Cargando…

Early Events of Photosensitized Oxidation of Sulfur-Containing Amino Acids Studied by Laser Flash Photolysis and Mass Spectrometry

[Image: see text] The mechanism of photooxidation of methionine (N-Ac-Met-NH-CH(3), 1) and methyl-cysteine (N-Ac-MeCys-NH-CH(3), 2) analogues by 3-carboxybenzophenone triplet (3CB*) in neutral aqueous solution was studied using techniques of nanosecond laser flash photolysis and steady-state photoly...

Descripción completa

Detalles Bibliográficos
Autores principales: Pedzinski, Tomasz, Grzyb, Katarzyna, Kaźmierczak, Franciszek, Frański, Rafał, Filipiak, Piotr, Marciniak, Bronislaw
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2020
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7498160/
https://www.ncbi.nlm.nih.gov/pubmed/32790392
http://dx.doi.org/10.1021/acs.jpcb.0c06008
Descripción
Sumario:[Image: see text] The mechanism of photooxidation of methionine (N-Ac-Met-NH-CH(3), 1) and methyl-cysteine (N-Ac-MeCys-NH-CH(3), 2) analogues by 3-carboxybenzophenone triplet (3CB*) in neutral aqueous solution was studied using techniques of nanosecond laser flash photolysis and steady-state photolysis. The short-lived transients derived from 3CB and sulfur-containing amino acids were identified, and their quantum yields and kinetics of formation and decay were determined. The stable photoproducts were analyzed using liquid chromatography coupled with high-resolution mass spectrometry. Substantial differences in the mechanisms were found for methionine and S-methyl-cysteine analogues for both primary and secondary photoreactions. A new secondary reaction channel (back hydrogen atom transfer from the ketyl radical to the carbon-centered α-thioalkyl radical yielding reactants in the ground states) was suggested. The detailed mechanisms of 3CB* sensitized photooxidation of 1 and 2 are proposed and discussed.