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Detection of thiols using hydroquinone on gold surface

Abstract:

Benzene, declared as an environmental contaminant, has commonlybeen used as an industrial solvent, a starting material for the synthesis ofother chemicals, and as an antiknock agent in gasoline, and is asignificant component of cigarette smoke. While not fully understood, thetoxicity of benzene is linked to the production of reactive metabolitesformed during cytochrome P450 2E1. Benzene is metabolized bycytochrome P450 CYP2E1 to benzene oxide, which spontaneously formsphenol. Phenol is converted to hydroquinone by P4502E1. Hydroquinoneand related metabolites are converted in the bone marrow, bygenotoxic compounds that undergo further metabolic activation, by oneelectronreducing enzymes, to generate semiquinones and reactiveoxygen species (ROS). As an excess of ROS is produced, oxidative stresscan occur and lead to altered cellular signaling. The production of ROS istightly regulated and the cell possesses detoxifying mechanisms such ascatalase, glutathione and superoxide dismutase to maintain appropriatecellular ROS levels. 1,4 benzoquinone (BQ) can alter signaling pathwaysand affect chromosomal integrity. Numerous attempts have been made tounderstand cytotoxic mechanisms influenced by the chemical structure ofBQ generate DNA breaks and apoptosis. It is also a strong topoisomeraseII poison. Its toxicity is mainly due to oxidative stress and/or formingMichael-type adducts with proteins and glutathione (GSH). Owing to theimportant physiological roles of quinones, such as hydroquinone, 1,4benzoquinone, and reduced thiols such as GSH, it is necessary to developsensitive and selective methods for the measurement of those substancesto study cellular mechanisms of chemical-induced toxicity. For thispurpose, the benzoquinone (BQ) is used in the electrochemicaldetermination of thiol molecules. The Addition of sulfur nucleophiles toquinones has been studied and Characterized as 1, 4-reductive addition ofthe Michael type. Quinones, containing a polarized double bond, areconsidered Michael acceptors, where the Michael donors are thiolnucleophiles. The final product of this reaction is hydroquinone with asulfur atom in the ortho position. If a metal surface is modified with adithiol (to form a thiolate with the metal surface, leaving a free thiol,-HS)molecule, the reaction with BQ will be easy to produce hydroquinone(H2Q) moiety. The latter product can be used to determineelectrochemically thiol-containing compounds in its structure. © 2012 by Nova Science Publishers, Inc. All rights reserved.