Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 20: DNA, RNA and Chromatin

BP 20.9: Talk

Thursday, March 26, 2009, 16:30–16:45, HÜL 186

Structural levels of organization in the TmHU/DNA-complex as studied by optical tweezers assisted force spectroscopy — •Carolin Wagner, Mathias Salomo, and Friedrich Kremer — Universität Leipzig, Germany

The interaction of the histone-like protein TmHU (from Thermotoga maritima) to DNA is analyzed on a single molecule level by use of optical tweezers. This technique provides a nm-resolution in positioning a micron-sized colloid and an accuracy of +/-50 fN in measuring the forces acting on it. As a further refinement, our set-up is now accomplished with a fast feed-back loop (regulation frequency: 30 Hz) which allows to carry out the experiment under conditions of a constant and adjustable force.

The proceeding of the condensation and its dependence on the applied force (2-40 pN) is investigated. At a pre-stretching of 2 pN the length of the DNA is reduced by about 80%. At higher forces, the reaction is disrupted at an incomplete level. The process shows two distinct regimes that can be related to different organizational levels. The condensation also shows a pronounced dependence on the concentration. By stretching the TmHU/DNA-complex, it is possible to disrupt the proteins from the DNA. The length of the smallest event conforms with the results of a simulated rupture.