High pressure-jump apparatus for kinetic studies of protein folding reactions using the small-angle synchrotron x-ray scattering technique

An apparatus suitable for pressure-jump experiments with variable pressure amplitude and a fast response time to facilitate time-resolved small-angle x-ray scattering at synchrotron facilities is described. The high pressure- jump apparatus is capable of performing bidirectional pressure jumps at a t ime resolution as high as 5 ms. The high pressure sample cell presented has flat diamond windows and is suited for pressures up to 0.7 GPa operating i n the temperature range from -40 to 120 degrees C. The cell is designed for investigating biological and other soft condensed matter materials. Modifi cations on the window supports allow also simultaneous wide-angle x-ray sca ttering data to be taken. We have used the equipment to study the kinetics of protein folding reactions. The performance of the apparatus is demonstra ted by presenting data on the pressure-induced un/refolding reaction of the water-soluble protein SNase WT. (C) 2000 American Institute of Physics. [S 0034- 6748(00)04410-5].