The monochromatic single crystal diffractometer BIODIFF is a joint project of the FRM II and the Forschungszentrum Jülich (FZJ).

BIODIFF is designed to handle crystals with large unit cells and is dedicated to the structure determination of biological macromolecules. In biological macromolecules, like proteins and nucleic acids, hydrogen atoms play an important role. Hydrogen atoms take part in the substrate binding process and are essential for proton transfer reactions du­ring the catalysis in many enzymes. Therefore the knowledge about the protonation states of amino acid residues in the active centre of proteins is often crucial for the understanding of their reaction mechanisms.  However, hydrogen atoms, especially rather flexible ones, are barely detectable in X-ray structure determinations of proteins. On the other hand, hydrogen atoms are clearly visible in neutron crystallography experiments even at moderate resolutions (d_min < 2.0 Å).