Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 31: Posters: Membranes and Vesicles

BP 31.8: Poster

Thursday, March 25, 2010, 17:15–20:00, Poster B1

Conformation of DNA molecules adsorbed on free-standing cationic lipid membranes — •Christoph Herold, Eugene P. Petrov, and Petra Schwille — Biophysics, BIOTEC, TU Dresden, Tatzberg 47/49, 01307 Dresden

We study ds-DNA fragments (5, 10, 20, and 48 kbp) electrostatically adsorbed on free-standing lipid membranes consisting of zwitterionic DOPC with added fractions of cationic DOTAP (1–10 %). The free-standing bilayers are modeled using giant unilamellar vesicles of sizes >100 µm. We found that DNA molecules are initially adsorbed on the cationic membrane in a coil conformation (gyration radius of ca. 2 µm for 48 kbp DNA) and then collapse into globules with a size below the optical resolution limit (gyration radius of ca. 0.3 µm). The fraction of collapsed DNA globules depends on the cationic lipid concentration and the DNA fragment length. DNA collapse is favored for high DOTAP concentration and long DNA fragments. At low DOTAP concentration and for shorter DNA fragments a coexistence of DNA molecules in coil and globule conformation is observed. We present results of a systematic study of this phenomenon using fluorescence video microscopy with single particle tracking.