High pressure synchrotron X-ray diffraction studies of biological molecules using the diamond anvil technique

A system for high pressure synchrotron X-ray diffraction studies of biological samples in a diamond anvil cell (DAC) is described. It is capable of operating in the whole temperature and pressure range of interest for studies of biological molecules, i.e., in the temperature range from -40 to 100 degrees C at pressures between 1 bar and 50 kbar. The pressure is calibrated by measuring the pressure dependence of the ruby fluorescence line at 694 nm. Two linear detectors connected in series are used to measure simultaneously the small- and wide-angle X-ray scattering. The advantage of the experimental technique is threefold: Firstly, the amount of sample can be kept to a minimum (ca. 30 nl) using the high intensity of synchrotron radiation. Secondly, only the diamond anvil technique allows to reach extreme pressures. Thirdly, the use of the dual detector system allows recording of diffraction data both in the small- and wide-angle region at the same time. Examples of hitherto unknown phases of aqueous lipid and protein samples illustrate the potential of the system.