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

Abstract

Within the reactive oxygen species (ROS) generated by cellular metabolisms, hydroxyl radicals (HO•) play an important role, being the most aggressive towards biomolecules. The reactions of HO• with methionine residues (Met) in peptides and proteins have been intensively studied, but some fundamental aspects remain unsolved. In the present study we examined the biomimetic model made of Ac-Met-OMe, as the simplest model peptide backbone, and of HO• generated by ionizing radiation in aqueous solutions under anoxic conditions. We performed the identification and quantification of transient species by pulse radiolysis and of final products by LC-MS and high-resolution MS/MS after γ-radiolysis. By parallel photochemical experiments, using 3-carboxybenzophenone (CB) triplet with the model peptide, we compared the outcomes in terms of short-lived intermediates and stable product identification. The result is a detailed mechanistic scheme of Met oxidation by HO•, and by CB triplets allowed for assigning transient species to the pathways of products formation.

Biomimetic Ketone Reduction by Disulfide Radical Anion

“…The pulse radiolysis experiments were performed with the LAE-10 linear accelerator at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland, with a typical electron pulse length of 10 ns and 10 MeV of energy. A detailed description of the experimental setup has been given elsewhere along with basic details on the equipment and its data collection system [ 37 , 38 , 39 ].…”

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

“…Within the framework of this direction, only 11 articles have been published [ 224 , 225 , 226 , 227 , 228 , 229 , 230 , 231 , 232 , 233 , 234 ], among which there is 1 review. In terms of its subject matter, this direction, to some extent, intersects with both Thematic Area 5 and Thematic Area 6, since ions and radicals are among the objects of Thematic Area 5, and the structure and reactivity of these compounds, obtained as a result of theoretical research (carried out, as a rule, by quantum–chemical methods), are among the objects of Thematic Area 6.…”

“…By analogy, with the systematization of articles indicated in Thematic Area 5, here, it is also advisable to subdivide all publications presented in it into two groups, in the first of which there will be articles on organic compounds, in the second, articles on inorganic compounds. Following this differentiation, the first of these groups should include 7 articles, namely [ 227 , 228 , 229 , 230 , 231 , 232 , 234 ], and the second, 4 articles [ 224 , 225 , 226 , 233 ]. The most significant among them, in our opinion, is review [ 231 ], devoted to the physical chemistry of one of the most stable known radicals, 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (also called diphenylpycrylhydrazil or DPPH), which was opened in 1992, and will make it exactly 100 years old, in 2022.…”

“…A similar situation with the number of publications devoted to radicals and ions takes place in the case of inorganic substances, where in three out of four articles, the objects of study were radicals, and, only in one [ 226 ], anions were formed by various fullerenes. In this regard, we would like to note publications [ 225 , 233 ], in the first of which the determination of the nitroxyl radical was carried out using 4-amino-2,2,6,6-tetramethylpiperidinyl-N-oxyl, and, in the second, the specificity of the reaction of the hydroxyl radical with methionine (Met) residues in peptides and proteins in a biomimetic model system consisting of Ac-Met-OMe was used as the simplest model peptide backbone. This thematic direction undoubtedly needs significant replenishment with new publications.…”

Hydrazine Radiolysis by Gamma-Ray in the N2H4–Cu+–HNO3 System

“…Various radicals and products, such as e aq − , • OH, and H 3 O + , are generated by the radiolysis of water [ 10 ]. The radiolysis products of water as represented in Equation (1) [ 11 ]. …”