Photo-initiated Dynamics and
Spectroscopy of the Deprotonated Green
Fluorescent Protein Chromophore
5
Anastasia V. Bochenkova and Lars H. Andersen
Abstract
This chapter combines recent advances in understanding the photophysics of the
chromophore anion of the Green Fluorescent Protein (GFP) from the jellyfish
Aequorea Victoria. GFP and its homologues are widely used for in vivo labeling
in biology through their remarkable fluorescent properties. Besides longtimescale light emission, the GFP proteins also show an unusual diversity in
terms of their non-radiative excited-state decay channels, including ultrafast
conical intersection dynamics and light-driven electron transfer, where GFP
acts as an electron donor in photochemical reactions. Knowledge of intrinsic
properties of the GFP photoabsorbing molecular unit is a prerequisite in understanding the atomic-scale interactions that play a key role for the diverse
functioning of these proteins. Here, we show how recent developments in action
and photoelectron spectroscopy combined with state-of-the-art electronic structure theory provide valuable insights into photo-initiated quantum dynamics and
enable to disclose mechanisms of multiple intrinsic excited-state decay channels
in the bare GFP chromophore anion. When taken out of the protein, the
deprotonated chromophore exhibits the ultrafast excited state dynamics, where
non-radiative decay occurs on a (sub)picosecond timescale. Deactivation
includes resonant electron emission and fast internal conversion followed by
slow statistical decay in the vibrationally hot ground state. Remarkably, both
electronic and nuclear excited-state decay channels may here efficiently compete with each other in spite of their inherently different intrinsic timescales. The
reason behind this is an efficient coupling between the nuclear and electronic
motion in the photo-initiated dynamics, where the energy may be transferred
from nuclei to electrons and from electrons to nuclei mediated by specific
vibrational modes. Prompt photodetachment occurs indirectly through vibrational autodetachment out of the first excited state within the energy range
A.V. Bochenkova (*) • L.H. Andersen
Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
e-mail: bochenkova@phys.au.dk
S. Brøndsted Nielsen and J.A. Wyer (eds.), Photophysics of Ionic Biochromophores,
Physical Chemistry in Action, DOI 10.1007/978-3-642-40190-9_5,
# Springer-Verlag Berlin Heidelberg 2013
67
Spectroscopy of the Deprotonated Green
Fluorescent Protein Chromophore
5
Anastasia V. Bochenkova and Lars H. Andersen
Abstract
This chapter combines recent advances in understanding the photophysics of the
chromophore anion of the Green Fluorescent Protein (GFP) from the jellyfish
Aequorea Victoria. GFP and its homologues are widely used for in vivo labeling
in biology through their remarkable fluorescent properties. Besides longtimescale light emission, the GFP proteins also show an unusual diversity in
terms of their non-radiative excited-state decay channels, including ultrafast
conical intersection dynamics and light-driven electron transfer, where GFP
acts as an electron donor in photochemical reactions. Knowledge of intrinsic
properties of the GFP photoabsorbing molecular unit is a prerequisite in understanding the atomic-scale interactions that play a key role for the diverse
functioning of these proteins. Here, we show how recent developments in action
and photoelectron spectroscopy combined with state-of-the-art electronic structure theory provide valuable insights into photo-initiated quantum dynamics and
enable to disclose mechanisms of multiple intrinsic excited-state decay channels
in the bare GFP chromophore anion. When taken out of the protein, the
deprotonated chromophore exhibits the ultrafast excited state dynamics, where
non-radiative decay occurs on a (sub)picosecond timescale. Deactivation
includes resonant electron emission and fast internal conversion followed by
slow statistical decay in the vibrationally hot ground state. Remarkably, both
electronic and nuclear excited-state decay channels may here efficiently compete with each other in spite of their inherently different intrinsic timescales. The
reason behind this is an efficient coupling between the nuclear and electronic
motion in the photo-initiated dynamics, where the energy may be transferred
from nuclei to electrons and from electrons to nuclei mediated by specific
vibrational modes. Prompt photodetachment occurs indirectly through vibrational autodetachment out of the first excited state within the energy range
A.V. Bochenkova (*) • L.H. Andersen
Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
e-mail: bochenkova@phys.au.dk
S. Brøndsted Nielsen and J.A. Wyer (eds.), Photophysics of Ionic Biochromophores,
Physical Chemistry in Action, DOI 10.1007/978-3-642-40190-9_5,
# Springer-Verlag Berlin Heidelberg 2013
67