Author
Linda I. Vogt
Bio: Linda I. Vogt is an academic researcher from University of Saskatchewan. The author has contributed to research in topics: Absorption spectroscopy & Sulfur. The author has an hindex of 5, co-authored 10 publications receiving 48 citations.
Papers
More filters
TL;DR: It is concluded that 3,4-dimethylthiolanes may be a common motif in Allium chemistry and is in fact a known compound from garlic with a structure different from that proposed, namely, 2( E)-3-(methylsulfinyl)-2-pro penyl 2-propenyl disulfide.
Abstract: Stereoisomers of 5-(2-allylsulfinyl)-3,4-dimethylthiolane-2-ol, a family of 3,4-dimethylthiolanes of formula C9H16O2S2 we name ajothiolanes, were isolated from garlic (Allium sativum) macerates and characterized by a variety of analytical and spectroscopic techniques, including ultraperformance liquid chromatography (UPLC), direct analysis in real time-mass spectrometry (DART-MS), and liquid chromatography–tandem mass spectrometry (LC-MS/MS). Ajothiolanes were found to be spectroscopically identical to a family of previously described compounds named garlicnins B1–4 (C9H16O2S2), whose structures we demonstrate have been misassigned. 2D 13C–13C NMR incredible natural abundance double quantum transfer experiments (INADEQUATE) were used to disprove the claim of nine contiguous carbons in these compounds, while X-ray absorption spectroscopy (XAS) along with computational modeling was used to disprove the claim that these compounds were thiolanesulfenic acids. On the basis of the similarity of their NMR spectr...
18 citations
TL;DR: In this article, a complementary X-ray-based spectroscopy technique, sulfur Kβ Xray emission spectrograph (XES), was explored as a potential analytical tool for sulfur speciation in complex samples.
Abstract: Until recently, sulfur was known as a "spectroscopically silent" element because of a paucity of convenient spectroscopic probes suitable for in situ chemical speciation. In recent years the technique of sulfur K-edge X-ray absorption spectroscopy (XAS) has been used extensively in sulfur speciation in a variety of different fields. With an initial focus on reduced forms of organic sulfur, we have explored a complementary X-ray based spectroscopy - sulfur Kβ X-ray emission spectroscopy (XES) - as a potential analytical tool for sulfur speciation in complex samples. We compare and contrast the sensitivity of sulfur Kβ XES with that of sulfur K-edge XAS, and find differing sensitivities for the two techniques. In some cases an approach involving both sulfur K-edge XAS and sulfur Kβ XES may be a powerful combination for deducing sulfur speciation in samples containing complex mixtures.
13 citations
TL;DR: Polarized sulfur K-edge spectra of single crystals of dibenzyl disulfide are used to confirm the assignments of the major transitions in the spectrum and show that the spectra change in a systematic and predictable manner with the nature of the external group.
Abstract: Sulfur K-edge X-ray absorption spectroscopy increasingly is used as a tool to provide speciation information about the sulfur chemical form in complex samples, with applications ranging from fossil fuels to soil science to health research. As part of an ongoing program of systematic investigations of the factors that affect the variability of sulfur K near-edge spectra, we have examined the X-ray absorption spectra of a series of organic symmetric disulfide compounds. We have used polarized sulfur K-edge spectra of single crystals of dibenzyl disulfide to confirm the assignments of the major transitions in the spectrum as 1s → (S–S)σ* and 1s → (S–C)σ*. We also have examined the solution spectra of an extended series of disulfides and show that the spectra change in a systematic and predictable manner with the nature of the external group.
10 citations
TL;DR: It is shown that solutions of thiophene-2-thiol contain significant quantities of the thione tautomer, which may be the energetically preferred 5H-thiophene 2-thione or the more accessible 3H- Thiophene 3-thion, both of which are important in food chemistry.
Abstract: Thiophenes are the simplest aromatic sulfur-containing compounds; they are widespread in fossil fuels and a variety of natural products, and they have vital roles in determining characteristic aromas that are important in food chemistry. We used a combination of sulfur K-edge X-ray absorption spectroscopy and density functional theory to investigate the chemical bonding in the novel sulfur-containing heterocycle thiophene-2-thiol. We show that solutions of thiophene-2-thiol contain significant quantities of the thione tautomer, which may be the energetically preferred 5H-thiophene-2-thione or the more accessible 3H-thiophene-2-thione.
9 citations
TL;DR: It is shown that the sulfur K-edge near-edge X-ray absorption spectra of aliphatic organic sulfides comprise two intense transitions in the near- edge spectrum, which can be assigned as 1s → (S-C)σ* and 1s •π* transitions, which are found to change in a systematic manner in sterically hindered sulfides composed of four-, five- and six-membered rings.
Abstract: Organic sulfides, sometimes called thioethers, are important in a variety of materials with diverse roles in biology and the environment. They also contribute a significant proportion of the sulfur in fossil fuels. We have studied a range of aliphatic sulfides using a combination of sulfur K-edge X-ray absorption spectroscopy and density functional theory calculations. We show that the sulfur K-edge near-edge X-ray absorption spectra of aliphatic organic sulfides comprise two intense transitions in the near-edge spectrum, which can be assigned as 1s → (S–C)σ* and 1s → (S–C)π* transitions. These transitions are found to change in a systematic manner in sterically hindered sulfides composed of four-, five- and six-membered rings. Both the 1s → (S–C)σ* and 1s → (S–C)π* transitions are sensitive to the presence of strain in the C–S–C angle, shifting to lower values with more strained ring systems. Steric effects can give obtuse C–S–C angles, which are predicted to cause the two transitions to converge to the ...
9 citations
Cited by
More filters
TL;DR: This review summarizes the current understanding of the occurrence, biosynthesis, and alliinase-triggered chemical conversion of S-alk(en)ylcysteine sulfoxides in Allium plants as well as the impact of S -alk(e)yl Cysteine sulfur-containing compounds and their derivatives on medicinal, food, and agricultural sciences.
Abstract: S-Alk(en)ylcysteine sulfoxides are sulfur-containing natural products characteristic of the genus Allium. Both the flavor and medicinal properties of Allium plants are attributed to a wide variety of sulfur-containing compounds that are generated from S-alk(en)ylcysteine sulfoxides. Previous radiotracer experiments proposed that S-alk(en)ylcysteine sulfoxides are biosynthesized from glutathione. The recent identification of γ-glutamyl transpeptidases and a flavin-containing S-oxygenase involved in the biosynthesis of S-allylcysteine sulfoxide (alliin) in garlic (Allium sativum) provided insights into the reaction order of deglutamylation and S-oxygenation together with the localization of the biosynthesis, although the rest of the enzymes in the pathway still await discovery. In intact plants, S-alk(en)ylcysteine sulfoxides are stored in the cytosol of storage mesophyll cells. During tissue damage, the vacuolar enzyme alliinase contacts and hydrolyzes S-alk(en)ylcysteine sulfoxides to produce the corresponding sulfenic acids, which are further converted into various sulfur-containing bioactive compounds mainly via spontaneous reactions. The formed sulfur-containing compounds exhibit bioactivities related to pathogen defense, the prevention and alleviation of cancer and cardiovascular diseases, and neuroprotection. This review summarizes the current understanding of the occurrence, biosynthesis, and alliinase-triggered chemical conversion of S-alk(en)ylcysteine sulfoxides in Allium plants as well as the impact of S-alk(en)ylcysteine sulfoxides and their derivatives on medicinal, food, and agricultural sciences.
58 citations
TL;DR: X-ray absorption spectra and analysis that support the direct observation of two different thiyl species generated photochemically by X-ray irradiation and detected by sulfur K-edge X-Ray absorption spectroscopy are reported.
Abstract: Sulfur-based thiyl radicals are known to be involved in a wide range of chemical and biological processes, but they are often highly reactive, which makes them difficult to observe directly. We report herein X-ray absorption spectra and analysis that support the direct observation of two different thiyl species generated photochemically by X-ray irradiation. The thiyl radical sulfur K-edge X-ray absorption spectra of both species are characterized by a uniquely low energy transition at about 2465 eV, which occurs at a lower energy than any previously observed feature at the sulfur K-edge and corresponds to a 1s→3p transition to the singly occupied molecular orbital of the free radical. Our results constitute the first observation of substantial levels of thiyl radicals generated by X-ray irradiation and detected by sulfur K-edge X-ray absorption spectroscopy.
19 citations
TL;DR: To understand the effect of lipid degradation on Maillard formation of meaty flavors, initial reaction intermediates in model systems of glucose-glutathione with hexanal, (E)-2-heptenal, or (E,E-2,4-decadienal were identified by HPLC-MS and by NMR.
16 citations
TL;DR: In this article , the authors review the range of hard X-ray photon-in, photon-out experiments that are presently possible, and highlight their recent applications in catalysis research, and discuss the ongoing need for conventional XAS applications, either in standalone applications or in combination with more advanced approaches.
Abstract: X-ray spectroscopy has had a significant and continually growing impact on catalysis research for nearly 50 years. In particular, the ability to obtain element selective electronic and geometric structural information via the X-ray absorption (XAS) edge and extended X-ray absorption fine structure regions, respectively, has been a major asset for catalysis research. In the last two decades, the development of dedicated synchrotron-based X-ray emission spectrometers has greatly expanded the range of possible experiments, enabling both nonresonant and resonant X-ray emission spectroscopy experiments that can provide greater selectivity and more detailed electronic and structural information. Herein, we briefly review the range of hard X-ray photon-in, photon-out experiments that are presently possible, and highlight their recent applications in catalysis research. We also discuss the ongoing need for conventional XAS applications, either in standalone applications or in combination with more advanced approaches. The open opportunities and ongoing challenges for applying these methods, and ultimately for analyzing and interpreting the data, are also discussed.
14 citations
TL;DR: In this article, a complementary X-ray-based spectroscopy technique, sulfur Kβ Xray emission spectrograph (XES), was explored as a potential analytical tool for sulfur speciation in complex samples.
Abstract: Until recently, sulfur was known as a "spectroscopically silent" element because of a paucity of convenient spectroscopic probes suitable for in situ chemical speciation. In recent years the technique of sulfur K-edge X-ray absorption spectroscopy (XAS) has been used extensively in sulfur speciation in a variety of different fields. With an initial focus on reduced forms of organic sulfur, we have explored a complementary X-ray based spectroscopy - sulfur Kβ X-ray emission spectroscopy (XES) - as a potential analytical tool for sulfur speciation in complex samples. We compare and contrast the sensitivity of sulfur Kβ XES with that of sulfur K-edge XAS, and find differing sensitivities for the two techniques. In some cases an approach involving both sulfur K-edge XAS and sulfur Kβ XES may be a powerful combination for deducing sulfur speciation in samples containing complex mixtures.
13 citations