Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 7: Posters I

BP 7.36: Poster

Monday, February 25, 2008, 17:00–19:30, Poster A

Quantum dots as substrates for nuclear-cytoplasmic transport. — •Ulrike Schmitz-Ziffels, Birgit Klaiberg, Jan-Peter Siebrasse, and Ulrich Kubitscheck — Institut für Physikalische und Theoretische Chemie, Wegelerstr. 12, 53115 Bonn

Nuclear-cytoplasmic transport of macromolecules is accomplished by the nuclear pore complex (NPC) - a transport machine imbedded in the nuclear envelope (NE). The NPC enables high selective translocation across the NE, known to be facilitated by the interaction of soluble transport receptors with the NPC's nucleoporins. However, detailed mechanisms and kinetics of the translocation still remain unknown. Single molecule fluorescence microscopy provides a direct observation of processes at the NPC with excellent spatial and time resolution. We use functionalized biocompatible quantum dots as transport substrates to investigate nuclear import in permeabilized cells at the single particle level. As bright and photostable probes, quantum dots yield an excellent localization precision (< 10nm). This is of great importance when tracking the import complex through the approximately 100 nm long NPC. Experiments with NTF2-functionalized quantum dots demonstrated that a specific interaction with the NPC can be achieved. We detected nuclear import of the smallest, green fluorescent quantum dots, yet their fluorescence is not bright enough to yield the required localization precision. The brighter red fluorescent quantum dots on the other hand could not pass the NPC, due to their larger stokes radius. Currently we are focussing on the preparation of smaller red fluorescent substrate-conjugated nanoprobes.