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 bi ological samples in a diamond anvil cell (DAC) is described. It is cap able of operating in the whole temperature and pressure range of inter est for studies of biological molecules, i.e., in the temperature rang e from -40 to 100 degrees C at pressures between 1 bar and 50 kbar. Th e pressure is calibrated by measuring the pressure dependence of the r uby fluorescence line at 694 nm. Two linear detectors connected in ser ies 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) us ing the high intensity of synchrotron radiation. Secondly, only the di amond anvil technique allows to reach extreme pressures. Thirdly, the use of the dual detector system allows recording of diffraction data b oth in the small- and wide-angle region at the same time. Examples of hitherto unknown phases of aqueous lipid and protein samples illustrat e the potential of the system.