The anionic wild-type Green Fluorescent Protein (GFP) chromophore defines the entire class of naturally occurring chromophores, which are based on the oxydized tyrosine side chain. The GFP chromophore exhibits an enriched photoinduced non-adiabatic dynamics in the multiple excited-state decay channels. Deactivation includes vibrational resonant photodetachment and internal conversion. Here, we provide a detailed insight in the efficiency of different vibrational modes in promoting a selective photoresponse in the bare GFP chromophore anion. We introduce a general theoretical model that is capable to account for the alternative non-equivalent pathways in internal conversion, and we outline the factors, by which the photo-initiated response may be altered in this channel. The topography around the planar minimum in S1 and the two distinct types of the S1/S0 conical intersections obtained through the high-level ab initio calculations provides direct support to the proposed model. There are alternative mode-selective ways to control the photoresponse and to direct it towards a single excited-state decay channel. By tuning the excitation wavelength, the photoresponse may be directed towards the ultrafast non-statistical electron emission coupled with vibrational (de)coherence, whereas a vibrational pre-excitation in the ground state may lead to the ultrafast non-statistical internal conversion through a conical intersection. We also discuss the implication of our results to the photo-initiated non-adiabatic dynamics in the proteins.
Faraday Discussions, 2013, Vol 2013, Issue 163, p. 297-319