Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 11, Issue 7, Pages 2470-2476Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.0c00294
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Funding
- NSFC [21520102005, 21688102, 21590801, 21421003]
- Fundamental Research Funds for Central Universities
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We have employed the QM(CASPT2//CASSCF)/MM method to explore the excited-state isomerization and decay mechanism of a single-bond-rotation locked photoactive yellow protein (PYP) chromophore in wild-type and mutant proteins. The S-1 state is a spectroscopically bright state in the Franck-Condon region. In this state, there exist two excited-state isomerization pathways separately related to the clockwise and anticlockwise rotations of the C=C bond. The clockwise path is favorable because of a small barrier of 2 kcal/mol and uses a novel bicycle-pedal unidirectional photoisomerization mechanism in which the involved two dihedral angles rotate asynchronously because of the reinforced hydrogen-bonding interaction between the chromophore and Cys69. Near the twisted S-1 minimum, the chromophore hops to the S-0 state via the S-1/S-0 conical intersection. Finally, the R52A mutation has small effects on the excited-state properties and photoisomerization of the locked PYP chromophore. The present work provides new insights for understanding the photochemistry of PYP chromophores in protein surroundings.
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