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

The development of third-generation synchrotron radiation sources has created considerable opportunities for the investigation of systems under extreme sample conditions of pressure and temperature. This paper presents the application of a recently developed pressure cell and pressurization and circulation system to the investigation of the hydrophobic hydration of noble gases 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 components 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 bar to 700 bar range. These results suggest questioning the conclusions of some recent computer simulations, in particular with regards to the potential impact of such studies on our understanding of pressure induced protein denaturation.