Three-dimensional (3D) Reconstruction of Single particles from Electron Micrographs

The research of our laboratory focuses on the three-dimensional structure determination of macromolecular assemblies using electron microscopy combined with image processing.

Structure and function of the NADH:ubiquinone oxidoreductase (complex I)

Currently we are investigating enzyme complexes of the respiratory chain and macromolecules with related functions. We are studying the structure and subunit arrangement of complex I from different species and the arrangement and interaction of respiratory chain molecules within the mitochondrial membrane. The importance of understanding the function and relationships between enzymes in the respiratory chain is highlighted by the fact that many mitochondrial diseases can be traced back to defects in the genes encoding complex I. Examples are LHON-disease (Lebers hereditary optic neuropathy), Lighs disease and Kearns-Sayre syndrome.

Development of new image processing methods for 3D electron microscopy.

A strong component of out research is the development of new image processing algorithms and techniques. Our current research is geared towards the development of better image alignment and classification methods and new techniques for sub-tomogram averaging.

Selected earlier work:

Microscopy techniques and image processing:

• Development of weighted backprojection methods for conical tilt tomography.
• Derivation of the equations for calculating resolution of 3D reconstruction by conical tomography in dependence on the number of projections and specimen shape (spherical enclosed, infinite slap).
• Analysis of the 3D point spread function in single axis and conical tomography: Influence of the missing data on the resolution in beam direction (equations that determine the ration between in-plane and z-resolution). Estimation of the artefacts (clutter) found within the reconstruction volume dependent on tilt geometry.
• Development of the  Random Conical Reconstruction Technique by combining conical tilt reconstruction with – at the time – new single particle 2D averaging and classification techniques.
• New techniques for transferfunction determination in tilt images.
• Development of new image processing techniques for 3D reconstruction, projection refinement, 2D and 3D alignment and noise reduction based on the properties of Radon transforms .

Structure and function studies of macromolecular assemblies:

• Procaryotic an Eucaryotic Ribosomes
• Ryanodine receptor, calcium release channel
• Nuclear pore complexes
• Centrosome
• Chromatine fibers
• V1-Atpase