Fig. 3 Differential pulse voltammograms for the oxidation signal of guanine (a) after and (b) before hybridization with target DNA at inosine-substituted probe modified AuSPE.

relied on the intercalative or electrostatic collection of toxic aromatic amines onto an immobilized double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) layer in connection with chronopotentiometric analysis. The anodic signal of the guanine bases of DNA-coated SPEs was affected by structural or conformational modifications of the DNA layer due to the DNA-analyte association. The changes in the guanine oxidation signal were taken as an index for the affinity of the analyte toward nucleic acids. Submicromolar detection limits were obtained for molecules with more than two aromatic rings after a 2-min accumulation.1-23-1

Indicator-based disposable electrochemical DNA biosensors were also described by using carbon SPEs in connection with a well-described intercalator, daunomy-cin, as an indicator of the hybridization reaction by Marrazza et al.[24,25] Synthetic probes have been immobilized onto carbon SPEs using adsorption at a controlled potential. The hybrids formed on the electrode surface were evaluated by chronopotentiometric stripping analysis of daunomycin. The DNA biosensor was able to detect 0.2 mg L"1 of a 21-base target sequence. The determination of low-molecular weight toxic compounds with affinity for DNA, such as polychlorinated biphenyls (PCBs) and aflatoxin B1, was carried out by monitoring their effect on the guanine oxidation signal.[25] River water samples were also used as real matrices for monitoring of these compounds by using the disposable DNA-modified SPEs.[25]

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Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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