Sensitized photo-oxidation of plant cytokinin-specific binding protein - Does the environment of the thioether group influence the oxidation reaction? From primary intermediates to stable products

Photo- and Radiation-Induced One-Electron Oxidation of Methionine in Various Structural Environments Studied by Time-Resolved Techniques

“…Provided that photo-and radiation-induced reaction pathways lead to the Scheme 16. Graphical scheme reaction of the mechanism of VrPhBp protein oxidation sensitized by CB in aqueous solutions methionine in Gly-Met-Gly tripeptide (adapted from [110]).…”

“…This may be due to complexity of the reactants, the diversity of possible target positions in the oxidation of proteins, and the experimental difficulties in analyzing the oxidation products. The mechanism of CB-sensitized photooxidation of plant cytokinin-specific binding proteins (VrPhBP) was recently studied using nanosecond flash photolysis and various methods for analyzing the stable photoproducts (chemical analysis, silver-staining gel electrophoresis, chromatography, and mass spectrometry including peptide mapping by proteolysis and coupling with chromatography) [110]. The results indicated oxidation of methionine and tyrosine residues within the protein.…”

Does the Presence of Ground State Complex between a PR-10 Protein and a Sensitizer Affect the Mechanism of Sensitized Photo-Oxidation?

“…Most of the protein modifications induced by oxidants appear at amino acid side chains prone to oxidation, such as those containing sulphur (Met, Cys) or an aromatic ring (Tyr, Phe, Trp and His) [1,2]. The sensitized photo-oxidation of proteins by the excited triplet state of carboxybenzophenone ( 3 CB*) is a good example of one-electron oxidation process [3][4][5]. Carboxybenzophenone (CB) is a photosensitizer with well-established chemical, photochemical and photophysical properties [6][7][8].…”

“…Carboxybenzophenone (CB) is a photosensitizer with well-established chemical, photochemical and photophysical properties [6][7][8]. 3 CB* can be quenched by different amino acid side chains with different quenching rate constants and different mechanisms, such as electron transfer or energy transfer [9][10][11]. Tyr, Met and Cys quench 3 CB* by electron transfer yielding, respectively, tyrosyl radicals (TyrO • ), sulphur-centered radical cation (Met>S +• ) and thiyl radicals (CysS • ) [5,12,13].…”

“…3 CB* can be quenched by different amino acid side chains with different quenching rate constants and different mechanisms, such as electron transfer or energy transfer [9][10][11]. Tyr, Met and Cys quench 3 CB* by electron transfer yielding, respectively, tyrosyl radicals (TyrO • ), sulphur-centered radical cation (Met>S +• ) and thiyl radicals (CysS • ) [5,12,13]. The sulphur radical cation, Met>S +• , can interact with electron-rich atoms (such as S, O or N), yielding well characterized two-centered three-electron bonds, depending on the geometry and neighboring amino acid side chains (Scheme 1) [4,9,[14][15][16].…”