Prof. Ulrich Bockelmann "Studying the dynamics and mechanics of biological polymers at the single molecule level"

We perform single molecule measurements with optical tweezers, nanopore translocation experiments and fluorescence energy transfer microscopy and also work on electronic detection of DNA with field effect transistor arrays. In this talk, we will first show that these techniques provide access to information that cannot be obtained by classical approaches and that the experimental data allow for quantitative comparison with theoretical descriptions based on statistical physics. We will then focus on two applications involving the manipulation of single DNA and RNA molecules.

(a) Double stranded DNA exhibits a structural transition at forces of about 65 pN, where its contour length increases by ~70%. Using fluorescence microscopy in combination with optical tweezers, we unraveled the mechanisms behind this overstretching transition.

(b) Ribosomal (r-) RNA is well structured in the ribosome, but the role of r-proteins in the assembly process is poorly understood. We address this question by using optical tweezers to unfold r-RNA fragments in the presence or absence of r-proteins. Focusing on Escherichia coli L20 that recognizes an essential subdomain of the 23S rRNA, we found that this protein acts as a clamp and not as a RNA chaperone.
 

References:
Quantifying how DNA stretches, melts and changes twist under tension, P. Gross, N. Laurens, L. Oddershede, U. Bockelmann, E. Peterman, G. Wuite. Nature Physics 7, 731 (2011).

Probing ribosomal protein - RNA interactions with an external force, P. Mangeol, Th. Bizebard, C. Chiaruttini, M. Dreyfus, M. Springer, U. Bockelmann. Proc. Natl. Acad. Sci. USA 108, 18272 (2011).