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PubMed2005

Structural insight into the interactions of SoxV, SoxW and SoxS in the process of transport of reductants during sulfur oxidation by the novel global sulfur oxidation reaction cycle.

Microbial redox reactions involving inorganic sulfur compounds, mainly the sulfur anions, are one of the vital reactions responsible for the environmental sulfur balance. These reactions are mediated by phylogenetically diverse prokaryotes, some of which also take part in the extraction of metal ions from their sulfur containing ores. These sulfur oxidizers oxidize inorganic sulfur compounds like sulfide, thiosulfate etc. to produce reductants that are used for carbon dioxide fixation or in respiratory electron transfer chains. The sulfur oxidizing gene cluster (sox) of alpha-Proteobacteria comprises of at least 15 genes, forming two transcriptional units, viz., soxSR and soxVWXYZABCDEFGH. SoxV is known to be a CcdA homolog involved in the transport of reductants from cytoplasm to periplasm. SoxW and SoxS are periplasmic thioredoxins, which (SoxW) interact with SoxV and thereby help in the redox reactions. We have employed homology modeling to construct the three-dimensional structures of the SoxV, SoxW and SoxS proteins from Rhodovulum sulfidophilum. With the help of docking and molecular dynamics simulations we have identified the amino acid residues of these proteins involved in the interaction. The probable biochemical mechanism of the transport of reductants through the interactions of these proteins has also been investigated. Our study provides a rational basis to interpret the molecular mechanism of the biochemistry of sulfur anion oxidation reactions by these ecologically important organisms.

Alphaproteobacteria↗
PubMed1983

Volatile sulfur containing compounds in simulated meat flavour and their comparison with the constituents of natural aroma.

The composition of sulfur containing compounds in simulated meat flavour goods for food industry and obtained through Maillard reaction from bakery yeast autolysate was studied for the first time. Gas chromatographic analysis on a series of four columns of different polarity identified 37 compounds, and structure of 13 from them were confirmed by mass spectrometry. 9 sulfur substances have been previously reported neither for model systems nor natural meat products. It was found that two from four gas chromatographic fractions reminiscent cooked meat aroma correspond to boiled beef. All these fractions were characterized by retention indices and odor description. 25 from identified sulfur compounds were shown to be also inherent for various meat products.

Animals↗
PubMed1997

The effect of zinc-containing chewing gum on volatile sulfur-containing compounds in the oral cavity.

Volatile sulfur-containing compounds (VSC) are known to constitute the major component of halitosis. Aqueous solutions of zinc salts have been shown to reduce the levels of VSC produced orally. The aim of the present study was to examine whether zinc could be made available in the oral cavity and inhibit VSC production when delivered by a chewing gum. VSC measurements were carried out on the 'morning breath' of 11 test subjects and re-examined after the use of test solutions containing 0.02% zinc chloride, 0.2% chlorhexidine, or water or the use of chewing gums containing 2 mg, 0.5 mg, or 0 mg zinc acetate. The results showed that similar amounts of zinc in mouthrinses or chewing gum had the same effect, with a reduction of the oral VSC of 45%. Chewing gum thus seems to be a viable alternative for delivering zinc to reduce VSC levels in the oral cavity.

Adolescent↗
PubMed2004

Antioxidative activity of sulfur-containing compounds in Allium species for human LDL oxidation in vitro.

Sulfur-containing compounds contributing to health promotion in Allium species are produced via enzymic and thermochemical reactions. Sulfur-containing amino acids and volatile organosulfur compounds were prepared for an antioxidative assay. The inhibitory activity of S-alk(en)yl-L-cysteines and their sulfoxides, volatile alk(en)yl disulfides and trisulfides, and vinyldithiins in Allium species against lipid hydroperoxide (LOOH) formation in human low-density lipoprotein (LDL) was examined. It was elucidated that the alk(en)yl substituents (methyl, propyl, and allyl) and the number of sulfur atoms in the compounds were important for the antioxidative activity. 3,4-Dihydro-3-vinyl-1,2-dithiin, which is produced by a thermochemical reaction of allyl 2-propenethiosulfinate, exhibited the highest antioxidative activity of human LDL among sulfur-containing compounds.

Allium↗
PubMed2006

The relationship between oral malodor and volatile sulfur compound-producing bacteria.

Halitosis can be a crippling social problem, and standard dental treatments and mouthwashes often provide only temporary relief. The mouth is home to hundreds of bacterial species that produce several fetid substances as a result of protein degradation. Volatile sulfur compound (VSC)-producing bacteria colonizing the lingual dorsum have recently been implicated in the generation of halitosis. Detection of VSCs, such as methylmercaptan and hydrogen sulfite, via organoleptic and objective methods, can aid in the identification of their source. Following comprehensive evaluation for possible causes, most halitosis in patients seen in an ENT practice can be localized to the tongue. We review methods of diagnosis and treatment of oral malodor from the overgrowth of proteolytic, anaerobic, gram-negative bacteria on the crevices of the lingual dorsum. Bacteriologic analysis of biofilm and scraped specimens obtained from the lingual dorsum and other oral sites, primarily gingival pockets and tonsillar crypts, can identify VSC-producing bacteria. Porphyromonas, Prevotella, Actinobacillus, and Fusobacterium species are the most common organisms identified. Halitosis is an oral phenomenon, with almost no cases originating distal to the tonsils. Halitosis arising from the lingual dorsum secondary to overpopulated VSC-producing bacteria can be successfully managed with a combination of mechanical cleansing using tongue brushes or scrapes and chemical solutions containing essential oils, zinc chloride, and cetylpyridinium chloride.

Halitosis↗
PubMed1994

Screening of potential chemopreventive agents using biochemical markers of carcinogenesis.

Ninety potential chemopreventive agents were screened using 6 chemoprevention-associated biochemical end points. These compounds were tested using rodent (tracheal epithelial or liver) cells and human cells [neonatal foreskin fibroblasts, bronchial epithelial cells, or human leukemic cells (HL-60)]. The effects measured were: (a) inhibition of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tyrosine kinase activity in HL-60 cells; (b) inhibition of TPA-induced ornithine decarboxylase (ODC) activity in rat tracheal epithelial cells; (c) inhibition of poly(ADP-ribose)polymerase in propane sultone-treated primary human fibroblasts; (d) inhibition of benzo[a]pyrene(B[a]P)-DNA binding in human bronchial epithelial cells; (e) induction of reduced glutathione in Buffalo rat liver cells; and (f) inhibition of TPA-induced free radical formation in primary human fibroblasts or HL-60 cells. Fifty compounds were highly effective in inhibiting TPA-induced tyrosine kinase activity. This assay identified compounds from a wide variety of chemical classes as effective inhibitors, including all the vitamins, retinoic acid analogues, protein kinase C inhibitors, and chemicals belonging to the amino acid category. Fifty-two chemicals were classified as highly positive compounds when examined for their ability to inhibit TPA-induced ODC activity. These agents showed a dose-dependent inhibition or inhibition at all doses. Retinoids, in general, exhibited strong inhibition of ODC activity. A category of compounds showing dose-dependent inhibition were the sulfur compounds, especially the thiols and thiones. Among the natural products, terpenes were strong inhibitors of ODC. Forty-seven compounds were classified as strong inhibitors of poly(ADP-ribose)polymerase. In the carcinogen-DNA binding inhibition assay, 21 compounds were identified as strong inhibitors, which include phenolic compounds as well as sulfur compounds. Vitamins and their analogues were also good inhibitors. Testing for induced glutathione yielded 19 compounds that were good inducers. Sulfur-containing compounds and most of the phenolic compounds were also inducers of glutathione. Twenty compounds were highly positive for inhibition of TPA-induced free radical formation. A significant number of phenolic and sulfur compounds were again strong oxygen radical scavengers. Some antiinflammatory agents were also identified as free radical inhibitors. In general, retinoids were quite active in all the assays. Eight compounds were positive in all of the six assays; these were vitamin C (ascorbic acid), bismuththiol, esculetin, etoperidone, folic acid, hydrocortisone, indole-3-carbinol, and tocopherol succinate. Agents that were positive in these assays may inhibit the carcinogenesis process by similar mechanisms in humans and are identified as candidates for development as chemopreventive agents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1997

A method for measuring nitric oxide radical scavenging activity. Scavenging properties of sulfur-containing compounds.

A new method for the quantification of the nitric oxide (.NO) scavenging activity of compounds in aqueous solutions is described using an amperometric .NO sensor. After correction for the spontaneous degradation of .NO, second-order rate kinetics of the scavenging reaction are observe. The rate constant for hemoglobin found with this method is comparable with that found with an established spectrophotometric method. To demonstrate the capability of the method, several sulfur-containing compounds were tested (GSH, GSSG, S-methyl glutathione, N-acetyl cysteine, lipoic acid and dihydrolipoic acid). Of these compounds, only those that contained a thiol group displayed a considerable .NO scavenging activity.

Electrochemistry↗
PubMed2001

Effects of metal salts on the oral production of volatile sulfur-containing compounds (VSC).

BACKGROUND/AIM: Halitosis, mainly caused by bacteria located on the posterior dorsum of the tongue and in periodontal pockets, is due to formation of volatile sulfur compounds (VSC). The hypothesis to be tested was that the affinity of a metal for sulfur determines its anti-VSC activity. METHOD: Clinical tests were carried out on 12 subjects who rinsed with cysteine to induce halitosis (baseline) before rinsing with 7.34 mM ZnCl2, SnF2 and CuCl2. Mouth air VSC analyses were repeated following cysteine rinses at 1 h, 2 h and 3 h using a gas chromatograph. In vitro experiments tested toxic metals Hg2+, Pb2+ and Cd2+. 10-microl aliquots of metal salts were added to 1-ml aliquots of human whole saliva from 30 subjects. Samples were incubated overnight at 37oC and saliva headspace was analyzed for VSC in a gas chromatograph. CLINICAL RESULTS: Cu2+>Sn2+>Zn2+ (supports hypothesis). Zn2+ had significantly less anti-VSC effect compared with Cu2+ and Sn2+ at 1, 2 and 3 h. In vitro results indicated that Hg2+, Cu2+ and Cd2+ had close to 100% anti-VSC effect, and that Pb2+ was less effective and Cd2+ more effective than expected in inhibiting VSC. CONCLUSIONS: Apart from Hg2+ and Cu2+, the metals had a significantly greater effect on H2S than on CH3SH. Cu2+ and Hg2+ have well-known antibacterial activity and may presumably also operate by this mechanism.

Adult↗
PubMed2005

SH radical: the key intermediate in sulfur transformation during thermal processing of coal.

To uncouple the complex behavior of sulfur transformation during thermal processing of coal and to elucidate the main mechanism, typical organic and inorganic sulfur compounds impregnated on or mixed with a low-ash char are studied through temperature-programmed decomposition coupled with online mass spectrum analysis (TPDMS) and followed by temperature-programmed oxidation coupled also with online mass spectrum analysis (TPOMS) in a temperature range of up to 800 degrees C. It is evident that the cleavages of Cal-S and Car-S bonds, where the subscripts al and ar stand for aliphatic and aromatic carbon, respectively, in the organic compounds result in the formation of SH radicals, which then undergo secondary reactions with the char to form various sulfur compounds such as H2S, SO2, COS, and elemental sulfur, as well as sulfur structures in the char. H2 has the ability to stabilize the -* SH radicals and weaken the interactions between the -* SH radicals and the char. For the sulfur compounds, which do not generate the *SH radical, the only sulfur products detected are those formed directly from the decomposition of the starting sulfur compounds, H2S from FeS2 in H2 or SO2 from Fe2(SO4)3 in He, for example, and no sulfur structure is formed in the char. Minerals have significant effects on the bond cleavage temperature and the reactions of the *SH radicals with the char. It is clear that the *SH radical is a key species interacting with the char to form secondary sulfur compounds, while H2S and SO2 play no role in the sulfur transformation to the carbon structure.

Carbon↗
PubMed2001

Monitoring odorous sulfur emissions using self-organizing maps for handling ion mobility spectrometry data.

Possibilities for monitoring emissions of reduced sulfur compounds in pulp and paper mills were investigated using ion mobility spectrometry (IMS) and a self-organizing map (SOM) algorithm. The reduced sulfur compounds measured were hydrogen sulfide (H2S), dimethyl sulfide (DMS), and methyl mercaptan (MM). Attention was paid to momentary concentrations because there is no monitoring device able to measure peak concentrations of reduced sulfur compounds under field conditions. These methods were evaluated by measuring the reduced sulfur compounds first in the laboratory and then at a process monitoring site at a pulp factory. The aim was to find out whether it would be possible to use the laboratory measurements to recognize the same reduced sulfur compounds at the monitoring site. Data collection was followed by analysis using the SOM algorithm and Sammon's mapping. The results showed that the IMS spectra of reduced sulfur compounds and their mixtures can be distinguished from each other by computationally intelligent methods and that the spectra from the process monitoring site corresponded with the laboratory measurements to a certain extent.

Air Pollutants↗
PubMed2004

Determination of nanogram level of VSCs using GC-SCD and an adsorption tube.

A quantitative analytical method was used for detection of low level of volatile sulfur compounds (VSCs) using GC with a sulfur chemiluminescence detector (SCD) in this study. A linear response over the range of 2-90 ngS injected was obtained with a good repeatability or reproducibility. Equimolar response for H2S, DMS, MeSH, and EtSH was obtained by use of SCD and the response of the SCD is nearly equimolar for different sulfur compounds. It was possible to quantify the total VSCs as well as individual VSC using one of the standard VSCs. VSC recovery was measured with respect to some storing methods. An adsorption tube packed with molecular sieve 5A showed almost perfect recovery for both H2S and dimethyl sulfide (DMS) during 6 days at a dark state below 2 degrees. Whereas, with a gas tight pyrex vial or tedlar bag, it was impossible to obtain the recovery of 50% after 6 days. It is strongly recommended to use the adsorption tube for determination of nanogram levels of volatile sulfur compounds and for storing and concentrating VSCs effectively with a minimum experimental error.

Adsorption↗
PubMed1978

Effect of sulfur-containing compounds on anaerobic degradation of cellulose to methane by mixed cultures obtained from sewage sludge.

Tests were made to determine the effects of inorganic and organic sulfur sources on the degradation of cellulose to methane in a chemically defined medium with sulfur-poor inoculum prepared from sewage sludge. The results show that a sulfur source of about a 0.85 mM concentration is essential for the degradation of cellulose to CH4. However, the production of CH4 from CO2 and H2 provided in the headspace occurred with 0.1 mM sulfate or sulfide. At a 9 mM concentration, all inorganic sulfur compounds other than sulfate inhibited both cellulose degradation and methane formation, and this inhibition increased in the order thiosulfate less than sulfite less than sulfide less than H2S. It appears that the degradation of cellulose to CH4 in a sulfate-free medium by inoculum maintained in a low-sulfur medium is inhibited because of the lack of availability of sulfur for growth of bacteria and synthesis of cell materials and sulfur-containing cofactors involved in cellulose degradation and methanogenesis. The reduction of methanogenesis by higher levels of sulfate probably occurs as a result of stimulation of reactions converting acetate and H2 to end products other than CH4.

Anaerobiosis↗
PubMed2005

A pulsed potential waveform displaying enhanced detection capabilities towards sulfur-containing compounds at a gold working electrode.

Pulsed electrochemical detection of sulfur-containing compounds was successfully investigated by applying a four-step potential waveform at a gold working electrode. This potential waveform called APAD, which stands for activated pulsed amperometric detection, is composed of an activation potential step added to a conventional three-step potential waveform. A key advantage of the APAD at the Au electrode is the ability to enhance sensitivity through the use of a short potential pulse (E(ACT) = +750 mV versus Ag/AgCl and tACT approximately 90 ms) during which the formation of redox active species (presumably OH*) are able to efficiently oxidize organosulfur compounds. The APAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of lipoic acid, biotin, iminobiotin, methionine, cystine, cysteine, homocysteine, homocystine, N-acetylcysteine and glutathione, following their separations by high-performance anion-exchange chromatography (HPAEC) using alkaline mobile phases. The detection limits (S/N = 3, 10 microL injected) ranged from 0.3 for cysteine (400 pg) to 0.02 micromol/L for biotin (50 pg) and methionine (30 pg). The response of sulfur-, amine- and alcohol-based compounds was compared by using four selected pulsed potential waveforms. It was found that the APAD exhibits excellent sensitivity for thiocompounds outperforming all other pulsed potential waveforms. Ratios of the peak areas for APAD and the six-step potential integrated waveform increased from 3.2 +/- 0.4 to 13.5 +/- 0.6 for lipoic acid and biotin, respectively.

Acetylcysteine↗
PubMed2003

Antioxidative activity of sulfur-containing compounds in Allium species for human low-density lipoprotein (LDL) oxidation in vitro.

Sulfur-containing compounds contributing to health promotion in Allium species are produced via enzymic and thermochemical reactions. Sulfur-containing amino acids and volatile organosulfur compounds were prepared for an antioxidative assay. The inhibitory activity of S-alk(en)yl-l-cysteines and their sulfoxides, volatile alk(en)yl disulfides and trisulfides, and vinyldithiins in Allium species against lipid hydroperoxide (LOOH) formation in human low-density lipoprotein (LDL) was examined. It was elucidated that the alk(en)yl substituents (methyl, propyl, and allyl) and the number of sulfur atoms in the compounds were important for the antioxidative activity. 3,4-Dihydro-3-vinyl-1,2-dithiin, which is produced by a thermochemical reaction of allyl 2-propenethiosulfinate, exhibited the highest antioxidative activity of human LDL among sulfur-containing compounds.

Allium↗
PubMed2002

Relationship between stressful situations, salivary flow rate and oral volatile sulfur-containing compounds.

The relationship between stress, salivary flow rate and oral volatile sulfur-containing compounds (VSCs) is not clearly established. Two stressful situations were studied: psychological stress caused by a biochemistry examination (Study I) and psychophysiological stress caused by premenstrual syndrome (PMS) (Study II). Seventy-one undergraduate dental students took part in Study I and VSCs were measured 1 wk before the examination, on the day of examination and 1 wk after. In Study II, 50 women were selected (23 with and 27 without PMS) and the measurements were made during non-menstrual, premenstrual and menstrual stages. Unstimulated salivary flow was determined in the subjects of both studies. On the day of the biochemistry examination, VSCs significantly increased and salivary flow decreased compared with baseline values. Women with PMS showed higher VSC concentrations during the premenstrual stage than those without PMS (P < 0.05), but the salivary flow was not statistically different. A change in VSCs was observed during different stages of the menstrual cycle for the groups of women, but the salivary flow did not change. The results suggest that a stressful situation can be a predisposing factor for the increase of VSCs in the mouth air, but the mechanism cannot be simply explained by reduction of the salivary flow.

Adolescent↗
PubMed2002

Comparative analysis of some mouthrinses on the production of volatile sulfur-containing compounds.

Oral malodor is mainly caused by the presence of volatile sulfur-containing compounds (VSC) produced by proteolytic periodontopathic bacteria in the oral cavity. Different solutions have been used as mouthrinses, trying to reduce malodor, and a large number is on the market. The aim of this study was to compare the effect of three commercially available mouthrinses with a simple inexpensive solution of zinc (zinc acetate 0.1%) on the production of VSC in vivo. Two of the solutions contained triclosan, one of them with fluoride and the other with sodium bicarbonate, and the third one contained herbal components. Seven healthy subjects rinsed with cysteine to induce production of VSC at baseline. After halitosis induction and VSC measurements, the subjects rinsed with the test solution, and mouth airVSC analyses were then performed by means of gas chromatography subsequent to repeated cysteine rinses after 30, 60, and 120 min. The data were calculated as percentage reduction of VSC from baseline. The percentage reduction of VSC decreased over time for all experimental groups. Zinc acetate had clearly the highest percentage reduction, starting from 95.68% at 30 min and with 69.27% after 2 h. The three other mouthrinses produced a VSC reduction of 23.92% 49.86% after 30 min, decreasing to 13.06%-37.09% after 2 h. One-way ANOVA (P = 0.05) was applied, and comparisons showed no differences between the commercially available solutions, but zinc acetate was significantly better than these. It may be concluded that some commercial mouthrinses are markedly less effective than a simple and cheap solution of zinc acetate.

Adult↗
PubMed2002

Formation of sulfur aroma compounds in reaction mixtures containing cysteine and three different forms of ribose.

The headspace volatiles produced from buffered and unbuffered cysteine model systems, containing inosine 5'-monophosphate, ribose 5-phosphate, or ribose, were examined by GC-MS. Sulfur compounds dominated the volatiles of all systems and included mercaptoketones, furanthiols, and disulfides. The inosine monophosphate systems produced much lower quantities of volatiles than ribose phosphate or ribose systems. In the systems buffered with phosphate or phthalate buffers, both ribose and ribose phosphate systems gave similar quantities of sulfur volatiles. However, in the absence of buffer, the ribose system was relatively unreactive, especially for volatiles formed via the 2,3-enolization route in the Maillard reaction, where 4-hydroxy-5-methyl-3(2H)-furanone is a key intermediate. A number of keto-enol tautomerisms, which are known to be acid-base-catalyzed, occur in the 2,3-enolization route. This may explain the catalysis of the ribose systems by the buffers. In the ribose phosphate systems, however, Maillard mechanisms probably played a less important role, because ribose 5-phosphate readily dephosphorylated to give 4-hydroxy-5-methyl-3(2H)-furanone on heating and thus provided an easier route to aroma compounds than the Maillard reaction.

Cysteine↗