Just a century after the first studies of structural crystallography, the level of complexity that we are capable of examining has multiplied by several million. But this is just the beginning. The new synchrotron radiation and free electron laser facilities, together with the new crystallographic methods and computers that are ever more powerful where they can be implemented, bodes for an accelerating growth of the fields of study using crystallographic knowledge.
Synchrotrons are particle accelerators capable of producing a beam of X-rays several orders of magnitude more intense than conventional laboratory equipment. These X-ray beams make it possible to carry out previously unfeasible experiments, such as those that produce very low diffracted intensity due to the nature of the crystal or the process studied. In 1972 the first dedicated synchrotron went into operation in Stanford, USA (first generation), and from there they have been continuously evolving, until reaching the most modern, third-generation synchrotrons such as the European Synchrotron Radiation Facility (Grenoble, France) or the Spanish synchrotron ALBA, in Barcelona.
Synchrotron light facilities are the cathedrals of crystallography, the great laboratories to which crystallographers make pilgrimage to unravel the intimate structure and behaviour of matter and to discover how life works.
In order to study how the molecular machines of life work, it is necessary to study more and more complex and detailed molecules. We are currently capable of understanding, for example, how T-cell receptors (in red) recognise and block invaders of the body (for example, a peptide, in blue).
Some problems of great importance in materials science or in nanotechnology are very difficult to study because the diffraction signal they produce is of very low intensity. Synchrotron radiation sources make it possible to deal with these problems. A typical example is the study of magnetic materials and interphases. In the figure, the crystalline and magnetic structures of the interphase between a superconductor and a ferromagnetic material are shown.
The future of X-ray diffraction lies in the new sources of X-ray radiation from free electron lasers (XFEL, X-Ray Free Electron Laser). This new source of X-rays is several orders of magnitude more intense than the last generation of synchrotrons, which enables the use of nanometric crystals and exposure times of only a few femtoseconds (one quadrillionth of a second), achieving structural information in extremely short times and using extremely small crystals. In fact, this new source of radiation in a certain way dodges the great problem of crystallization.
Free electron lasers produce ultra-short pulses of radiation at exceptionally high intensity, which opens the door to studying extremely quick chemical and biological processes. For example, it is already possible to study how electrons jump between the fragments of an exploding molecule.
|Map of the intensities made using two hundred thousand diffraction patterns of the enzyme cathepsin B of the parasite Trypanosoma brucei obtained with free electron laser.||Structural information derived from that map.|
But what is really revolutionary about this new technique is that such extraordinarily short exposure times make it possible to obtain dynamic information about what goes on inside a molecule or a biological macromolecule. The future couldn´t be more fascinating. Not only are we going to get to know the structure of matter but also we are going to see, in real time, how atoms move, how reactions are produced, how life works.