TIME-RESOLVED X-RAY-DIFFRACTION STUDIES ON BIOLOGICAL-SYSTEMS

Understanding of biological function requires knowledge both on structural and dynamical aspects. The aim of time-resolved X-ray diffraction is to combine structural and kinetic methods by monitoring structural or conformational changes within a single protein or assemblies of proteins during their biological action in real time. This requires (i) a powerful X-ray source, (ii) appropriate detectors capable of dealing with high local and total count rates and (iii) a suitable trigger mechanism. These aspects are briefly discussed with emphasis on light as trigger for initiation of structural or conformational changes. Examples are presented on muscle contraction, lipid-phase transitions, the photocycle of bacteriorhodopsin and the application of Laue crystallography on the protein p21.