Photooxidation of methionine and related compounds

Cohen, Saul G.; Ojanpera, Salme

doi:10.1021/ja00852a079

Cited by 55 publications

(42 citation statements)

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“…Abiotic, oxidative incorporation of NH 3 into DOM has been observed in other systems, including the incorporation of NH 3 into triglycerides via a photochemically mediated process (Kieber et al 1997). Aldehydes and ketoacids, products of the photooxidation of humic substances, also readily form imines from NH 3 and DPA, which can hydrolyze abiotically, releasing NH 4 + gradually (Cohen & Ojanpera 1975). Ammonia also appears to react with keto and quinone groups in humic substances, in a process associated with oxidation, and is incorporated into biologically unavailable forms, such as pyrrole and indole N (Thorn & Mikita 1992).…”

Section: Photochemically Mediated Loss Of Nh 4 + In Groundwatersmentioning

confidence: 95%

Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters

Koopmans¹,

Bronk²

2002

Aquat. Microb. Ecol.

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Recent studies have shown that in a number of humic-rich surface waters in North America, NH 4 + is released when dissolved organic matter (DOM) is exposed to sunlight. However, photochemical NH 4 + production has not been observed in all surface waters, and factors that contribute to it are not well understood. We hypothesized that the presence or absence of NH 4 + photoproduction may be affected by the light exposure history of DOM. The present study was undertaken to determine whether DOM from surficial groundwaters, with minimal light exposure history, would produce labile nitrogen (N) photoproducts more consistently. In this study, estuarine surface waters and surficial groundwaters, collected just adjacent to estuaries in Georgia and South Carolina, USA, were exposed to sunlight to quantify the photochemical production of NH 4 + , dissolved primary amines (DPA), and NO 2 -. The photoproduction of NH 4 + was observed in 4 of 5 irradiated estuarine surface water samples but in only 2 of 13 groundwater samples. In contrast, NH 4 + concentrations decreased in 5 of 13 groundwater samples when exposed to sunlight. The results indicate that a small amount of NH 4 + may be lost from waters in which groundwater-derived DOM is first exposed to sunlight. No consistent trends were observed in the photoproduction or loss of DPA and NO 2 -.

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Section: Photochemically Mediated Loss Of Nh 4 + In Groundwatersmentioning

confidence: 95%

Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters

Koopmans¹,

Bronk²

2002

Aquat. Microb. Ecol.

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“…In these experiments, 1 O 2 was generated via energy transfer from the triplet excited state of a sensitizer to 3 O 2 (type II photosensitization) [25]. Photooxidation of Met [24,[26][27][28][29][30][31][32] depends on various parameters (e.g., pH, O 2 concentration, solvent composition, buffer ions, and combination of light and sensitizers). Determination of 1 O 2 -mediated oxidation kinetics was also challenged by the competition between radical-and 1 O 2 -mediated reactions, and the interaction between substrates and excited sensitizers.…”

mentioning

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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“…Reduction of the excited state of a ketone by an amine leads to radical formation, which initiates polymer chain reaction. The photoreduction of benzophenone in the presence of amines has been intensively investigated by Cohen [11,12] and Peters. [13] The benzophenone-derivative triplet state is photoreduced by amines via the photoinduced intermolecular electron transfer mechanism (PET), which is followed by transformations yielding free radicals able to initiate polymerization.…”

Section: Introductionmentioning

confidence: 99%

“…Both these forms exist in an equilibrium, but only the first one can lose CO 2 , to form an a-aminoalkyl radical that can initiate polymerization of acrylates. [11,15,18] The triplet excited states of common aromatic ketones are known to have an np Ã configuration. They are formed by promotion of an electron from a nonbonding (n) orbital of oxygen onto an antibonding p Ã orbital that is delocalized over the aromatic p system.…”

Section: Introductionmentioning

confidence: 99%

Tetraalkylammonium Salts of Amino Acids and Sulfur‐Containing Amino Acids as Effective Co‐Initiators of Free Radical Polymerization in the Presence of Aromatic Ketones

Ścigalski

Pączkowski

2008

Macro Chemistry & Physics

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Photoredox pairs, composed of xanthone or thioxanthone derivatives acting as light absorbers and tetrabutylammonium salts of amino acids or sulfur-containing amino acids as co-initiators, were studied as photoinitiators for free-radical polymerization. The mechanism of free-radical formation was established using the laser flash photolysis. Measurements of polymerization kinetics show that the photoinitiation ability of the xanthone-or thioxanthone-derivative/ amino acid or sulfur-containing amino acid pairs depends on the initiator and co-initiator properties, mostly on the triplet state lifetime of xanthone or thioxanthone derivatives.

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Photooxidation of methionine and related compounds

Cited by 55 publications

References 0 publications

Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters

Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters

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

Tetraalkylammonium Salts of Amino Acids and Sulfur‐Containing Amino Acids as Effective Co‐Initiators of Free Radical Polymerization in the Presence of Aromatic Ketones

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Photooxidation of methionine and related compounds

Cited by 55 publications

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Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters

Photochemical production of dissolved inorganic nitrogen and primary amines from dissolved organic nitrogen in waters of two estuaries and adjacent surficial groundwaters

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

Tetraalkylammonium Salts of Amino Acids and Sulfur‐Containing Amino Acids as Effective Co‐Initiators of Free Radical Polymerization in the Presence of Aromatic Ketones

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