Berlin 2005 – scientific programme

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AKB: Biologische Physik

AKB 100: Poster Session I

AKB 100.13: Poster

Saturday, March 5, 2005, 16:45–18:45, Poster TU D

DNA binding ligands investigated with optical tweezers. — •Andy Sischka¹, Katja Tönsing¹, Robert Ros¹, Heiko Ihmels², and Dario Anselmetti¹ — ¹Experimental Biophysics and Applied Nanosciences, Faculty of Physics, Bielefeld University — ²Organic Chemistry, University of Siegen

We used a compact, single beam optical tweezer system to investigate mechanical properties of double stranded DNA in the presence of different binding ligands. Individual binding modes could be distinguished by analyzing the mechanical response of a lambda-DNA molecule to an applied external force. We compared the effects of the minor groove binder distamycin-A, a major groove binding alpha-helical peptide, the intercalators ethidium bromide, YO-1 and daunomycin as well as the bisintercalator YOYO-1 on lambda-DNA. Significant force hysteresis effects occurring during stretching/relaxation cycles with different velocities were found for daunomycin and YOYO-1. These time dependent mechanical properties directly reflect the kinetics of the binding and unbinding behaviour. Furthermore, mechanical properties of organic dyes particularly intercalating with dsDNA were investigated. These dyes change their absorption and fluorescence properties upon binding, and induce DNA damage during irradiation with visible light. Both binding interactions and photochemical modifications of the DNA result in the change of DNA structure may be usefull in applications of photochemotherapy of cancer.