3D images of molecules at atomic scale for insights into molecular interactions and biological processes
Instruct has 3 centres offering X-ray crystallography beamline across Europe. Navigate the map and click on the pins to discover centres near you.
X-ray diffraction is a technique allowing the visualization of molecules at the atomic level, and thus offering incredible insights into the molecular mechanisms of biological processes.
The collection of X-ray diffraction data from a crystal is the last experimental step in a structure determination process and it is therefore critical that these measurements are optimal. For any given experiment, the accuracy of collected of data is largely dependent on using the most modern equipment The use of a synchrotron is especially well suited for these experiments as it provides small highly intense radiation.
Each synchrotron X-ray crystallography beamline is tailored to optimize the radiation for each individual X-ray diffraction experiment. The unique properties of such synchrotron based beamlines ensure that highly intense and focused X-rays beams are delivered onto small biologically important crystals. The X-ray diffraction resulting from such crystals is then collected using the most modern charge coupled detectors (CCD) and pixel counting X-ray detectors.
An X-ray crystallography beamline is therefore a highly complex piece of advanced engineering designed to give the most accurate measurement of X-ray diffraction data possible.
Most synchrotrons already offer access to their suite of X-ray crystallography beamlines to applicants selected on the basis of peer-review. Applications for beamline time are generally made through web-based proposal systems and should be consulted first. Instruct hopes to provide an additional portal of access to some of these X-ray beamlines in the near future, once its application process has been implemented.
A typical X-ray diffraction experiment may take anything from a few (1-2 minutes) on an insertion device beamline, to tens of minutes on bending magnet beamlines. However, while the experiment itself is relatively fast, a number of crystals need to be screened for their diffraction properties, in order to select the optimal one or two for a successful experiment. For the most challenging structures, hundreds or even thousands of crystals may need to be screened.
This screening is normally facilitated by robotic sample changers, allowing many crystals to be tested. Users should mount their crystals onto SPINE standard pins and vial, which are supported by all European synchrotrons.
Most sites also provide online sample characterisation using programs such as EDNA (http://wiki.edna-site.org/index.php/Main_Page) and we recommend using such software for selecting the best diffracting crystals. These selection results are fed into databases such as ISPyB for further analysis and book-keeping. Once the best crystal has been remounted, data is carefully collected using an optimized strategy, again using EDNA.
Many sites now also offer automatic data processing, and indeed other automated structure solving routines, whose results are also saved in ISPyB. The last step is to ensure that data is properly backed-up, either using ftp servers or external hard drives. Please consult the beamline webpages before coming, to ensure you are able to retrieve or back-up your data.