Sulfane sulfur
Publisher Summary
This chapter discusses the determination of sulfane sulfur. The term, “sulfane,” designates sulfur atoms that are bonded covalently in chains only to other sulfur atoms. Sulfane atoms are somewhat unstable, readily oxidizing in air, reducing with thiols, and decomposing slowly in dilute acid to release free sulfur. Most sulfane-containing compounds are stable in alkali, but polythionates decompose in strong alkali to form various products including thiosulfate, sulfite, sulfate, and elemental sulfur. Sulfane sulfurs are identified by susceptibility to cyanolysis. The chapter presents the cyanolysis methods used for determination of sulfane sulfur. The first method is cold cyanolysis of thiosulfate that is done if cupric ion is added as a catalyst. Persulfides, polysulfides, aryl thiosulfonates, and higher polythionates react quantitatively with cyanide in alkaline solution, at temperatures between 10° and ambient room temperature. This is known as “cold cyanolysis.” The next method is hot cyanolysis that provides for analysis of alkyl thiosulfonates, thiosulfate, and trithionate, which react too slowly for cold cyanolysis. The third method described in the chapter is cold cyanolysis in presence of cupric ion. Catalysis by cupric ion is necessary for the quantitative conversion of thiosulfate to thiocyanate.
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Cited by (193)
Analysis and characterization of sulfane sulfur
2024, Analytical BiochemistryIn 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.
Differences in nonoxidative sulfur metabolism between normal human breast MCF-12A and adenocarcinoma MCF-7 cell lines
2024, Analytical BiochemistryRecent studies have revealed the role of endogenous hydrogen sulfide (H2S) in the development of breast cancer. The capacity of cells to generate H2S and the activity and expression of the main enzymes (cystathionine beta synthase; CBS, cystathionase γ-lyase; CGL, 3-mercaptopyruvate sulfurtransferase; MPST and thiosulfate sulfurtransferase; TST) involved in H2S metabolism were analyzed using an in vitro model of a non-tumourigenic breast cell line (MCF-12A) and a human breast adenocarcinoma cell line (MCF-7). In both cell lines, MPST, CGL, and TST expression was confirmed at the mRNA (RT-PCR) and the protein (Western Blot) level, while CBS expression was detected only in MCF-7 cells. Elevated levels of GSH, sulfane sulfur and increased CBS and TST activity were presented in the MCF-7 compared to the MCF-12A cells. It appears that cysteine might be mainly a substrate for GSH synthesis in breast adenocarcinoma. Increased capacity of the cells to generate H2S was shown for MCF-12A compared to MCF-7 cell line. Results suggest an important function of CBS in H2S metabolism in breast adenocarcinoma. The presented work may contribute to further research on new therapeutic possibilities for breast cancer - one of the most frequently diagnosed types of cancer among women.
Using the sulfide-oxidizing bacterium Geobacillus thermodenitrificans to restrict H<inf>2</inf>S release during chicken manure composting
2024, Journal of Environmental ManagementHydrogen sulfide (H2S) is a toxic gas massively released during chicken manure composting. Diminishing its release requires efficient and low cost methods. In recent years, heterotrophic bacteria capable of rapid H2S oxidation have been discovered but their applications in environmental improvement are rarely reported. Herein, we investigated H2S oxidation activity of a heterotrophic thermophilic bacterium Geobacillus thermodenitrificans DSM465, which contains a H2S oxidation pathway composed by sulfide:quinone oxidoreductase (SQR) and persulfide dioxygenase (PDO). This strain rapidly oxidized H2S to sulfane sulfur and thiosulfate. The oxidation rate reached 5.73 μmol min−1·g−1 of cell dry weight. We used G. thermodenitrificans DSM465 to restrict H2S release during chicken manure composting. The H2S emission during composting process reduced by 27.5% and sulfate content in the final compost increased by 34.4%. In addition, this strain prolonged the high temperature phase by 7 days. Thus, using G. thermodenitrificans DSM465 to control H2S release was an efficient and economic method. This study provided a new strategy for making waste composting environmental friendly and shed light on perspective applications of heterotrophic H2S oxidation bacteria in environmental improvements.
Disulfides form persulfides at alkaline pH leading to potential overestimations in the cold cyanolysis method
2023, Free Radical Biology and MedicineIt is well established that proteins and peptides can release sulfur under alkaline treatment, mainly through the β-elimination of disulfides with the concomitant formation of persulfides and dehydroalanine derivatives. In this study, we evaluated the formation of glutathione persulfide (GSSH/GSS-) by exposure of glutathione disulfide (GSSG) to alkaline conditions. The kinetics of the reaction between GSSG and HO- was investigated by UV–Vis absorbance, reaction with 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB), and cold cyanolysis, obtaining an apparent second-order rate constant of ∼10-3 M-1 s-1 at 25 °C. The formation of GSSH and the dehydroalanine derivative was confirmed by HPLC and/or mass spectrometry. However, the mixtures did not equilibrate in a timescale of hours, and additional species, including thiol and diverse sulfane sulfur compounds were also formed, probably through further reactions of the persulfide. Cold cyanolysis is frequently used to quantify persulfides, since it measures sulfane sulfur. This method involves a step in which the sample to be analyzed is incubated with cyanide at alkaline pH. When cold cyanolysis was applied to samples containing GSSG, sulfane sulfur products that were not present in the original sample were measured. Thus, our results reveal the risk of overestimating the amount of sulfane sulfur compounds in samples that contain disulfides due to their decay to persulfides and other sulfane sulfur compounds at alkaline pH. Overall, our study highlights that the β-elimination of disulfides is a potential source of persulfides, although we do not recommend the preparation of GSSH from incubation of GSSG in alkali. Our study also highlights the importance of being cautious when doing and interpreting cold cyanolysis experiments.
Increased intracellular persulfide levels attenuate HlyU-mediated hemolysin transcriptional activation in Vibrio cholerae
2023, Journal of Biological ChemistryThe vertebrate host's immune system and resident commensal bacteria deploy a range of highly reactive small molecules that provide a barrier against infections by microbial pathogens. Gut pathogens, such as Vibrio cholerae, sense and respond to these stressors by modulating the expression of exotoxins that are crucial for colonization. Here, we employ mass spectrometry–based profiling, metabolomics, expression assays, and biophysical approaches to show that transcriptional activation of the hemolysin gene hlyA in V. cholerae is regulated by intracellular forms of sulfur with sulfur–sulfur bonds, termed reactive sulfur species (RSS). We first present a comprehensive sequence similarity network analysis of the arsenic repressor superfamily of transcriptional regulators, where RSS and hydrogen peroxide sensors segregate into distinct clusters of sequences. We show that HlyU, transcriptional activator of hlyA in V. cholerae, belongs to the RSS-sensing cluster and readily reacts with organic persulfides, showing no reactivity or DNA dissociation following treatment with glutathione disulfide or hydrogen peroxide. Surprisingly, in V. cholerae cell cultures, both sulfide and peroxide treatment downregulate HlyU-dependent transcriptional activation of hlyA. However, RSS metabolite profiling shows that both sulfide and peroxide treatment raise the endogenous inorganic sulfide and disulfide levels to a similar extent, accounting for this crosstalk, and confirming that V. cholerae attenuates HlyU-mediated activation of hlyA in a specific response to intracellular RSS. These findings provide new evidence that gut pathogens may harness RSS-sensing as an evolutionary adaptation that allows them to overcome the gut inflammatory response by modulating the expression of exotoxins.
Prodrugs of sulfide and persulfide species: Implications in their different pharmacological activities
2023, Current Opinion in Chemical BiologyReactive sulfur species (RSS), such as H2S, hydrogen polysulfide (H2Sn, n ≥ 2), and hydropersulfides (RSSnH, n ≥ 1), are known to mediate diverse signaling pathways and possess a plethora of exciting therapeutic opportunities. Historically, due to the rapid inter-conversion among those species in vivo, the biological differences of distinct sulfur species were often overlooked. These species were considered to enrich the global sulfur pool in almost an equal fashion. However, advancement in this field has revealed that sulfur species at different oxidation states result in different pharmacological effects including scavenging reactive oxygen species (ROS), activating ion channels, and exhibiting analgesic effects. Here, we summarize recent advances in studying the biological and pharmacological differences of distinct sulfur species; discuss this phenomenon from the view of chemical properties and sulfur signaling pathways; and lay out a roadmap to transforming such new knowledge into general principles in developing sulfur-based therapeutics.