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Mäusle SM, Agarwala N, Eichmann VG, Dau H, Nürnberg DJ, Hastings G. Nanosecond time-resolved infrared spectroscopy for the study of electron transfer in photosystem I. PHOTOSYNTHESIS RESEARCH 2024; 159:229-239. [PMID: 37420121 PMCID: PMC10991071 DOI: 10.1007/s11120-023-01035-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 06/21/2023] [Indexed: 07/09/2023]
Abstract
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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Affiliation(s)
- Sarah M Mäusle
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Neva Agarwala
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, 30303, USA
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Viktor G Eichmann
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Holger Dau
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
| | - Dennis J Nürnberg
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
- Dahlem Centre of Plant Sciences, Freie Universität Berlin, Berlin, Germany.
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, 30303, USA.
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Agarwala N, Hastings G. Time-resolved FTIR difference spectroscopy for the study of photosystem I with high potential naphthoquinones incorporated into the A 1 binding site 2: Identification of neutral state quinone bands. PHOTOSYNTHESIS RESEARCH 2023; 158:1-11. [PMID: 37477846 DOI: 10.1007/s11120-023-01036-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 06/23/2023] [Indexed: 07/22/2023]
Abstract
Time-resolved step-scan FTIR difference spectroscopy at 77 K has been used to study photosystem I (PSI) from Synechocystis sp. PCC 6803 with four high-potential, 1,4-naphthoquinones (NQs) incorporated into the A1 binding site. The incorporated quinones are 2-chloro-NQ (2ClNQ), 2-bromo-NQ (2BrNQ), 2,3-dichloro-NQ (Cl2NQ), and 2,3-dibromo-NQ (Br2NQ). For completeness 2-methyl-NQ (2MNQ) was also incorporated and studied. Previously, PSI with the same quinones incorporated were studied in the, so-called, anion spectral region between 1550 and 1400 cm-1 (Agarwala et al. in Biochim Biophys Acta 1864(1):148918, 2023). Here we focus on spectra in the previously unexplored 1400-1200 cm-1 spectral region. In this region several bands are identified and assigned to the neutral state of the incorporated quinones. This is important as identification of neutral state quinone bands in the regular 1700-1600 cm-1 region has proven difficult in the past. For neutral PhQ in PSI a broad, intense band appears at ~ 1300 cm-1. For the symmetric di-substituted NQs (Cl2NQ/Br2NQ) 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 at ~ 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 based vibrational frequency calculations were undertaken allowing an identification of the normal modes associated with the neutral state quinone bands.
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Affiliation(s)
- Neva Agarwala
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA
- Department of Chemistry, Georgia State University, Atlanta, GA, USA
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA.
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Agarwala N, Makita H, Hastings G. Time-resolved FTIR difference spectroscopy for the study of photosystem I with high potential naphthoquinones incorporated into the A 1 binding site. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148918. [PMID: 36116485 DOI: 10.1016/j.bbabio.2022.148918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 09/08/2022] [Accepted: 09/11/2022] [Indexed: 11/28/2022]
Abstract
Time-resolved step-scan Fourier transform infrared difference spectroscopy has been used to study cyanobacterial photosystem I photosynthetic reaction centers from Synechocystis sp. PCC 6803 (S6803) with four high-potential, 1,4-naphthoquinones incorporated into the A1 binding site. The high-potential naphthoquinones are 2-chloro-, 2-bromo-, 2,3-dichloro- and 2,3-dibromo-1,4-naphthoquinone. "Foreign minus native" double difference spectra (DDS) were constructed by subtracting difference spectra for native photosystem I (with phylloquinone in the A1 binding site) from corresponding spectra obtained using photosystem I with the different quinones incorporated. To help assess and assign bands in the difference and double difference spectra, density functional theory based vibrational frequency calculations for the different quinones in solvent, or in the presence of a single asymmetric H- bond to either a water molecule or a peptide backbone NH group, were undertaken. Calculated and experimental spectra agree best for the peptide backbone asymmetrically H- bonded system. By comparing multiple sets of double difference spectra, several new bands for the native quinone (phylloquinone) are identified. By comparing calculated and experimental spectra we conclude that the mono-substituted halogenated NQs can occupy the binding site in either of two different orientations, with the chlorine or bromine atom being either ortho or meta to the H- bonded CO group.
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Affiliation(s)
- Neva Agarwala
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA
| | - Hiroki Makita
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA.
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Agarwala N, Rohani L, Hastings G. Experimental and calculated infrared spectra of disubstituted naphthoquinones. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 268:120674. [PMID: 34894562 DOI: 10.1016/j.saa.2021.120674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 10/21/2021] [Accepted: 11/26/2021] [Indexed: 06/14/2023]
Abstract
In recent years there has been interest in incorporating substituted 1,4-naphthoquinones (NQs) into the A1 binding site in photosystem I (PSI) photosynthetic protein complexes. This interest in part stems from the considerably altered bioenergetics of electron transfer that occur in PSI with such substitutions. Time resolved FTIR studies of PSI complexes with disubstituted NQs incorporated have and currently are being undertaken, and with this in mind it is worth considering FTIR absorption spectra of these disubstituted NQs in solution. Here we present FTIR absorbance spectra for 2-bromo-3-methyl-1,4-naphthoquinone (BrMeNQ), 2-chloromethyl-3-methyl-1,4-naphthoquinone (CMMeNQ) and 2-ethylthio-3-methyl-1,4-naphthoquinone (ETMeNQ) in tetrahydrofuran (THF). The FTIR spectra of these di-substituted naphthoquinones (NQs) were compared to FTIR spectra of 2-methyl-3-phytyl-1,4-naphthoquinone [phylloquinone (PhQ)], 2,3-dimethyl-1,4-naphthoquinone (DMNQ), and 2-methyl-1,4-naphthoquinone (2MNQ). To aid in the assignment of bands in the experimental spectra, density functional theory (DFT) based vibrational frequency calculations for all the substituted NQs in solution were undertaken. The calculated and experimental spectra agree well. By calculating normal mode potential energy distributions, unambiguous quantitative band assignments were made. The calculated and experimental spectra together make predictions about what may be observable in time resolved FTIR difference spectra obtained using PSI with the different NQs incorporated. Time resolved FTIR difference spectra are presented that support these predictions.
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Affiliation(s)
- Neva Agarwala
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA
| | - Leyla Rohani
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA.
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Agarwala N, Makita H, Luo L, Xu W, Hastings G. Reversible inhibition and reactivation of electron transfer in photosystem I. PHOTOSYNTHESIS RESEARCH 2020; 145:97-109. [PMID: 32447611 DOI: 10.1007/s11120-020-00760-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 05/12/2020] [Indexed: 06/11/2023]
Abstract
In photosystem I (PSI) complexes at room temperature electron transfer from A1- to FX is an order of magnitude faster on the B-branch compared to the A-branch. One factor that might contribute to this branch asymmetry in time constants is TrpB673 (Thermosynechococcus elongatus numbering), which is located between A1B and FX. The corresponding residue on the A-branch, between A1A and FX, is GlyA693. Here, microsecond time-resolved step-scan FTIR difference spectroscopy at 77 K has been used to study isolated PSI complexes from wild type and TrpB673Phe mutant (WB673F mutant) cells from Synechocystis sp. PCC 6803. WB673F mutant cells require glucose for growth and are light sensitive. Photoaccumulated FTIR difference spectra indicate changes in amide I and II protein vibrations upon mutation of TrpB673 to Phe, indicating the protein environment near FX is altered upon mutation. In the WB673F mutant PSI samples, but not in WT PSI samples, the phylloquinone molecule that occupies the A1 binding site is likely doubly protonated following long periods of repetitive flash illumination at room temperature. PSI with (doubly) protonated quinone in the A1 binding site are not functional in electron transfer. However, electron transfer functionality can be restored by incubating the light-treated mutant PSI samples in the presence of added phylloquinone.
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Affiliation(s)
- Neva Agarwala
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, 30303, USA
| | - Hiroki Makita
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, 30303, USA
| | - Lujun Luo
- Department of Chemistry, University of Louisiana At Lafayette, Lafayette, LA, 70503, USA
| | - Wu Xu
- Department of Chemistry, University of Louisiana At Lafayette, Lafayette, LA, 70503, USA
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, Atlanta, GA, 30303, USA.
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Gorka M, Golbeck JH. Generating dihydrogen by tethering an [FeFe]hydrogenase via a molecular wire to the A 1A/A 1B sites of photosystem I. PHOTOSYNTHESIS RESEARCH 2020; 143:155-163. [PMID: 31673863 DOI: 10.1007/s11120-019-00685-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 10/15/2019] [Indexed: 06/10/2023]
Abstract
Photosystem I complexes from the menB deletion mutant of Synechocystis sp. PCC 6803 were previously wired to a Pt nanoparticle via a molecular wire consisting of 15-(3-methyl-1,4-naphthoquinone-2-yl)]pentadecyl sulfide. In the presence of a sacrificial electron donor and an electron transport mediator, the PS I-NQ(CH2)15S-Pt nanoconstruct generated dihydrogen at a rate of 44.3 µmol of H2 mg Chl-1 h-1 during illumination at pH 8.3. The menB deletion strain contains an interruption in the biosynthetic pathway of phylloquinone, which results in the presence of a displaceable plastoquinone-9 in the A1A/A1B sites. The synthesized quinone contains a headgroup identical to the native phylloquinone along with a 15-carbon long tail that is terminated in a thiol. The thiol on the molecular wire is used to bind the Pt nanoparticle. In this short communication, we replaced the Pt nanoparticle with an [FeFe]H2ase variant from Clostridium acetobutylicum that contains an exposed iron on the distal [4Fe-4S] cluster afforded by mutating the surface exposed Cys97 residue to Gly. The thiol on the molecular wire is then used to coordinate the corner iron atom of the iron-sulfur cluster. When all three components are combined and illuminated in the presence of a sacrificial electron donor and an electron transport mediator, the PS I-NQ(CH2)15S-[FeFe]H2ase nanoconstruct generated dihydrogen at a rate of 50.3 ± 9.96 μmol of H2 mg Chl-1 h-1 during illumination at pH 8.3. This successful in vitro experiment sets the stage for assembling a PS I-NQ(CH2)15S-[FeFe]H2ase nanoconstruct in vivo in the menB mutant of Synechocystis sp. PCC 6803.
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Affiliation(s)
- Michael Gorka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA.
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA.
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, S328 Frear Building, University Park, PA, 16802, USA.
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Makita H, Hastings G. Time-resolved step-scan FTIR difference spectroscopy for the study of photosystem I with different benzoquinones incorporated into the A1 binding site. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1199-1206. [DOI: 10.1016/j.bbabio.2018.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 08/16/2018] [Accepted: 08/21/2018] [Indexed: 11/28/2022]
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Makita H, Hastings G. Photosystem I with benzoquinone analogues incorporated into the A 1 binding site. PHOTOSYNTHESIS RESEARCH 2018; 137:85-93. [PMID: 29332243 DOI: 10.1007/s11120-018-0480-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 01/02/2018] [Indexed: 06/07/2023]
Abstract
Time-resolved FTIR difference spectroscopy has been used to study photosystem I (PSI) particles with three different benzoquinones [plastoquinone-9 (PQ), 2,6-dimethyl-1,4-benzoquinone (DMBQ), 2,3,5,6-tetrachloro-1,4-benzoquinone (Cl4BQ)] incorporated into the A1 binding site. If PSI samples are cooled in the dark to 77 K, the incorporated benzoquinones are shown to be functional, allowing the production of time-resolved (P700+A1--P700A1) FTIR difference spectra. If samples are subjected to repetitive flash illumination at room temperature prior to cooling, however, the time-resolved FTIR difference spectra at 77 K display contributions typical of the P700 triplet state (3P700), indicating a loss of functionality of the incorporated benzoquinones, that occurs because of double protonation of the incorporated benzoquinones. The benzoquinone protonation mechanism likely involves nearby water molecules but does not involve the terminal iron-sulfur clusters FA and FB. These results and conclusions resolve discrepancies between results from previous low-temperature FTIR and EPR studies on similar PSI samples with PQ incorporated.
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Affiliation(s)
- Hiroki Makita
- Department of Physics and Astronomy, Georgia State University, 25 Park Place, Suite 605, Atlanta, GA, 30303, USA
| | - Gary Hastings
- Department of Physics and Astronomy, Georgia State University, 25 Park Place, Suite 605, Atlanta, GA, 30303, USA.
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Inverted-region electron transfer as a mechanism for enhancing photosynthetic solar energy conversion efficiency. Proc Natl Acad Sci U S A 2017; 114:9267-9272. [PMID: 28814630 DOI: 10.1073/pnas.1704855114] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In all photosynthetic organisms, light energy is used to drive electrons from a donor chlorophyll species via a series of acceptors across a biological membrane. These light-induced electron-transfer processes display a remarkably high quantum efficiency, indicating a near-complete inhibition of unproductive charge recombination reactions. It has been suggested that unproductive charge recombination could be inhibited if the reaction occurs in the so-called inverted region. However, inverted-region electron transfer has never been demonstrated in any native photosynthetic system. Here we demonstrate that the unproductive charge recombination in native photosystem I photosynthetic reaction centers does occur in the inverted region, at both room and cryogenic temperatures. Computational modeling of light-induced electron-transfer processes in photosystem I demonstrate a marked decrease in photosynthetic quantum efficiency, from 98% to below 72%, if the unproductive charge recombination process does not occur in the inverted region. Inverted-region electron transfer is therefore demonstrated to be an important mechanism contributing to efficient solar energy conversion in photosystem I. Inverted-region electron transfer does not appear to be an important mechanism in other photosystems; it is likely because of the highly reducing nature of photosystem I, and the energetic requirements placed on the pigments to operate in such a regime, that the inverted-region electron transfer mechanism becomes important.
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Mezzetti A, Leibl W. Time-resolved infrared spectroscopy in the study of photosynthetic systems. PHOTOSYNTHESIS RESEARCH 2017; 131:121-144. [PMID: 27678250 DOI: 10.1007/s11120-016-0305-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Accepted: 09/05/2016] [Indexed: 06/06/2023]
Abstract
Time-resolved (TR) infrared (IR) spectroscopy in the nanosecond to second timescale has been extensively used, in the last 30 years, in the study of photosynthetic systems. Interesting results have also been obtained at lower time resolution (minutes or even hours). In this review, we first describe the used techniques-dispersive IR, laser diode IR, rapid-scan Fourier transform (FT)IR, step-scan FTIR-underlying the advantages and disadvantages of each of them. Then, the main TR-IR results obtained so far in the investigation of photosynthetic reactions (in reaction centers, in light-harvesting systems, but also in entire membranes or even in living organisms) are presented. Finally, after the general conclusions, the perspectives in the field of TR-IR applied to photosynthesis are described.
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Affiliation(s)
- Alberto Mezzetti
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 7197, Laboratoire de Réactivité de Surfaces, 4 Pl. Jussieu, 75005, Paris, France.
- Institut de Biologie Intégrative de la Cellule (I2BC), IBITECS, CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette, France.
| | - Winfried Leibl
- Institut de Biologie Intégrative de la Cellule (I2BC), IBITECS, CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette, France
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