期刊
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
卷 14, 期 7, 页码 1784-1793出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.2c03619
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The relationship between the unique Cl- binding site of monkey green (MG) pigment and the spectral tuning in green pigments is still unknown. This study presents computational structural modeling and quantum-chemical simulation of MG pigments, investigating the spectral redshift and physicochemical relevance when Cl- is present. The modeled protein structures are consistent with the experimental observations, and the red-shifted absorption energies are successfully reproduced by excited-state calculations.
The visual pigments of the cones perceive red, green, and blue colors. The monkey green (MG) pigment possesses a unique Cl- binding site; however, its relationship to the spectral tuning in green pigments remains elusive. Recently, FTIR spectroscopy revealed the characteristic structural modifications of the retinal binding site by Cl- binding. Herein, we report the computational structural modeling of MG pigments and quantum-chemical simulation to investigate its spectral redshift and physicochemical relevance when Cl- is present. Our protein structures reflect the previously suggested structural changes. AlphaFold2 failed to predict these structural changes. Excited-state calculations successfully reproduced the experimental red-shifted absorption energies, corroborating our protein structures. Electrostatic energy decomposition revealed that the redshift results from the His197 protonation state and conformations of Glu129, Ser202, and Ala308; however, Cl- itself contributes to the blueshift. Site-directed mutagenesis supported our analysis. These modeled structures may provide a valuable foundation for studying cone pigments.
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