Ultrafast Photoreaction Dynamics of a Light-Driven Sodium-Ion-Pumping Retinal Protein from Krokinobacter eikastus Revealed by Femtosecond Time-Resolved Absorption Spectroscopy

We report the first femtosecond time-resolved absorption study on ultrafast photoreaction dynamics of a recently discovered retinal protein, KR2, which functions as a light-driven sodium-ion pump. The obtained data show that the excited-state absorption around 460 nm and the stimulated emission around 720 nm decay concomitantly with a time constant of 180 fs. This demonstrates that the deactivation of the S1 state of KR2, which involves...