Ultrafast infrared spectroscopy of bacteriorhodopsin.

Picosecond infrared spectroscopy is developed and used for the first time to study the dynamics of photoexcited bacteriorhodopsin (BR). Both spectral and time-resolved data are obtained. The results open an entirely new approach to investigations of the BR photocycle. The infrared difference spectrum (K minus BR570) recorded at ambient temperature between 1,560 and 1,700 cm-1 is not identical with the spectrum reported for a frozen sample. Three bands of the K state at 1,622, 1,610, and 1,580 cm-1 and the bleaching at 1,637 cm-1 (C = NH stretch) are seen. These new spectral lines appear in less than 10 ps.