Oxoacids Of Sulfur Research Articles

Expanding the Reactive Sulfur Metabolome: Intracellular and Efflux Measurements of Small Oxoacids of Sulfur (SOS) and H2S in Human Primary Vascular Cell Culture.

Hydrogen sulfide (H2S) is an endogenous signaling molecule which is important for cardiovascular health, but its mechanism of action remains poorly understood. Here, we report measurements of H2S as well as its oxidized metabolites, termed small oxoacids of sulfur (SOS = HSOH and HOSOH), in four human primary vascular cell lines: smooth muscle and endothelial cells derived from both human arterial and coronary tissues. We use a methodology that targets small molecular weight sulfur species; mass spectrometric analysis allows for species quantification to report cellular concentrations based on an H2S calibration curve. The production of H2S and SOS is orders of magnitude higher in smooth muscle (nanomolar) as compared to endothelial cell lines (picomolar). In all the primary lines measured, the distributions of these three species were HOSOH >H2S > HSOH, with much higher SOS than seen previously in non-vascular cell lines. H2S and SOS were effluxed from smooth muscle cells in higher concentrations than endothelial cells. Aortic smooth muscle cells were used to examine changes under hypoxic growth conditions. Hypoxia caused notable increases in HSOH and ROS, which we attribute to enhanced sulfide quinone oxidase activity that results in reverse electron transport.

Characterization of Endogenous and Extruded H2S and Small Oxoacids of Sulfur (SOS) in Cell Cultures.

This report characterizes and quantifies endogenous hydrogen sulfide (H2S) and small oxoacids of sulfur (SOS = HOSH, HOSOH) in a panel of cell lines including human cancer (A375 melanoma cells, HeLa cervical cells) and noncancer (HEK293 embryonic kidney cells), as well as E. coli DH5α and S. cerevisiae S288C. The methodology used is a translation of well-studied nucleophilic and electrophilic traps for cysteine and oxidized cysteines residues to target small molecular weight sulfur species; mass spectrometric analysis allows for species quantification. The observed intracellular concentrations of H2S and SOS vary in different cell types, from nanomolar to femtomolar, typically with H2S > HOSOH > HOSH. We propose the term sulfome, a subset of the metabolome, describing the nonproteinaceous metabolites of H2S; the sulfomic index is as a measure of the S-oxide redox status, which gives a profile of endogenous sulfur at different oxidation states. An important observation is that H2S and SOS were found to be continuously extruded into surrounding media against a concentration gradient, implying an active efflux process. Small molecule inhibition of several H2S generating enzymes suggest that SOS are not derived solely from H2S oxidation. Even after successful inhibition of H2S production, cells maintain constant efflux and repopulate H2S and SOS over time. This work proves that these small sulfur oxoacids are generated in cells of all types, and their efflux implies that they play a role in cell signaling and possibly other vascular physiology attributed to H2S.

Successive Hydrogenation of SO and SO2 in Solid para-H2: Formation of Elusive Small Oxoacids of Sulfur

The small oxoacids of sulfur (SOS), HxSOy (x, y = 1, 2), are considered to be key reactive intermediates in organic synthesis, biochemical processes, and atmospheric chemistry. They play a major ro...

Sulfane rush: Small Oxoacids of Sulfur (SOS) are the Reactive Intermediates in Polysulfide Generation

Sulfane rush: Small Oxoacids of Sulfur (SOS) are the Reactive Intermediates in Polysulfide Generation

Reactivity of Small Oxoacids of Sulfur.

Oxidation of sulfide to sulfate is known to consist of several steps. Key intermediates in this process are the so-called small oxoacids of sulfur (SOS)—sulfenic HSOH (hydrogen thioperoxide, oxadisulfane, or sulfur hydride hydroxide) and sulfoxylic S(OH)2 acids. Sulfur monoxide can be considered as a dehydrated form of sulfoxylic acid. Although all of these species play an important role in atmospheric chemistry and in organic synthesis, and are also invoked in biochemical processes, they are quite unstable compounds so much so that their physical and chemical properties are still subject to intense studies. It is well-established that sulfoxylic acid has very strong reducing properties, while sulfenic acid is capable of both oxidizing and reducing various substrates. Here, in this review, the mechanisms of sulfide oxidation as well as data on the structure and reactivity of small sulfur-containing oxoacids, sulfur monoxide, and its precursors are discussed.

73 - Chemical Trapping and Characterization of small Oxoacids of Sulfur (SOS) and Selenium (SOSe) Generated in Aqueous Oxidations of H2S and H2Se

Small oxoacids of sulfur (SOS) are elusive molecules like sulfenic acid, HSOH, and sulfinic acid, HS(O)OH, generated by oxidation of hydro-gen sulfide, H2S, in aqueous solution. Like their alkyl homologs, SOS may exhibit both nucleophilic and electrophilic reactivity due to interconversion between S(II) and S(IV) tautomers. We find that SOS may be trapped in situ by derivate-ization with nucleophilic and electrophilic trapping agents and then characterized by high resolution LC/MS. Herein, we compare SOS formation from H2S oxidation by a variety of biologically relevant oxidants. Analogous small oxoacids of selenium, SOSe, are generated during aqueous oxidations of hydrogen selenide (H2Se). These SOS and SOSe species appear relatively long lived in aqueous solution, and thus may be involved in the observed physiological effects derived from H2S and potentially H2Se.

Chemical trapping and characterization of small oxoacids of sulfur (SOS) generated in aqueous oxidations of H2S

Small oxoacids of sulfur (SOS) are elusive molecules like sulfenic acid, HSOH, and sulfinic acid, HS(O)OH, generated during the oxidation of hydrogen sulfide, H2S, in aqueous solution. Unlike their alkyl homologs, there is a little data on their generation and speciation during H2S oxidation. These SOS may exhibit both nucleophilic and electrophilic reactivity, which we attribute to interconversion between S(II) and S(IV) tautomers. We find that SOS may be trapped in situ by derivatization with nucleophilic and electrophilic trapping agents and then characterized by high resolution LC MS. In this report, we compare SOS formation from H2S oxidation by a variety of biologically relevant oxidants. These SOS appear relatively long lived in aqueous solution, and thus may be involved in the observed physiological effects of H2S.

Dissociation of sulfur oxoacids by two water molecules studied using ab initio and density functional theory calculations

Using ab initio [SCS-MP2 and CCSD(T)] and density functional theory (M062X) calculations, we have studied the geometries and energies of sulfur oxoacids H2SmO6 (m = 2–4) and their monohydrated and dihydrated clusters. When including the results from previously reported disulfuric acid (H2S2O7) cases, the gas phase acidity is ordered as H2S2O6 < H2S3O6 < H2S2O7 < H2S4O6. The intramolecular H-bonding, which may indicate the degree of structural flexibility in this molecular series, is an important factor for the order of the gas phase acidity. All these sulfur oxoacids show dissociated (or deprotonated) geometries with only two water molecules, although the energies of the dissociated conformers are ranked differently. All of the dissociated conformers form a unique H-bonding network structure in which the protonated first water (H3O+) is triply H-bonded to each oxygen atom of two SO3 moieties as well as the second water, which in turn is H-bonded to a SO3 moiety. H2S3O6 has the best molecular flexibility for adopting such an H-bonding network structure, and thereby all the low-lying conformers of H2S3O6(H2O)2 are dissociated. In contrast, the least flexible H2S2O6 forms such a structure with a high strain, and dissociation of H2S2O6(H2O)2 is found from the third lowest conformer. Although the gas phase acidity of H2S4O6 is the highest in this series, the lowest dissociated conformer and the lowest undissociated conformer of H2S4O6(H2O)2 are very close in energy. This is because forming the H-bonding network structure is somewhat difficult due to the large distance between the two SO3 moieties.

Oxyhalogen-sulfur chemistry: Kinetics and mechanism of oxidation of n-acetylthiourea by aqueous bromate and acidified bromate

The oxidation of N-acetylthiourea (ACTU) by acidic bromate has been studied by observing formation of bromine in excess bromate conditions. The reaction displays an induction period before formation of bromine. The stoichiometry of the reaction was determined to be 4:3: 4BrO 3 – +3(CH 3 CO)NH(NH 2 )C=S+3H 2 O®4Br – +3(CH 3 CO)NH(NH 2 )C=O+3SO 4 2– +6H + (A) with a complete desulfurization of ACTU to its urea analogue. In excess bromate conditions the stoichiometry was 8:5: 8BrO 3 – + 5(CH 3 CO)NH(NH 2 )C=S + H 2 O ® 4Br 2 + 5(CH 3 CO)NH(NH 2 )C=O + 5SO 4 2+ + 2H + (B). Bromine is derived from an extraneous reaction in which bromide fromstoichiometry (A) reacts with excess acidic bromate. The oxidation of ACTU by aqueous bromine gave stoichiometry (C): 4Br 2 (aq)+(CH 3 CO)NH(NH 2 )C=S+5H 2 O®8Br – +CH 3 CO)NH(NH 2 )C=O+SO 4 2– + 10 H + .Reaction (C) is much faster than reactions (A) and (B), with a lower limit bimolecular rate constant of 2.1 ×10 5 M –1 s –1 such that appearance of bromine signals complete consumption of ACTU. We were unable to trap any intermediate sulfur oxo-acids of ACTU on its oxidation pathway to N-acetylurea. As opposed to other substituted thioureas, none of its intermediates were stable enough to be isolated and detected. KEYWORDS Kinetics, mechanisms, oxyhalogen chemistry, s-oxygenation, bioactivation.

Prediction of acidity constants of some important selenium oxoacids in aqueous solution by computational techniques

The acidity constants (pKa) of two important series of selenium oxoacids including H2SeOn (n = 1–5) and H2Se2On (n = 1, 3, 4, 6 and 7) were predicted by using two different computational methods for the first time. The calculations were performed using MP2 level of theory employing a very large basis set, 6-311++G(3df,3pd), and a new density functional method, M06-2X, with the same basis set, separately. A new continuum solvation model, SMD, based on the quantum mechanical charge density of a solute molecule interacting with a continuum description of the solvent, was used to account the solvent effects. The calculated values of pKa were corrected using the different correlation equations, reported in the literature, to improve the accuracy of results. Also, the calculated results in this work were compared with the corresponding results related to sulfur oxoacids obtained in our previous work. The same trend was observed for the variation of the acidity constants of selenium oxoacids and corresponding sulfur oxoacids (with the number of oxygen atoms). Comparison of the pKa1 of selenium and sulfur oxoacids showed that the acidity strength of sulfur is higher than selenium while for pKa2, selenium oxoacids are stronger acids than sulfur oxoacids. The predicted values of pKa of selenium oxoacids are important and useful in the different chemical aspects of these compounds in chemistry and biochemistry.

Acidity constants of some sulfur oxoacids in aqueous solution using CCSD and MP2 methods

The calculations of the acidity constants (pKa) of a series of sulfur oxoacids including H2SOn (n = 1-5) and H2S2On (n = 1, 3, 4, 6 and 7) are presented for the first time. The calculations were performed using two expensive correlated levels of theory including MP2/6-311++G(3df,3pd) and CCSD/6-311++G(d,p) in both gas and aqueous phases. The new continuum solvation model, SMD, based on the quantum mechanical charge density of a solute molecule interacting with a continuum description of the solvent, used to account the solvent effects. The calculated pKas were corrected using the different correlation equations (Zimmermann and Tossell, J. Phys. Chem. A, 2009, 113, 5105-5111) to improve the accuracy of results. Also, the calculated results showed the effect of the intramolecular hydrogen bonding on the acidity strength.

Molecules and models: the molecular structures of main group element compounds

1. Atomic properties: one-electron atoms 2. Atomic properties: two-electron atoms 3. Atoms with more than two electrons: atomic properties and periodic trends 4. Homonuclear diatomic molecules 5. Gaseous alkali metal halides: ionic compounds 6. Other heteronuclear diatomic molecules: polar covalent bonds 7. Lewis' cubical atom model. Molecular orbital calculations on the one-electron molecule H2+ and the two-electron molecule H2 8. Molecular orbital calculations on heteronuclear diatomic molecules, hybridization, and estimation of net atomic charges from calculated electron densities 9. Homonuclear diatomic species of the Second Period elements from Li2 to Ne2 10. Structure and bonding in the gaseous dihalides and dialkyls of the Group 2 and Group 12 metals 11. Structure and bonding in the gaseous monochlorides, trichlorides and trimethyl derivatives of the Group 13 elements 12. Electron defficient molecules: three-centre, two-electron bonds 13. Structure and bonding in simple compounds of the Group 14 elements 14. Structure and bonding in some simple hydrocarbons and in ethane and ethene analogous of the heavier Group 14 elements 15. Structure and bonding in simple compounds of the Group 15 elements 16. Electron donor-acceptor complexes 17. Structure and bonding in simple compounds of the Group 16 elements 18. Structure and bonding in simple compounds of the Group 17 elements. 19. Structure and bonding in simple compounds of the noble gases 20. Structure and bonding in oxides and oxoacids of carbon, sulfur, nitrogen, phosphorus and chlorine

ChemInform Abstract: Sulfur Compounds. Part 220. Gas‐Phase Structures and Acidities of the Sulfur Oxoacids H2SnO6 (n = 2—4) and H2S2O7

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Gas-Phase Structures and Acidities of the Sulfur Oxoacids H2SnO6 (n = 2−4) and H2S2O7

The gas-phase geometries, dipole moments, enthalpies, and Gibbs free energies of dithionic acid H2S2O6, trithionic acid H2S3O6, tetrathionic acid H2S4O6, and disulfuric acid H2S2O7 have been determined by ab initio MO calculations at various levels of theory. The most stable conformations of H2S2O6 and H2S2O7 are of C2 symmetry, the other two acids are of C1 symmetry. The gas-phase acidities defined as ΔG°298 of the deprotonation reaction obtained at the {MP2/6-311++ G(3df, 3pd)//MP2/6-31+ G(d) + ZPVE[HF/6-31+ G(d)]} level are as follows [kJ·mol−1]: H2S2O6 1180, H2S3O6 1162, H2S4O6 1156, H2S2O7 1171. All four acids are much stronger than fluorosulfuric acid and chlorosulfuric acid in the gas phase. The decomposition of H2S2O7 into SO3 and H2SO4 is slightly endothermic and the same holds for the decomposition of H2S3O6 into SO3 and H2S2O3, but the reaction of H2S2O6 to SO2 and H2SO4 is strongly exothermic. The structures of the monoanions HS2O6−, HS3O6−, HS4O6−, and HS2O7− are characterized by intramolecular hydrogen bonds.

Gas-Phase Acidities of Nine Sulfur Oxoacids of Composition [H2,S,On] (n = 1–4)

The gas-phase acidities of the most stable conformations of nine sulfur oxo acids were determined by ab initio MO calculations at the CBS-Q, G2(MP2), and G2 levels of theory. The most accurate G2 results are as follows (ΔG°298 of the deprotonation reaction in kJ mol–1): H–S–O–H 1468, H–S–O–H 1449, (HO)2S 1426, H–S(=O)OH 1406, H2S/O 1394, H–S(=O)OH 1361, (HO)2S/O 1324, H2S(=O)2 1321, H2O→S 1294, H–S(=O)2OH 1287, H–S(=O)2OH 1279, (HO)2S(=O)2 1268. These values are in excellent agreement with the few experimental data that can be considered reliable. For molecules of analogous structure, the acidity increases with increasing oxidation number of the sulfur atom. While sulfenic acid, HSOH, is as weak an acid as HOCl, sulfurous acid, (HO)2SO, is as strong a proton donor as nitric acid, HNO3, and sulfonic acid, HS(O)2OH, is even stronger than hydrogen iodide, HI, surpassed only by sulfuric acid, H2SO4. These results are of relevance to phenomena such as acid rain and aerosol formation in the earth′s atmosphere.

The Reaction of H2S with SO2: Molecular Structures, Energies, and Vibrational Data of Seven Isomeric Forms of H2S3O

AbstractHigh‐level ab initio MO calculations (MP2/6‐311G**//MP2/6‐311G**) on 16 isomeric forms of H2S3O (including rotamers) have been performed. The nonhelical hydroxotrisulfane HOSSSH 1a (motif + + −) is the most stable isomer, while the chains with motifs + + + and + − + are less stable by 1.7 and 3.7 kJ mol−1, respectively. The other isomers of H2S3O increase in energy in the order HSS(O)SH &lt; HOS(S)SH &lt; HSOSSH &lt; HS(O)SSH &lt; HS(S)SOH &lt; HS(S)OSH. The trisulfane‐2‐oxide HSS(O)SH 2a (symmetry C1) is less stable than 1 a by 67 kJ mol−1. These molecules may be formed from H2S and SO2 via H2S2O2 by condensation with H2S. The calculated reaction energies support the view that H2S3O is a key intermediate in the room‐temperature reaction of H2S and SO2 resulting in the formation of lower oxoacids of sulfur and finally in sulfane oxides.

Molten Potassium Pyrosulfate: Reactions of Five Alkali-Metal Salts of Sulfur Oxo Acids

The reactions of five alkali-metal salts of sulfur oxo acids with molten K2S2O7 were investigated. Na2SO3, Na2S2O3, Na2S2O4, Na2S2O5 and K2S2O3 reacted with molten K2S2O7 to form sulfate, elemental sulfur and SO2 as the final reaction products. Reaction pathways have been postulated to explain the final products. The stoichiometries of the reactions have been determined.

Lower valent oxo acids of phosphorus and sulfur

Lower valent oxo acids of phosphorus and sulfur

Anorganische Dünnschicht‐Chromatographie 9. Mitteilung Dünnschichtchromatographische Trennung von Sulfaten und Polythionaten

AbstractThin laver chromatography is applied to the separation and identification of several oxoacids of sulfur and some polythionic acids.