A mechanistic approach towards the formation of bityrosine in proteins by ionizing radiation – GYG model peptide

• Published in: Radiation physics and chemistry (Oxford, England : 1993) Vol. 188; p. 109644
• Main Authors: Sowiński, Sebastian, Varca, Gustavo H.C., Kadłubowski, Sławomir, Lugão, Ademar B., Ulański, Piotr
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-11-2021; Elsevier BV
• Subjects: Bityrosine; Buffers; Complex systems; Crosslinking; Electron beams; Electron irradiation; GYG tripeptide; Hydroxyl radicals; Ionizing radiation; Kinetics; Mechanism; Nanoparticles; Peptides; Protein crosslinking; Protein synthesis; Proteins; Pulse radiolysis; Radiation; Radiation effects; Radiolysis; Rate constants; Tyrosine; Water chemistry; Ionizing radiation; GYG tripeptide; Bityrosine; Pulse radiolysis; Mechanism; Protein crosslinking
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/j.radphyschem.2021.109644

One of the methods of protein crosslinking used in the synthesis of protein-based nanoparticles is the formation of bityrosine bridges, which may be achieved by the recombination of phenoxyl-type radicals in irradiated protein solutions. Radiation-induced formation of phenoxyl radicals in tyrosine is promoted in presence of H+. In this work, kinetics of this process and the influence of pH were studied by pulse radiolysis measurements of a model peptide H-Gly-Tyr-Gly-OH (GYG), which may help to solve questions raised for bigger, more complex systems in comparable conditions. The main route of phenoxyl radicals formation consists of the addition reaction of hydroxyl radical to the phenol ring on the tyrosine side-chain and proton catalyzed water molecule elimination. A similar effect was observed in studies of tripeptide solutions containing phosphate buffer. The presented data include time-resolved optical spectroscopy of transient species formed under pulse electron beam irradiation and a comparison of the kinetics of the phenoxyl radicals formation in samples at various pH and in presence of phosphate buffer. The postulated mechanism and obtained values of rate constants of the formation and decay of transient species were additionally checked by simple probabilistic simulations.
•Pulse radiolysis of H-Gly-Tyr-Gly-OH peptide.•Mechanism and kinetics of hydroxyl radicals reaction with tyrosine residue.•Evaluation of pH and phosphate buffer influence on phenoxyl radicals formation.•Leading role of H+-induced water elimination in the formation of phenoxyl radicals.