January 2nd, 2013

SIAS group leader Dr. Lars Redecke was affiliated to the Schleswig-Holstein excellence cluster "Inflammation at Interfaces"

November 29th, 2012

First new biological structure solved by a FEL

The Junior Research Group SIAS significantly contributed to the elucidation of the first new biological structure using a free-electron laser (FEL), in close cooperation with international research groups including teams from Prof. Henry Chapman, Center for Free-Electron Laser Science (CFEL) at DESY, Prof. Christian Betzel, University of Hamburg, and Prof. Michael Duszenko, University of Tübingen.

The structure of the enzyme cathepsin B of the parasite Trypanosoma brucei, which causes sleeping sickness (human African Trypanosomiasis) and threatens particularly in sub-Saharan Africa more than 60 millions of people, was solved up to a resolution of 2.1 Å at the US research center SLAC in California using the world’s most powerful X-ray laser to date. The enzyme had emerged as a promising drug target in earlier trials since its knockdown in the parasite did cure the infection in mice.

The structural data was obtained by an entirely new technique applying the emerging method of serial femtosecond crystallography (SFX): A large number of enzyme crystals that have been grown in vivo within insect cells have been irradiated using high intensity X-ray pulses of the FEL, instead of using a single, large crystal with conventional synchrotron radiation. The analyzed crystals were only about a micron in diameter and about ten microns long on average. Due to the short duration of the laser pulses of only a few femtoseconds, diffraction data could be collected before the crystals exploded induced by the high energy of the radiation. A total of 293 195 single diffraction images have been used to calculate the final enzyme structure. Cathepsin B crystallized in vivo in complex with its native inhibiting propeptide. Thus, the detailed structural analysis revealed significant differences between the propeptide binding in human and parasite cathepsin B, which could be used to develop a novel synthetic inhibitor. However, there is still a long way to go to develop a new drug to treat sleeping disease, although this structure provides the most complete structural basis for the design of a specific cathepsin B inhibitor.

catbstructurediffractionLeft: Molecular structure of Trypanosoma brucei Cathepsin B. The blocking peptide and carbohydrate chains are depicted in green. They provide the initial new structural information produced by a free electron laser. Right: Diffraction pattern of a single CatB crystal. The detector consists of 64 unique CCD elements to be recognized as a tiled pattern. Pictures: Karol Nass.

The team included members from SIAS, the Universities of Hamburg, Lübeck, Tübingen, Uppsala and Gothenburg, the Arizona State University, DESY, SLAC, Lawrence Livermore National Laboratory, the Max Planck institute for medical research in Heidelberg and the Max Planck advanced study group at CFEL.

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August 1st, 2012
New BMBF-funded joint project "BIOSCAT"

The joint project „BIOSCAT“ between SIAS and the European Laboratory for Molecular Biology DESEY Outstation (EMBL, Dr. D.I. Svergun) for the development of synchroton-based x-ray scattering methods with highest brilliance for biological and nanotechnological structure determination will be funded for 3 years by BMBF in line with the German-Russian cooperation for "Development and Use of Accelerator-Driven Photon Sources". During this cooperation between SIAS, EMBL and three Russian partner institutes the prospects of synchrotron-based small-angle x-ray scattering (SAXS) at the new BioSAXS Beamline P12 at PETRA-3 are to be investigated. In addition to essential methodical improvements, the aim is also to adapt the new method to biological and nanotechnological questions. Especially the application of anomal scattering will be the focus for establishment of time-resolved SAXS measurement techniques which could not be used so far. At the same time two scientifically highly relevant model systems will be investigated: a) non-structural proteins of influenza A virus and b) the interaction of magnetic nanoparticles with biological macromolecules.

February 2nd, 2012

In vivo crystals show diffraction at free electron laser

Protein crystallization in cells has been observed several times in nature. However, owing to their small size these crystals have not yet been used for X-ray crystallographic analysis. We prepared nano-sized in vivo-grown crystals of Trypanosoma brucei enzymes and applied the emerging method of free-electron laser-based serial femtosecond crystallography to record interpretable diffraction data. This combined approach will open new opportunities in structural systems biology.

Electron microscopy image of a protein crystal sticking out of an insect cell.
(image: Michael Duszenko/University of T�bingen)

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