Health and biology

With the X-ray flashes of the European XFEL, scientists are able to analyse the structure of biomolecules and biological entities such as proteins, cells, or membranes. Researchers will also be able to study how these entities change while working. Understanding the structure of these entities, as well as their temporal changes, will provide insights into their functions, and can form an important basis for the development of future medicines and therapies.

To determine the arrangement of the atoms in a molecule or material with X-rays, it is currently still necessary to have that molecule or material in a crystalline solid form in which the molecules are placed in the same orientation periodically in space. Crystallization of biological molecules is by no means simple, and the efforts to obtain crystals to of sufficient size and quality for synchrotron investigation have lasted years, if not decades, whereas the successive steps are much faster.

X-ray FELs have already shown a qualitative improvement over synchrotrons in the capability to obtain structural information from very small (micrometer or less) nanocrystals. For instance at LCLS in Stanford, in 2012 the previously unknown structure of a protein (cysteine protease cathepsin B) was determined to a resolution of 0.21 nm, from the investigation of nanocrystals at room temperature.  It was the first new biological structure solved with a free-electron laser. The protein plays a very important role in the pathogenesis of sleeping sickness, a disease that is widespread in Africa and causes about 30 000 deaths per year. The new knowledge can be used for treatment approaches against the parasite causing the disease.

The European XFEL pulses are going to improve the structural determination of nanocrystals considerably, and could even pave the way towards the ultimate dream of structural biology, the determination of the structure from single, non-crystalized molecules.

The scientific community expects that the European XFEL will become a very efficient decoder, obtaining in a much shorter time and with reduced effort a large number of structures for molecules such as membrane proteins, from which crystals larger than a micrometer in size are hard to obtain. This will advance progress in our understanding of pathogens and the development of pharmaceutical remedies.

As biomolecules are the machines of life, like mechanical machines with moving parts, they modify their structure in the course of performing their respective tasks. It would also be extremely illuminating to follow these modifications and see the motion of the moving parts in a movie. To make a film of a moving object, it is necessary to take many snapshots. Faster movement requires a shorter exposure time and a greater number of snapshots to avoid blurring the pictures. This is where the ultrashort duration of the FEL pulses will ensure sharp, non-blurred pictures of very fast processes.