Molecular Sulfur Research Articles

Characterization of Caramel Colour IV

A large number of commercial Caramel Colour IV samples were characterized in order to assess the uniformity of the class and to provide data to be used in specifications development. Owing to the chemical and physical complexity of caramel colour it was not feasible to perform detailed analysis of all constituents for assessment of uniformity. Instead, selected parameters were evaluated and judgements were made with respect to compositional uniformity based on the similarities of these parameters among the various samples. As Caramel Colour IV is required by the food industry in a range of colour intensities, there must be a range of properties that differ from sample to sample, but that are sufficiently similar for the material to still be considered as part of the Caramel Colour IV class. Fractions as well as whole caramel were analysed using selected spectrophotometric, chromatographic and chemical techniques. Samples were fractionated based on molecular weight and polarity. The data presented here provide evidence for the uniformity in composition of Caramel Colour IV with respect to molecular weight distribution, to nitrogen and sulphur content and their distribution throughout the fractions, to absorbance properties and to specific low molecular weight compounds. Thus, it can be concluded that Caramel Colour IV exhibits compositional uniformity within the range of colour intensity required by the food industry worldwide.

Recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach.

Study of organic matter in immature sediments from a Messinian evaporitic basin shows that consideration of structures, modes of occurrence, and carbon isotopic compositions of free and sulfur-bound carbon skeletons allow identification of biochemical precursors. Detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way. Moreover, unprecedented biochemicals were recognized; these extend the horizon of biomarker geochemistry.

Organic sulphur in macromolecular sedimentary organic matter. II. Analysis of distributions of sulphur-containing pyrolysis products using multivariate techniques

This study describes the analysis of sulphur-containing products from Curie-point pyrolysis (Py) of eighty-five samples (kerogens, bitumen, and petroleum asphaltenes and coals) using gas chromatography (GC) in combination with sulphur-selective detection. Peak areas of approximately forty individual organic sulphur pyrolysis products (OSPP) were measured, and the results analysed with the aid of multivariate data reduction techniques (principal components analysis, (PCA)). The structural relationships proposed in an earlier publication ( Sinninghe Damsté et al., 1989a) in which OSPP can be grouped according to common “carbon skeletons” are supported by PCA. The distribution of OSPP varies both as a function of kerogen type (as defined by elemental composition) and maturity, reflecting differences in the relative abundance of the various carbon skeleton types. Sulphur-containing products from Type I, Type II, and, to some extent, Type II-S kerogens are dominated by OSPP derived from “moieties” (i.e., discrete structural components within the macromolecule) possessing linear carbon skeletons, while coals and Type III kerogens give rise to higher relative abundances of OSPP with branched carbon skeletons. Type I kerogens are distinguished from Type II kerogens due to the type of linear carbon skeleton, the former yielding higher relative amounts of 2- n-alkylthiophenes and thiolanes and the latter 2,5-di-substituted sulphur-containing products. Products from sulphur-rich (Type II-S) kerogens differ by higher relative abundances of OSPP derived from precursors with isoprenoid and/or steroidal side-chain carbon skeletons, and by higher absolute abundances of all OSPP. Petroleum and, to a lesser extent, bitumen asphaltenes give rise to OSPP with longer carbon skeletons than do kerogens or coals. This observation supports the models proposed by Sinninghe Damsté et al. (1990a) in which sulphur-containing moieties in asphaltenes are bound by fewer intermolecular bridges (i.e., are less extensively cross-linked) and, consequently, more readily yield longer chain products on pyrolysis. From these observations, we suggest that Py-GC in combination with PCA provides useful information concerning the chemical nature of organically bound sulphur in geomacromolecules. This information can be rationalised based on carbon skeleton relationships established for low molecular weight organic sulphur compounds, and in terms of kerogen type and overall sulphur content

Plasma polymerization of organoisothiocyanates. II. Structure of polymer film

AbstractMethyl‐, n‐propyl‐, allyl‐, and phenyl isothiocyanates (MITC, PITC, AITC, and PHITC respectively) were polymerized in an RF (13.56 MHz) plasma electrodeless flow system. The plasma produced polymers were characterized using IR, GPC, GC/MS, and direct pyrolysis mass spectrometry (DPMS) techniques. The solubility tests and chromatographic examinations of the polymers revealed a small soluble fraction which contained a mixture of oligomers with a predominance of dimers and trimers. Molecular structure of the components of these fractions, identified by GC/MS, suggests fragmentation of the monomers to reactive fragments: \documentclass{article}\pagestyle{empty}\begin{document}$$ ^ \cdot {\rm RSCN},^ \cdot {\rm RCN},{\rm R}^ \cdot ,^ \cdot {\rm CN} $$\end{document} (in the case of MITC, PITC, AITC) and \documentclass{article}\pagestyle{empty}\begin{document}$ ^ \cdot {\rm ArNCS},{\rm PhS}^ \cdot ,{\rm Ph}^ \cdot ,^ \cdot {\rm CN} $\end{document} (in the case of PHITC). The DPMS data, being generally consistent with IR and GS/MS results, proved the presence in the polymers of sulfide, polysulfide, thiocarbonyl (–CS–S–and–S–CS–S–) groups, and molecular sulfur S8. Elementary plasma reactions involved in the formation of the observed structural units are proposed.

Product energy disposal in the nonadiabatic reaction S(1D)+CS2→S2 (X 3Σ−g)+CS (X 1Σ+)

The product energy disposal in the reaction S(1D)+CS2→S2+CS is measured via laser-induced fluorescence. Molecular sulphur is produced exclusively in its electronic ground state (3Σ−g) with up to 3 quanta of vibrational excitation and rotational excitation that roughly approximates a 1000 K Boltzmann distribution. The CS produced from the reaction is formed predominantly in its vibrationless state. The total internal energy content of the product molecular sulphur is only about 12% of the total available energy of the reaction; the CS fragment also has minimal internal energy, implying that most of the reaction energy resides in product translation. These results are different from those observed in the isovalent S+OCS reaction and suggest that a different detailed mechanism is operative.

Cellular thiols in rat liver cell lines possessing different growth characteristics

Thiol levels were measured in three cell lines derived from rat hepatocytes with different growth rates and degrees of tumorigenicity: IAR20 having normal epithelial morphology and no tumour forming ability; IAR6.1 being a chemically-transformed malignant cell line; and IAR6.1RT7 derived from an epithelial tumour obtained after injection of IAR6.1 cells into a syngenic animal. The mean levels of GSH, GSSG, low molecular weight thiols (LMWT), macromolecular thiols (MT) and total reactive protein sulphur (TRPS), expressed as nmoles-SH mg-1 protein, were found to be 25.5, 7.5, 50.1, 114.5 and 143.6 respectively for IAR20; 37.6, 3.9, 65.4, 126.8 and 148.4 for IAR6.1; 17.2, 4.4, 52.3, 141.0 and 168.2 for IAR6.1RT7. Cultures were treated with D,L-buthionine-S,R-sulphoximine (BSO) to cause greater than 70 per cent depletion of GSH and the measurements of cellular thiols repeated. Although treatment with BSO caused a substantive decrease in the LMWT fraction, there were no major changes in macromolecular thiols or in total reactive protein sulphur. The respective mean values for LMWT, MT and TRPS (expressed as nmoles-SH mg-1 protein) were 19.4, 109.8, 136.3 for IAR20; 17.2, 119.3, 143.6 for IAR6.1; 21.6, 150.7 and 163.5 for IAR6.1RT7. It is concluded that significant differences in thiol levels exist between the three rat liver cell lines studied. However, severe acute depletion of GSH is not reflected by changes in the levels of macromolecular thiols which suggests that there is only a slow equilibrium between these two major thiol pools.

Synthesis and structural analysis of curdlan sulfate with a potent inhibitory effect in vitro of AIDS virus infection

Curdlan, a natural linear (1→3)-β-D-glucan, was sulfated by piperidine-N-sulfonic acid in dimethyl sulfoxide to give curdlan sulfates with several molecular sizes and different sulfur contents. Curdlan sulfate with a sulfur content of 14.4% completely inhibited the infection of HIV in the drug concentration of as low as 3.3 μm/mL. This is one of the most potent anti-AIDS viral polysaccharides

A literature survey and an experimental study of coal devolatilization at mild and severe conditions: influences of heating rate, temperature, and reactor type on products yield and composition

Coal devolatilization studies to maximize the yield of condensable products by operating at elevated temperatures and heating rates have been published. The objectives of this study were to investigate the influences of relatively mild operating conditions (e.g. relatively low temperature and pressure) on product quality, by comparing devolatilized products obtained at various temperatures and heating rates. Fixed bed, fluid bed, and entrained flow reactor units were used to obtain pyrolysis products. In addition, literature data on tar yields in various reactor units at a range of temperatures and residence times were surveyed and compared with experimental data. The liquids were characterized by a number of techniques, including field ionization mass spectroscopy (f.i.m.s.), sequential elution solvent chromatography (s.e.s.c.) and elemental analysis. The results demonstrate that the quality and yield of liquids obtained at a rapid heating rate are functions of peak pyrolysis temperature. It was shown that at a rapid heating rate, the yields of heavier polyfunctional groups (i.e. hydrocarbons with greater mean molecular weight) are greater than those obtained in the fixed bed slow heating rate reactor. The liquids generated at a slow heating rate are of lower molecular weight, viscosity, and sulphur content, and of higher H C atomic ratios compared with the liquids obtained in a rapid heating rate unit. The effect of increasing the maximum pyrolysis temperature (at a constant slow heating rate) was to increase the yield of light gases (mainly H) at the expense of char hydrogen content and char reactivity. The tar yield is not markedly influenced when the peak devolatilization temperature is increased at a relatively slow heating rate. However, the quality (as defined by the H C (atomic) ratio) of the liquids, and the reactivity (in air) of char, was reduced when the peak pyrolysis temperature was increased. At a rapid heating rate, the primary products, which have many structural characteristics of the parent coal, are devolatilized. The quality of the liquids obtained at a rapid heating rate is, therefore, determined by the devolatilized primary coal fragments evolved at the devolatilization temperature. In a slow heating rate fixed bed unit, however, the primary coal fragments undergo additional cracking reactions which involve stabilization of free radicals by donatable hydrogen. This leads to the formation of low molecular weight hydrocarbons of relatively higher quality. In-situ (both intraparticle or extraparticle) stabilization of reactive coal fragments by donatable hydrogen may lead to a significant improvement in the overall quality of the pyrolysis liquids in a fixed bed system in which time-temperature history is conducive for such reactions.

Further characterization of dextran sulfate as a cofactor of protein C inhibitor

In the present study, we further investigated the relationship between the potency of dextran sulfate as a cofactor of PCI and its molecular size and/or sulfur content. We also examined the potency of polyaspartic acid and hyaluronic acid to accelerate the APC inhibition by PCI, since both contain many carboxyl groups but no sulfate groups

Upgrading of atmospheric residue with tetralin.

Upgrading of atmospheric residue (AR) with tetralin whose AR/tetralin volume ratios were 1/1, 2/1, 3/1 was investigated in a tube reactor with or without a catalyst at temperature between 400 and 500°C and at liquid hour space velocity (LHSV) of 1hr-1 under 1000psig. The results show that the properties of the cracked oils have been improved as indicated by the increase in API gravity and decreases in average molecular weight, sulfur content, and Conradson carbon content. The higher liquid yields and better qualities of cracked oils obtained catalytically compared with those noncatalytically indicate that Ni-Mo hydrocracking catalyst plays a role of transferring hydrogen from tetralin to the cracked oils. In both cases, 450°C was observed to be optimal of cracked oils in terms of yield and quality.

Lower excited electronic states of sulfur (S 8): A two-photon study by the thermal lensing method

Thermal lensing is applied to the study of multiphoton excitations in sulfur solution and crystal. The polarized two-photon absorption spectrum of sulfur and the polarization ratio for both the solution and crystal have been measured from 3000 to 2500 Å (crystal) and to 2200 Å (solution). The results are discussed in terms of electronic energy levels and two-photon absorption tensors of molecular sulfur calculated with semi-empirical methods.

A comparative synthetic and structural study of µ-oxo and µ-sulphido derivatives of N,N′-ethylenebis(acetylacetoneiminato)iron(III), including the synthesis and structural characterization of the parent compound

The synthesis of [{ Fe(acen)}2](1)[acen =N,N′-ethylenebis(acetylacetoneiminate) dianion, µeff.= 4.84] was performed by treating anhydrous FeCl2·1.5thf with H2acen in the presence of Na(OMe). Complex (1) has a monomeric structure in solution (M= 288 in C6H6) but is dimeric in the solid state as shown by an X-ray analysis. It has good solubility in organic solvents. Iron(II) achieves five-co-ordination either through dimerization or by binding of a molecule of solvent, e.g. pyridine, to form [Fe(acen)(py)](2). Complex (1) undergoes one-electron oxidation by molecular oxygen and elemental sulphur to form the corresponding iron(III) derivatives [{Fe-(acen)}2(µ-O)](3) and [{Fe(acen)}2(µ-S)](4) respectively. In complexes (3) and (4) the two d5 high-spin configurations are strongly antiferromagnetic [µeff.= 1.80 at 290 K for (3) and 2.16 at 293 K for (4)]. X-Ray analysis of (3) and (4) has allowed a comparison of the most significant parameters associated with the Fe–X–Fe backbone [Fe–O 1.775(13), Fe–S 2.210(3) and 2.204(2)A; Fe–O–Fe 150.7(13), Fe–S–Fe 120.8(1)°].

Fluorescence in the dissociative excitation of sulphur dioxide by electron impact

Electron-impact excitation of sulphur dioxide at energies > ca. 10 eV results in optical emission from the A3Π and B3Π states of the SO radical. The threshold energy for production of the SO(A3Π) was found to be 10.6 ± 0.5 eV, a value similar to the minimum thermochemical energy requirements. Optical emission excitation functions for the SO(A) state show that in the energy region 10–20 eV an important excitation channel involves the triplet manifold of sulphur dioxide, although there is still a significant contribution from singlet excitation, particularly at higher energies. The SO(A) state is quenched by molecular SO2 with near-unit collisional efficiency, with an estimated rate constant of 8.4 × 10–11 cm3 molecule–1 s–1. Detailed studies on production of SO(B) could not be undertaken owing to considerable spectral interference from molecular sulphur dioxide emission.

Thrombin inhibitory activity of heparin cofactor ii depends on the molecular weight and sulfate amount of dextran sulfate

The effect of molecular weight and sulfate amount of sulfated polysaccharide on the thrombin inhibitory activity of heparin cofactor II was investigated by using various dextran sulfate fractions with different molecular weight and sulfur content. The activity of dextran sulfate fractions of each size increased as the sulfur content was increased from 9 to 18% , and the activity decreased in molecules below 10 kDa. The maximum second order rate constant of heparin cofactor II-thrombin reaction in the presence of the fractions of over-10 kDa and 18% sulfur was 2.7 × 108 M −1 min −1 that was almost same as in the presence of heparin or dermatan sulfate. On the other hand, dextran sulfate accelerated antithrombin III-thrombin reaction only about 40-fold less than heparin. These results indicate that a large molecular size and significant amount of sulfate groups are only essential in the acceleration of the thrombin inhibitory activity of heparin cofactor II, whereas a specific sequence of heparin is required to that of antithrombin III.

Hydrophobic effects of sulfur and xanthate on metal and mineral surfaces

The hydrophobic character of a variety of base-metal sulfides and gold has been examined in the presence of sodium hydrosulfide and potassium ethylxanthate. The degree of hydrophobicity induced by electrodeposition of sulfur and by electrochemical reaction between the minerals and ethylxanthate were determined by contact-angle measurements on polished surfaces and by flotation of mineral particles. During flotation, mineral—reagent interactions were followed by monitoring the solution composition spectrophotometrically. Results have shown that on gold and chalcopyrite, the oxidation of hydrosulfide to molecular sulfur and the oxidation of ethylxanthate to dixanthogen produced hydrophobic surfaces; on pyrite, sulfur deposition was more effective than dixanthogen in producing a hydrophobic surface. Chalcocite, in contrast to gold, chalcopyrite, and pyrite, was found to react directly with ethylxanthate and hydrosulfide, but only the metal xanthate product was hydrophobic.

ChemInform Abstract: Laser Induced Synthesis: Selective Formation of Cyclohexene Episulphide from Molecular Sulphur S8.

AbstractCyclohexen (I) liefert unter Laser‐Bestrahlung mit Schwefel die Epithioverbindung (II).

Microcrystalline structure and surface area of elemental sulphur as factors influencing its oxidation by Thiobacillus albertis

The effect of particle size, surface area per unit weight, and molecular composition of S0 on the rate of S0 oxidation by Thiobacillus albertis was studied. Spherical S0 prills varying in size and surface areas were prepared and added as the sulphur source to synthetic salts medium. The rate of S0 oxidation by T. albertis was found to be a function of surface area/unit weight of sulphur. In all these experiments [Formula: see text] was produced in a linear manner with time indicating sterically favorable cell–sulphur oxidation binding sites for bacterial growth. Different powdered forms of S0 (high-purity orthohombic, high-purity polymeric, and mixed molecular sulphur) were oxidized at a significantly faster rate than the prilled S0. Also the initial oxidation was exponential up to 3 days at which point [Formula: see text] production from mixed molecular sulphur utilization fell off substantially with time as compared with similar [Formula: see text] rate curves obtained with high-purity orthorhombic and high-purity polymeric oxidation. It was implied that the increased Sx content in mixed molecular sulphur was responsible for the slower oxidation rate by altering the sulphur crystal lattice formation which affected the number of sterically favorable oxidation binding sites for T. albertis growth. Thiobacillus albertis was shown to colonize S0 surfaces as microcolonies. It was concluded that particle size, surface area/unit weight, and the crystal microstructure of S0 affects the oxidation rate of S0 by T. albertis.

Evaluation of the Mechanisms Involved in Sodium Diethyl Dithiocarbamate-Induced Immunomodulation Using the Hydrophilic Analog, Sodium N-Methyl-<i>D</i>-Glucamine Dithiocarbamate

Sodium diethyl dithiocarbamate (DE-DTC) is a lipophilic low molecular weight sulphur compound previously demonstrated to be a potent immunomodulator but cytotoxic in vitro. In this work, we studied the effects on a hydrophilic analog of DE-DTC, sodium N-Methyl-D-glucamine dithiocarbamate (NMG-DTC) on immune responses to a hapten carrier conjugate and on mitogen-induced lymphoproliferation. NMG-DTC, in contrast to DE-DTC, did not modify the responses to a hapten-carrier conjugate. The immunomodulatory activity of DE-DTC appeared to be linked with its lipophilicity. NMG-DTC had a slight inhibitory effect on thymidine incorporation by lymphocytes stimulated by mitogens as compared to that of DE-DTC. DE-DTC was cytotoxic possibly at the cell membrane level; cytotoxicity was not related to the chelating properties of DE-DTC in the culture medium. On the other hand, NMG-DTC appeared to be a less cytotoxic molecule. Therefore it could be useful to study the effects of the dithiocarbamate moiety at the cellular level.

Hydroliquefaction of low-sulfur coals using iron carbonyl complexes—Sulfur as catalysts

Hydroliquefaction of low-sulfur Australian coals (Wandoan and Yallourn) was studied using iron carbonyl complexes as catalyst. The addition of Fe(CO) 5 (2.8 wt% Fe of coal) increased coal conversion from 48.6 to 85.2% for Wandoan coal, and from 36.7 to 69.7% for Yallourn coal in 1-methylnaphthalene at 425°C under an initial hydrogen pressure of 50 kg cm −2. When molecular sulfur was added to iron carbonyls (Fe(CO) 5, Fe 2(CO) 9 and Fe 3(CO) 12), higher coal converions ( > 92%) and higher oil yields (>46%) were obtained, along with an increase in the amount of hydrogen transferred to coal from the gas phase (0.2 to 2.8%, d.a.f. coal basis). In the liquefaction studies using a hydrogen donor solvent, tetralin, Fe(CO) 5S catalyst increased the amount of hydrogen absorbed from the gaseous phase and decreased the amount of naphthalene dehydrogenated from tetralin. The direct hydrogen transfer reaction from molecular hydrogen to coal fragment radicals seems to be a major reaction pathway. Organic sulfur compounds, dimethyldisulfide and benzothiophene, and inorganic FeS 2 and NiS were found to be good sulfur sources to Fe(CO) 5. From X-ray diffraction analyses of liquefaction residues, it is concluded that Fe(CO) 5 was converted into pyrrhotite (Fe 1− x S) when sulfur was present, but into Fe 3O 4 in the absence of sulfur.

Two contrary modes of chemolithotrophy in the same archaebacterium.

Sulphur-dependent archaebacteria, which are found around nearly boiling continental solfataric springs and mud holes, can be assigned to two distinct branches: the aerobic, sulphur-oxidizing Sulfolobales and the strictly anaerobic sulphur-reducing Thermoproteales. Here, we report the isolation of a group of extremely thermophilic solfataric archaebacteria that are able to grow either strictly anaerobically by reduction, or fully aerobically by oxidation of molecular sulphur, depending on the oxygen supply. We have also established that the ability to grow in these two ways is shared by Sulfolobus brierleyi, a well-known less thermophilic sulphur-oxidizing archaebacterium capable of ore-leaching. The phenomenon may be dependent on a fundamental switch in genome expression. These organisms might represent the primitive fore-runners of sulphur-oxidizing archaebacteria, meeting their energy requirements either by oxidation or by reduction of the same element.