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Cells Jan 2023Oxysterols, derived from cholesterol oxidation, are formed either by autoxidation, via enzymes, or by both processes [...].
Oxysterols, derived from cholesterol oxidation, are formed either by autoxidation, via enzymes, or by both processes [...].
Topics: Oxysterols; Cholesterol; Oxidation-Reduction
PubMed: 36672175
DOI: 10.3390/cells12020241 -
Journal of the American Chemical Society May 2022We describe the first total synthesis of complex aspidosperma alkaloids (-)-voacinol and (-)-voacandimine C via a late-stage C7-methylenation strategy inspired by a...
We describe the first total synthesis of complex aspidosperma alkaloids (-)-voacinol and (-)-voacandimine C via a late-stage C7-methylenation strategy inspired by a biogenetic hypothesis. We envisioned rapid access to these natural alkaloids from a common, symmetrical precursor assembled by methylenation of a D-ring-oxidized variant of the structurally related natural product (-)-deoxoapodine. Chemoselective N9-oxidation of a pentacyclic deoxoapodine precursor enabled the synthesis of the corresponding hexacyclic C8-aminonitrile. Stereocontrolled methylenation of a C8-enamine derivative of deoxoapodine, accessed by ionization of the C8-aminonitrile, afforded a symmetrical dodecacyclic bisaminonitrile as a versatile precursor to these bisindole alkaloids. The final-stage, biosynthesis-inspired, controlled reductive opening of the oxolane substructures of this dodecacyclic intermediate provided a unified approach to (-)-voacinol and (-)-voacandimine C, while direct reduction of the same intermediate afforded the structurally related (-)-methylenebisdeoxoapodine.
Topics: Alkaloids; Biological Products; Cyclization; Oxidation-Reduction; Stereoisomerism
PubMed: 35543738
DOI: 10.1021/jacs.2c03057 -
Chemistry (Weinheim An Der Bergstrasse,... Oct 2021Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several...
Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron-transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron-transfer mediator were used for the substrate-selective dehydrogenation reaction of various N-heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good-to-excellent yields.
Topics: Biomimetics; Catalysis; Ferrous Compounds; Iron; Oxidation-Reduction
PubMed: 34324754
DOI: 10.1002/chem.202102483 -
Molecules (Basel, Switzerland) Jul 2022A Knoevenagel based redox-reaction promoted by intramolecular phosphine sources is presented for the first time. The influence of different diketones, aldehydes, bases...
A Knoevenagel based redox-reaction promoted by intramolecular phosphine sources is presented for the first time. The influence of different diketones, aldehydes, bases and acids was investigated. The effects of different substituents were evaluated based on their electronical influence on the diketone structure. With the obtained results a mechanism is proposed, giving information about transition states formed during the reaction, which can lead to different products. This type of an internal redox transformation with a phosphine oxide moiety remaining in the molecule after the redox reaction represents a new type of reaction.
Topics: Catalysis; Ketones; Oxidation-Reduction; Phosphines; Stereoisomerism
PubMed: 35956825
DOI: 10.3390/molecules27154875 -
Redox Biology Apr 2020
Topics: Biology; Oxidation-Reduction; Sex Characteristics
PubMed: 32279981
DOI: 10.1016/j.redox.2020.101533 -
International Journal of Molecular... Nov 2023Oxidative stress is frequently described as the balance between the production of reactive species (including oxygen and nitrogen) in biological systems and the ability...
Oxidative stress is frequently described as the balance between the production of reactive species (including oxygen and nitrogen) in biological systems and the ability of the latter to defend itself through the sophisticated antioxidant machinery [...].
Topics: Reactive Oxygen Species; Oxidative Stress; Oxidation-Reduction; Antioxidants
PubMed: 37959000
DOI: 10.3390/ijms242116018 -
Current Opinion in Structural Biology Jun 2022Complex I is one of the major respiratory complexes, conserved from bacteria to mammals. It oxidises NADH, reduces quinone and pumps protons across the membrane, thus... (Review)
Review
Complex I is one of the major respiratory complexes, conserved from bacteria to mammals. It oxidises NADH, reduces quinone and pumps protons across the membrane, thus playing a central role in the oxidative energy metabolism. In this review we discuss our current state of understanding the structure of complex I from various species of mammals, plants, fungi, and bacteria, as well as of several complex I-related proteins. By comparing the structural evidence from these systems in different redox states and data from mutagenesis and molecular simulations, we formulate the mechanisms of electron transfer and proton pumping and explain how they are conformationally and electrostatically coupled. Finally, we discuss the structural basis of the deactivation phenomenon in mammalian complex I.
Topics: Animals; Electron Transport; Electron Transport Complex I; Energy Metabolism; Mammals; Oxidation-Reduction; Protons
PubMed: 35316665
DOI: 10.1016/j.sbi.2022.102350 -
Food Chemistry Feb 2023In mayonnaise, lipid and protein oxidation are closely related and the interplay between them is critical for understanding the chemical shelf-life stability of...
In mayonnaise, lipid and protein oxidation are closely related and the interplay between them is critical for understanding the chemical shelf-life stability of mayonnaise. This is in particular the case for comprehending the role of low-density lipoprotein (LDL) particles acting as a main emulsifier. Here, we monitored oxidation and the concomitant aggregation of LDLs by bright-field light microscopy and cryogenic transmission electron microscopy. We further probed the formation of protein radicals and protein oxidation by imaging the accumulation of a water-soluble fluorescent spin trap and protein autofluorescence. The effect of variation of pH and addition of EDTA on the accumulation of the spin trap validated that protein radicals were induced by lipid radicals. Our data suggests two main pathways of oxidative protein radical formation in LDL particles: (1) at the droplet interface, induced by lipid free radicals formed in oil droplets, and (2) in the continuous phase induced by an independent LDL-specific mechanism.
Topics: Free Radicals; Oxidation-Reduction; Lipoproteins, LDL; Condiments; Lipid Peroxidation
PubMed: 36303379
DOI: 10.1016/j.foodchem.2022.134417 -
Angewandte Chemie (International Ed. in... Apr 2022The concurrent operation of chemical and biocatalytic reactions in one pot is still a challenging task, and, in particular for chemical photocatalysts, examples besides...
The concurrent operation of chemical and biocatalytic reactions in one pot is still a challenging task, and, in particular for chemical photocatalysts, examples besides simple cofactor recycling systems are rare. However, especially due to the complementary chemistry that the two fields of catalysis promote, their combination in one pot has the potential to unlock intriguing, unprecedented overall reactivities. Herein we demonstrate a concurrent biocatalytic reduction and photocatalytic oxidation process. Specifically, the enantioselective biocatalytic sulfoxide reduction using (S)-selective methionine sulfoxide reductases was coupled to an unselective light-dependent sulfoxidation. Protochlorophyllide was established as a new green photocatalyst for the sulfoxidation. Overall, a cyclic deracemization process to produce nonracemic sulfoxides was achieved and the target compounds were obtained with excellent conversions (up to 91 %) and superb optical purity (>99 % ee).
Topics: Oxidation-Reduction; Sulfoxides
PubMed: 35188997
DOI: 10.1002/anie.202117103 -
Molecules (Basel, Switzerland) Oct 2022Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1'-dimethanolferrocene and...
Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1'-dimethanolferrocene and potassium ferrocyanide. Electrochemical responses were examined after different oxidation treatments, then simulated and interpreted using the Kissa 1D software and existing models. Our experiments indicate that a crude carbon fiber behaves as an assembly of sites with different electrochemical reactivities. In such case, the Butler-Volmer law is not appropriate to describe the electron transfer kinetics because of the large created overpotential. Oxidation of the fiber erases the effect by increasing the kinetics of the electron transfer probably by a homogenization and increase of the reactivity on all the fiber. Additionally, analysis of the signal shows the large influence of the convection that affects the electrochemical response even at moderate scan rates (typically below 0.1-0.2 V s).
Topics: Carbon; Carbon Fiber; Electron Transport; Microelectrodes; Oxidation-Reduction
PubMed: 36235121
DOI: 10.3390/molecules27196584