Proteins in action: the physics of structural fluctuations and conformational changes.

Structural dynamics is essential for the biological function of proteins. Results from new experimental techniques should be compared with those from previous experiments in order to obtain a consistent picture of the physics of intramolecular fluctuations and conformational changes. The high intensity and time structure of synchrotron radiation have made possible time-resolved X-ray structure analysis and the determination of phonon density spectra through the Mössbauer effect. By combining results from Mössbauer absorption spectroscopy, incoherent neutron scattering, low-temperature crystallography and optical spectroscopy, a physical picture of protein dynamics emerges.