Mathematisch-Naturwissenschaftliche Fakultät

Institut fr Chemie

Fachgebiet: Analytische Chemie

Betreuer: PD Dr. Gerd-Uwe Flechsig

Diplom-Biocehmiker Jrg Peter
(e-mail: )

Electrochemical Detektion of DNA Hybridization on Heated Gold Electrodes

In the recent work unheated, indirect and direct heated electrodes for the determination of hybridization of labelled nucleic acids was studied. It was found that these 3 types of electrodes are applicable to this method of nucleic acid detection.

A comparison of the monothiol-probe coverage of disk and wire electrode show that only the wire electrode have an nearly optimal probe coverage after a two step immobilization of probe and a short alkanethiol. At the disk electrode is this magnitude 3-5 times higher. It was demonstrate that probes with a linker with more than one thiol group give higher stable hybridization signals. The use of a mixture from probe and alkanethiol improve the stability of the signal and the probe coverage on the disk electrodes.

It was shown that the hybridization signal on a rotating disk electrode is reduplicate only in a range of rotation speed from 0 to 1000 rpm during the hybridization at room temperature. This effect was not observed at 7 C. That means that the hybridization reaction at the electrode surface is controlled by the diffusion at the surface.

It was demonstrate that the difference between the limits of detection of the indirect heated electrodes and the unheated disk electrodes is very small. The studies of the influence of the temperature of hybridization show that the temperature optima of these two electrode types are vary in 1 C. It was shown that the rotating disk electrode and the wire electrode are able for the selective detection of complementary targets.

In this work was ferrocen, osmium-bipyridine und the dye label dabcyl use. The highest hybridization signals were obtained with the osmium labelled targets. The lowest peak currents were measured with the dabcyl label. The pure dye dabcyl react on a hanging mercury electrode at an electrode potential of -450 mV reversible and at more than -1.5 V vs. Ag/AgCl in a second reaction step irreversible. In contrast to the pure dye react the dabcyl labelled DNA at a probe modified gold electrode at the same potential irreversible. These reaction properties of dabycl label involve the use of high concentrations of target. Thus it appears that the effects of temperature, concentration and time of hybridization are much smaller in comparison to the other labels.