Photo-induced protein dynamics measured by femtosecond time-resolved luminescence

The early stage in the photo-induced dynamics of photoactive yellow protein in aqueous solution has been investigated at room temperature by the femtosecond luminescence spectroscopy using an optical Kerr-gate technique. Remarkable oscillatory components have been directly observed with the time resolution of 180 fs and the spectral resolution of 5 nm. Mapping the phase of oscillations in time at each wavelength reveals that each oscillation is restricted in the respective narrow spectral region, the period and amplitude of which are 500–800 fs and 100–200 cm−1, respectively. Since the mean spectral position of each component seems to be related to the molecular vibrational energy, the oscillatory components are possibly attributed to the combination of the intramolecular vibrations of the chromophore and the surrounding protein motions.