Berlin 2012 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 24: Posters: DNA/RNA and Related Enzymes

BP 24.10: Poster

Donnerstag, 29. März 2012, 17:30–19:30, Poster A

AFM imaging of conformational changes in DNA after hydroxyl radical attack — Janine Wilken¹ and •Stephan Block² — ¹Institut für Physik, Ernst-Moritz-Arndt Universität, Felix-Hausdorff-Str. 6, D-17487 Greifswald, Germany — ²ZIK HIKE - Zentrum für Innovationskompetenz Humorale Immunreaktionen bei kardiovaskulären Erkrankungen, Fleischmannstr. 42 - 44, D-17487 Greifswald, Germany

AFM is used to directly visualise changes in the conformation of DNA after attack of reactive oxygen species (ROS). In detail, the plasmid pBR322 is mixed with Fentons reagent, whereby the ratio R of hydroxyl radical molecules to DNA base pairs is varied. After the radical attack the negatively charged plasmid is immobilized onto mica surfaces that are functionalized with positively charged poly(allylamine hydrochloride) (PAH). At R = 2.5 most of the plasmid adopts the supercoiled (double-stranded) conformation and only few chains are split up by the radical attack. An increase in hydroxyl radical concentration also increases the power of the radical attack, leading to a rising number of shorter (single-stranded) fragments of plasmids. Interestingly, these fragments are often surrounded by plateaus (0.2 nm in height) which might be attributed to the aggregation of base pairs, which are chemically modified after the radical attack.