Soft X-Ray Diffraction up to Wavelengths of 6.0Å Becomes Feasible at ID1 of ESRF

Recent experiments carried out at the Anomalous Scattering Beamline ID1 of ESRF are described which show that a cold helium atmosphere provides optimal conditions for protein crystallography with soft X-rays at wavelengths up to 6Å. Image plates are suitable detectors for this wavelength range. The improvement with respect to earlier experiments is considerable. This observation opens the way to the use of anomalous dispersion at the K-edge of light elements, like phosphorus, sulphur, chlorine and calcium. Moreover, there is an interest to use the strong anomalous dispersion of some heavy elements such as uranium (110 anomalous electron units at its M_V edge) to solve large biological structures. The methods of multiwavelength anomalous diffraction and diffraction anomalous fine structure find new resonant labels which are wide spread in living matter and materials.