Regensburg 2002 – wissenschaftliches Programm

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O: Oberflächenphysik

O 26: Postersitzung (Rastersondentechniken, Nanostrukturen, Teilchen und Cluster, Methodisches, Oxide und Isolatoren, Grenzfl
äche fest-flüssig, Struktur und Dynamik reiner Oberfl
ächen, Oberfl
ächenreaktionen, Zeitaufg. Spektroskopie, Phasenüberg
änge

O 26.15: Poster

Mittwoch, 13. März 2002, 14:30–17:30, Bereich C

Investigation of UV-induced damage in DNA by scanning force microscopy — •Y. Zhao¹, W. Nellen², and F. Träger¹ — ¹Experimentalphysik I, Universität Kassel, Heinrich-Plett-Straße 40, 34132 Kassel — ²FG Genetik, Universität Kassel, Heinrich-Plett-Straße 40, 34132 Kassel

The effects of UV radiation on DNA have been widely studied [1]. Several methods have been applied to analyze DNA damage. Scanning force microscopy (SFM) permits direct measurement of individual DNA molecules with an accuracy of a few nanometers independently of theoretical models, which was not previously achievable by other techniques.

Using SFM, we have investigated UV-induced DNA strand breaks in plasmids. The supercoiled plasmid pGem7z(+) (3 kb) were irradiated with a pulsed UV-laser that emits 6 ns pulses at 266 nm. Only one single strand break (SSB) is sufficient to relax DNA in supercoiled form to open-circular form. One double strand break (DSB) will produce linear molecule. The SFM images showed that the extent of strand breakage was dose dependent. As a function of dose, the number of supercoiled DNA decreased and the number of open-circular and linear molecules increased. With increasing dose we observed the appearance of heterogeneous linear pieces of DNA that were less than unit length. The shortest fragment was observed with about 300 bp. These results provide clear experimental evidence for the existence of DNA double strand breaks and demonstrate that short DNA fragments may be produced by high intensity UV radiation.

[1] see, for example, E. Rabbow, PhD thesis, RWTH Aachen, 1999.