Open AccessExcited-State Vibronic Dynamics of Bacteriorhodopsin from Two-Dimensional Electronic Photon Echo Spectroscopy and Multiconfigurational Quantum Chemistry
Author(s) -
Samer Gozem,
Philip J. M. Johnson,
Alexei Halpin,
Hoi Ling Luk,
Takefumi Morizumi,
Valentyn I. Prokhorenko,
Oliver P. Ernst,
Massimo Olivucci,
R. J. Dwayne Miller
Publication year - 2020
Publication title -
the journal of physical chemistry letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.563
H-Index - 203
ISSN - 1948-7185
DOI - 10.1021/acs.jpclett.0c01063
Subject(s) - photoisomerization , excited state , chromophore , chemistry , spectroscopy , isomerization , bacteriorhodopsin , ultrashort pulse , excitation , molecular physics , photochemistry , chemical physics , atomic physics , physics , laser , optics , quantum mechanics , biochemistry , membrane , catalysis
Owing to the ultrafast time scale of the photoinduced reaction and high degree of spectral overlap among the reactant, product, and excited electronic states in bacteriorhodopsin (bR), it has been a challenge for traditional spectroscopies to resolve the interplay between vibrational dynamics and electronic processes occurring in the retinal chromophore of bR. Here, we employ ultrafast two-dimensional electronic photon echo spectroscopy to follow the early excited-state dynamics of bR preceding the isomerization. We detect an early periodic photoinduced absorptive signal that, employing a hybrid multiconfigurational quantum/molecular mechanical model of bR, we attribute to periodic mixing of the first and second electronic excited states (S 1 and S 2 , respectively). This recurrent interaction between S 1 and S 2 , induced by a bond length alternation of the retinal chromohore, supports the hypothesis that the ultrafast photoisomerization in bR is initiated by a process involving coupled nuclear and electronic motion on three different electronic states.