Web Release Date: April 9,
Operation of the Proton Wire in Green Fluorescent Protein. A Quantum Dynamics Simulation
and
Departament de Química Universitat Aut
noma de Barcelona, 08193 Bellaterra (Barcelona), Spain, Institut de
Biotecnologia i de Biomedicina, Universitat Autnoma de Barcelona, 08193 Bellaterra (Barcelona), Spain, and
Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229,
69120 Heidelberg, Germany
Received: February 8, 2008
Abstract:
A nuclear quantum dynamical simulation of the proton shuttle operating in the green fluorescent protein has
been carried out on a high-quality, high-dimensionality potential energy surface describing the photoactive
* excited state, and including motion of both the three protons and of the donor and acceptor atoms of the
hydrogen bonds in a closed proton wire. The results of the simulations show that proton transfer along the
wire is essentially concerted, synchronous, and very fast, with a substantial amount of the green fluorescent
species forming within several tens of femtoseconds. In this regard, analysis of the population of the fluorescent
species indicates that at least two dynamical regimes are present for its formation. Within the first hundreds
of femtoseconds, dynamics is very fast and impulsive. Later on, a slower pace of formation appears. It is
discussed that the two largest decay times for the protonated chromophore reported experimentally (Chattoraj,
M.; King, B. A.; Bublitz, G. U.; Boxer, S. G. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 8362-8367) might
correspond to some irreversible process occurring after formation of the fluorescent species, rather than to
cleavage of the chromophore's phenolic O-H bond.
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