Automated analysis of vapor diffusion crystallization drops with an X-ray beam.

Crystallogenesis, usually based on the vapor diffusion method, is currently considered one of the most difficult steps in macromolecular X-ray crystallography. Due to the increasing number of crystallization assays performed by protein crystallographers, several automated analysis methods are under development. Most of these methods are based on microscope images and shape recognition. We propose an alternative method of identifying protein crystals: by directly exposing the crystallization drops to an X-ray beam. The resulting diffraction provides far more information than classical microscope images. Not only is the presence of diffracting crystals revealed, but also a first estimation of the space group, cell parameters, and mosaicity is obtained. In certain cases, it is also possible to collect enough data to verify the presence of a specific substrate or a heavy atom. All these steps are performed without the sometimes tedious necessity of removing crystals from their crystallization drop.

A new highly integrated sample environment for protein crystallography.

Protein crystallography is becoming a popular technique that is routinely used to access structural information. At one end of the process, sample preparation is now facilitated by commercially available crystallization kits. At the other end, structure determination has been made easier by automated software. Data collection, the step in between, is now usually performed on synchrotron sources. However, it is still restricted to experienced users and requires significant help from beamline staff. Part of this difficulty arises from the sophisticated experimental setup, which comprises a goniometer, a magnetic head, a device for changing the sample and monitoring accessories. It was proposed that this setup could be simplified by replacing these elements by a robotic arm that can perform all of the required tasks. In the present paper, it is demonstrated that this new setup can be used on a synchrotron beamline to mount and centre the sample and to collect diffraction data. This new system completely changes the design of the experimental setup by merging functions that were previously considered to be distinct. Moreover, automation of sample handling need not be considered as a specific development and is now included in a unique multipurpose device.