A Long Story of Sensitized One‐Electron Photo‐oxidation of Methionine

Abstract

The one‐electron oxidation of methionine residues in peptides and proteins has been studied for more than 20 years thanks to the time‐resolved techniques of pulse radiolysis and flash photolysis. Methionine oxidation causes highly damaging effects associated with aging processes and disease states such as Alzheimer’s or prion disease and cerebral amyloid angiopathy. In this Minireview, we focus on the photoinduced processes that help in the understanding of the primary processes of methionine residue oxidation. The photosensitizers were mostly derivatives of carboxybenzophenone. The methionine radical cations are stabilized by two‐center three‐electron bonds of various natures. However, despite numerous studies, data about the final product are still missing.

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

“…For these reasons, it is important to characterize spectrally and kinetically these very first steps. Radiolysis of water and photo-excitation of benzophenone carboxyl derivatives in aqueous solutions provide very convenient source of hydroxyl radicals HO • and excited triplet states (CB*), respectively, which were very useful for studying one-electron oxidation reactions of Met [5,6]. The transient nature of free radicals requires specific time-resolved methods.…”

“…The transient nature of free radicals requires specific time-resolved methods. Therefore, these reactions were followed either in radiation-or photochemical and excited triplet states (CB*), respectively, which were very useful for studying oneelectron oxidation reactions of Met [5,6]. The transient nature of free radicals requires specific time-resolved methods.…”

“…Molecules 2022, 27, x FOR PEER REVIEW 2 of 34 and excited triplet states (CB*), respectively, which were very useful for studying oneelectron oxidation reactions of Met [5,6]. The transient nature of free radicals requires specific time-resolved methods.…”

Radiation- and Photo-Induced Oxidation Pathways of Methionine in Model Peptide Backbone under Anoxic Conditions

“…Excited triplet states of benzophenones carboxyl derivatives ( 3 CB) were also shown to be very useful for studying one-electron oxidation reactions of Met-containing molecules of biological significance [ 21 , 23 , 24 ]. The mechanism of primary photo-induced processes occurring during Met oxidation in aqueous solutions is summarized in Scheme 2 .…”

Methionine one-electron oxidation: Coherent contributions from radiolysis, IRMPD spectroscopy, DFT calculations and electrochemistry

“…In peptides and proteins, it can be nitrogen, oxygen or another sulphur atom [2,3]. The identification of these free radicals was performed by their absorption spectra obtained in pulse radiolysis or in flash photolysis ( [4,5] and references therein), by EPR and CIDNP [6][7][8]. The reduction potential of methionine has never been measured and one relies on that of small compounds like dimethyl sulphide, without knowing in what sense the neighbouring residues could modify it.…”