Electron Transfer from Thioethers

Glass, Richard S.; Hojjatie, Massoud; Petsom, Amorn; Wilson, George S.; Göbl, Manfred; Mahling, Sabine; Asmus, K.‐D.

doi:10.1080/03086648508073384

Cited by 14 publications

(14 citation statements)

References 32 publications

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“…As reported previously, , the oxidation of the alcohols containing the thioether functionality leads to a radical species which exists in acid−base equilibrium, as shown in reaction 8. The acidic forms of the ( • S−O) radicals formed from 3-MTP and 3,3‘-DHP absorb at λ max = 390 nm with ε's of ≈1000 and 1450 M -1 cm -1 .…”

Section: Resultssupporting

confidence: 56%

Mechanism of One-Electron Oxidation of β-, γ-, and δ-Hydroxyalkyl Sulfides. Catalysis through Intramolecular Proton Transfer and Sulfur−Oxygen Bond Formation

et al. 1997

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The mechanism of photoinduced electron transfer between sulfur-containing alcohols and the 4-carboxybenzophenone (CB) triplet state in aqueous solution was investigated using laser flash photolysis and steady-state photolysis techniques. Bimolecular rate constants for quenching of the CB triplet state by five hydroxyalkyl sulfides, 2-(methylthio)ethanol (2-MTE), 2,2‘-dihydroxydiethyl sulfide (2,2‘-DHE), 3-(methylthio)propanol (3-MTP), 3,3‘-dihydroxydipropyl sulfide (3,3‘-DHP), and 4-(methylthio)butanol (4-MTB), with varying numbers of OH groups and varying locations with respect to the sulfur atom, were determined to be in the range (3.3−4.8) × 109 M-1 s-1 for neutral solutions. The intermediates identified were the CB ketyl radical anion (CB•-), the CB ketyl radical (CBH•), and intermolecularly (S∴S)-bonded radical cations. An additional absorption band at approximately 400 nm in the transient spectra for some of the hydroxyalkyl sulfides was assigned to the intramolecularly (•S−O)-bonded species (only for hydroxyalkyl sulfides which could adopt a five-membered ring structure). The spectra of appropriate (S∴S)+ and (•S−O) intermediates for the hydroxyalkyl sulfides were determined from complementary pulse radiolysis studies in acid and neutral aqueous solutions of the hydroxyalkyl sulfides, respectively. The observation of ketyl radical anions and intermolecular (S∴S)-bonded radical cations of the hydroxyalkyl sulfides was direct evidence for the participation of electron transfer in the mechanism of quenching. Quantum yields of formation of intermediates from flash photolysis experiments and quantum yields of formaldehyde formation from the steady-state measurements were determined. The values of these quantum yields indicated that the diffusion apart (escape of the radical ions) of the charge-transfer complex, formed as a primary photochemical step, is a minor photochemical pathway (with a contribution of ∼5−25% depending on the numbers of OH groups). Competing processes of proton transfer and back electron transfer within the CT complex gave significant contributions to these yields. Detailed mechanisms for the CB-sensitized photooxidation of sulfur-containing alcohols are proposed, discussed, and compared with that for the •OH-induced oxidation. One striking feature of the mechanisms is that there is a catalytic influence of neighboring groups on the radical reaction pathways during one-electron oxidation of the hydroxyalkyl sulfides in comparison to comparable reactions of nonsubstituted alkyl sulfides. Support for the mechanisms came in part from an analysis of observed solvent isotope effects on radical quantum yields.

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Section: Resultssupporting

confidence: 56%

Mechanism of One-Electron Oxidation of β-, γ-, and δ-Hydroxyalkyl Sulfides. Catalysis through Intramolecular Proton Transfer and Sulfur−Oxygen Bond Formation

et al. 1997

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“…38,39 In the helical C-terminus of βAP 1-40, the stabilization of oxidized Met 35 through association with the CdO group of the peptide bond C-terminal to Ile 31 may be possible, as the ca. 3.6 Å average S-O distance between Met 35 and Ile 31 -CdO in the native sequence 40 is close to the sum of the van der Waals radii of the two atoms. 41 Our recent molecular modeling results 42 confirmed a "privileged" conformation of β-amyloid peptide congeners containing the R-helical C-terminal sequence of βAP- (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) where structural and dynamic properties can promote the formation and stabilization of MetS •+ .…”

Section: Introductionmentioning

confidence: 66%

“…3.6 Å average S-O distance between Met 35 and Ile 31 -CdO in the native sequence 40 is close to the sum of the van der Waals radii of the two atoms. 41 Our recent molecular modeling results 42 confirmed a "privileged" conformation of β-amyloid peptide congeners containing the R-helical C-terminal sequence of βAP- (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) where structural and dynamic properties can promote the formation and stabilization of MetS •+ . The tendency to stabilize MetS •+ in the form of an S-O bond may explain the tendency of the native βAP1-40 to reduce Cu II , 42,43 generate free radicals, and induce protein oxidation.…”

Section: Introductionmentioning

confidence: 66%

“…40 To obtain an initial structure of 2i •+ the structure of βAP1-40 was truncated to βAP30-37, then all residues except Met 35 were mutated to Gly. Initially, the βAP-like secondary structure of 2i •+ was preserved by "freezing" of the internal coordinates of the atoms of the peptide backbone (except that belonging to the Met 35 and Ile 31 Gly •+ , 2i (1,16)…”

Section: Radicals Derived From N-acetyl-l-methionine Amide (2e) and N...mentioning

confidence: 99%

“…For example, the electrochemical oxidation of dialkyl sulfides showed lower peak potentials when appended with neighboring carboxylate and alcohol groups. 19,[31][32][33] Met oxidation is important during conditions of biological oxidative stress. 9,[34][35][36][37] Specifically, the oxidation of Met 35 in β-amyloid peptides (βAP) 1-40 or 1-42, the major constituents of senile plaques in Alzheimer's disease, has been associated with part of the neurotoxicity of these sequences.…”

Section: Introductionmentioning

confidence: 99%

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Computational Characterization of Sulfur−Oxygen Three-Electron-Bonded Radicals in Methionine and Methionine-Containing Peptides: Important Intermediates in One-Electron Oxidation Processes

2003

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Density functional theory and semiempirical methods were employed to characterize the structure and properties of sulfur-oxygen-bonded radical cations formed during the one-electron oxidation of various organic sulfides and methionine-containing peptides. In general, all of the examined sulfur-oxygen bonds can be described as two-center, three-electron-bonded systems. The usefulness of approximate computational approaches (SCC-DFTB, AM1 and PM3) for the reliable description of three-electron-bonded species was examined.

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Dications from Cyclic Polythioethers

Fujihara

Furukawa

1990

Sulfur-Centered Reactive Intermediates in Chemistry and Biology

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Electron Transfer from Thioethers

Cited by 14 publications

References 32 publications

Mechanism of One-Electron Oxidation of β-, γ-, and δ-Hydroxyalkyl Sulfides. Catalysis through Intramolecular Proton Transfer and Sulfur−Oxygen Bond Formation

Mechanism of One-Electron Oxidation of β-, γ-, and δ-Hydroxyalkyl Sulfides. Catalysis through Intramolecular Proton Transfer and Sulfur−Oxygen Bond Formation

Computational Characterization of Sulfur−Oxygen Three-Electron-Bonded Radicals in Methionine and Methionine-Containing Peptides: Important Intermediates in One-Electron Oxidation Processes

Dications from Cyclic Polythioethers

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