Water Molecules Are Active During the Primary Photoreaction of Bacteriorhodopsin

摘要

FI-IR difference spectra of the primary photoreaction of bacteriorhodopsin, thelight driven proton pump from Halobacterium halobium, are presented with data above 3500/cm. Samples were hydrated in H20, H2(18)O and D2O in order to distinguish vibrational bands due to water. In the bR yielding K difference spectrum, evidence is found for a water molecule which undergoes a strengthening in hydrogen bonding. In contrast, during the K yielding L and L yielding M steps of the photocycle one or more additional water molecules undergo a weakening in hydrogen bonding.