Exploitable Knowledge

The BIOXHIT project has actively stimulated commercial activities in the field. During the four years of the project, four developments resulted in commercial products. These are listed below and three of them are described in more detail. Numerous further developments have made their way into freely available scientific instruments or software and are thus not listed here.

1. X-ray beam position monitors

BIOXHIT successfully developed X-ray beam position monitors (XBPMs) capable of tracking the X-ray beam from source to sample position in a manner suitable for deployment as medium and high energy sources with sampling rates from 1 sec to ms resolution. The work was carried out at Partner 4 (SLS) and Partner 9 (BESSY) sites.

CVD diamond XBPMs, developed by SLS, constitute excellent high speed and high accuracy devices. The difficulty in producing workable devices lies mainly in the production of appropriate wafers. Initial difficulties have been overcome and three CVD diamond wafers are being processed and will serve as a basis for new high-speed beam position monitors, Figure 1 a.

The development of fast imaging beam monitors based on lens coupled CCDs and the necessary image analysis software has been undertaken by BESSY, Figures 1 b,c. In order to deploy these devices, radiation-hard fluorescing layers in a transmitting material have been developed and a solution was developed for monochromatic beams within the X-ray range of interest to MX. A new electrophoretic phosphor-deposition (EPD) method has been established and extended to further phosphor materials. After consolidation of the process parameters, an optimised electrophoresis protocol has been installed in the BESSY Optics lab. Long term tests with the monochromatic, narrow beam monitor showed the necessity to improve the radiation hardness for high flux density setups. The development is still ongoing, employing in-house coated EPD screens. The mechanical positioning of the monitor has been improved to allow for micrometer positioning reproducibility. The final construction of three prototype monitors has been performed in collaboration with an SME FMB Feinwerk- und Messtechnik GmbH. These three units are each geared towards a specific destination along the beamline: (1) polychromatic, wide beam, (2) monochromatic, wide beam and (3) monochromatic, narrow beam. The XBPMs were delivered in June 2007 and functionally evaluated at the BESSY-MX beamline BL14.1.

2. New fluorescence detector system for recording subtle differences in X-ray diffraction pattern (anomalous diffraction signal) for subsequent phasing of the crystal structure

Partner 9 (BESSY) has developed a complete new fluorescence detector with an optimised signal processing system for the integration into protein crystallography beamlines in close collaboration with Roentec GmbH (now Bruker/AXS), Berlin-Adlershof (see BIOXHIT annual reports for details). An alternative XRF detector configuration (90 deg azimuth / periscope), for a use at the background-scattering-optimised position perpendicular to the beam in the storage ring plane, developed in Year 3 of the project, has been integrated into the new experimental end-station at BESSY BL14.1, Figure 2. The detector control software has been adapted to be compatible with the new BLISS/SPEC/TANGO environment at BESSY in collaboration with the BLISS group (ESRF). Partner 9 has also supported Partner 1A (EMBL-HH) in ordering and integrating the XRF detector design with minimised footprint for inclusion in the crystallographic end-station of beamline X12. The new detector has proven record of excellent characteristics and is in routine operation on beamline X12.

3. Standard test crystal systems

A number of macromolecular test crystal systems Have been developed with which one can easily assess the quality of the beam before the real diffraction experiment is undertaken. One of the limiting factors is that macromolecular crystals do not exhibit infinite lifetime in an X-ray beam. Even at liquid nitrogen temperature, they are damaged by the radiation, which reduces the quality of the diffraction data. The challenge is to find the correct conditions for stabilisation of the crystals and to develop reproducible protocols for pre-testing them. Two candidate test crystal systems (cubic insulin and doubly cross-linked lysozyme) have been extensively evaluated.

A test system for detector sensitivity with cubic insulin is exemplified in Figure 3 a, where the reflections in red are those which are systematically higher their expected value and those in blue having lower than the expected value. Particularly for mosaic CCD detectors diffracted reflections sometimes appear through the cracks between the adjacent CCD chips and this problem is probably caused by a fall in the sensitivity at the edges of the chips. After the problem has been identified with the BIOXHIT standard crystal set, the detector manufacturers were informed and the BIOXHIT Partner 5 (GPHL) has started investigating was of correcting for it.

The test crystal system on cross-linked lyzozyme has been commercialised, Figure 3 b. Most synchrotron sites have been quick to use these test crystals, with the newer synchrotrons (DIAMOND and SOLEIL) now also adopting these. These test crystals are no longer dissolvable in water, glycerol or sterene. They are also robust, stable and easily transported. Even after months of storage and repeated freezing and thawing the test crystals still retain thgeir diffraction properties.