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Hydrogen atom abstraction
About: Hydrogen atom abstraction is a research topic. Over the lifetime, 7059 publications have been published within this topic receiving 151781 citations.
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TL;DR: In this paper, the specific cleavage of N-Cα bonds on the peptide backbone to form the so-called "c" and "z + 2" products, which can be used for the rapid determination of protein amino-acid sequences, has been examined to clarify the mechanism(s) that occur during hydrogen abstraction induced by bombardment with 337-nm laser photons in matrix-assisted laser desorption/ionization (MALDI) method.
102 citations
TL;DR: Experimental and theoretical evidence is provided and an attractive mechanism for the role of ABLM in double-strand cleavage is proposed, which would generate a reactive Fe(IV)=O species, capable of a second DNA strand cleavage, as observed in vivo.
Abstract: Bleomycin (BLM), a glycopeptide antibiotic chemotherapy agent, is capable of single- and double-strand DNA damage. Activated bleomycin (ABLM), a low-spin FeIII−OOH complex, is the last intermediate detected prior to DNA cleavage following hydrogen-atom abstraction from the C-4‘ of a deoxyribose sugar moiety. The mechanism of this C−H bond cleavage reaction and the nature of the active oxidizing species are still open issues. We have used kinetic measurements in combination with density functional calculations to study the reactivity of ABLM and the mechanism of the initial attack on DNA. Circular dichroism spectroscopy was used to directly monitor the kinetics of the ABLM reaction. These experiments yield a deuterium isotope effect, kH/kD ≈ 3 for ABLM decay, indicating the involvement of a hydrogen atom in the rate-determining step. H-atom donors with relatively weak X−H bonds accelerate the reaction rate, establishing that ABLM is capable of hydrogen-atom abstraction. Density functional calculations were...
102 citations
TL;DR: The present results are consistent with the hypothesis that the appearance and structure of the transient radical mimic stages in the normal reaction pathway of ribonucleotide reductase, postulated to proceed via 3'-hydrogen abstraction and cation radical formation of the substrate nucleotide.
102 citations
TL;DR: The newly synthesized manganese(IV) complex having two hydroxide ligands, [Mn(Me(2)EBC)(2)(OH)(2)](PF(6))(2), serves as the prototypic example to address this issue, by investigating the difference in the hydrogen abstracting abilities of the Mn( IV)O and Mn(IV)-OH functional groups.
Abstract: Clarifying the difference in redox reactivity between the metal oxo and metal hydroxo moieties for the same redox active metal ion in identical structures and oxidation states, that is, Mn+═O and Mn+−OH, contributes to the understanding of nature’s choice between them (Mn+═O or Mn+−OH) as key active intermediates in redox enzymes and electron transfer enzymes, and provides a basis for the design of synthetic oxidation catalysts. The newly synthesized manganese(IV) complex having two hydroxide ligands, [Mn(Me2EBC)2(OH)2](PF6)2, serves as the prototypic example to address this issue, by investigating the difference in the hydrogen abstracting abilities of the MnIV═O and MnIV−OH functional groups. Independent thermodynamic evaluations of the O−H bond dissociation energies (BDEOH) for the corresponding reduction products, MnIII−OH and MnIII−OH2, reveal very similar oxidizing power for MnIV═O and MnIV−OH (83 vs 84.3 kcal/mol). Experimental tests showed that hydrogen abstraction proceeds at reasonable rates for...
102 citations
TL;DR: The first example of aryl radical formation via the visible light-mediated decarboxylation of aRYl carboxylic acids using photoredox catalysis is presented.
Abstract: Herein we present the first example of aryl radical formation via the visible light-mediated decarboxylation of aryl carboxylic acids using photoredox catalysis. This method constitutes a mild protocol for the decarboxylation of cheap and abundant aryl carboxylic acids and tolerates both electron-rich substrates and those lacking ortho-substitution. The in situ formation of an acyl hypobromite is proposed to prevent unproductive hydrogen atom abstraction and trapping of the intermediate aroyloxy radical, enabling mild decarboxylation.
102 citations