Identification of carcinogen DNA adducts in human saliva by linear quadrupole ion trap/multistage tandem mass spectrometry.

DNA adducts of carcinogens derived from tobacco smoke and cooked meat were identified by liquid chromatography-electrospray ionization/multistage tandem mass spectrometry (LC-ESI/MS/MS(n)) in saliva samples from 37 human volunteers on unrestricted diets. The N-(deoxyguanosin-8-yl) (dG-C8) adducts of the heterocyclic aromatic amines 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-9H-pyrido[2,3-b]indole (AalphaC), 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), and the aromatic amine, 4-aminobiphenyl (4-ABP), were characterized and quantified by LC-ESI/MS/MS(n), employing consecutive reaction monitoring at the MS(3) scan stage mode with a linear quadrupole ion trap (LIT) mass spectrometer (MS). DNA adducts of PhIP were found most frequently: dG-C8-PhIP was detected in saliva samples from 13 of 29 ever-smokers and in saliva samples from 2 of 8 never-smokers. dG-C8-AalphaC and dG-C8-MeIQx were identified solely in saliva samples of three current smokers, and dG-C8-4-ABP was detected in saliva from two current smokers. The levels of these different adducts ranged from 1 to 9 adducts per 10(8) DNA bases. These findings demonstrate that PhIP is a significant DNA-damaging agent in humans. Saliva appears to be a promising biological fluid in which to assay DNA adducts of tobacco and dietary carcinogens by selective LIT MS techniques.

Assembling and evaluation of new dehydrogenase enzyme electrode probes obtained by electropolymerization of aminobenzine isomers and PQQ on gold, platinum and carbon electrodes.

Pt, Au and graphite electrodes have been coated by electropolymerization of 1,2-, 1,3-, 1,4-diaminobenzene (DAB) and 4-aminobiphenyl in the presence of PQQ using cyclic voltammetry. The activity of the modified electrodes for the oxidation of paracetamol, ascorbic and uric acid was reduced by approximately 90% as compared to the bare electrodes. Polymerization in the presence 4,5-dihydro-4,5-dioxo-1H-pyrrolo(2,3-f)quinoline-2,7,9-tricarboxilic+ ++ acid, pyrroloquinolinequinone (PQQ) led, after optimization, to electrodes capable of catalysing the electrooxidation of beta-nicotinamide adenine dinucleotide, reduced form (NADH), in the range 10(-4)-10(-2) mol/l with a detection limit of 5 x 10(-5) mol/l. Amperometric measurements of NADH have been carried out at +0.2 V and the efficiency of different electrodes based on different materials has been studied. By co-entrapment of dehydrogenase highly selective enzymes, electrodes for glucose, L-lactate and L-glutamate were obtained. Dehydrogenase substrates such as glucose, lactate and glutamate were measured in the range 5 x 10(-5)-1 x 10(-2) mol/l, with detection limits of 10(-5) and 5 x 10(-6) mol/l, respectively. Probe stability under non-dynamic conditions was evaluated over 2 months. All the probes showed a decrease of 10% over 1 month and a residual activity of 50% over 2 months.