Resolving the primary dynamics of bacteriorhodopsin, and of a 'C-13=C-14 locked' analog, in the reactive excited state

The evolution of stimulated emission from the reactive excited state of bac teriorhodopsin is compared with that of a modified protein containing a syn thetic retinal which is unable to twist around the C-13=C-14 bond. The rise of the emission is demonstrated to be structured, multistaged and waveleng th dependent, appearing later in the red edge of the emission bands in both proteins. Spectral modulations associated with vibronic wavepacket motion are also observed in both. The mechanism of strong Stokes shifting of the e mission resolved here, and the nature of coherences observed in the excited state are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.