Plenary Lecture “Nuclear Genome Nanostructure Imaging at Single Molecule Resolution”
1970 Diploma in Physics (Univ. München);
1976 Dr.rer.nat. in Biophysics/Genetics (Univ. Freiburg);
1983 Habilitation, Dr.med.habil. for General Human Genetics and Experimental Cytogenetics (Univ. Freiburg);
1983 – present Professor (Ordinarius) University Heidelberg
1983 - 2011 Director "Applied Optics and Information Processing", KIP / Kirchhoff Institute for Physics. Since 2005 Director Biophysics of Genome Structure, Institute for Pharmacy and Molecular Biotechnology (IPMB), University Heidelberg
Member Faculty of Physics and Astronomy and (cooptated) Faculty for Biosciences and the Medical Faculty Mannheim Mannheim, University Heidelberg.
2006 - 2009 Second Speaker of the Academic Senate of Heidelberg University.
2003 - 2014 Adjunct Senior Staff Scientist, The Jackson Laboratory, Bar Harbor/ME
Since August 1, 2011 Head Lightoptical Nanoscopy/Super-Resolution Microscopy, Institute of Molecular Biophysics, D-55128 Mainz, Germany
Since 2013 Honorary Professor (Physics), University Mainz (JGU)
Since 2015 Research Associate Max Planck Institute for Chemistry, Mainz
Present topics of research
Functional nuclear organization has emerged as an important topic of epigenetics. For this, methods of far field lightoptical resolution are required beyond the possibilities of conventional epifluorescence microscopy (optical resolution about 200 nm laterally, 600 nm axially). Towards this goal, we have established a variety of superresolution microscopy (“nanoscopy”) methods. Our present spectrum for ‘nanoimaging’ of nuclear structures comprises confocal laser scanning 4Pi-microscopy, Spatially Modulated Illumination (SMI) and Patterned Excitation Microscopy (PEM) devices, and Spectrally Assigned Localization Microscopy (SALM). While 4Pi microcoscopy was applied to superresolution of nuclear pore complex distribution, replication complexes and other nuclear nanostructures (axial optical resolution in the 120 nm range), SMI microscopy made it possible to measure the size of telomeric complexes with a resolution down to few tens of nanometer, and to perform precise size measurements of the compaction status of small, specifically labelled chromatin domains. Using a recently developed SALM technique, Spectral Precision Distance/Position Determination Microscopy (SPDM) with Physically Modifiable Fluorophores (SPDMPhymod), nuclear nanostructures can now be studied on a large scale in 3D intact nuclei down to a lateral optical resolution of individual molecules in the macromolecular range in optical sections of down to few tens of nm thickness. These techniques can be performed with standard fluorescence proteins/fluorochromes. For example, the distribution of individually resolved nuclear pore complex proteins, histones, DNA, FISH labelled repetitive short DNA sequences was determined with a lateral optical resolution down to about 15 nm; the spatial location of two species of single molecules in human cell nuclei (e.g. histones and chromatin remodelling factors; histones and polymerase II) was determined simultaneously by dual color localization microscopy up to a density of ca. 10,000 molecules/µm2. Nanoscopy experiments of other cellular features combining SPDMPhymod and Structured Illumination Microscopy (SIM) indicate that in this way, appropriately labeled chromatin structures may be analysed in 3D intact cells at an optical 3D resolution of 40 – 50 nm.
These superresolution microscopy can also be applied to other biological nanostructures. Our present experience using SPDM comprises single molecule resolution in membranes, cell junctions, bacteria, and viruses. Under optimum conditions, we presently achieve an optical resolution potential of 5 nm (ca. 1/100 of the exciting wavelength).
Perspectives: The focus of our future research will be to further improve these methods and apply them in collaborative projects in epigenetics and biophysics.