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Ultrafast Hydrogen-Bonding Dynamics in the Electronic Excited State of Photoactive Yellow Protein Revealed by Femtosecond Stimulated Raman Spectroscopy
journal contribution
posted on 2012-12-27, 00:00 authored by Ryosuke Nakamura, Norio Hamada, Kenta Abe, Masayuki YoshizawaThe ultrafast structural dynamics in the electronic excited
state
of photoactive yellow protein (PYP) is studied by femtosecond stimulated
Raman spectroscopy. Stimulated Raman spectra in the electronic excited
state, S1, can be obtained by using a Raman pump pulse
in resonance with the S1–S0 transition.
This is confirmed by comparing the experimental results with numerical
calculations based on the density matrix treatment. We also investigate
the hydrogen-bonding network surrounding the wild-type (WT)-PYP chromophore
in the ground and excited states by comparing its stimulated Raman
spectra with those of the E46Q-PYP mutant. We focus on the relative
intensity of the Raman band at 1555 cm–1, which
includes both vinyl bond CC stretching and ring vibrations
and is sensitive to the hydrogen-bonding network around the phenolic
oxygen of the chromophore. The relative intensity for the WT-PYP decreases
after actinic excitation within the 150 fs time resolution and reaches
a similar intensity to that for E46Q-PYP. These observations indicate
that the WT-PYP hydrogen-bonding network is immediately rearranged
in the electronic excited state to form a structure similar to that
of E46Q-PYP.