Automatic Sample Centering for High Throughput MX (a.k.a. PX) Beamlines

Bernard Lavault
Eur. Mol. Biol. Lab., Grenoble

Fully automated data collection at synchrotron beamlines is a key component of high-throughput macromolecular crystallography. One of the important tasks of such a pipeline is to center the crystal automatically with respect to the beam. The diversity of crystals in terms of shape, color, size, transparency, and the possible complexity of artefacts in the visualization environment require the development of special algorithms. The EMBL-Grenoble has developed C3D, a standalone program which is able to calculate the 3D coordinates of the center of a crystal inside a nylon loop from a series of images taken on the goniostat. The last version of C3D relies on a scoring system, which filters interesting objects inside the loop and connects them together. The centering strategy and the visualization system are also key contributor to the result. C3D enabled the first fully automated pipeline for crystal screening at the ESRF beamline and performed with a good success rate.