A New Approach to Evaluating the Extent of Michael Adduct Formation to PAH Quinones:  Tetramethylammonium Hydroxide (TMAH) Thermochemolysis with GC/MS

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that are converted to cytotoxic and carcinogenic metabolites, quinones, by detoxifying enzyme systems in animals. PAH metabolites such as the quinones can form Michael adducts with biological macromolecules containing reactive nucleophiles, making detection of exposure to PAHs difficult using conventional techniques. A technique has been developed for detecting exposure to PAHs. Tetramethylammonium hydroxide (TMAH) thermochemolysis coupled with GC/MS is proposed as an assay method for PAH quinones that have formed Michael adducts with biological molecules. Three PAH quinones (1,4-naphthoquinone, 1,2-naphthoquinone, and 1,4-anthraquinone) and 1,4-benzoquinone were reacted with cysteine, and the TMAH thermochemolysis method was used to assay for both thiol and amine adduction between the quinones and the cysteine. Additional studies with 1,4-naphthoquinone adducts to glutathione and bovine serum albumin showed the same thiol and amine TMAH thermochemolysis products with larger peptides as was observed with cysteine adducts. The TMAH GC/MS method clearly shows great promise for detecting PAH quinones, produced by enzymatic conversion of PAHs in biological systems, that have been converted to respective Michael adducts.

New evidence for covalent coupling of peptides to humic acids based on 2D NMR spectroscopy: A means for preservation

“…Covalent coupling of peptides to humic acids affinity for nucleophiles like peptides is well known (Mason and Liebler, 2000;Briggs et al, 2003). Corroboration of their reactivity was substantiated when we chose 1,4-naphthoquinone as a model compound to react with the 15 N-labeled GGGR peptide as similar changes in NMR spectra are observed in the peptide/humic acids mixture and the peptide/quinone mixture.…”

“…Based on the knowledge that small peptides have been shown to react at both the N and S atoms (Sridhar et al, 2001, Briggs et al, 2003, both of which display Michael nucleophile characteristics, it is likely that the described interactions above can generally occur with a large number and variety of peptides.…”

Recent applications in analytical thermochemolysis

“…Tocophery quinones play a role in cytotoxicity, apoptosis and mutagenesis. In an analogue study Briggs et al [172] evaluated the extent of Michael adduct formation to PAH quinines by thermochemolysis-TMAH. PAH quinines were reacted with cysteine and the resulting thiol and amine adducts were identified by thermochemolysis.…”

Carbon Nanoparticle Surface Electrochemistry: High‐Density Covalent Immobilisation and Pore‐Reactivity of 9,10‐Anthraquinone

“…Anthraquinone functionality has been exploited in processes involving oxygen reduction to peroxides [21,22], reactions with thiols [23], as a redox mediator [24], and in sensing of pH [25,26]. Anthraquinones in solution provide a tunable redox system [27].…”