Titan meets Orbi Integrated structure determination approaches. Research in our laboratory combines biochemical approaches, proteomics and cryo-electron microscopy to study the structure and function of large macromolecular assemblies. Cryo-electron tomography is the ideal tool to observe molecular machines at work in their native environment. Since the attainable resolution of the tomograms is moderate, the challenge ahead is to integrate information provided by complementary approaches in order to bridge the resolution gap towards the high-resolution techniques (NMR, X-ray crystallography). Mass spectrometry approaches can provide the auxiliary information that is necessary to tackle this challenge. Targeted mass spectrometry can handle complex protein mixtures and, in combination with heavy labeled reference peptides, provides quantitative information about protein stoichiometries within macromolecular assemblies. Together with cross-linking techniques, the protein interfaces are revealed. The spatial information obtained in this way facilitates the fitting of high-resolution structures into cryo-EM maps in order to build atomic models of entire molecular machines.

Subunit switch Cell-type specific protein complexes. The function of a large fraction of all protein complexes is fine-tuned towards context specific needs by compositional remodeling across different cell-types. Structural variations occur through stoichiometric changes, subunit switches or competing protein interfaces. We employ integrated approaches as described above to study compositional variations of protein complexes.

Nuclear Pore Nuclear Pore Complexes reside within the nuclear envelope of eukaryotic cells and facilitate the nucleocytoplasmic exchange of macromolecules. Structure determination of the nuclear pore complex is challenging due to its size, membrane associated nature and intricate composition. We use integrated mass spectrometry and electron microscopy approaches to investigate structure and function of the human nuclear pore.

computer Computational Biology is an important aspect of our work. To employ integrated structure determination approaches, algorithms often need to be adapted to the available data in a case by case manner. We primarily focus on image processing for electron microscopy namely feature recognition and classification and the analysis of quantitative mass spectrometry data, such as statistical validation, relative and absolute quantification.