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Characterization of the Site‐Specific Acid‐Base Equilibria of 3‐Nitrotyrosine
Author(s) -
Pálla Tamás,
Fogarasi Erzsébet,
Noszál Béla,
Tóth Gergő
Publication year - 2019
Publication title -
chemistry and biodiversity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 70
eISSN - 1612-1880
pISSN - 1612-1872
DOI - 10.1002/cbdv.201900358
Subject(s) - chemistry , protonation , deprotonation , titration , proton nmr , molecule , nitrotyrosine , carbon 13 nmr , stereochemistry , medicinal chemistry , organic chemistry , enzyme , ion , nitric oxide synthase
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.