Time-resolved FTIR difference spectroscopy for the study of photosystem I with high potential naphthoquinones incorporated into the A1 binding site

Agarwala, Neva; Makita, Hiroki; Hastings, Gary

doi:10.1016/j.bbabio.2022.148918

Cited by 6 publications

(2 citation statements)

References 57 publications

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“…Photoaccumulated (P700 + − P700) FTIR DS (at both RT and 77 K) and TRSS FTIR DS (at 77 K), all at 4 cm –1 spectral resolution, were collected as described previously (Agarwala et al 2023 ; Makita and Hastings 2020 ). PSI samples for single-frequency TRIR DS experiments were prepared in a similar manner: After thawing on ice, the sample was diluted in 50 mM TRIS buffer (pH 8), and 0.04% β-DM, such that a chlorophyll concentration of 0.2 mg/ml was reached.…”

Section: Methodsmentioning

confidence: 99%

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: Methodsmentioning

confidence: 99%

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

et al. 2023

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“…Photoaccumulated (P700 + − P700) FTIR DS (at both RT and 77 K) and TRSS FTIR DS (at 77 K), all at 4 cm -1 spectral resolution, were collected as described previously (Agarwala et al 2023; Makita and Hastings 2020). PSI samples for single-frequency TRIR DS experiments were prepared in a similar manner: After thawing on ice, the sample was diluted in 50 mM TRIS buffer (pH 8), and 0.04% b-DM, such that a chlorophyll concentration of 0.2 mg/ml was reached.…”

Section: Methodsmentioning

confidence: 99%

Nanosecond Time-Resolved Infrared Spectroscopy for the Study of Electron Transfer in Photosystem I

Mäusle

Agarwala

Eichmann

et al. 2023

Preprint

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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. Photoaccumulated (P700+ – P700) FTIR difference spectra were also obtained for PSI from T. vestitus at both 77 and 293 K. The FTIR difference spectra are presented here for the first time. To greatly extend upon these FTIR studies nanosecond time-resolved infrared difference spectroscopy was also used to study PSI from T. vestitus at 293 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 293 K, the infrared flash-induced absorption changes indicate electron transfer down the A- and B-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 293 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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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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Time-resolved FTIR difference spectroscopy for the study of photosystem I with high potential naphthoquinones incorporated into the A1 binding site

Cited by 6 publications

References 57 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

Nanosecond Time-Resolved Infrared Spectroscopy for the Study of Electron Transfer 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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