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2 results on '"-radiolysis"'

1. Final Products of One-Electron Oxidation of Cyclic Dipeptides Containing Methionine Investigated by IRMPD Spectroscopy: Does the Free Radical Choose the Final Compound?

Author

Yining Jiang, Suvasthika Indrajith, Ariel Francis Perez Mellor, Thomas Bürgi, Marc Lecouvey, Carine Clavaguéra, Enrico Bodo, Chantal Houée-Levin, Estelle Loire, Giel Berden, Jos Oomens, Debora Scuderi, Institut de Chimie Physique (ICP), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Stockholm University, Université de Genève = University of Geneva (UNIGE), Chimie, Structures et Propriétés de Biomatériaux et d'Agents Thérapeutiques (CSPBAT), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Nord, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), Radboud University [Nijmegen], van ‘t Hoff Institute for Molecular Sciences, Universiteit van Amsterdam (UvA), and Molecular Spectroscopy (HIMS, FNWI)

Subjects
FELIX Molecular Structure and Dynamics, IRMPD spectroscopy, Spectrum Analysis, -radiolysis, One-electron oxidation, cyclic peptides, Electrons, Dipeptides, Hydrogen Peroxide, Sulfenic Acids, Surfaces, Coatings and Films, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Methionine, One-electron oxidation -radiolysis IRMPD spectroscopy tandem mass spectrometry cyclic peptides, tandem mass spectrometry, Materials Chemistry, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Physical and Theoretical Chemistry, Sulfur
Abstract

Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and the hydroxyl radical (•OH) have specific functions in biological processes, while their uncontrolled production and reactivity are known to be determining factors in pathophysiology. Methionine (Met) residues act as endogenous antioxidants, when they are oxidized into methionine sulfoxide (MetSO), thus depleting ROS and protecting the protein. We employed tandem mass spectrometry combined with IR multiple photon dissociation spectroscopy to study the oxidation induced by OH radicals produced by γradiolysis on model cyclic dipeptides c(LMetLMet), c(LMetDMet), and c(GlyMet). Our aim was to characterize the geometries of the oxidized peptides in the gas phase and to understand the relationship between the structure of the 2-center 3-electron (2c-3e) free radical formed in the first step of the oxidation process and the final compound. Density functional theory calculations were performed to characterize the lowest energy structures of the final product of oxidation and to interpret the IR spectra. Collision-induced dissociation tandem mass spectrometry (CID-MS2) experiments of oxidized c(LMetLMet)H+ and c(LMetDMet)H+ led to the loss of one or two oxidized sulfenic acid molecules, indicating that the addition of one or two oxygen atoms occurs on the sulfur atom of both methionine side chains and no sulfone formation was observed. The CID-MS2 fragmentation mass spectrum of oxidized c(GlyMet)H+ showed only the loss of one oxidized sulfenic acid molecule. Thus, the final products of oxidation are the same regardless of the structure of the precursor sulfur-centered free radical.

Published
2022
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2. Monte-Carlo Simulation of -ray and Fast Neutron Radiolysis of Liquid Water and 0.4 M H2SO4 Solutions at Temperatures up to 325oC

Author

G.R. Sunaryo, M. Jintana, and J.P.J. Gerin

Subjects
Monte-Carlo, -Radiolysis, Fast neutrons, Nuclear engineering. Atomic power, TK9001-9401
Abstract

Monte-Carlo simulations were used to study the radiolysis of liquid water at 25-325C when subjected to low linear energy transfer (LET) of 60Co -ray radiation and fast neutrons of 2 and 0.8 MeV. The energy deposited in the early stage of 60Co -ray irradiation was approximated by considering short segments (~150 m) of 300 MeV proton tracks, corresponding to an average LET of ~0.3 keV/m. In case of 2 MeV fast neutrons, the energy deposited was considered by using short segments (~5 m) of energy at 1.264, 0.465, 0.171, 0.063 and 0.24 MeV. 0.8 MeV fast neutrons were approximated by 0.505, 0.186, 0.069 and 0.025 MeV protons. The effect of 0.4 M H2SO4 solution on radiolysis was also studied by this method for both 60Co -rays and 0.8 MeV fast neutrons. The simulated results at the time of 10-7s after irradiation were obtained and compared with the available experimental results published by other researchers to be in excellent agreement with them over the entire temperature ranges and radiation sources studied. Except for g(H2) that increase with temperature rises, the general behaviors of higher radical products and lower molecular products at higher temperatures were obtained. The LET effect is also validated by this study, showing that the increase in LET would yield higher molecular and lower radical products. Studies on 0.4 M H2SO4 solutions also show good agreement between the computed and experimental data for -ray irrradiation: the presence of 0.4 M H+, except for g(H2) that gives lower value at 25C and higher value at 325C, gives the higher values for radicals and g(H2O2) at 25C and lower values at 325C, compared with that for neutral water. The computed data show good agreement with the experimental data for 0.4 M H2SO4 solutions induced by 0.8 MeV fast neutrons, except for g(H2) and g(H●) that gives good agreement up to 50C, then the opposite tendencies with the further temperature rises. However, the simulated fast neutron radiolysis on acidic demonstrates similar tendencies on temperature dependence with that for simulated 60Co -radiolysis, but in different magnitude. For better understanding, more experimental data for fast neutrons are needed, especially under the acidic conditions

Published
2011

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