Biological crystal alignment using image processing

Crystal location and alignment to the x-ray beam is an enabling technology necessary for automation of the macromolecular crystallography at synchrotron beamlines. In a process of crystal structure determination, a small size x-ray synchrotron beam with FWHM as small as 70 μm (bending magnet beamlines) and 20 μm (undulator beamlines) is focused at or downstream of the crystal sample. Protein crystals used in structure determination become smaller and approach 50 μm or less, and need to be precisely placed in the focused x-ray beam. At the Structural Biology Center the crystals are mounted on a goniostat, allowing precise crystal xyz positioning and rotations. One low and two high magnification cameras integrated into synchrotron beamline permit imaging of the crystal mounted on a goniostat. The crystals are held near liquid nitrogen temperatures using cryostream to control secondary radiation damage. Image processing techniques are used for automatic and precise placing of protein crystals in synchrotron beam. Here we are discussing automatic crystal centering process considered for Structure Biology Center utilizing several image processing techniques.