Neutron and X-ray for the study of biological macromolecules

Over the years neutron protein crystallography has emerged as a powerful technique that yields unique information for an understanding of macromolecular function. It allows visualisation of protonation states and water networks surrounding biological macromolecules which has been a longstanding challenge in structural biology.  The insights provided are crucial for an understanding of enzymatic catalysis, redox reactions, and protein engineering relevant to areas such as bio-fuel cells, biosensors and biochips, and drug design. It is also well established that accurate neutron diffraction data can provide an unbiased picture of the Atomic Displacement Parameters (ADP) of all the atoms of small molecules, and many neutron diffraction studies have been conducted exploiting the ability of neutrons to provide detailed and reliable information on the nuclear coordinates and anisotropic ADPs.

An unprecedented resolution of 0.88Å was obtained from a cryo-cooled sample of perdeuterated rubredoxin, uncovering a world of structural details beyond what can be observed with X-ray crystallography with highly structured water networks. Using a similar crystal of rubredoxin we have also shown for the first time that neutron anomalous dispersion can be used in a routine way to determine experimental phases of a protein crystal structure.

In this talk we present a few of these structures and emphasize the complementarity of the technique with respect to X-rays as well as its potential for new applications. The importance of appropriate data integration software will also be addressed.