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"Sulfur compounds"
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The metabolite dimethylsulfoxonium propionate extends the marine organosulfur cycle
Algae produce massive amounts of dimethylsulfoniopropionate (DMSP), which fuel the organosulfur cycle
1
,
2
. On a global scale, several petagrams of this sulfur species are produced annually, thereby driving fundamental processes and the marine food web
1
. An important DMSP transformation product is dimethylsulfide, which can be either emitted to the atmosphere
3
,
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or oxidized to dimethylsulfoxide (DMSO) and other products
5
. Here we report the discovery of a structurally unusual metabolite, dimethylsulfoxonium propionate (DMSOP), that is synthesized by several DMSP-producing microalgae and marine bacteria. As with DMSP, DMSOP is a low-molecular-weight zwitterionic metabolite that carries both a positively and a negatively charged functional group. Isotope labelling studies demonstrate that DMSOP is produced from DMSP, and is readily metabolized to DMSO by marine bacteria. DMSOP was found in near nanomolar amounts in field samples and in algal culture media, and thus represents—to our knowledge—a previously undescribed biogenic source for DMSO in the marine environment. The estimated annual oceanic production of oxidized sulfur from this pathway is in the teragram range, similar to the calculated dimethylsulfide flux to the atmosphere
3
. This sulfoxonium metabolite is therefore a key metabolite of a previously undescribed pathway in the marine sulfur cycle. These findings highlight the importance of DMSOP in the marine organosulfur cycle.
A structurally unusual zwitterionic metabolite, dimethylsulfoxonium propionate (DMSOP), is synthesized by several dimethylsulfoniopropionate-producing microalgae and marine bacteria and is readily metabolized into dimethylsulfoxide by marine bacteria, expanding our knowledge of the marine organosulfur cycle.
Journal Article
Physiology, ecology and industrial applications of aroma formation in yeast
Abstract
Yeast cells are often employed in industrial fermentation processes for their ability to efficiently convert relatively high concentrations of sugars into ethanol and carbon dioxide. Additionally, fermenting yeast cells produce a wide range of other compounds, including various higher alcohols, carbonyl compounds, phenolic compounds, fatty acid derivatives and sulfur compounds. Interestingly, many of these secondary metabolites are volatile and have pungent aromas that are often vital for product quality. In this review, we summarize the different biochemical pathways underlying aroma production in yeast as well as the relevance of these compounds for industrial applications and the factors that influence their production during fermentation. Additionally, we discuss the different physiological and ecological roles of aroma-active metabolites, including recent findings that point at their role as signaling molecules and attractants for insect vectors.
This review explores the biochemical pathways leading to production of a wide array of aroma compounds, the various industrial applications that have been developed around use of aroma compounds, as well as the newly uncovered physiological and ecological roles the various compounds may play.
Journal Article
Hydrogen sulfide production during early yeast fermentation correlates with volatile sulfur compound biogenesis but not thiol release
Abstract
Yeasts undergo intensive metabolic changes during the early stages of fermentation. Previous reports suggest the early production of hydrogen sulfide (H2S) is associated with the release of a range of volatile sulfur compounds (VSCs), as well as the production of varietal thiol compounds 3-sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA) from six-carbon precursors, including (E)-hex-2-enal. In this study, we investigated the early H2S potential, VSCs/thiol output, and precursor metabolism of 11 commonly used laboratory and commercial Saccharomyces cerevisiae strains in chemically defined synthetic grape medium (SGM) within 12 h after inoculation. Considerable variability in early H2S potential was observed among the strains surveyed. Chemical profiling suggested that early H2S production correlates with the production of dimethyl disulfide, 2-mercaptoethanol, and diethyl sulfide, but not with 3SH or 3SHA. All strains were capable of metabolizing (E)-hex-2-enal, while the F15 strain showed significantly higher residue at 12 h. Early production of 3SH, but not 3SHA, can be detected in the presence of exogenous (E)-hex-2-enal and H2S. Therefore, the natural variability of early yeast H2S production contributes to the early output of selected VSCs, but the threshold of which is likely not high enough to contribute substantially to free varietal thiols in SGM.
Endogenous H2S produced during early fermentation by yeast correlates with volatile sulfur compound formation; however, these H2S concentrations are insufficient to result in varietal thiol production via the (E)-hex-2-enal pathway.
Journal Article
Natural Sulfur Compounds in Mineral Waters: Implications for Human Health and Disease
Natural sulfur compounds found in various mineral spring waters have attracted considerable interest due to their possible health benefits and healing qualities. Key substances such as hydrogen sulfide (H2S), sulfate (SO42−), and thiosulfate (S2O32−) are essential to numerous physiological functions. This overview delves into the biochemical pathways through which these sulfur compounds exert their influence, emphasizing their roles as antioxidants, anti-inflammatories, and detoxifying agents. Furthermore, it investigates the therapeutic promise of mineral waters rich in sulfur for various diseases like arthritis, skin ailments, and heart diseases. Emerging studies indicate that regular use or topical application of these waters could enhance health outcomes and aid in the prevention of a multitude of diseases. Nonetheless, additional research is required to clarify sulfur water’s mechanisms of action and to develop standardized protocols for their therapeutic applications. This descriptive review highlights the significance of integrating natural sulfur compounds into comprehensive health strategies and advocates for ongoing investigation into their advantages in medical contexts.
Journal Article
Covalent targeted radioligands potentiate radionuclide therapy
Targeted radionuclide therapy, in which radiopharmaceuticals deliver potent radionuclides to tumours for localized irradiation, has addressed unmet clinical needs and improved outcomes for patients with cancer
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,
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,
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–
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. A therapeutic radiopharmaceutical must achieve both sustainable tumour targeting and fast clearance from healthy tissue, which remains a major challenge
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,
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. A targeted ligation strategy that selectively fixes the radiopharmaceutical to the target protein in the tumour would be an ideal solution. Here we installed a sulfur (VI) fluoride exchange (SuFEx) chemistry-based linker on radiopharmaceuticals to prevent excessively fast tumour clearance. When the engineered radiopharmaceutical binds to the tumour-specific protein, the system undergoes a binding-to-ligation transition and readily conjugates to the tyrosine residues through the ‘click’ SuFEx reaction. The application of this strategy to a fibroblast activation protein (FAP) inhibitor (FAPI) triggered more than 80% covalent binding to the protein and almost no dissociation for six days. In mice, SuFEx-engineered FAPI showed 257% greater tumour uptake than did the original FAPI, and increased tumour retention by 13-fold. The uptake in healthy tissues was rapidly cleared. In a pilot imaging study, this strategy identified more tumour lesions in patients with cancer than did other methods. SuFEx-engineered FAPI also successfully achieved targeted β- and α-radionuclide therapy, causing nearly complete tumour regression in mice. Another SuFEx-engineered radioligand that targets prostate-specific membrane antigen (PSMA) also showed enhanced therapeutic efficacy. Considering the broad scope of proteins that can potentially be ligated to SuFEx warheads, it might be possible to adapt this strategy to other cancer targets.
Radiopharmaceuticals engineered with click chemistry to selectively bind to tumour-specific proteins can be used to successfully target tumour cells, boosting the pharmacokinetics of radionuclide therapy and improving tumour regression.
Journal Article
Tissue-Specific Accumulation of Sulfur Compounds and Saponins in Different Parts of Garlic Cloves from Purple and White Ecotypes
This study set out to determine the distribution of sulfur compounds and saponin metabolites in different parts of garlic cloves. Three fractions from purple and white garlic ecotypes were obtained: the tunic (SS), internal (IS) and external (ES) parts of the clove. Liquid Chromatography coupled to High Resolution Mass spectrometry (LC-HRMS), together with bioinformatics including Principal Component Analysis (PCA), Hierarchical Clustering (HCL) and correlation network analyses were carried out. Results showed that the distribution of these metabolites in the different parts of garlic bulbs was different for the purple and the white ecotypes, with the main difference being a slightly higher number of sulfur compounds in purple garlic. The SS fraction in purple garlic had a higher content of sulfur metabolites, while the ES in white garlic was more enriched by these compounds. The correlation network indicated that diallyl disulfide was the most relevant metabolite with regards to sulfur compound metabolism in garlic. The total number of saponins was almost 40-fold higher in purple garlic than in the white variety, with ES having the highest content. Interestingly, five saponins including desgalactotigonin-rhamnose, proto-desgalactotigonin, proto-desgalactotigonin-rhamnose, voghieroside D1, sativoside B1-rhamnose and sativoside R1 were exclusive to the purple variety. Data obtained from saponin analyses revealed a very different network between white and purple garlic, thus suggesting a very robust and tight coregulation of saponin metabolism in garlic. Findings in this study point to the possibility of using tunics from purple garlic in the food and medical industries, since it contains many functional compounds which can be exploited as ingredients.
Journal Article
Role of Sulfur Compounds in Vegetable and Mushroom Aroma
At the base of the food pyramid is vegetables, which should be consumed most often of all food products, especially in raw and unprocessed form. Vegetables and mushrooms are rich sources of bioactive compounds that can fulfill various functions in plants, starting from protection against herbivores and being natural insecticides to pro-health functions in human nutrition. Many of these compounds contain sulfur in their structure. From the point of view of food producers, it is extremely important to know that some of them have flavor properties. Volatile sulfur compounds are often potent odorants, and in many vegetables, belonging mainly to Brassicaeae and Allium (Amaryllidaceae), sulfur compounds determine their specific flavor. Interestingly, some of the pathways that form volatile sulfur compounds in vegetables are also found in selected edible mushrooms. The most important odor-active organosulfur compounds can be divided into isothiocyanates, nitriles, epithionitriles, thiols, sulfides, and polysulfides, as well as others, such as sulfur containing carbonyl compounds and esters, R-L-cysteine sulfoxides, and finally heterocyclic sulfur compounds found in shiitake mushrooms or truffles. This review paper summarizes their precursors and biosynthesis, as well as their sensory properties and changes in selected technological processes.
Journal Article
Sulfur metabolites in the pelagic ocean
Marine microorganisms play crucial roles in Earth’s element cycles through the production and consumption of organic matter. One of the elements whose fate is governed by microbial activities is sulfur, an essential constituent of biomass and a crucial player in climate processes. With sulfur already being well studied in the ocean in its inorganic forms, organic sulfur compounds are emerging as important chemical links between marine phytoplankton and bacteria. The high concentration of inorganic sulfur in seawater, which can readily be reduced by phytoplankton, provides a freely available source of sulfur for biomolecule synthesis. Mechanisms such as exudation and cell lysis release these phytoplankton-derived sulfur metabolites into seawater, from which they are rapidly assimilated by marine bacteria and archaea. Energy-limited bacteria use scavenged sulfur metabolites as substrates or for the synthesis of vitamins, cofactors, signalling compounds and antibiotics. In this Review, we examine the current knowledge of sulfur metabolites released into and taken up from the marine dissolved organic matter pool by microorganisms, and the ecological links facilitated by their diversity in structures, oxidation states and chemistry.
Journal Article
Chemical, carbon and sulfur isotopic compositions constrain the origin of Upper Carboniferous-Lower Triassic gases in eastern Sichuan Basin, SW China
Methane dominated gas is one of the cleanest energy resources; however, there is no direct method to determine its source rock. Natural gases produced from the eastern Sichuan Basin together with seismic data were studied for their sources and secondary alteration by thermochemical sulfate reduction (TSR). Our results demonstrate that Upper Permian to Lower Triassic (P
3
ch-T
1
f) gases in the surrounding of the Kaijiang-Liangping area show volatile organic sulfur compounds (VOSCs)
δ
34
S values close to those of the associated H
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S, and may have been altered by methane-dominated TSR, resulting in positive shift in methane
δ
13
C
1
values with increasing TSR extents. Other (or group 2) gases produced from the P
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ch-T
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f reservoirs from the southern area and the Upper Carboniferous to Middle Permian (C
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h-P
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q) from the eastern Sichuan Basin are not significantly changed by TSR, show similar
δ
34
S values between the kerogens and some VOSCs, and may have been derived from the Lower Silurian and Middle Permian source rocks. This study demonstrates a case for the first time showing the
δ
34
S values of VOSCs can be used as a tool for direct correlation between non-TSR altered gas and source rocks. Methane-dominated gas pools can be found using gas and source rock geochemistry combined with seismic data.
Journal Article