Making sense of a crystal

Oeiras, 08.10.09

This week, the Nobel Prize in Chemistry was attributed to researchers working with X-ray crystallography. Venkatraman Ramakrishnan, Thomas A. Steitz, and Ada E. Yonath were jointly awarded this prestigious prize "for studies of the structure and function of the ribosome".

As the document prepared by the royal Swedish Academy for this year’s Nobel Prize explains, "in X-ray crystallography, scientists aim X-rays towards a crystal of, for example, a protein. When the rays hit the crystal’s atoms they are scattered. (…) On the other side of the crystal, scientists register how the rays have spread out. By analyzing the pattern of dots, scientists can determine exactly how the atoms are positioned in a protein.

For this to work, however, the crystal has to be almost perfect; the molecules need to form a precise pattern, which is repeated over and over again. With a little luck, when salt water is allowed to slowly evaporate, beautiful salt crystals are formed. However, if a pan full of salt water is allowed to boil dry, the salt only forms a dull layer at the bottom of the pan. Different conditions thus render more or less useful crystals. To a large extent, this also applies to crystals for X-ray crystallography. To obtain high quality crystals from a protein can be a very tough task, and the larger the protein complex, the harder the task." And this makes every protein structure deciphered a story of success.

At ITQB, the Macromolecular Crystallography Unit also resorts to the technique of X-ray Crystallography to determine the three-dimensional structures of molecules. Aiming at the structural characterization of biological macromolecules, such as proteins and nucleic acids, researchers help to elucidate the detailed mechanisms by which these macromolecules carry out their functions in living cells and organisms. Some of the projects at the Macromolecular Crystallography Unit include 3D-structural studies of proteins involved in catalytic reactions (enzymes), electron transfer processes, or transport. Others are related with human health and may have potential medical or industrial applications.

Examples of the research carried out at ITQB can be found in prominent scientific journals and are as diverse as the work on the sorbitol operon regulator suggesting a novel transcriptional regulation mechanism (de Sanctis, J Mol Biol 2009), on the dynamics of RNA degradation by RNAse II (Frazão, Nature 2006),  on the sulfur incorporation into biological systems via a proteic nano-reactor (Ulrich, Science 2006), on RuvBL1 involved in  essential signaling pathways (Matias, J Biol Chem. 2006), on the membrane-bound cytochrome c nitrite reductase complex (Rodrigues, EMBO J. 2006), or on the ligand-binding domain of the human androgen receptor, which represented  an important contribution towards the design of new drugs (Matias, J. Biol. Chem. 2000).

The importance of X-ray Crystallography to biology and science as a whole is highlighted by the number of scientists from this field who have been Nobel Prize laureates, from its earliest days - Wilhelm Roentgen (Physics 1901) – to the present day with the Nobel Prize in Chemistry 2009. In total over 20 Nobel Prizes have been awarded for scientific achievements directly related to, or involving the use of, crystallographic methods and techniques.