Every shot hits the mark

 

Unpicking the mysteries of microcrystals can be a huge challenge for scientists. But a European team led by scientists from DESY – a German national research centre composed of a series of particle accelerators – have now used Diamond to develop a new type of sample holder in which several thousand microcrystals can be positioned on a single silicon chip at the same time and then be examined by crystallographic methods. Scientists crystallise biological molecules such as proteins or viruses, and then use X-ray crystallography to visualise their atomic structure allowing us to understand how they function. Many of these structures are essential to understanding biological processes and developing new types of drugs. However, obtaining crystals can be difficult and time consuming.

 

At Diamond, crystals are exposed to intense light in the form of X-rays; this results in the diffraction patterns from which the atomic structure is determined. Recent developments in X-ray sources with increasing brilliance, such as Diamond, DESY’s PETRA III, or the new generation of free electron lasers (FELs), have opened the door to examining ever smaller crystals. These microcrystals are considerably easier to “grow”, but because of their small size they call for new approaches in preparing specimens.

 

Researchers from DESY in Germany, the Paul Scherrer Institute in Switzerland and Diamond Light Source in the UK have developed a new type of sample holder for ‘serial protein crystallography’. The holder consists of a single crystal of silicon with a regular array of pores. As the tiny crystals fall into the pores, the holder allows them to be positioned with great precision, while at the same time producing virtually no disruptive signal of its own during the X-ray diffraction experiment, something that is unavoidable using conventional methods. About 20,000 microcrystals fit on the two square millimetre silicon chip, all of which could be scanned in less than three minutes at a source such as the LCLS in California, making it an extremely effective mechanism for crystallography experiments.