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Non‐Bonded Interactions Drive the Sub‐Picosecond Bilin Photoisomerization in the P fr State of Phytochrome Cph1
Author(s) -
Yang Yang,
Heyne Karsten,
Mathies Richard A.,
Dasgupta Jyotishman
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201501073
Subject(s) - photoisomerization , photoswitch , picosecond , phytochrome , photochemistry , isomerization , excited state , chemistry , femtosecond , spectroscopy , ultrashort pulse , chemical physics , physics , optics , organic chemistry , laser , atomic physics , red light , botany , quantum mechanics , biology , catalysis
Phytochromes are protein‐based photoreceptors harboring a bilin‐based photoswitch in the active site. The timescale of photosignaling via C 15 =C 16 E‐to‐Z photoisomerization has been ambiguous in the far‐red‐absorbing P fr state. Here we present a unified view of the structural events in phytochrome Cph1 post excitation with femtosecond precision, obtained via stimulated Raman and polarization‐resolved transient IR spectroscopy. We demonstrate that photoproduct formation occurs within 700 fs, determined by a two‐step partitioning process initiated by a planarization on the electronic excited state with a 300 fs time scale. The ultrafast isomerization timescale for P fr ‐to‐P r conversion highlights the active role of the nonbonding methyl–methyl clash initiating the reaction in the excited state. We envision that our results will motivate the synthesis of new artificial photoswitches with precisely tuned non‐bonded interactions for ultrafast response.