) and tert-butylhydroquinone (TBHQ) individually. There are currently no reports of these analytes being detected simultaneously. By assembling graphene-based materials on gold surfaces, it is possible to improve the charge transfer of both analytes. This study utilized non-thermal plasma-assisted synthesis with a sulfur-containing precursor to functionalize graphene (S-Graph), resulting in the fabrication of an ultrasensitive electrochemical sensor that can detect both BPA and TBHQ, simultaneously. Compared with native graphene or a traditional surface of gold electrode, S-Graph/Au retained superior electrochemical activity for both analytes that showed significantly enhanced sensing performance, including a wide linear range, with a detection limit of 13 and 54 nmol L−1 for TBHQ and BPA, respectively. The enhanced long-term storage stability, as well as reproducibility showed that S-Graph is a promising strategy for promoting the application of novel graphene-based materials.

Visualizing Drug Release from a Stimuli-Responsive Soft Material Based on Amine-Thiol Displacement.

In this research, we developed a photoluminescent platform using amine-coupled fluorophores, generated from a single conjugate acceptor containing bis-vinylogous thioesters. Based on the experimental and computational results, the fluorescence turn-on mechanism was proposed to be charge separated induced energy radiative transition for the amine-coupled fluorophore, while the sulfur-containing precursor was not fluorescent since the energy internal conversion occurred through vibrational 2RS- (R represents alkyl groups) as energy acceptor(s). Further utilizing the conjugate acceptor, we establish a new fluorogenic approach via a highly cross-linked soft material to selectively detect cysteine under neutral aqueous conditions. Turn-on fluorescence emission and macroscopic degradation occurred in the presence of cysteine as the stimuli, which can be visually tracked due to the generation of an optical indicator and the cleavage of linkers within the matrix. Furthermore, a novel drug delivery system was constructed, achieving controlled release of sulfhydryl drug (6-mercaptopurine) which was tracked by photoluminescence and high-performance liquid chromatography. The photoluminescent molecules developed herein are suitable for visualizing polymeric degradation, making them suitable for additional "smart" material applications.

Harmful impact on presynaptic glutamate and GABA transport by carbon dots synthesized from sulfur-containing carbohydrate precursor.

Carbon nanoparticles that may be potent air pollutants with adverse effects on human health often contain heteroatoms including sulfur. In order to study in detail their effects on different physiological and biochemical processes, artificially produced carbon dots (CDs) with well-controlled composition that allows fluorescence detection may be of great use. Having been prepared from different types of organic precursors, CDs expose different atoms at their surface suggesting a broad variation of functional groups. Recently, we demonstrated neurotoxic properties of CDs synthesized from the amino acid β-alanine, and it is of importance to analyze whether CDs obtained from different precursors and particularly those exposing sulfur atoms induce similar neurotoxic effects. This study focused on synthesis of CDs from the sulfur-containing precursor thiourea-CDs (TU-CDs) with a size less than 10nm, their characterization, and neuroactivity assessment. Neuroactive properties of TU-CDs were analyzed based on their effects on the key characteristics of glutamatergic and γ-aminobutyric acid (GABA) neurotransmission in isolated rat brain nerve terminals. It was observed that TU-CDs (0.5-1.0mg/ml) attenuated the initial velocity of Na+-dependent transporter-mediated uptake and accumulation of L-[14C]glutamate and [3H]GABA by nerve terminals in a dose-dependent manner and increased the ambient level of the neurotransmitters. Starting from the concentration of 0.2mg/ml, TU-CDs evoked a gradual dose-dependent depolarization of the plasma membrane of nerve terminals measured with the cationic potentiometric dye rhodamine 6G. Within the concentration range of 0.1-0.5mg/ml, TU-CDs caused an "unphysiological" step-like increase in fluorescence intensity of the рН-sensitive fluorescent dye acridine orange accumulated by synaptic vesicles. Therefore, despite different surface properties and fluorescent features of CDs prepared from different starting materials (thiourea and β-alanine), their principal neurotoxic effects are analogous but displayed at a different level of efficiency. Sulfur-containing TU-CDs exhibit lower effects (by ~30%) on glutamate and GABA transport in the nerve terminals in comparison with sulfur-free β-alanine CDs. Our results suggest considering that an uncontrolled presence of carbon-containing particulate matter in the human environment may pose a toxicity risk for the central nervous system.

Protic ionic liquid derived nitrogen/sulfur-codoped carbon materials as high-performance electrodes for supercapacitor

A protic ionic liquid (PIL), [Phne][HSO4], was reported for the preparation of N/S-codoped carbon materials (N/S-CM) as a programmable nitrogen and sulfur-containing precursor. The [Phne][HSO4] was obtained by a simple neutralization reaction between phenothiazine and sulfuric acid, followed by directly carbonation and subsequent chemical activation by KOH. The obtained N/S-CM shows features including a large specific surface area (SBET), high porosity, and doped nitrogen/sulfur atoms. Using as an electrode material in supercapacitor, it has exhibited a high specific capacitance of 430Fg−1 at 0.2Ag−1 and an excellent stability with only about 10% capacity loss after 5000 cycles, which made it a promising electrode material for supercapacitor.

Identification of 3-Sulfinopropionyl Coenzyme A (CoA) Desulfinases within the Acyl-CoA Dehydrogenase Superfamily

In a previous study, the essential role of 3-sulfinopropionyl coenzyme A (3SP-CoA) desulfinase acyl-CoA dehydrogenase (Acd) in Advenella mimigardefordensis strain DPN7(T) (AcdDPN7) during degradation of 3,3'-dithiodipropionic acid (DTDP) was elucidated. DTDP is a sulfur-containing precursor substrate for biosynthesis of polythioesters (PTEs). AcdDPN7 showed high amino acid sequence similarity to acyl-CoA dehydrogenases but was unable to catalyze a dehydrogenation reaction. Hence, it was investigated in the present study whether 3SP-CoA desulfinase activity is an uncommon or a widespread property within the acyl-CoA dehydrogenase superfamily. Therefore, proteins of the acyl-CoA dehydrogenase superfamily from Advenella kashmirensis WT001, Bacillus cereus DSM31, Cupriavidus necator N-1, Escherichia coli BL21, Pseudomonas putida KT2440, Burkholderia xenovorans LB400, Ralstonia eutropha H16, Variovorax paradoxus B4, Variovorax paradoxus S110, and Variovorax paradoxus TBEA6 were expressed in E. coli strains. All purified acyl-CoA dehydrogenases appeared as homotetramers, as revealed by size exclusion chromatography. AcdS110, AcdB4, AcdH16, and AcdKT2440 were able to dehydrogenate isobutyryl-CoA. AcdKT2440 additionally dehydrogenated butyryl-CoA and valeryl-CoA, whereas AcdDSM31 dehydrogenated only butyryl-CoA and valeryl-CoA. No dehydrogenation reactions were observed with propionyl-CoA, isovaleryl-CoA, succinyl-CoA, and glutaryl-CoA for any of the investigated acyl-CoA dehydrogenases. Only AcdTBEA6, AcdN-1, and AcdLB400 desulfinated 3SP-CoA and were thus identified as 3SP-CoA desulfinases within the acyl-CoA dehydrogenase family, although none of these three Acds dehydrogenated any of the tested acyl-CoA thioesters. No appropriate substrates were identified for AcdBL21 and AcdWT001. Spectrophotometric assays provided apparent Km and Vmax values for active substrates and indicated the applicability of phylogenetic analyses to predict the substrate range of uncharacterized acyl-CoA dehydrogenases. Furthermore, C. necator N-1 was found to utilize 3SP as the sole source of carbon and energy.

A Novel 3-Sulfinopropionyl Coenzyme A (3SP-CoA) Desulfinase from Advenella mimigardefordensis Strain DPN7 T Acting as a Key Enzyme during Catabolism of 3,3′-Dithiodipropionic Acid Is a Member of the Acyl-CoA Dehydrogenase Superfamily

3-Sulfinopropionyl coenzyme A (3SP-CoA) desulfinase (AcdDPN7) is a new desulfinase that catalyzes the sulfur abstraction from 3SP-CoA in the betaproteobacterium Advenella mimigardefordensis strain DPN7(T). During investigation of a Tn5::mob-induced mutant defective in growth on 3,3'-dithiodipropionate (DTDP) and also 3-sulfinopropionate (3SP), the transposon insertion was mapped to an open reading frame with the highest homology to an acyl-CoA dehydrogenase (Acd) from Burkholderia phenoliruptrix strain BR3459a (83% identical and 91% similar amino acids). An A. mimigardefordensis Δacd mutant was generated and verified the observed phenotype of the Tn5::mob-induced mutant. For enzymatic studies, AcdDPN7 was heterologously expressed in Escherichia coli BL21(DE3)/pLysS by using pET23a::acdDPN7. The purified protein is yellow and contains a noncovalently bound flavin adenine dinucleotide (FAD) cofactor, as verified by high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) analyses. Size-exclusion chromatography revealed a native molecular mass of about 173 kDa, indicating a homotetrameric structure (theoretically 179 kDa), which is in accordance with other members of the acyl-CoA dehydrogenase superfamily. In vitro assays unequivocally demonstrated that the purified enzyme converted 3SP-CoA into propionyl-CoA and sulfite (SO3(2-)). Kinetic studies of AcdDPN7 revealed a Vmax of 4.19 μmol min(-1) mg(-1), an apparent Km of 0.013 mM, and a kcat/Km of 240.8 s(-1) mM(-1) for 3SP-CoA. However, AcdDPN7 is unable to perform a dehydrogenation, which is the usual reaction catalyzed by members of the acyl-CoA dehydrogenase superfamily. Comparison to other known desulfinases showed a comparably high catalytic efficiency of AcdDPN7 and indicated a novel reaction mechanism. Hence, AcdDPN7 encodes a new desulfinase based on an acyl-CoA dehydrogenase (EC 1.3.8.x) scaffold. Concomitantly, we identified the gene product that is responsible for the final desulfination step during catabolism of 3,3'-dithiodipropionate (DTDP), a sulfur-containing precursor substrate for biosynthesis of polythioesters.

Curved nanostructures of unsupported and Al2O3-supported MoS2 catalysts: Synthesis and HDS catalytic properties

The active phase of hydrodesulfurization (HDS) catalysts is usually composed of MoS2 slabs promoted by cobalt and/or nickel. Because of the anisotropic structure of molybdenum disulfide, the active sites are believed to be present only on the edges of the slabs, exhibiting dangling bonds. However, slabs of MoS2-based industrial catalysts often exhibit disordered bent morphology which might generate strain effects creating new active sites. In order to evaluate a possible effect of bending MoS2 slabs on HDS catalytic properties, synthesis of well-defined curved morphologies was carried out in the present study. Two different strategies were evaluated herein: acidification of ammonium tetrathiomolybdate, (NH4)2MoS4 (ATM) in the presence of polyethyleneglycol or decomposition of ammonium thiodimolybdate, (NH4)2Mo2S12 (ATDM). The resulting amorphous sulfides, deposited or not on γ-Al2O3, were then post-treated at 400°C or 750°C under N2 or H2 in the presence or not of H2S. Cobalt promotion was also attempted on the final post-treated solids. The results show that the nature of the sulfur-containing precursor strongly influences the final morphology. Using ATM, the as-obtained nanospheres are formed of bundles of slabs while using ATDM, fullerenic-like MoS2 particles are obtained after post-treatment at 750°C. These fullerenic-like particles exhibit non constant radius of curvature with flat regions separated by strongly localized distorted zones suggesting the formation of defect sites on basal planes. The possibility of promoting these systems by Co sustains the presence of such surface sites. XPS and TPR results also show a marked weakening of the metal–sulfur bond strength when compared to flat crystals. Finally, catalytic activities determined for the HDS of thiophene and the simultaneous hydrogenation (HYD) of toluene and isomerization of cyclohexane are rather noticeable despite the absence of conventional edge sites. Bending MoS2 slabs therefore seems to lead to the creation of new active sites on basal planes with original catalytic properties.

Influence of precursor sulfur content on film formation and compositional changes in Cu2ZnSnS4 films and solar cells

Cu2ZnSnS4 (CZTS) thin films are made using sulfurisation of co-sputtered metallic and sulfur-containing precursor films. The CZTS grain size is larger for metallic precursors than for sulfur-containing precursors while more uniform films with fewer voids are obtained in the latter case. During sulfurisation of precursors with tin-excess in closed quartz ampoules, tin is lost from the films with greater losses from metallic precursors. We suggest that the reduced grain size and the reduced tin-loss for sulfur-containing precursors can be explained by a larger number of CZTS nuclei being formed early in the sulfurisation process. In sulfur containing precursors with large tin excess, SnS2 is observed together with CZTS, and a tin-rich bottom layer segregates. This indicates that tin-diffusion in CZTS is relatively slow. Solar cell devices made for a range of compositions at and around stoichiometric CZTS show highest efficiencies in two compositional groups; Zn-rich and Cu-poor/Sn-rich, while close to stoichiometric material gives poor devices. Devices including the tin-rich bottom layer show efficiencies of up to 3.2%. The role of secondary phases such as ZnS and SnS2 on device performance is discussed.

New synthetic routes to poly(isothianaphthene): III. Polymerization of dithiophthalide and 1,1,3,3-tetrachlorothiophthalan

In this paper, the polymerization of sulfur-containing precursor molecules to poly(isothianaphthene) (PITN) is described. Most attention has been devoted to the polymerization of dithiophthalide, as other useful precursors were synthetically less accessible. The thermal polymerization of dithiophthalide leads to the formation of undoped PITN, which had a conductivity in the order of 10 −4 S cm −1. The insoluble polymer was characterized by IR, Raman and solid state NMR spectroscopy, and elemental analysis. The polymerization proceeds by simply heating the precursor without the presence of any added reagent or solvent and is the first non-oxidative route to PITN.

Carbonyl sulfide (OCS) as a sulfur-containing precursor in MOCVD: a study of mixtures of Me2Cd and OCS in the gas and solid phases and their use in MOCVD

Mixtures of dimethylcadmium (Me2Cd) and carbonyl sulfide (OCS) have been examined in the gas and solid phases over a wide range of temperatures. No interaction is observed between Me2Cd and OCS in a 1:1 molar ratio at room temperature in the gas phase, nor is any interaction detected in the solid phase at liquid-nitrogen temperature. On heating the 1:1 mixtures of Me2Cd and OCS to 250 °C in a sealed vessel, gaseous products are formed. These consist of methane, carbon monoxide and ethane in an approximately 12:2:1 molar ratio, although a large excess of unreacted OCS is also present showing that this compound does not react fully with Me2Cd at 250 °C. In a flow system at 300 °C only methane and carbon monoxide are formed, in the molar ratio 6:1, although the amount of reaction of the OCS is much less (as evidenced by a higher proportion of unreacted OCS). When the flow reaction is repeated at 450 °C more of the OCS reacts and the proportion of carbon monoxide in the gaseous reaction products is much higher. Using a commercial MOCVD apparatus, high-quality layers of cadmium sulfide are obtained from Me2Cd–OCS mixtures. Temperatures in the range 350–450 °C lead to somewhat slow growth rates which only reach 1 µm h–1 when a 200-fold molar excess of OCS over Me2Cd is used. A small amount of prereaction is observed, but only when H2 is used as the carrier gas. This is attributed to the formation of very small concentrations of H2S by reaction of OCS with H2. The resulting epitaxial layers have good thickness and electrical uniformity. These experiments confirm that OCS may be used as a precursor for the growth of thin layers of CdS by MOCVD. However, the large excess of OCS required here suggests that the compound might be more useful for doping than for the growth of pure layers of CdS.

Incorporation of Iron and Sulfur from NifB Cofactor into the Iron-Molybdenum Cofactor of Dinitrogenase

NifB-co is an iron- and sulfur-containing precursor to the iron-molybdenum cofactor (FeMo-co) of dinitrogenase. The synthesis of NifB-co requires at least the product of the nifB gene. Incorporation of 55Fe and 35S from NifB-co into FeMo-co was observed only when all components of the in vitro FeMo-co synthesis system were present. Incorporation of iron and sulfur from NifB-co into dinitrogenase was not observed in control experiments in which the apodinitrogenase (lacking FeMo-co) was initially activated with purified, unlabeled FeMo-co or in assays where NifB-co was oxygen-inactivated prior to addition to the synthesis system. These data clearly demonstrate that iron and sulfur from active NifB-co are specifically incorporated into FeMo-co of dinitrogenase and provide direct biochemical identification of an iron-sulfur precursor of FeMo-co. Under different in vitro FeMo-co synthesis conditions, iron and sulfur from NifB-co were associated with at least two other proteins (NIFNE and gamma) that are involved in the formation of active dinitrogenase. The results presented here suggest that multiple FeMo-co processing steps might occur on NIFNE and that FeMo-co synthesis is most likely completed prior to the association of FeMo-co with gamma.

Growth of II–VI compounds by metal–organic chemical vapour deposition. Propylene sulfide: a novel sulfur-containing precursor for MOCVD growth of ZnS

As part of our continuing investigations into the problem of pre-reaction in MOCVD systems, layers of ZnS have been grown onto GaAs substrates using Me2Zn and the novel sulfur-containing precursor propylene sulfide. Layers have been produced in the temperature range 300–550 °C and have been characterized by XRD. The results indicate that the layers with the highest degree of crystallinity are grown towards the higher end of this temperature range. Most significantly, no pre-reaction is observed between these precursors.

Propylene sulfide as a sulfur-containing precursor in MOCVD: study of mixtures of Me2Cd and propylene sulfide in the gas, liquid and solid phases and their use in MOCVD

Mixtures of dimethylcadmium (Me2Cd) and propylene sulfide have been examined in the gas and liquid phases over a range of temperatures. No interaction is observed between Me2Cd and propylene sulfide in a 1:1 molar ratio at room temperature in the gas or liquid phases, although a weak interaction is detected in the solid phase at liquid-nitrogen temperature. On heating the 1:1 mixtures of Me2Cd and propylene sulfide to 85–250 °C, in sealed vessels, gaseous products are formed. These are principally propene and methane, in an approximately 2:1 molar ratio, while in a flow system not only are propene and methane found as the major gaseous products at 300 °C, but also a layer of solid CdS is deposited.

Oxygen dependence of glutathione synthesis in hepatocytes

The O 2 dependence of glutathione (GSH) synthesis was studied in freshly isolated hepatocytes of white male rats. The rate of synthesis with methionine as the sulfur-containing amino acid precursor was decreased at hypoxic O 2 concentrations and was half-maximal at 5 μ m O 2. ATP-dependent formation of S-adenosylmethionine was the rate-limiting step in GSH synthesis under these hypoxic conditions as shown by studies of S-adenosylmethionine concentrations and effects of compounds that inhibit mitochondrial ATP production. GSH synthesis with cysteine as the sulfur-containing precursor amino acid was relatively resistant to O 2 deficiency. The rate under anoxia was 48% of the aerobic rate and the O 2-dependent rate was half-maximal at 0.9 μ m O 2. These results indicate that GSH synthesis from methionine is likely to be impaired under physiological and pathological conditions involving hypoxia, but synthesis from cysteine is not likely to be greatly affected except during anoxia. In addition, the sensitivity of the cystathionine pathway to hypoxia suggests that other products of the pathway, such as choline, creatine, epinephrine, and methylated tRNA's, may also be decreased by hypoxia.