Oxidative Events Research Articles

The role of oxygen in the functioning of the Earth system: past, present and future

In the Solar System, the coming into existence of a peculiar, fully developed atmosphere on Earth was determined by the ‘Great Oxidation Event’ at the turn of the Proterozoic and Palaeozoic. Within about 600 million years, there were large changes in oxygen concentrations in this atmosphere, ranging from 15 to 35 per cent, having been determined by a combination of cosmic-climatic, tectonic-volcanic and biological phenomena. A particular environmental change occurred at the beginning of the 19th century, as a result of the overlap of the end of the natural Little Ice Age and the beginning of anthropogenic warming of the ‘industrial revolution’. According to the author, the rate of human impact on environmental changes is estimated at about 15 per cent. The appearance of mankind brought new changes in the natural environment, including the oxygen content of the air. The current scale of anthropogenic impact justifies the introduction of a new time slice in the planet’s history - the Anthropocene. The functioning of civilisation is conditioned by meeting energy needs, to be implemented by creating a system of energy generators, among which the heat of the Earth should be an important component. The energy generated from this inexhaustible and cost-free geo-resource should be seen as the most ecological among all currently used energy carriers.

Features of the Kinetics of the Fenton Reaction

The Fenton reaction is of considerable interest due to the fact that it can be applied in chemical, biochemical and biomedical research. The Fenton reaction makes it possible to estimate the content of hydroperoxides. Hydroperoxides in a large number of cases are the trace that remains after the occurrence of redox reactions. To perform such studies, it is necessary to know the characteristics of the reaction at different ratios between the concentrations of hydroperoxides and ferrous iron. The reaction yield is determined by registering chemiluminescence. The number of oxidation events of ferrous iron N(Fe2+ ® Fe3+) in the Fenton reaction is calculated in this work for the cases [Fe2+] > [H2 O2 ] and [Fe2+] < [H2 O2 ] at concentrations of Fe2+ and H2 O2 ranging from 10-3 to 10-7 mol/L. It is shown that the peroxide concentration can be unambiguously determined only for the case [Fe2+] > [H2 O2 ]. In the case of [Fe2+] < [H2 O2 ], due to a strong decrease in the reaction rate, it is not always possible to register the total chemiluminescence yield. The kinetics of the formation of luminous products in the Fenton reaction after the introduction of luminol has been calculated. Conditions are considered when chemiluminescence with luminol is proportional to the concentration of hydroperoxides. The considered features of the Fenton reaction must be taken into account when performing specific research work.

Ruthenium terpyridine Phenol-Substituent supports PCET and semiquinone-like behavior

Ligands play a central role in dictating the electronic properties of metal complexes to which they are coordinated. A fundamental understanding of changes in ligand properties can be used as design principles for more efficient catalysts. Designing ligands that have multiple protonation states that will change the properties of the coordination complex would be useful as potential ways of controlling catalysis, for example, as an on/off switch where one redox state exists below thermodynamic potential and another exists above. Thus, phenol moieties built into strongly coordinating ligands, like that of tpyPhOH (4′-(4-hydroxyphenyl)-2,2′:6′,2′'-terpyridine) may provide such a handle. Herein, we report the electrochemical and spectral characterization, and the crystallographic and computational analysis of two ruthenium analogs: [Ru(tpy)(tpyPhOH)](PF6)2 and [Ru(tpyPhOH)2](PF6)2 (tpy = 2,2′:6′,2′'-terpyridine). Cyclic voltammetry and differential pulse voltammetry indicate that two redox events occur, one of which is pH independent and we hypothesize that these follow an electrochemical-chemical-electrochemical (ECE) mechanism. XRD results of the ruthenium complexes’ protonated forms are generally consistent with expected bond lengths and angles and are in agreement with computational modeling. The properties are compared to a previously reported analog that contains the –OH group directly connected to terpyridine, [Ru(tpyOH)2](PF6)2, where tpyOH is 4′-hydroxy-2,2′:6′,2′'-terpyridine, with some intriguing differences. Overall, these data indicate that the phenyl-substituent decouples the phenol such that it behaves both as an electron withdrawing substituent and a location for a ligand centered oxidation event to occur.

Pangenomic Analysis of Nucleo-Cytoplasmic Large DNA Viruses. I: The Phylogenetic Distribution of Conserved Oxygen-Dependent Enzymes Reveals a Capture-Gene Process

The Nucleo-Cytoplasmic Large DNA Viruses (NCLDVs) infect a wide range of eukaryotic species, including amoeba, algae, fish, amphibia, arthropods, birds, and mammals. This group of viruses has linear or circular double-stranded DNA genomes whose size spans approximately one order of magnitude, from 100 to 2500 kbp. The ultimate origin of this peculiar group of viruses remains an open issue. Some have argued that NCLDVs’ origin may lie in a bacteriophage ancestor that increased its genome size by subsequent recruitment of eukaryotic and bacterial genes. Others have suggested that NCLDVs families originated from cells that underwent an irreversible process of genome reduction. However, the hypothesis that a number of NCLDVs sequences have been recruited from the host genomes has been largely ignored. In the present work, we have performed pangenomic analyses of each of the seven known NCLDVs families. We show that these families' core- and shell genes have cellular homologs, supporting possible escaping-gene events as part of its evolution. Furthermore, the detection of sequences that belong to two protein families (small chain ribonucleotide reductase and Erv1/Air) and to one superfamily [2OG-Fe(II) oxygenases] that are for distribution in all NCLDVs core and shell clusters encoding for oxygen-dependent enzymes suggests that the highly conserved core these viruses originated after the Proterozoic Great Oxidation Event that transformed the terrestrial atmosphere 2.4–2.3 Ga ago.

Cys-regulation: oxidized CHK1 controls cross-compartment circuit of chemoresistance

In a recent study published in Cell, Zhang et al. integrate genome-wide CRISPRi screening with cysteine chemoproteomics to identify functionally relevant oxidation events associated with the cellular response to chemotherapy. This work uncovered checkpoint kinase 1 (CHK1) as a nuclear reactive oxygen species (ROS) sensor that mediates chemoresistance through the suppression of mitochondrial protein synthesis.

Marble trace element and C-O isotope geochemistry of the Paleoproterozoic Jingshan Group, North China: Insights into BIF formation during the Lomagundi-Jatuli Event

The North China Craton, one of the oldest continental blocks in the world, comprises Paleoproterozoic metamorphic sedimentary formations that record the effects of multiple major events in early Earth history, including the Great Oxidation Event (GOE) and its consequent Lomagundi-Jatuli carbon isotope event (LJE). The lack of focused research on the geological record of LJE-equivalent rocks of the Jiaodong Peninsula, Shandong Province, eastern China, has hindered our understanding of the Precambrian atmospheric oxygen evolution recorded by rocks of the North China Craton. This paper considers carbon and oxygen isotope and trace element geochemical data recovered from marble deposits of the Paleoproterozoic Jingshan Group (2.20–1.90 Ga) of the Jiaolai Basin. The investigated strata display a pronounced positive δ13CV-PDB excursion greater than 4.2 ‰. δ13CV-PDB and δ18OV-SMOW values range from −3.7 ‰ to 5.4 ‰ and 4.5 ‰ to 18.7 ‰, respectively. Positive co-variance of carbon and oxygen isotope values of the analyzed Jingshan Group samples is interpreted to reflect the effects of metamorphism and water–rock reactions. Marble deposits of the Jingshan Group experienced recrystallization, metamorphism, and silicification resulting in strong decarbonation. High amphibolite facies metamorphism may have reduced δ13CV-PDB by 3 ‰ to 5 ‰. Thus, estimated original sedimentary δ13CV-PDB values of as great as +8.4 ‰ suggest the existence of a strong positive anomaly that may reflect the global Lomagundi-Jatuli event. Rare earth and other trace element geochemical results of the present study suggest that banded iron formation (BIF) deposits associated with the Jingshan Group marble formed in a redox stratified ocean in the Jiaolai Basin dominated by ferruginous conditions. Moreover, our results suggest that positive carbon isotope anomaly associated with the LJE is largely constrained to sediment deposited in shallow and coastal marine environments.

Direct Regioselective Dehydrogenation of α-Substituted Cyclic Ketones.

We disclose a highly regioselective, catalytic one-step dehydrogenation of α-substituted cyclic ketones in the presence of 2,3-dichlorobenzo-5,6-dicyano-1,4-benzoquinone (DDQ). The high regioselectivity originates from a phosphoric acid-catalyzed enolization, selectively affording the thermodynamically preferred enol, followed by the subsequent oxidation event. Our method provides reliable access to several α-aryl and α-alkyl substituted α,β-unsaturated ketones.

Direkte Regioselektive Dehydrierung von α‐Substituierten Cyclischen Ketonen

AbstractWir berichten über eine hochregioselektive, katalytische einstufige Dehydrierung von α‐substituierten cyclischen Ketonen in Gegenwart von 2,3‐Dichlorbenzo‐5,6‐dicyano‐1,4‐benzochinon (DDQ). Die exzellente Regioselektivität beruht auf einer Phosphorsäure‐katalysierten Enolisierung, die selektiv das thermodynamisch bevorzugte Enol liefert. Die anschließende Oxidation ermöglicht einen zuverlässigen Zugang zu mehreren α‐Aryl‐ und α‐Alkyl‐substituierten α,β‐ungesättigten Ketonen.

Contact between water vapor and silicate surface causes abiotic formation of reactive oxygen species in an anoxic atmosphere

Spontaneous generation of reactive oxygen species (ROS) in aqueous microdroplets or at a water vapor-silicate interface is a new source of redox chemistry. However, such generation occurs with difficulty in liquid water having a large ionic strength. We report that ROS is spontaneously produced when water vapor contacts hydrogen-bonded hydroxyl groups on a silicate surface. The evolution of hydrogen-bonded species such as hydroxyl groups was investigated by using two-dimensional, time-resolved FT-IR spectroscopy. The participation of water vapor in ROS generation is confirmed by investigating the reaction of D2O vapor and hydroxyl groups on a silicate surface. We propose a reaction pathway for ROS generation based on the change of the hydrogen-bonding network and corresponding electron transfer onto the silicate surface in the water vapor-solid contact process. Our observations suggest that ROS production from water vapor-silicate contact electrification could have contributed to oxidation during the Archean Eon before the Great Oxidation Event.

Chemical Signatures of Ge in Magnetite of Wugang BIF, China

Magnetite is a representative ore mineral found in various deposits. The trace element composition of ore deposits is controlled by several physiochemical factors such as temperature, pressure, and oxygen or sulfur fugacity. The chemical behavior of Germanium (Ge) is distinct in different environments. Consequently, the composition patterns of Ge in magnetite can be used to infer the provenance conditions. This study focuses on the Ge composition in magnetite from the Wugang banded iron formation (BIF) to understand the compositional characteristics of BIF sources and reconstruct of origin of Wugang BIF. The magnetite of the Wugang BIF has a porous texture, indicating high dissolution-reprecipitation processes and easy fluid infiltration, owing to its increased effective permeability. The Ge in the magnetite of the Wugang BIF was incorporated into iron hydroxide from the hydrothermal fluid and seawater during precipitation. The formation period of the Wugang BIF was consistent with significant oxidation events that led to the oxidation of ferrous ions in the Precambrian Ocean. Certain processes promote the chemisorption and coprecipitation of Ge into iron hydroxides or oxides.

RBOHF activates stomatal immunity by modulating both reactive oxygen species and apoplastic pH dynamics in Arabidopsis.

Stomatal defences are important for plants to prevent pathogen entry and further colonisation of leaves. Apoplastic reactive oxygen species (ROS) generated by NADPH oxidases and apoplastic peroxidases play an important role in activating stomatal closure upon perception of bacteria. However, downstream events, particularly the factors influencing cytosolic hydrogen peroxide (H2 O2 ) signatures in guard cells are poorly understood. We used the H2 O2 sensor roGFP2-Orp1 and a ROS-specific fluorescein probe to study intracellular oxidative events during stomatal immune response using Arabidopsis mutants involved in the apoplastic ROS burst. Surprisingly, the NADPH oxidase mutant rbohF showed over-oxidation of roGFP2-Orp1 by a pathogen-associated molecular pattern (PAMP) in guard cells. However, stomatal closure was not tightly correlated with high roGFP2-Orp1 oxidation. In contrast, RBOHF was necessary for PAMP-mediated ROS production measured by a fluorescein-based probe in guard cells. Unlike previous reports, the rbohF mutant, but not rbohD, was impaired in PAMP-triggered stomatal closure resulting in defects in stomatal defences against bacteria. Interestingly, RBOHF also participated in PAMP-induced apoplastic alkalinisation. The rbohF mutants were also partly impaired in H2 O2 -mediated stomatal closure at 100 μm while higher H2 O2 concentration up to 1 mm did not promote stomatal closure in wild-type plants. Our results provide novel insights on the interplay between apoplastic and cytosolic ROS dynamics and highlight the importance of RBOHF in plant immunity.

The evolution and spread of sulfur cycling enzymes reflect the redox state of the early Earth.

The biogeochemical sulfur cycle plays a central role in fueling microbial metabolisms, regulating the Earth's redox state, and affecting climate. However, geochemical reconstructions of the ancient sulfur cycle are confounded by ambiguous isotopic signals. We use phylogenetic reconciliation to ascertain the timing of ancient sulfur cycling gene events across the tree of life. Our results suggest that metabolisms using sulfide oxidation emerged in the Archean, but those involving thiosulfate emerged only after the Great Oxidation Event. Our data reveal that observed geochemical signatures resulted not from the expansion of a single type of organism but were instead associated with genomic innovation across the biosphere. Moreover, our results provide the first indication of organic sulfur cycling from the Mid-Proterozoic onwards, with implications for climate regulation and atmospheric biosignatures. Overall, our results provide insights into how the biological sulfur cycle evolved in tandem with the redox state of the early Earth.

Genesis of the Longwanggou iron deposit in the Yudongzi Complex, South China: Implications for the redox state of seawater at the onset of the Great oxidation Event

Banded iron formations (BIFs) deposited during the onset of the Great Oxidation Event (GOE) are crucial to understanding fundamental changes in the redox conditions of Earth’s surface environments, however, they are poorly understood in South China. Here, we investigate the petrographic, geochronological, and geochemical characteristics of a set of continuous magnetite quartzite samples from a drill core through the Longwanggou iron deposit in the Yudongzi Complex, South China. These magnetite quartzite samples exhibit diagnostic features of BIFs — 1) they comprise alternating magnetite and quartz layers at the centimeter–millimeter scales, 2) they are dominantly composed of SiO2 + Fe2O3T (87.8–95.8 wt%, average = 91.4 wt%), and 3) they are characterized by shale-normalized rare earth elements plus yttrium patterns similar to seawater. The maximum depositional age of the Longwanggou BIF (i.e., magnetite quartzite) is constrained to ca. 2.49 Ga based on U–Pb dating of detrital zircon grains from chlorite schist that is intercalated with the BIF. The metamorphic complex of the Yudongzi Complex that hosts the BIF was intruded by ca. 2.5–2.45 Ga granitoid gneisses, indicating that the BIF must be older than 2.45 Gyr. Accordingly, the depositional age of the Longwanggou BIF is constrained to ca. 2.49–2.45 Ga, coincident with the onset of the GOE. The positive Eu anomalies (1.3–4.2; average = 2.2) that occur throughout BIF samples suggest a continuous flux of submarine, high-temperature hydrothermal fluids to the ocean at the Archean–Proterozoic boundary. Based on elemental mass balance, the proportion of submarine, high-temperature hydrothermal fluids that contributed to the deposition of the BIF was less than 0.1%. Unlike BIFs deposited during the GOE, the Longwanggou BIF samples lack negative Ce anomalies, suggesting that the water column in which the BIF was deposited was at least locally anoxic during the onset of the GOE. Identification of the Longwanggou BIF provides new constraints for the Precambrian evolution of South China and lays the foundation for further study of the environmental changes at the Archean–Proterozoic boundary.

Mineral evolution facilitated Earth’s oxidation

Oxygenation events remarkably altered the distribution, diversity, and abundance of minerals on Earth’s surface. However, the causality in the opposite direction—the influence of mineral evolution on atmospheric oxygen levels—has rarely been explored. Here I propose that mineral evolution might have led Earth’s oxygen cycle to lose stability, facilitating oxygenation events in deep time. First, I introduce a conceptual model for the system of organic matter and minerals and investigate their interactions via a probabilistic approach. Second, in light of the theoretical results, I suggest that the evolution of iron and clay minerals likely had an underappreciated relevance to the Great Oxidation Event and Neoproterozoic Oxidation Event, respectively. Finally, I use the parameter values estimated from observations in modern environments as benchmarks to test these speculations. This study provides a minimalistic theoretical framework illustrating the possible influence of mineral evolution on Earth’s oxygen cycle over geologic time.

Red or green: Overprinting of the climatic signal in Miocene sediments, South China Sea (IODP Expedition 368, Site U1502)

AbstractSedimentary beds of alternating red and green colour are commonly interpreted to reflect orbitally‐forced cyclic climatic, syn‐depositional conditions, although colour changes caused by post‐depositional fluids are also documented. Results from IODP Hole U1502A marine sediments in the South China Sea exemplify post‐depositional reducing fluid–rock interactions that locally changed the sediment colour from red to green. Petrographic, rock magnetic and paleomagnetic data on cores show that the red colouration originates from an early, basin‐wide, pervasive diagenetic oxidation event (forming haematite), whereas the green colouration results from subsequent fluid‐driven reduction (forming pyrrhotite‐magnetite). The dense sulfidic stockwork in the basaltic basement underlying these sediments was the likely source of reducing fluids. Drilling deep holes into marine basin basements can thus provide useful information on fluid transfer from the basement to the overlying sedimentary layers.

Untargeted Metabolomics Identifies Biomarkers for MCADD Neonates in Dried Blood Spots.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited mitochondrial metabolic disease of fatty acid β-oxidation, especially in newborns. MCADD is clinically diagnosed using Newborn Bloodspot Screening (NBS) and genetic testing. Still, these methods have limitations, such as false negatives or positives in NBS and the variants of uncertain significance in genetic testing. Thus, complementary diagnostic approaches for MCADD are needed. Recently, untargeted metabolomics has been proposed as a diagnostic approach for inherited metabolic diseases (IMDs) due to its ability to detect a wide range of metabolic alterations. We performed an untargeted metabolic profiling of dried blood spots (DBS) from MCADD newborns (n = 14) and healthy controls (n = 14) to discover potential metabolic biomarkers/pathways associated with MCADD. Extracted metabolites from DBS samples were analyzed using UPLC-QToF-MS for untargeted metabolomics analyses. Multivariate and univariate analyses were used to analyze the metabolomics data, and pathway and biomarker analyses were also performed on the significantly identified endogenous metabolites. The MCADD newborns had 1034 significantly dysregulated metabolites compared to healthy newborns (moderated t-test, no correction, p-value ≤ 0.05, FC 1.5). A total of 23 endogenous metabolites were up-regulated, while 84 endogenous metabolites were down-regulated. Pathway analyses showed phenylalanine, tyrosine, and tryptophan biosynthesis as the most affected pathways. Potential metabolic biomarkers for MCADD were PGP (a21:0/PG/F1alpha) and glutathione, with an area under the curve (AUC) of 0.949 and 0.898, respectively. PGP (a21:0/PG/F1alpha) was the first oxidized lipid in the top 15 biomarker list affected by MCADD. Additionally, glutathione was chosen to indicate oxidative stress events that could happen during fatty acid oxidation defects. Our findings suggest that MCADD newborns may have oxidative stress events as signs of the disease. However, further validations of these biomarkers are needed in future studies to ensure their accuracy and reliability as complementary markers with established MCADD markers for clinical diagnosis.

Morin hydrate suppresses lipoteichoic acid-induced oxidative stress-mediated inflammatory events in macrophages via augmenting Nrf2/HO-1 and antioxidant defense molecules

Objectives Oxidative stress induces chronic inflammatory diseases in aerobic organisms, and antioxidants from plants represent an efficient strategy to prevent this condition. Morin hydrate (MH), a bioactive flavonoid, has a wide range of pharmacological properties, including anti-inflammatory and anti-oxidant. This study evaluated the protective effects of MH on lipoteichoic acid (LTA)-induced inflammation in RAW 264.7 macrophages by testing the main oxidative and inflammatory biomarkers and also investigating the molecular pathways involved. Methods The antioxidant and anti-inflammatory effects of MH were evaluated in a cell-free system and RAW264.7 cells. Quantitative real-time PCR (RT-qPCR) and assay kits were used to measure the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) mRNA, as well as the activity of antioxidant enzymes. The effects of MH on LTA-induced inducible nitric oxide synthase (iNOS), IL-1β, and TNF-α mRNA and protein expression were also evaluated by RT-qPCR and Western blotting. Results MH reduced DPPH and ABTS radicals in a cell-free system and LTA-induced ROS and NO production in RAW264.7 cells. MH upregulated Nrf2 and HO-1 mRNA expression and reversed LTA-mediated reduction of antioxidant enzymes, at a high concentration of 20 µM pretreated cells. MH also effectively attenuated LTA-induced iNOS, IL-1β, and TNF-α mRNA and protein expression, and these effects were reversed by ML385. Conclusions The study found that the Nrf2/HO-1 played role in the inhibition of LTA-induced oxidative stress in macrophages by MH. This study may consider to be a promising induced macrophage-targeted strategy via regulating anti-oxidative defense to control inflammatory-related disease.

Stability of protein particle based Pickering emulsions in various environments: Review on strategies to inhibit coalescence and oxidation.

The emerging research interests in fabrication of protein particles as soft-particle emulsifiers show the prospective potential of using protein particles in novel poly-phase dispersing food systems. This review first provides a comprehensive summary and analysis on the dominant role of key physicochemical properties of protein particles including wettability, morphology, surface charge and protein concentration on their emulsifying abilities to construct Pickering emulsions. It was found that the constructed emulsions showed high sensitivity to changes in pH, ionic strength and temperature (thermal and freeze-thaw treatment). Moreover, oxidation remains as a challenge for protein particle based Pickering emulsions during prolonged storage, reducing their acceptance in food products. Current strategies for improving the stability of these emulsions to variable aqueous conditions and variable temperatures, and restricting oxidation event are summarized. In summary, an "ideal" protein particle-based Pickering emulsion system is proposed, encompassing aspects of interfacial property, emulsion network and texture, and antioxidant enrichment, thus promoting industrial translation into novel food and nutraceutical products.

Molybdenum in basalt-hosted seafloor hydrothermal systems: Experimental, theoretical, and field sampling approaches

Seafloor hydrothermal vents represent potential sources of Mo and other biologically relevant transition metals to the global ocean, complementing continental runoff. Here, we use a combination of experimental, theoretical, and field-sampling approaches to investigate the behavior of Mo in basalt-hosted seafloor hydrothermal systems to provide insight into the processes controlling Mo concentrations in hydrothermal fluids and to derive estimates of vent fluid Mo concentrations and fluxes. Results of this study demonstrate that reaction fluids generated from 350 °C, 500 bar hydrothermal basalt alteration experiments contain 775–801 nmol/kg Mo and are thus comparable to a recently collected time series of natural seafloor vent fluids that contained 200–220 nmol/kg Mo at 302 °C and 29–30 nmol/kg at 281–282 °C (Evans et al., 2023). Synchrotron-based analyses of experimentally altered basalt produced in this study and additional natural samples of altered oceanic crust originally collected from Pito Deep Rift reveal the presence of Mo-rich particles consistent with trace molybdenite. Comparisons of Mo:Cu ratios in natural vent fluids and near-vent sediment trap samples from Main Endeavour Field indicate that vent fluid Mo is readily incorporated into buoyant plume particles and advected out of the near-vent field, analogous to previous mass balance studies of Cu in this region.Thermodynamic calculations of molybdenite solubility in the context of mineral-buffered hydrothermal fluids and comparisons with natural and experimental hydrothermal fluids suggest that high-temperature vent fluids contain 30–1500 nmol/kg Mo. While a minor component of the modern Mo budget, hydrothermal Mo fluxes are estimated to have constituted 0.3–200× the contemporaneous continental weathering fluxes prior to the ∼2.4 Ga ago “Great Oxidation Event” and widespread oxidative continental weathering. Overall, identification of hydrothermal vents as a source of Mo-rich plume particles with potential for dispersal into the wider marine environment has significant implications for hypotheses regarding the co-evolution of Life and Earth’s environments, specifically the form and availability of Mo in anoxic Archean-Eon oceans, where Mo-dependent enzymatic pathways are thought to have emerged and subsequently evolved.

Acyl Azolium-Photoredox-Enabled Synthesis of β-Keto Sulfides.

α-Heteroatom functionalization is a key strategy for C-C bond formation in organic synthesis, as exemplified by the addition of a nucleophile to electrophilic functional groups, such as iminium ions; oxocarbenium ions; and their sulfur analogues, sulfenium ions. We envisioned a photoredox-enabled radical Pummerer-type reaction realized through the single-electron oxidation of a sulfide. Following this oxidative event, α-deprotonation would afford α-thio radicals that participate in radical-radical coupling reactions with azolium-bound ketyl radicals, thereby accessing a commonly proposed mechanistic intermediate of the radical-radical coupling en route to functionalized additive Pummerer products. This system provides a complementary synthetic approach to highly functionalized sulfurous products, including modification of methionine residues in peptides, and beckons further exploration in C-C bond formations previously limited in the standard two-electron process.