Hydrogen vs. electron transfer mechanisms in the chain decomposition of phenacyl bromides. Use of isotopic labeling as a mechanistic probe

1996 ◽  
Vol 74 (9) ◽  
pp. 1724-1730 ◽  
Author(s):  
Jocelyn Renaud ◽  
J. C. Scaiano
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Key Words ◽  
Hydrogen Transfer ◽  
Isotopic Labeling ◽  
Chain Reaction ◽  
Phenacyl Bromides ◽  
Mechanistic Probe ◽  
A Chain ◽  
Transfer Mechanisms

Ring-substituted α-bromoacetophenones react with alcohols in a chain reaction leading to the corresponding acetophenone, HBr, and the carbonyl compound from oxidation of the alcohol. Two different mechanisms, involving hydrogen or electron transfer by ketyl radicals, have been proposed in order to accommodate the unusual selectivities of these reactions. By studying the efficiency of isotope incorporation from deuterated alcohols, it has been possible to determine the relative contributions from both mechanisms. For example, electron transfer dominates in the case of 2-propanol, while hydrogen transfer is more important for methanol. The results demonstrate that ring substitution in the starting ketone is not a main contributing factor in the discrimination between the two mechanisms. The only parameter that seems to be playing a major role is the nature (reducing strength) of the ketyl radicals. Key words: dehydrobromination, charge transfer, isotope effect, ketyl radicals.

Uncovering alternate charge transfer mechanisms in Escherichia coli chemically functionalized with conjugated oligoelectrolytes

2014 ◽  
Vol 50 (60) ◽  
pp. 8223-8226 ◽  
Author(s):  
Victor Bochuan Wang ◽  
Natalia Yantara ◽  
Teck Ming Koh ◽  
Staffan Kjelleberg ◽  
Qichun Zhang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Electron Transfer ◽  
Charge Transfer ◽  
Extracellular Electron Transfer ◽  
Transfer Mechanisms

Conjugated oligoelectrolytes integrated in Escherichia coli have been proposed to induce release of electroactive cytosolic components, which contributes to extracellular electron transfer.

scholarly journals Quaternary Charge-Transfer Complex Enables Photoenzymatic In-termolecular Hydroalkylation of Olefins

2020 ◽  
Author(s):  
Claire Page ◽  
Simon Cooper ◽  
Jacob DeHovitz ◽  
Daniel G. Oblinsky ◽  
Kyle Biegasiewicz ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Active Site ◽  
Charge Transfer Complex ◽  
Hydrogen Atom Transfer ◽  
Radical Initiation ◽  
Bond Forming ◽  
Transfer Mechanisms ◽  
Protein Active Site ◽  
Unique Mechanism

Intermolecular C–C bond-forming reactions are underdeveloped transformations in the field of biocatalysis. Here we report a photoenzymatic intermolecular hydroalkylation of olefins catalyzed by flavin-dependent ‘ene’reductases. Radical initiation occurs via photoexcitation of a rare high-order enzyme-templated charge-transfer complex that forms between an alkene, 𝛼-chloroamide, and flavin hydroquinone. This unique mechanism ensures that radical formation only occurs when both substrates are present within the protein active site. This active site can control the radical terminating hydrogen atom transfer, enabling the synthesis of enantioenriched γ-stereogenic amides. This work highlights the potential for photoenzymatic catalysis to enable new biocatalytic transformations via previously unknown electron transfer mechanisms.

The role of acid–base equilibria in formal hydrogen transfer reactions: tryptophan radical repair by uric acid as a paradigmatic case

2017 ◽  
Vol 19 (23) ◽  
pp. 15296-15309 ◽  
Author(s):  
Leonardo Muñoz-Rugeles ◽  
Annia Galano ◽  
Juan Raúl Alvarez-Idaboy
Keyword(s):  
Electron Transfer ◽  
Uric Acid ◽  
Hydrogen Transfer ◽  
Transfer Reactions ◽  
Acid Base ◽  
Transfer Mechanisms ◽  
Hydrogen Transfer Reactions

The sequential proton gain electron transfer and proton electron sequential transfer mechanisms play the most important roles in tryptophan repair by uric acid.

Investigation of Dissociative Electron Transfer Mechanisms and Reactivity Patterns through Kinetic Amplification by a Chain Process

2000 ◽  
Vol 122 (23) ◽  
pp. 5623-5635 ◽  
Author(s):  
Cyrille Costentin ◽  
Philippe Hapiot ◽  
Maurice Médebielle ◽  
Jean-Michel Savéant
Keyword(s):  
Electron Transfer ◽  
Chain Process ◽  
Dissociative Electron Transfer ◽  
A Chain ◽  
Transfer Mechanisms

scholarly journals Disentangling the syntrophic electron transfer mechanisms of Candidatus geobacter eutrophica through electrochemical stimulation and machine learning

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Heyang Yuan ◽  
Xuehao Wang ◽  
Tzu-Yu Lin ◽  
Jinha Kim ◽  
Wen-Tso Liu
Keyword(s):  
Machine Learning ◽  
Electron Transfer ◽  
Hydrogen Transfer ◽  
Draft Genome ◽  
Extracellular Electron Transfer ◽  
Hydrogen Metabolism ◽  
Genetic Potential ◽  
Fermentative Bacteria ◽  
Genes Encoding ◽  
Transfer Mechanisms

AbstractInterspecies hydrogen transfer (IHT) and direct interspecies electron transfer (DIET) are two syntrophy models for methanogenesis. Their relative importance in methanogenic environments is still unclear. Our recent discovery of a novel species Candidatus Geobacter eutrophica with the genetic potential of IHT and DIET may serve as a model species to address this knowledge gap. To experimentally demonstrate its DIET ability, we performed electrochemical enrichment of Ca. G. eutrophica-dominating communities under 0 and 0.4 V vs. Ag/AgCl based on the presumption that DIET and extracellular electron transfer (EET) share similar metabolic pathways. After three batches of enrichment, Geobacter OTU650, which was phylogenetically close to Ca. G. eutrophica, was outcompeted in the control but remained abundant and active under electrochemical stimulation, indicating Ca. G. eutrophica’s EET ability. The high-quality draft genome further showed high phylogenomic similarity with Ca. G. eutrophica, and the genes encoding outer membrane cytochromes and enzymes for hydrogen metabolism were actively expressed. A Bayesian network was trained with the genes encoding enzymes for alcohol metabolism, hydrogen metabolism, EET, and methanogenesis from dominant fermentative bacteria, Geobacter, and Methanobacterium. Methane production could not be accurately predicted when the genes for IHT were in silico knocked out, inferring its more important role in methanogenesis. The genomics-enabled machine learning modeling approach can provide predictive insights into the importance of IHT and DIET.

The photochemistry of aqueous solutions of Tl(III) perchlorate

1970 ◽  
Vol 48 (19) ◽  
pp. 2955-2959 ◽  
Author(s):  
C. E. Burchill ◽  
W. H. Wolodarsky
Keyword(s):  
Charge Transfer ◽  
Quantum Yield ◽  
Flash Photolysis ◽  
Primary Process ◽  
Chain Reaction ◽  
Perchloric Acid Solution ◽  
Upper Limit ◽  
Aqueous Perchloric Acid ◽  
A Chain ◽  
A Charge

In deaerated aqueous perchloric acid solution Tl(III) is reduced and 2-propanol oxidized to acetone in equivalent yields via a chain reaction initiated by light of 2537 Å. Initiation is attributed to a charge-transfer-to-metal excitation followed by dissociation[Formula: see text]The formation of Tl(II) in the primary process is demonstrated by flash photolysis. An upper limit of 0.36 ± 0.07 is estimated for the primary quantum yield.

scholarly journals Quaternary Charge-Transfer Complex Enables Photoenzymatic In-termolecular Hydroalkylation of Olefins

2020 ◽  
Author(s):  
Claire Page ◽  
Simon Cooper ◽  
Jacob DeHovitz ◽  
Daniel G. Oblinsky ◽  
Kyle Biegasiewicz ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Active Site ◽  
Charge Transfer Complex ◽  
Hydrogen Atom Transfer ◽  
Radical Initiation ◽  
Bond Forming ◽  
Transfer Mechanisms ◽  
Protein Active Site ◽  
Unique Mechanism

Intermolecular C–C bond-forming reactions are underdeveloped transformations in the field of biocatalysis. Here we report a photoenzymatic intermolecular hydroalkylation of olefins catalyzed by flavin-dependent ‘ene’reductases. Radical initiation occurs via photoexcitation of a rare high-order enzyme-templated charge-transfer complex that forms between an alkene, 𝛼-chloroamide, and flavin hydroquinone. This unique mechanism ensures that radical formation only occurs when both substrates are present within the protein active site. This active site can control the radical terminating hydrogen atom transfer, enabling the synthesis of enantioenriched γ-stereogenic amides. This work highlights the potential for photoenzymatic catalysis to enable new biocatalytic transformations via previously unknown electron transfer mechanisms.

Observations on a Relationship between Steroid Metabolism and the Concentration of Plasma Fibrinogen

1963 ◽  
Vol 10 (02) ◽  
pp. 400-405 ◽  
Author(s):  
B. A Amundson ◽  
L. O Pilgeram
Keyword(s):  
Blood Coagulation ◽  
Methyl Ether ◽  
Broad Spectrum ◽  
Human Subjects ◽  
Plasma Fibrinogen ◽  
Steroid Metabolism ◽  
Specific Site ◽  
Chain Reaction ◽  
Normal Human ◽  
A Chain

SummaryEnovid (5 mg norethynodrel and 0.075 mg ethynylestradiol-3-methyl ether) therapy in young normal human subjects causes an increase in plasma fibrinogen of 32.4% (P >C 0.001). Consideration of this effect together with other effects of Enovid on the activity of specific blood coagulatory factors suggests that the steroids are exerting their effect at a specific site of the blood coagulation and/or fibrinolytic system. The broad spectrum of changes which are induced by the steroids may be attributed to a combination of a chain reaction and feed-back control.

scholarly journals Pathogenesis and Management of COVID-19

2021 ◽  
Vol 11 (2) ◽  
pp. 77-93
Author(s):  
Khalid O. Alfarouk ◽  
Sari T. S. AlHoufie ◽  
Samrein B. M. Ahmed ◽  
Mona Shabana ◽  
Ahmed Ahmed ◽  
...  
Keyword(s):  
Multiple Organ Failure ◽  
Human Body ◽  
Inflammatory Mediators ◽  
Expression Patterns ◽  
Multiple Organ ◽  
Cytokine Storm ◽  
Chain Reaction ◽  
Road Map ◽  
A Chain ◽  
Global War

COVID-19, occurring due to SARS-COV-2 infection, is the most recent pandemic disease that has led to three million deaths at the time of writing. A great deal of effort has been directed towards altering the virus trajectory and/or managing the interactions of the virus with its subsequent targets in the human body; these interactions can lead to a chain reaction-like state manifested by a cytokine storm and progress to multiple organ failure. During cytokine storms the ratio of pro-inflammatory to anti-inflammatory mediators is generally increased, which contributes to the instigation of hyper-inflammation and confers advantages to the virus. Because cytokine expression patterns fluctuate from one person to another and even within the same person from one time to another, we suggest a road map of COVID-19 management using an individual approach instead of focusing on the blockbuster process (one treatment for most people, if not all). Here, we highlight the biology of the virus, study the interaction between the virus and humans, and present potential pharmacological and non-pharmacological modulators that might contribute to the global war against SARS-COV-2. We suggest an algorithmic roadmap to manage COVID-19.

scholarly journals Modeling biofilms with dual extracellular electron transfer mechanisms

2013 ◽  
Vol 15 (44) ◽  
pp. 19262 ◽  
Author(s):  
Ryan Renslow ◽  
Jerome Babauta ◽  
Andrew Kuprat ◽  
Jim Schenk ◽  
Cornelius Ivory ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Extracellular Electron Transfer ◽  
Transfer Mechanisms
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