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BP: Fachverband Biologische Physik

BP 2: DNA/RNA and related enzymes

BP 2.11: Vortrag

Montag, 31. März 2014, 12:30–12:45, ZEU 250

Kinetics of conformational fluctuations in DNA hairpin-loops in crowded fluids — •Olivia Stiehl and Matthias Weiss — Experimentalphysik I, Universität Bayreuth, Germany

Biochemical reactions in crowded solutions are commonly anticipated to differ strongly from those in dilute solutions. Macromolecular crowding not only induces excluded-volume interactions with surrounding molecules but it has also been frequently reported to initiate anomalous diffusion (subdiffusion). Both facets are supposed to stabilize complex formation of reaction partners.

A typical biochemical reaction is the thermally driven opening and closing transition of DNA hairpin-loops. Using fluorescence correlation spectroscopy (FCS), we have revealed that crowding not only slows down the opening/closing kinetics but also increases the steady-state fraction of the closed state significantly [1]. Our results also show that subdiffusion leads to an even stronger shift of the two-state equilibirum towards the closed state in comparison to pure excluded-volume effects. For that reason, we conclude that biochemical reactions are sensitive to both, excluded-volume interactions and changes of the diffusive behavior of the reactants.

Preliminary UV-absorption data also support the notion that the simplification of a two state model is no more justified in crowded solutions as soon as the DNA strand exceeds a certain length.

[1] O. Stiehl, K. Weidner-Hertrampf and M. Weiss: Kinetics of conformational fluctuations in DNA hairpin-loops in crowded fluids. New J. Phys. 15 (2013) 113010.