Characterization of the Site-Specific Acid-Base Equilibria of 3-Nitrotyrosine.
Chem Biodivers
; 16(9): e1900358, 2019 Sep.
Article
em En
| MEDLINE
| ID: mdl-31364276
ABSTRACT
The complete macro- and microequilibrium analyses of 3-nitrotyrosine, a biomarker of oxidative stress damage, are presented for the first time. The protonation macroconstants were determined by 1 H-NMR-pH titration, while microconstants were elucidated by a combination of deductive and NMR methods, in which properties of the methyl ester derivative as an auxiliary compound were also studied. Combination of the NMR-pH characterization of the title and auxiliary compounds and the pair-interactivity parameters of 3-iodotyrosine provided the sufficient system to evaluate all the microconstants. NMR-pH profiles, macroscopic and microscopic protonation schemes, and species-specific distribution diagrams are included. The phenolate basicity of 3-nitrotyrosine is 500 times below that of tyrosine, and it is even lower than that of 3-iodotyrosine. This phenomenon can be explained by the stronger electron withdrawing and the negative mesomeric effect of the nitro group. Based on our results, 89 % of the phenolic OH groups are deprotonated in 3-NT molecules at the pH of the blood plasma.
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01-internacional
Base de dados:
MEDLINE
Assunto principal:
Tirosina
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article