X-ray absorption spectroscopy investigations of the hydrophobic hydration of krypton at high pressure

The development of third-generation synchrotron radiation sources has creat ed considerable opportunities for the investigation of systems under extrem e sample conditions of pressure and temperature. This paper presents the ap plication of a recently developed pressure cell and pressurization and circ ulation system to the investigation of the hydrophobic hydration of noble g ases by X-ray absorption spectroscopy. This system operates in the pressure range from 1 bar to 1 kbar, and allows for mixing of gaseous and liquid co mponents and the control of the ultimate gas in liquid concentration. First results demonstrate the remarkable resilience of the first hydration shell of a nonpolar solute (krypton) to the application of pressure in the 150 b ar to 700 bar range. These results suggest questioning the conclusions of s ome recent computer simulations, in particular with regards to the potentia l impact of such studies on our understanding of pressure induced protein d enaturation.