Dataset Information

Direct oxidation of boronates by peroxynitrite: mechanism and implications in fluorescence imaging of peroxynitrite.

ABSTRACT: In this study, we show that boronates, a class of synthetic organic compounds, react rapidly and stoichiometrically with peroxynitrite (ONOO(-)) to form stable hydroxy derivatives as major products. Using a stopped-flow kinetic technique, we measured the second-order rate constants for the reaction with ONOO(-), hypochlorous acid (HOCl), and hydrogen peroxide (H(2)O(2)) and found that ONOO(-) reacts with 4-acetylphenylboronic acid nearly a million times (k=1.6x10(6) M(-1) s(-1)) faster than does H(2)O(2) (k=2.2 M(-1) s(-1)) and over 200 times faster than does HOCl (k=6.2x10(3) M(-1) s(-1)). Nitric oxide and superoxide together, but not alone, oxidized boronates to the same phenolic products. Similar reaction profiles were obtained with other boronates. Results from this study may be helpful in developing a novel class of fluorescent probes for the detection and imaging of ONOO(-) formed in cellular and cell-free systems.

SUBMITTER: Sikora A

PROVIDER: S-EPMC3375817 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Direct oxidation of boronates by peroxynitrite: mechanism and implications in fluorescence imaging of peroxynitrite.

Sikora Adam A Zielonka Jacek J Lopez Marcos M Joseph Joy J Kalyanaraman B B

Free radical biology & medicine 20090814 10

In this study, we show that boronates, a class of synthetic organic compounds, react rapidly and stoichiometrically with peroxynitrite (ONOO(-)) to form stable hydroxy derivatives as major products. Using a stopped-flow kinetic technique, we measured the second-order rate constants for the reaction with ONOO(-), hypochlorous acid (HOCl), and hydrogen peroxide (H(2)O(2)) and found that ONOO(-) reacts with 4-acetylphenylboronic acid nearly a million times (k=1.6x10(6) M(-1) s(-1)) faster than does ...[more]

PMID: 19686842

Similar Datasets

Project description:Recently, we showed that peroxynitrite (ONOO(-)) reacts directly and rapidly with aromatic and aliphatic boronic acids (k ? 10(6) M(-1)s(-1)). Product analyses and substrate consumption data indicated that ONOO(-) reacts stoichiometrically with boronates, yielding the corresponding phenols as the major product (?85-90%), and the remaining products (10-15%) were proposed to originate from free radical intermediates (phenyl and phenoxyl radicals). Here, we investigated in detail the minor, free radical pathway of boronate reaction with ONOO(-). The electron paramagnetic resonance (EPR) spin-trapping technique was used to characterize the free radical intermediates formed from the reaction between boronates and ONOO(-). Using 2-methyl-2-nitrosopropane (MNP) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps, phenyl radicals were trapped and detected. Although phenoxyl radicals were not detected, the positive effects of molecular oxygen, and inhibitory effects of hydrogen atom donors (acetonitrile, and 2-propanol) and general radical scavengers (GSH, NADH, ascorbic acid, and tyrosine) on the formation of phenoxyl radical-derived nitrated product, suggest that the phenoxyl radical was formed as the secondary species. We propose that the initial step of the reaction involves the addition of ONOO(-) to the boron atom in boronates. The anionic intermediate undergoes both heterolytic (major pathway) and homolytic (minor pathway) cleavage of the peroxy (O-O) bond to form phenol and nitrite as a major product (via a nonradical mechanism), or a radical pair PhB(OH)(2)O(•-)···(•)NO(2) as a minor product. It is conceivable that phenyl radicals are formed by the fragmentation of the PhB(OH)(2)O(•-) radical anion. According to the DFT quantum mechanical calculations, the energy barrier for the dissociation of PhB(OH)(2)O(•-) radical anion to form phenyl radical is only a few kcal/mol, suggesting rapid and spontaneous fragmentation of the PhB(OH)(2)O(•-) radical anion in aqueous media. Biological implications of the minor free radical pathway are discussed in the context of ONOO(-) detection, using the boronate probes.

Dataset Information

Direct oxidation of boronates by peroxynitrite: mechanism and implications in fluorescence imaging of peroxynitrite.

Publications

Direct oxidation of boronates by peroxynitrite: mechanism and implications in fluorescence imaging of peroxynitrite.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets