394 - Oxidation of deoxyribonucleic acid at carbon electrodes. The effect of the quality of the deoxyribonucleic acid sample

Electrochemical Label-Free Nucleotide Sensors

Numerous researchers have devoted a great deal of effort over the last few decades to the development of electrochemical oligonucleotide detection techniques, owing to their advantages of simple design, inherently small dimensions, and low power requirements. Their simplicity and rapidity of detection makes label-free oligonucleotide sensors of great potential use as first-aid screening tools in the analytical field of environmental measurements and healthcare management. This review article covers label-free oligonucleotide sensors, focusing specifically on topical electrochemical techniques, including intrinsic redox reaction of bases, conductive polymers, the use of electrochemical indicators, and highly ordered probe structures.

Electrochemical study of dsDNA on carbon nanotubes paste electrodes applying cyclic and differential pulse voltammetry

Abstract Carbon nanotubes paste electrodes (CNTPEs) in combination with adsorptive transfer stripping voltammetry are shown to be very suitable for the determination of calf thymus double-stranded DNA (dsDNA). The performance of three types of multi-walled carbon nanotubes paste electrodes (MWCNTPEs) is investigated. The effects of surface pre-treatment and accumulation conditions on the adsorption and electrooxidation of the dsDNA at MWCNTPEs are also described. The results indicate that the electroactivity inherent to carbon nanotubes/paste electrodes allows a large enhancement of the guanine oxidation signal compared to that obtained at the conventional carbon paste electrodes (CPEs). Moreover, the extent of the enhancement dependents on the type of MWCNTs incorporated into the paste. Based on the signal of guanine, under optimal conditions, very low levels of dsDNA can be detected following short accumulation times for all three types of MWCNTPEs (MWCNTPE1, MWCNTPE2, MWCNTPE3), with detection limits of 2.64 mg L−1, 2.02 mg L−1 and 1.46 mg L−1, respectively. Additionally, the dsDNA isolated from rat liver tissues is determined by use of the previously mentioned MWCNTPEs. Graphical abstract

Sequence-dependent conformational changes in DNA induced by polynuclear platinum complexes

In this work, the B-->Z transition of poly(dG-dC).poly(dG-dC) and the B-->A transition of poly(dG).poly(dC) and of calf thymus (CT) DNA fragments modified by antitumor bifunctional polynuclear platinum complexes were investigated by circular dichroism (CD). The transition from the B- to Z-form of DNA was inducible with all three compounds studied, as indicated by an inversion of the B-form spectra. The B-->A transition in poly(dG).poly(dC) was induced easily by platinum complex binding alone, while the B-->A transition in CT DNA was induced by ethanol but inhibited by coordination of all polynuclear platinum compounds used here. It was shown that the compound [¿cis-PtCl(NH3)2¿2 mu-¿H2N(CH2)6NH2¿] (NO3)2 (1,1/c,c) was most effective at inhibiting the B-->A transition in CT DNA, and [¿trans-PtCl(NH3)2¿2 mu-¿trans-Pt(NH3)2(H2N(CH2)6NH2)2¿] (NO3)4 (1,0,1/t,t,t) was least effective, while the effectiveness of [¿trans-PtCl(NH3)2¿2 mu-¿H2N(CH2)6NH2¿] (NO3)2 (1,1/t,t) fell between the two. This corresponded to the relative amounts of interstrand crosslinks in double-stranded DNA caused by each compound.

DNA modified by platinum derivatives cannot adopt the A-form

DNA fragments from chicken erythrocytes were modified by cis-diamminedichloroplatinum(II), its trans-isomer and chlorodiethylenetriaminoplatinum(II) chloride. The conformation of the modified DNA fragments in ethanolic solutions was studied by circular dichroism spectroscopy. Non-modified DNA adopted the A-form in 81% ethanol. The modification of DNA by the three platinum compounds inhibited the B to A transition of DNA induced by high concentrations of ethanol roughly to the same extent. The results support the view that the binding of the platinum complexes to B-DNA lowers the conformational freedom of DNA so that it cannot acquire the A-conformation.