Visible and Near Infrared Absorption Spectrum of the Excited Singlet State of Chlorophyll a

Cherepanov, Dmitry A.; Гостев, Ф. Е.; Шелаев, И. В.; Aibush, A. V.; Semenov, Alexei; Mamedov, Mahir D.; Shuvalov, Vladimir V; Надточенко, В. А.

doi:10.1134/s0018143920020058

Cited by 8 publications

(1 citation statement)

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“…However, the minimum at 690 nm observed at the shortest delay is now known to represent the reduced accessory Chl 2A and Chl 2B monomers [35], while the electron equilibration between Chl 2A /Chl 2B and Chl 3A /Chl 3B proceeds at 2-5 ps [10,16,44]. The excited-state absorption maxima in the region of 650-670 nm may belong to both the excited state of Chl a [45,46] and to the A 0 anion [5].…”

Section: Transient Absorption Changes Of Photosystem I Variantsmentioning

confidence: 99%

Symmetry breaking in photosystem I: ultrafast optical studies of variants near the accessory chlorophylls in the A- and B-branches of electron transfer cofactors

Cherepanov

Шелаев

Гостев

et al. 2021

Photochem Photobiol Sci

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Femtosecond absorption spectroscopy of Photosystem I (PS I) complexes from the cyanobacterium Synechocystis sp. PCC 6803 was carried out on three pairs of complementary amino acid substitutions located near the second pair of chlorophyll molecules Chl 2A and Chl 2B (also termed A -1A and A -1B ). The absorption dynamics at delays of 0.1-500 ps were analyzed by decomposition into discrete decay-associated spectra and continuously distributed exponential components. The multiexponential deconvolution of the absorption changes revealed that the electron transfer reactions in the PsaA-N600M, PsaA-N600H, and PsaA-N600L variants near the B-branch of cofactors are similar to those of the wild type, while the PsaB-N582M, PsaB-N582H, and PsaB-N582L variants near the A-branch of cofactors cause significant alterations of the photochemical processes, making them heterogeneous and poorly described by a discrete exponential kinetic model. A redistribution of the unpaired electron between the second and the third monomers Chl 2A /Chl 2B and Chl 3A /Chl 3B was identified in the time range of 9-20 ps, and the subsequent reduction of A 1 was identified in the time range of 24-70 ps. In the PsaA-N600L and PsaB-N582H/L variants, the reduction of A 1 occurred with a decreased quantum yield of charge separation. The decreased quantum yield correlates with a slowing of the phylloquinone A 0 → A 1 reduction, but not with the initial transient spectra measured at the shortest time delay. The results support a branch competition model, where the electron is sheared between Chl 2A -Chl 3A and Chl 2B -Chl 3B cofactors before its transfer to phylloquinone in either A 1A or A 1B sites.

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