Reversible inhibition and reactivation of electron transfer in photosystem I

Agarwala, Neva; Makita, Hiroki; Luo, Le; Xu, Wu; Hastings, Gary

doi:10.1007/s11120-020-00760-9

Cited by 11 publications

(6 citation statements)

References 63 publications

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“…Nonetheless one might expect electrochromic effects from protein or pigment species near the reduced iron sulfur clusters to contribute to some degree in photoaccumulated FTIR DS. In a more recent study of PSI site directed mutants we did suggest possible small contributions to photoaccumulated FTIR DS from modes that might be impacted by F X reduction (Agarwala et al 2020 ).…”

Section: Resultsmentioning

confidence: 89%

Nanosecond time-resolved infrared spectroscopy for the study of electron transfer in photosystem I

et al. 2023

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Microsecond time-resolved step-scan FTIR difference spectroscopy was used to study photosystem I (PSI) from Thermosynechococcus vestitus BP-1 (T. vestitus, formerly known as T. elongatus) at 77 K. In addition, photoaccumulated (P700+–P700) FTIR difference spectra were obtained at both 77 and 293 K. The FTIR difference spectra are presented here for the first time. To extend upon these FTIR studies nanosecond time-resolved infrared difference spectroscopy was also used to study PSI from T. vestitus at 296 K. Nanosecond infrared spectroscopy has never been used to study PSI samples at physiological temperatures, and here it is shown that such an approach has great value as it allows a direct probe of electron transfer down both branches in PSI. In PSI at 296 K, the infrared flash-induced absorption changes indicate electron transfer down the B- and A-branches is characterized by time constants of 33 and 364 ns, respectively, in good agreement with visible spectroscopy studies. These time constants are associated with forward electron transfer from A1– to FX on the B- and A-branches, respectively. At several infrared wavelengths flash-induced absorption changes at 296 K recover in tens to hundreds of milliseconds. The dominant decay phase is characterized by a lifetime of 128 ms. These millisecond changes are assigned to radical pair recombination reactions, with the changes being associated primarily with P700+ rereduction. This conclusion follows from the observation that the millisecond infrared spectrum is very similar to the photoaccumulated (P700+–P700) FTIR difference spectrum.

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Section: Resultsmentioning

confidence: 89%

Nanosecond time-resolved infrared spectroscopy for the study of electron transfer in photosystem I

et al. 2023

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“…The carboxyl oxygens of PsaB-Asp575 are 3.3 and 2.8 Å from the closest water oxygen, and a theoretical study has predicted that the protonation state of PsaB-Asp575 influences the redox potential of PhQ A by ~ 80 mV 59 . Recent FTIR studies have also shown that a mutation on PsaB-Trp673 disturbs the water cluster coordination, and results in protonation of phylloquinones 68 . However, at 2.75 Å resolution electron density may show ambiguity for water positions and highly mobile waters cannot be modelled accurately.…”

Section: Discussionmentioning

confidence: 99%

Room temperature XFEL crystallography reveals asymmetry in the vicinity of the two phylloquinones in photosystem I

Keable

Kölsch

Simon

et al. 2021

Sci Rep

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Photosystem I (PS I) has a symmetric structure with two highly similar branches of pigments at the center that are involved in electron transfer, but shows very different efficiency along the two branches. We have determined the structure of cyanobacterial PS I at room temperature (RT) using femtosecond X-ray pulses from an X-ray free electron laser (XFEL) that shows a clear expansion of the entire protein complex in the direction of the membrane plane, when compared to previous cryogenic structures. This trend was observed by complementary datasets taken at multiple XFEL beamlines. In the RT structure of PS I, we also observe conformational differences between the two branches in the reaction center around the secondary electron acceptors A1A and A1B. The π-stacked Phe residues are rotated with a more parallel orientation in the A-branch and an almost perpendicular confirmation in the B-branch, and the symmetry breaking PsaB-Trp673 is tilted and further away from A1A. These changes increase the asymmetry between the branches and may provide insights into the preferential directionality of electron transfer.

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“…Static, photo − accumulated [P700 + − P700] FTIR DS were obtained at 77K as described previously using a Bruker Vertex80 FTIR spectrometer equipped with a MCT detector (Bruker Optics, Billerica, MA) [40][41][42][43].…”

Section: Ftir Spectroscopymentioning

confidence: 99%

Time-resolved FTIR difference spectroscopy for the study of photosystem I with high potential naphthoquinones incorporated into the A1 binding site 2: Identification of neutral state quinone bands

Agarwala

Hastings

2023

Photosynth Res

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Time-resolved step-scan FTIR difference spectroscopy at 77 K has been used to study cyanobacterial photosystem I (PSI) from Synechocystis sp. PCC 6803 with four high-potential, 1,4-naphthoquinones (NQs) incorporated into the A 1 binding site. The incorporated quinones are 2-chloro-NQ (2ClNQ), 2bromo-NQ (2BrNQ), 2,3-dichloro-NQ (Cl 2 NQ), and 2,3-dibromo-NQ (Br 2 NQ). For completeness 2methyl-NQ (2MNQ) was also incorporated and studied. Here we focus on spectra in the previously unexplored 1400 − 1200 cm − 1 spectral region. In this region several bands are identi ed and assigned to the neutral state of the incorporated quinones. This is important as identi cation of neutral state quinone bands in the regular 1700 − 1600 cm − 1 region has proven di cult in the past.For neutral PhQ in PSI a broad, intense band appears at 1300 cm − 1 . For the symmetric di-substituted NQs (Cl 2 NQ/Br 2 NQ) a single intense neutral state band is found at ~ 1280/1269 cm − 1 , respectively. For both mono-substituted NQs, 2ClNQ and 2BrNQ, however, two neutral state bands are observed near 1280 and 1250 cm − 1 , respectively. These observations from time-resolved spectra agree well with conclusions drawn from absorption spectra of the NQs in THF, which are also presented here. Density functional theory (DFT) based vibrational frequency calculations are also undertaken allowing an identi cation of the normal modes associated with the neutral state quinone bands.Multiple types of double difference spectra are compared and it is shown that this comparison is a potent approach for band identi cation in highly convoluted spectra.

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Reversible inhibition and reactivation of electron transfer in photosystem I

Cited by 11 publications

References 63 publications

Nanosecond time-resolved infrared spectroscopy for the study of electron transfer in photosystem I

Nanosecond time-resolved infrared spectroscopy for the study of electron transfer in photosystem I

Room temperature XFEL crystallography reveals asymmetry in the vicinity of the two phylloquinones in photosystem I

Time-resolved FTIR difference spectroscopy for the study of photosystem I with high potential naphthoquinones incorporated into the A1 binding site 2: Identification of neutral state quinone bands

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