2004 年 44 巻 3 号 p. 113-117
Internal water molecules are considered to play a crucial role in the functional processes of ion pump proteins, though little has been known about their structure and function. We have studied hydrogen-bonding alterations of internal water molecules in a light-driven proton pump, bacteriorhodopsin, by means of low-temperature Fourier-transform infrared (FTIR) spectroscopy. Highly accurate measurements enabled us to detect even a single stretching vibration of such water molecules. In addition, analysis of the water molecules hydrating with negative charges led to a proposal of the "hydration switch model" for the primary proton transfer reaction in bacteriorhodopsin.