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Hydrogen‐Bond Network Determines the Early Photoisomerization Processes of Cph1 and AnPixJ Phytochromes
Author(s) -
Liu XiangYang,
Zhang TengShuo,
Fang Qiu,
Fang WeiHai,
González Leticia,
Cui Ganglong
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202104853
Subject(s) - photoisomerization , phytochrome , chromophore , phycocyanobilin , chemistry , hydrogen bond , photochemistry , intersystem crossing , chemical physics , excited state , biophysics , isomerization , molecule , physics , atomic physics , organic chemistry , biology , cyanobacteria , botany , red light , bacteria , singlet state , catalysis , genetics , phycocyanin
Abstract Phytochrome proteins are light receptors that play a pivotal role in regulating the life cycles of plants and microorganisms. Intriguingly, while cyanobacterial phytochrome Cph1 and cyanobacteriochrome AnPixJ use the same phycocyanobilin (PCB) chromophore to absorb light, their excited‐state behavior is very different. We employ multiscale calculations to rationalize the different early photoisomerization mechanisms of PCB in Cph1 and AnPixJ. We found that their electronic S 1 , T 1 , and S 0 potential minima exhibit distinct geometric and electronic structures due to different hydrogen bond networks with the protein environment. These specific interactions influence the S 1 electronic structures along the photoisomerization paths, ultimately leading to internal conversion in Cph1 but intersystem crossing in AnPixJ. This explains why the excited‐state relaxation in AnPixJ is much slower (ca. 100 ns) than in Cph1 (ca. 30 ps). Further, we predict that efficient internal conversion in AnPixJ can be achieved upon protonating the carboxylic group that interacts with PCB.