Ultrafast geminate electron-radical recombination dynamics in photoactive yellow protein
1 Department of Physics and Astronomy, Faculty of Sciences, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
2 Laboratory for Microbiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1010 WV Amsterdam, The Netherlands
Photoinduced ionization of the chromophore inside photoactive yellow protein (PYP) was investigated by ultrafast spectroscopy in the visible-near infrared spectral region. A solvated electron absorption-like band was observed that extended from around 550nm to 850nm, centred at 700nm. Simulation of the decay traces of the band with a classic diffusion model indicated that ejected electrons were located an average distance of ~3Å away from the radical centre, and around 40% the solvated electrons were annihilated by geminate recombination. The remaining 60% escaped out of the protein pocket to be annihilated by bulk recombination. This result indicates that the chromophore is in a local environment inside PYP that is only slightly different from the bath solvent.
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