1. α- and β-casein aggregation induced by riboflavin-sensitized photo-oxidation occurs via di-tyrosine cross-links and is oxygen concentration dependent.
- Author
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Fuentes-Lemus E, Silva E, Leinisch F, Dorta E, Lorentzen LG, Davies MJ, and López-Alarcón C
- Subjects
- Caseins metabolism, Cross-Linking Reagents pharmacology, Oxidation-Reduction, Protein Structure, Quaternary, Caseins chemistry, Oxygen metabolism, Photochemical Processes, Protein Aggregates drug effects, Protein Multimerization drug effects, Riboflavin pharmacology, Tyrosine metabolism
- Abstract
Type I photo-oxidation generates Trp-(TrpN) and Tyr-derived (TyrO) radicals in proteins which can dimerize producing cross-links, or alternatively react with O
2 . It was therefore hypothesized that the O2 concentration may have a significant effect on dye-photosensitized reactions. We studied photo-oxidation of α- and β-caseins induced by riboflavin (RF), a photosensitizing vitamin present in milk, under aerobic and anaerobic conditions. Triplet-state RF induced oxidative modifications on both caseins, and significant levels of cross-links. The extent of damage, and the yield of cross-links versus oxidized products, was dependent on the O2 concentration. In the absence of O2 , the overall extent of damage was decreased, but the yield of cross-linked products was significantly elevated. These cross-links are consistent with inter- and intra-molecular di-Tyr or di-Trp bridges. Alternative cross-links were detected in the presence of O2 , consistent with pathways involving the reaction of protein radicals with O2 or O2 - ., (Copyright © 2018 Elsevier Ltd. All rights reserved.)- Published
- 2018
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