Chemistry of singlet oxygen. 45. Mechanism of the photooxidation of sulfides

Liang, Ji-Yuan; Gu, Chee Liang; Kacher, Mark L.; Foote, Christopher S.

doi:10.1021/ja00352a033

Cited by 173 publications

(156 citation statements)

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“…For complex 3, this isomerization would be much more difficult due to the steric bulk of the four methyl groups, thus making it possible to observe complex 5. 1 The concentration dependence for the photooxidation of 6 (Scheme 2b) is consistent with several competing pathways. At high concentration, a small amount (2%) of mono sulfenate 7 is observed indicating that intermolecular oxygen transfer is one of the reactive channels during the reaction.…”

Section: Photooxidation Of Ni(ii)-and Pd(ii)-dithiolato Complexessupporting

confidence: 61%

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Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

Zhang

Hernandez

Selke

2008

Journal of Sulfur Chemistry

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A variety of reactions of singlet oxygen with metal-bound thiolates are described, and contrasted with the photooxidation of organic sulfides. Superficially, these two processes appear to involve similar mechanisms, but there are important differences: unlike the photooxidation of organic sulfides, the rate of the initial reaction of metal-thiolates with singlet oxygen (k t ) appears to be affected by protic solvents and acids. The nucleophilicity of the thiolate moiety is reduced by addition of acids or in protic solvents, leading to significantly lower k t values. The primary intermediate in the photooxidation of organic sulfides is a nucleophilic persulfoxide, which can be stabilized by protic solvents or by addition of acid. However, the primary intermediate in the photooxidation of metal thiolates cannot be trapped with phosphite, suggesting that it may be less nucleophilic than its organic counterpart. Support for this hypothesis is also derived from the rather modest (compared with organic sulfides) acceleration of the rate of product formation by addition of acid.

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Section: Photooxidation Of Ni(ii)-and Pd(ii)-dithiolato Complexessupporting

confidence: 61%

“…The reaction of singlet oxygen with organic sulfides proceeds via at least two transient intermediates (1)(2)(3)(4). A large amount of research has focused on the nature of these extremely unstable species, none of which has been directly observed.…”

Section: Introductionmentioning

confidence: 99%

Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

Zhang

Hernandez

Selke

2008

Journal of Sulfur Chemistry

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“…6) alkylsulfides react with oxygen in a metal-independent manner to produce a sulfoxide. It is thought that this sulfide oxidation proceeds through a sulfoperoxy radical or persulfoxide intermediate (18). Conceivably, such a reactive intermediate could initiate the type of radical process we have observed with PAP or decay with release of ROS.…”

Section: Discussionmentioning

confidence: 83%

“…4C). In contrast to the PBS buffer, an amyloid-derived signal did not appear in Hepes/PBN until [12][13][14][15][16][17][18][19][20][21][22][23][24] P35-25, 1825-35(scram), and BSA Spin Trapping. In a preliminary effort to assess the relationship between free radical production and peptide structure, we studied the reverse and scrambled analogues of ,B25-35, which are not neurotoxic (4).…”

mentioning

confidence: 99%

A model for beta-amyloid aggregation and neurotoxicity based on free radical generation by the peptide: relevance to Alzheimer disease.

Hensley

Carney

Mattson

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

1,024

718

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ABSTRACT-Amylold is a 39-to 43-amino-add neurotoxic peptide that aggregtes to form the core of Ahemer disease-sociated senile (amyloid) plaques. No EPR Spectrscopy and Spin Trapping. 8APs were solubilized to 1.0 mg/ml by addition of buffer [150 mM phosphatebuffered saline at pH 7.4 (PBS) or Hepes at pH 7.4] to lyophilized powder. BSA was solubilized similarly, to concentrations of 1-62 mg/ml. Buffer used for spin trapping contained 50 mM N-tert-butyl-a-phenylnitrone (PBN) (Sigma or Aldrich). In studies designed to inhibit putative metalcatalyzed reactions, the chelator deferoxamine mesylate or EDTA (Sigma) was dissolved to 10 mM in PBS/PBN prior to peptide addition. In a further attempt to nullify buffer-borne metals, PBS/PBN was stirred overnight with Chelex 100, a nonspecific metal-chelating agent.Peptide solutions were aliquoted into a 300-A4 aqueous quartz EPR flat cell that was subsequently sealed at both ends and immersed in a 3rC water bath for 0-135 hr and removed periodically for EPR analysis. EPR spectra were acquired on a Bruker (Billerica, MA) 300 EPR spectrometer equipped with computerized data acquisition software. Instrumental parameters were microwave power = 20 mW, modulation amplitude = 0.% G, gain = 1 x i1W, and conversion time =

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“…Solvent effects were simulated using the PCM model. In PES calculations, the following reaction steps were assumed following Foote's sulfide photooxidation mechanism [74], of which the first step corresponds to formation of a key intermediate persulfoxide, and the with another [Met -H] -leading to two sulfoxides.…”

Section: O 2 Concentrations In Solutionmentioning

confidence: 99%

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Liu

Yin

2015

J. Am. Soc. Mass Spectrom.

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Abstract. We report a reaction apparatus developed to monitor singlet oxygen ( 1 O 2 ) reactions in solution using on-line ESI mass spectrometry and spectroscopy measurements. 1O 2 was generated in the gas phase by the reaction of H 2 O 2 with Cl 2 , detected by its emission at 1270 nm, and bubbled into aqueous solution continuously. O 2 oxidation were monitored by UV-Vis absorption and positive/negative ESI mass spectra, and product structures were elucidated using collision-induced dissociation-tandem mass spectrometry. To suppress electrical discharge in negative ESI of aqueous solution, methanol was added to electrospray via in-spray solution mixing using theta-glass ESI emitters. Capitalizing on this apparatus, the reaction of 1 O 2 with methionine was investigated. We have identified methionine oxidation intermediates and products at different pH, and measured reaction rate constants.1 O 2 oxidation of methionine is mediated by persulfoxide in both acidic and basic solutions. Persulfoxide continues to react with another methionine, yielding methionine sulfoxide as end-product albeit with a much lower reaction rate in basic solution. Density functional theory was used to explore reaction potential energy surfaces and establish kinetic models, with solvation effects simulated using the polarized continuum model. Combined with our previous study of gas-phase methionine ions with 1 O 2 , evolution of methionine oxidation pathways at different ionization states and in different media is described.

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Chemistry of singlet oxygen. 45. Mechanism of the photooxidation of sulfides

Cited by 173 publications

References 0 publications

Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

A model for beta-amyloid aggregation and neurotoxicity based on free radical generation by the peptide: relevance to Alzheimer disease.

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

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Chemistry of singlet oxygen. 45. Mechanism of the photooxidation of sulfides

Cited by 173 publications

References 0 publications

Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

Photooxidation of metal-bound thiolates: reactivity of sulfur containing peroxidic intermediates

A model for beta-amyloid aggregation and neurotoxicity based on free radical generation by the peptide: relevance to Alzheimer disease.

Mechanistic and Kinetic Study of Singlet O2 Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

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Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry