2009 - 2010
IDK Student Representative
PhD student in the group of Prof. Hermann Gaub, LMU Munich
2007 - 2008
Diploma Thesis in the group of Prof. Hermann Gaub, LMU Munich
Topic of Diploma Thesis: “Differentielle Kraftmessungen von Protein-DNA- Wechselwirkungen” (“Differential Force Measurements of Protein-DNA Interactions”)
UBC, University of British Columbia, Vancouver, Canada Department of Chemistry Hongbin Li, Ph.D. Ass. Prof. and Canada Research Chair Visiting Scholar Work on: “single molecule force measurements of polymer chain-chain interactions under different solvent conditions.”
2002 - 2008
Study of Physics at the LMU Munich
Scholarship of the IDK-NBT (Elitenetwork of Bavaria)
Research fellowship of the Bayerische Forschungsstiftung
One of the key advantages of the Differential Force Assay in comparison to other force spectroscopy methods like AFM or optical tweezers is the possibility to probe an ensemble in the order of a billion Molecular Force Balances (MBFs) per experiment. A MFB consists of two receptor-ligand-systems, which are connected in series and marked by a fluorescent dye. Because of the setup of the experiment in molecular scale every probed MFB presents still a single molecule force measurement. As a consequence one gets an enormous statistic in each experiment. This allows to resolve smallest differences of the molecular stability of two receptor-ligand-systems, like to distinguish a single SNP mismatch in a 30 base pair long DNA double strand. Based on this principle it was possible to detect different kinds of DNA-binding molecules in a range of dissociation constants from mM to pM.
Another key advantage is the possibility to parallelize the experiment: this means that different kinds of MFBs are probed in one experiment on separate spots. By means of a novel setup, which was developed in the scope of my Diploma Thesis, it was shown, that an area of 5 micrometer x 5 micrometer is sufficient for a quantitative measurement. This area is comparable to the spot size of recent microarrays. Like microarray technology has spread into many areas by combining it with other techniques, a combination of both techniques could allow a quantitative genome-wide screening of DNA-binding molecules. The crucial advantage of the MFB in comparison to other methods is, that no protein-specific antibodies or epitope tagged proteins are needed. In these other techniques the proteins must be directly detected by markers. In our approach the protein-DNA complex is detected by the change of the mechanical stability of the DNA.
My interest in this PhD project is to develop this combined setup of MFB and microarray for the screening of the binding-properties of transcription factors to varying DNA-sequences and under different solvent conditions. This would allow to get a better understanding in the field of gene regulation.
P.M.D. Severin, D. Ho, H.E. Gaub:
"A high throughput molecular force assay for protein-DNA interactions"
Lab Chip, 11, 856–862 (2011)
D. Ho, K. Falter, P. Severin, H. E. Gaub:
"DNA as a force sensor in an aptamer-based biochip for adenosine"
Anal. Chem., 81 (8), pp 3159–3164 (2009)
D. Ho, J. L. Zimmermann, F. A. Dehmelt, U. Steinbach, M. Erdmann, P. Severin, K. Falter, H. E. Gaub:
"Force-driven separation of short double stranded DNA"
Biophysical Journal. 97:3158-3167 (2009)
D. Ho, C. Dose, C. H. Albrecht, P. Severin, K. Falter, P. B. Dervan, H. E. Gaub:
"Quantitative detection of small molecule/DNA complexes employing a force-based and label-free DNA-microarray"
Biophys J. 2009 Jun 3;96(11):4661-71 (2009)