scholarly journals Hybrid radical-polar pathway for excision of ethylene from 2-oxoglutarate by an iron oxygenase

Science ◽  
2021 ◽  
pp. eabj4290
Author(s):  
Rachelle Copeland ◽  
Shengbin Zhou ◽  
Irene Schaperdoth ◽  
Tokufu Kent Shoda ◽  
J. Martin Bollinger ◽  
...  
Keyword(s):  
High Energy ◽  
Primary Metabolite ◽  
Hybrid Mechanism ◽  
Carboxyl Radical ◽  
Cis And Trans

Microbial ethylene-forming enzyme (EFE) converts the C3-C4 fragment of the ubiquitous primary metabolite, 2-oxoglutarate (2OG), to its namesake alkene product. This reaction is very different from the simple decarboxylation of 2OG to succinate promoted by related enzymes and has inspired disparate mechanistic hypotheses. We show that EFE produces stereochemically random (equal cis and trans) 1,2-[2H2]-ethylene from (3S,4R)-[2H2]-2OG, appends an oxygen from O2 upon the C1-derived (bi)carbonate, and can be diverted to ω-hydroxylated monoacid products by modifications to 2OG or the enzyme. These results implicate an unusual radical-polar hybrid mechanism involving iron(II)-coordinated acylperoxycarbonate and alkylcarbonate intermediates. The mechanism explains how EFE accesses a high-energy carboxyl radical to initiate its fragmentation cascade, and it hints at new capabilities of 2OG-dependent enzymes that may await discovery and exploitation.

Interactions gauches et chemins réactionnels. Etudes conformationnelles d'hydroxyalkyl-4 cyclohexènes contraints

1981 ◽  
Vol 59 (5) ◽  
pp. 859-864
Author(s):  
Jeanine Bouteiller-Prati ◽  
Jean-Claude Bouteiller ◽  
Jean-Pierre Aycard
Keyword(s):  
Free Energy ◽  
Reaction Path ◽  
High Energy ◽  
Nmr Study ◽  
Conformational Equilibria ◽  
The Stability ◽  
Cis And Trans ◽  
Conformational Free Energy

From J and δ values determined by the nmr study of alcohols obtained by addition of CH3Li and LiAlH4 to the exocyclic carbonyl of cis and trans 3-alkyl 4-carbomethoxy (or acetyl) cyclohexenes (alkyl = H, CH3, C(CH3)3), we have deduced the conformational free energy values (ΔG0X) of the CH(CH3)OH and C(CH3)2OH substituents (0.62 and 2.08 kcal mol−1 respectively) as well as the values for some related conformational equilibria. For transtert-butyl derivatives the stability of the diaxial conformer agrees with a reaction path involving high energy conformers.

A THEORETICAL STUDY OF UNSATURATED OLEFIN HYDROGENATION AND ISOMERIZATION ON Pd(111)

2008 ◽  
Vol 15 (03) ◽  
pp. 249-259 ◽  
Author(s):  
PATRICIA G. BELELLI ◽  
NORBERTO J. CASTELLANI
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Theoretical Study ◽  
High Energy ◽  
Slab Model ◽  
Functional Theory ◽  
Hydrogen Addition ◽  
High Energy Barrier ◽  
The Density Functional Theory ◽  
Cis And Trans

The addition of hydrogen to the carbon–carbon double bond of 2-butenes adsorbed on Pd (111) was studied within the density functional theory (DFT) and using a periodic slab model. For that purpose, the Horiuti–Polanyi mechanisms for both complete hydrogenation and isomerization were considered. The hydrogenation of cis and trans-2-butene to produce butane proceeds via the formation of eclipsed and staggered-2-butyl intermediates, respectively. In both cases, a relatively high energy barrier to produce the half-hydrogenated intermediate makes the first hydrogen addition the slowest step of the reaction. The competitive production of trans-2-butene from cis-2-butene requires the conversion from the eclipsed-2-butyl to the staggered-2-butyl isomer. As the corresponding energy barrier is relatively small and because the first of these isomers is less stable than the second, an easy conversion is predicted.

Ultrasensitive Measurement of Δ-9-tetrahydrocannabinol with a High Energy Dynode Detector and Electron-Capture Negative Chemical-Ionization Mass Spectrometry

1991 ◽  
Vol 37 (12) ◽  
pp. 2062-2068 ◽  
Author(s):  
Leslie M Shaw ◽  
Judith Edling-Owens ◽  
Richard Mattes
Keyword(s):  
Chemical Ionization ◽  
Limit Of Detection ◽  
Plasma Concentrations ◽  
High Energy ◽  
Detector System ◽  
Ionization Mass ◽  
Negative Chemical Ionization ◽  
Gas Chromatograph ◽  
Primary Metabolite ◽  
Ionization Mode

Abstract Plasma concentrations of Δ-9-tetrahydrocannabinol, the principal psychoactive cannabinoid in marijuana, decline to values substantially <1 μg/L within a few hours after a subject has smoked a marijuana cigarette. Using a single-quadrupole gas chromatograph-mass spectrometer (GC/MS) operated in the negative chemical-ionization mode and retrofitted with a High Energy Dynode detector system, we measured Δ-9-tetrahydrocannabinol and a primary metabolite, 11-nor-Δ-9-tetrahydrocannabinol-9-COOH. Using a trifluoroacetic anhydride derivatization procedure and the High Energy Dynode detector system, we improved by 6.25-fold the limit of detection for Δ-9-tetrahydrocannabinol in plasma over that obtained with the same GC/MS system without the new detector (80 vs 500 ng/L). The new detector system will thus permit further investigation of the post-distribution pharmacokinetics of Δ-9-tetrahydrocannabinol and detection of Δ-9-tetrahydrocannabinol in plasma for a longer time after ingestion of the drug in forensic cases. The High Energy Dynode detector system should be applicable to a wide variety of other GC/MS analyses that require significantly improved sensitivity.

The reactivity of the high-energy intermediates formed in the reactions of Group 13 metal atoms and aromatic alkenes

1998 ◽  
Vol 76 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Helen A Joly ◽  
Maria Kepes ◽  
Natalie Roy ◽  
Jason Prpic
Keyword(s):  
Metal Atom ◽  
High Energy ◽  
Spectroscopic Studies ◽  
Reductive Coupling ◽  
Group 13 ◽  
Metal Atoms ◽  
Metal Atom Reactions ◽  
Cis And Trans ◽  
Rotating Cryostat

Group 13 metal atoms were reacted with aromatic alkenes in a specialized metal atom reactor known as a "rotating cryostat." The nature of the intermediates formed was deduced from a GC-MS study of their hydrolysis and deuterolysis products. The product studies suggest that 2-phenylaluminacyclopropane, cis- and trans-3,4-diphenylaluminacyclopentane, and cis- and trans- 2,4-diphenylaluminacyclopentane are formed when Al atoms react with styrene, and 2-methyl-2-phenylaluminacyclopropane and 3,4-dimethyl- 3,4-diphenylaluminacyclopentane are formed when Al atoms react with α -methylstyrene. These findings are consistent with the radicals detected in the EPR spectroscopic studies of Al-alkene reaction mixtures prepared under similar conditions. Mechanisms for the formation of the organoaluminium intermediates are discussed. Analogous organogallium intermediates are formed when gallium atoms react with styrene. The reductive coupling of styrene did not occur when In and Tl atoms were used. Only trace quantities of phenylethane were detected in the hydrolyzed reaction mixture.Key words: Group 13 metal atoms, aluminium atoms, organoaluminium intermediates, metal atom reactions.

Formation of fluorescent excited states of liquid cis- and trans-decalin by high energy radiation

1983 ◽  
Vol 21 (1-2) ◽  
pp. 21-26 ◽  
Author(s):  
L.H. Luthjens ◽  
H.D.K. Codee ◽  
H.C. De Leng ◽  
A. Hummel ◽  
G. Beck
Keyword(s):  
Excited States ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Cis And Trans

The E-ring: interactions with plasma and implications for its evolution

1984 ◽  
Vol 75 ◽  
pp. 599-602
Author(s):  
T.V. Johnson ◽  
G.E. Morfill ◽  
E. Grun
Keyword(s):  
Time Scale ◽  
Particle Density ◽  
High Energy ◽  
Particle Removal ◽  
Density Region ◽  
Drag Forces ◽  
Orbit Evolution ◽  
History Of ◽  
Ring Particle ◽  
Ring Material

A number of lines of evidence suggest that the particles making up the E-ring are small, on the order of a few microns or less in size (Terrile and Tokunaga, 1980, BAAS; Pang et al., 1982 Saturn meeting; Tucson, AZ). This suggests that a variety of electromagnetic and plasma affects may be important in considering the history of such particles. We have shown (Morfill et al., 1982, J. Geophys. Res., in press) that plasma drags forces from the corotating plasma will rapidly evolve E-ring particle orbits to increasing distance from Saturn until a point is reached where radiation drag forces acting to decrease orbital radius balance this outward acceleration. This occurs at approximately Rhea's orbit, although the exact value is subject to many uncertainties. The time scale for plasma drag to move particles from Enceladus' orbit to the outer E-ring is ~104yr. A variety of effects also act to remove particles, primarily sputtering by both high energy charged particles (Cheng et al., 1982, J. Geophys. Res., in press) and corotating plasma (Morfill et al., 1982). The time scale for sputtering away one micron particles is also short, 102 - 10 yrs. Thus the detailed particle density profile in the E-ring is set by a competition between orbit evolution and particle removal. The high density region near Enceladus' orbit may result from the sputtering yeild of corotating ions being less than unity at this radius (e.g. Eviatar et al., 1982, Saturn meeting). In any case, an active source of E-ring material is required if the feature is not very ephemeral - Enceladus itself, with its geologically recent surface, appears still to be the best candidate for the ultimate source of E-ring material.

Sign in / Sign up

Export Citation Format

Share Document