This contribution deals with the methodology of X-ray crystallography, which offers the most powerful techniques for the elucidation of the three-dimensional structure of molecules or molecular assemblies at atomic resolution, in particular of natural products. Modern crystallography can roughly be divided into two sub-disciplines, the crystallography of “small molecules” (i.e. of molecules with molecular masses up to few thousand Daltons) and “macromolecular” crystallography (dealing with molecules or molecular assemblies above, say, 5 kDa).

Structure elucidation of natural compounds by X-ray crystallography.

Neutrons in biology - a perspective

The detergent micelles surrounding membrane protein molecules in single crystals can be investigated using neutron crystallography combined with H2O/D2O contrast variation. If the protein structure is known then the contrast variation method allows phases to be determined at a contrast where the detergent dominates the scattering. The application of various constraints allows the resulting scattering length density map to be realistically modeled. The method has been applied to two different forms of the membrane protein porin. In one case both hydrogenated and partially deuterated protein were used, allowing the head group and tail to be distinguished.

P. A. Timmins

Papers

Protein-Detergent Interactions in Single Crystals of Membrane Proteins Studied by Neutron Crystallography