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N. V. Karapetyan - One of the best experts on this subject based on the ideXlab platform.

  • fluorescence of the various red antenna states in photosystem i complexes from cyanobacteria is affected differently by the redox state of P700
    Biochimica et Biophysica Acta, 2011
    Co-Authors: Eberhard Schlodder, N. V. Karapetyan, Marianne Çetin, Martin Hussels, Marc Brecht
    Abstract:

    Abstract Photosystem I of cyanobacteria contains different spectral pools of chlorophylls called red or long-wavelength chlorophylls that absorb at longer wavelengths than the primary electron donor P700. We measured the fluorescence spectra at the ensemble and the single-molecule level at low temperatures in the presence of oxidized and reduced P700. In accordance with the literature, it was observed that the fluorescence is quenched by P700+. However, the efficiency of the fluorescence quenching by oxidized P700+ was found to be extremely different for the various red states in PS I from different cyanobacteria. The emission of the longest-wavelength absorbing antenna state in PS I trimers from Thermosynechococcus elongatus (absorption maximum at 5 K: ≅ 719 nm; emission maximum at 5 K: ≅ 740 nm) was found to be strongly quenched by P700+ similar to the reddest state in PS I trimers from Arthrospira platensis emitting at 760 nm at 5 K. The fluorescence of these red states is diminished by more than a factor of 10 in the presence of oxidized P700. For the first time, the emission of the reddest states in A. platensis and T. elongatus has been monitored using single-molecule fluorescence techniques.

  • quantum yield of P700 photodestruction in isolated photosystem i complexes of the cyanobacterium arthrospira platensis
    Photochemical and Photobiological Sciences, 2008
    Co-Authors: Vladimir V Shubin, Irina V Terekhova, Boris A Kirillov, N. V. Karapetyan
    Abstract:

    The photostability of P700 cation radical (P700+) was studied by evaluating the quantum yields of P700+ photodestruction in photosystem I (PSI) complexes of the cyanobacteriumArthrospira platensis. The time courses of P700+ photodestruction in PSI trimers and monomers have been measured in aerobic conditions under selective excitation of far-red absorption band of P700+ by intense light of laser diodes. Long-term exposure of PSI complexes to 808 or 870 nm laser light caused destruction of P700+ and antenna chlorophylls. The true integral quantum yield of P700+ photodestruction calculated from these data was less than 0.7–1.4 × 10−8. Illumination of PSI complexes by 650 nm light caused destruction of antenna chlorophylls with true quantum yield of about 6–7 × 10−6 and damage of P700 with apparent quantum yield 2–3 × 10−8. Preferential photodestruction of the long-wavelength antenna chlorophyll absorbing at 710 nm as compared with bulk chlorophylls was observed. About three orders of difference in magnitude between quantum yields of P700+ and bulk chlorophyll photodestruction indicates that P700+ is extremely photostable for functioning as an efficient quencher of singlet excitation energy in PSI.

  • Effects of oxygen and photosynthesis carbon cycle reactions on kinetics of P700 redox transients in cyanobacterium Arthrospira platensis cells
    Biochemistry (Moscow), 2007
    Co-Authors: Yu. V. Bolychevtseva, M. Roegner, Irina V Terekhova, N. V. Karapetyan
    Abstract:

    Effects of oxygen and photosynthesis and respiration inhibitors on the electron transport in photosystem I (PSI) of the cyanobacterium Arthrospira platensis cells were studied. Redox transients of P700 were induced by illumination at 730 nm and monitored as kinetics of the absorption changes at 810 nm; to block electron influx from PSII, the measurements were performed in the presence of 30 μM 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Inhibitors of terminal oxidases (potassium cyanide and pentachlorophenol) insignificantly influenced the fast oxidation of P700 under aerobic conditions, whereas removal of oxygen significantly decelerated the accumulation of P700+. In the absence of oxygen the slow oxidation of P700 observed on the first illumination was accelerated on each subsequent illumination, suggesting an activation of the carbon cycle enzymes. Under the same conditions, pentachlorophenol (an uncoupler) markedly accelerated the P700 photooxidation. Under anaerobic conditions, potassium cyanide (an inhibitor of carbon dioxide assimilation) failed to influence the kinetics of redox transients of P700, whereas iodoacetamide (an inhibitor of NADP(H)-glyceraldehyde-3-phosphate dehydrogenase) completely prevented the photooxidation of P700. Thus, the fast photooxidation of P700 in the A. platensis cells under aerobic conditions in the presence of DCMU was caused by electron transport from PSI onto oxygen, and complicated transient changes in the P700 photooxidation kinetics under anaerobic conditions (in the presence of DCMU) were due to involvement of NADP+ generated during the reducing phase of the carbon cycle.

  • P700 and 3P700 induced quenching of the fluorescence at 760 nm in trimeric photosystem i complexes from the cyanobacterium arthrospira platensis
    Biochimica et Biophysica Acta, 2005
    Co-Authors: Eberhard Schlodder, Irina V Terekhova, Marianne Çetin, Martin Byrdin, N. V. Karapetyan
    Abstract:

    Abstract The 5 K absorption spectrum of Photosystem I (PS I) trimers from Arthrospira platensis (old name: Spirulina platensis ) exhibits long-wavelength antenna (exciton) states absorbing at 707 nm (called C707) and at 740 nm (called C740). The lowest energy state (C740) fluoresces around 760 nm (F760) at low temperature. The analysis of the spectral properties (peak position and line width) of the lowest energy transition (C740) as a function of temperature within the linear electron–phonon approximation indicates a large optical reorganization energy of ∼110 cm −1 and a broad inhomogeneous site distribution characterized by a line width of ∼115 cm −1 . Linear dichroism (LD) measurements indicate that the transition dipole moment of the red-most state is virtually parallel to the membrane plane. The relative fluorescence yield at 760 nm of PS I with P700 oxidized increases only slightly when the temperature is lowered to 77 K, whereas in the presence of reduced P700 the fluorescence yield increases nearly 40-fold at 77 K as compared to that at room temperature (RT). A fluorescence induction effect could not be resolved at RT. At 77 K the fluorescence yield of PS I trimers frozen in the dark in the presence of sodium ascorbate decreases during illumination by about a factor of 5 due to the irreversible formation of P700 + F A/B − in about 60% of the centers and the reversible accumulation of the longer-lived state P700 + F X − . The quenching efficiency of different functionally relevant intermediate states of the photochemistry in PS I has been studied. The redox state of the acceptors beyond A 0 does not affect F760. Direct kinetic evidence is presented that the fluorescence at 760 nm is strongly quenched not only by P700 + but also by 3 P700. Similar kinetics were observed for flash-induced absorbance changes attributed to the decay of 3 P700 or P700 + , respectively, and flash-induced fluorescence changes at 760 nm measured under identical conditions. A nonlinear relationship between the variable fluorescence around 760 nm and the [P700 red ]/[P700 total ] ratio was derived from titration curves of the absorbance change at 826 nm and the variable fluorescence at 760 nm as a function of the redox potential imposed on the sample solution at room temperature before freezing. The result indicates that the energy exchange between the antennae of different monomers within a PS I trimer stimulates quenching of F760 by P700 + .

  • P700 +- and 3P700-induced quenching of the fluorescence at 760 nm in trimeric Photosystem I complexes from the cyanobacterium Arthrospira platensis
    Biochimica et Biophysica Acta - Bioenergetics, 2005
    Co-Authors: Eberhard Schlodder, Irina V Terekhova, Marianne Çetin, Martin Byrdin, N. V. Karapetyan
    Abstract:

    The 5 K absorption spectrum of Photosystem I (PS I) trimers from Arthrospira platensis (old name: Spirulina platensis) exhibits long-wavelength antenna (exciton) states absorbing at 707 nm (called C707) and at 740 nm (called C740). The lowest energy state (C740) fluoresces around 760 nm (F760) at low temperature. The analysis of the spectral properties (peak position and line width) of the lowest energy transition (C740) as a function of temperature within the linear electron-phonon approximation indicates a large optical reorganization energy of ∼110 cm -1 and a broad inhomogeneous site distribution characterized by a line width of ∼115 cm -1. Linear dichroism (LD) measurements indicate that the transition dipole moment of the red-most state is virtually parallel to the membrane plane. The relative fluorescence yield at 760 nm of PS I with P700 oxidized increases only slightly when the temperature is lowered to 77 K, whereas in the presence of reduced P700 the fluorescence yield increases nearly 40-fold at 77 K as compared to that at room temperature (RT). A fluorescence induction effect could not be resolved at RT. At 77 K the fluorescence yield of PS I trimers frozen in the dark in the presence of sodium ascorbate decreases during illumination by about a factor of 5 due to the irreversible formation of P700 +F A/B- in about 60% of the centers and the reversible accumulation of the longer-lived state P700 +F X-. The quenching efficiency of different functionally relevant intermediate states of the photochemistry in PS I has been studied. The redox state of the acceptors beyond A 0 does not affect F760. Direct kinetic evidence is presented that the fluorescence at 760 nm is strongly quenched not only by P700 + but also by 3P700. Similar kinetics were observed for flash-induced absorbance changes attributed to the decay of 3P700 or P700 +, respectively, and flash-induced fluorescence changes at 760 nm measured under identical conditions. A nonlinear relationship between the variable fluorescence around 760 nm and the [P700 red]/[P700 total] ratio was derived from titration curves of the absorbance change at 826 nm and the variable fluorescence at 760 nm as a function of the redox potential imposed on the sample solution at room temperature before freezing. The result indicates that the energy exchange between the antennae of different monomers within a PS I trimer stimulates quenching of F760 by P700 +. © 2004 Elsevier B.V. All rights reserved.

Eberhard Schlodder - One of the best experts on this subject based on the ideXlab platform.

  • fluorescence of the various red antenna states in photosystem i complexes from cyanobacteria is affected differently by the redox state of P700
    Biochimica et Biophysica Acta, 2011
    Co-Authors: Eberhard Schlodder, N. V. Karapetyan, Marianne Çetin, Martin Hussels, Marc Brecht
    Abstract:

    Abstract Photosystem I of cyanobacteria contains different spectral pools of chlorophylls called red or long-wavelength chlorophylls that absorb at longer wavelengths than the primary electron donor P700. We measured the fluorescence spectra at the ensemble and the single-molecule level at low temperatures in the presence of oxidized and reduced P700. In accordance with the literature, it was observed that the fluorescence is quenched by P700+. However, the efficiency of the fluorescence quenching by oxidized P700+ was found to be extremely different for the various red states in PS I from different cyanobacteria. The emission of the longest-wavelength absorbing antenna state in PS I trimers from Thermosynechococcus elongatus (absorption maximum at 5 K: ≅ 719 nm; emission maximum at 5 K: ≅ 740 nm) was found to be strongly quenched by P700+ similar to the reddest state in PS I trimers from Arthrospira platensis emitting at 760 nm at 5 K. The fluorescence of these red states is diminished by more than a factor of 10 in the presence of oxidized P700. For the first time, the emission of the reddest states in A. platensis and T. elongatus has been monitored using single-molecule fluorescence techniques.

  • P700 and 3P700 induced quenching of the fluorescence at 760 nm in trimeric photosystem i complexes from the cyanobacterium arthrospira platensis
    Biochimica et Biophysica Acta, 2005
    Co-Authors: Eberhard Schlodder, Irina V Terekhova, Marianne Çetin, Martin Byrdin, N. V. Karapetyan
    Abstract:

    Abstract The 5 K absorption spectrum of Photosystem I (PS I) trimers from Arthrospira platensis (old name: Spirulina platensis ) exhibits long-wavelength antenna (exciton) states absorbing at 707 nm (called C707) and at 740 nm (called C740). The lowest energy state (C740) fluoresces around 760 nm (F760) at low temperature. The analysis of the spectral properties (peak position and line width) of the lowest energy transition (C740) as a function of temperature within the linear electron–phonon approximation indicates a large optical reorganization energy of ∼110 cm −1 and a broad inhomogeneous site distribution characterized by a line width of ∼115 cm −1 . Linear dichroism (LD) measurements indicate that the transition dipole moment of the red-most state is virtually parallel to the membrane plane. The relative fluorescence yield at 760 nm of PS I with P700 oxidized increases only slightly when the temperature is lowered to 77 K, whereas in the presence of reduced P700 the fluorescence yield increases nearly 40-fold at 77 K as compared to that at room temperature (RT). A fluorescence induction effect could not be resolved at RT. At 77 K the fluorescence yield of PS I trimers frozen in the dark in the presence of sodium ascorbate decreases during illumination by about a factor of 5 due to the irreversible formation of P700 + F A/B − in about 60% of the centers and the reversible accumulation of the longer-lived state P700 + F X − . The quenching efficiency of different functionally relevant intermediate states of the photochemistry in PS I has been studied. The redox state of the acceptors beyond A 0 does not affect F760. Direct kinetic evidence is presented that the fluorescence at 760 nm is strongly quenched not only by P700 + but also by 3 P700. Similar kinetics were observed for flash-induced absorbance changes attributed to the decay of 3 P700 or P700 + , respectively, and flash-induced fluorescence changes at 760 nm measured under identical conditions. A nonlinear relationship between the variable fluorescence around 760 nm and the [P700 red ]/[P700 total ] ratio was derived from titration curves of the absorbance change at 826 nm and the variable fluorescence at 760 nm as a function of the redox potential imposed on the sample solution at room temperature before freezing. The result indicates that the energy exchange between the antennae of different monomers within a PS I trimer stimulates quenching of F760 by P700 + .

  • P700 +- and 3P700-induced quenching of the fluorescence at 760 nm in trimeric Photosystem I complexes from the cyanobacterium Arthrospira platensis
    Biochimica et Biophysica Acta - Bioenergetics, 2005
    Co-Authors: Eberhard Schlodder, Irina V Terekhova, Marianne Çetin, Martin Byrdin, N. V. Karapetyan
    Abstract:

    The 5 K absorption spectrum of Photosystem I (PS I) trimers from Arthrospira platensis (old name: Spirulina platensis) exhibits long-wavelength antenna (exciton) states absorbing at 707 nm (called C707) and at 740 nm (called C740). The lowest energy state (C740) fluoresces around 760 nm (F760) at low temperature. The analysis of the spectral properties (peak position and line width) of the lowest energy transition (C740) as a function of temperature within the linear electron-phonon approximation indicates a large optical reorganization energy of ∼110 cm -1 and a broad inhomogeneous site distribution characterized by a line width of ∼115 cm -1. Linear dichroism (LD) measurements indicate that the transition dipole moment of the red-most state is virtually parallel to the membrane plane. The relative fluorescence yield at 760 nm of PS I with P700 oxidized increases only slightly when the temperature is lowered to 77 K, whereas in the presence of reduced P700 the fluorescence yield increases nearly 40-fold at 77 K as compared to that at room temperature (RT). A fluorescence induction effect could not be resolved at RT. At 77 K the fluorescence yield of PS I trimers frozen in the dark in the presence of sodium ascorbate decreases during illumination by about a factor of 5 due to the irreversible formation of P700 +F A/B- in about 60% of the centers and the reversible accumulation of the longer-lived state P700 +F X-. The quenching efficiency of different functionally relevant intermediate states of the photochemistry in PS I has been studied. The redox state of the acceptors beyond A 0 does not affect F760. Direct kinetic evidence is presented that the fluorescence at 760 nm is strongly quenched not only by P700 + but also by 3P700. Similar kinetics were observed for flash-induced absorbance changes attributed to the decay of 3P700 or P700 +, respectively, and flash-induced fluorescence changes at 760 nm measured under identical conditions. A nonlinear relationship between the variable fluorescence around 760 nm and the [P700 red]/[P700 total] ratio was derived from titration curves of the absorbance change at 826 nm and the variable fluorescence at 760 nm as a function of the redox potential imposed on the sample solution at room temperature before freezing. The result indicates that the energy exchange between the antennae of different monomers within a PS I trimer stimulates quenching of F760 by P700 +. © 2004 Elsevier B.V. All rights reserved.

  • species specific differences of the spectroscopic properties of P700 analysis of the influence of non conserved amino acid residues by site directed mutagenesis of photosystem i from chlamydomonas reinhardtii
    Journal of Biological Chemistry, 2003
    Co-Authors: Heike Witt, N. V. Karapetyan, Enrica Bordignon, Donatella Carbonera, Jan P Dekker, Christian Teutloff, Andrew N Webber, Wolfgang Lubitz, Eberhard Schlodder
    Abstract:

    Abstract We applied optical spectroscopy, magnetic resonance techniques, and redox titrations to investigate the properties of the primary electron donor P700 in photosystem I (PS I) core complexes from cyanobacteria (Thermosynechococcus elongatus, Spirulina platensis, and Synechocystis sp. PCC 6803), algae (Chlamydomonas reinhardtii CC2696), and higher plants (Spinacia oleracea). Remarkable species-specific differences of the optical properties of P700 were revealed monitoring the (3P700P700) and (P700+·–P700) absorbance and CD difference spectra. The main bleaching band in the Qy region differs in peak position and line width for the various species. In cyanobacteria the absorbance of P700 extends more to the red compared with algae and higher plants which is favorable for energy transfer from red core antenna chlorophylls to P700 in cyanobacteria. The amino acids in the environment of P700 are highly conserved with two distinct deviations. In C. reinhardtii a Tyr is found at position PsaB659 instead of a Trp present in all other organisms, whereas in Synechocystis a Phe is found instead of a Trp at the homologous position PsaA679. We constructed several mutants in C. reinhardtii CC2696. Strikingly, no PS I could be detected in the mutant YW B659 indicating steric constraints unique to this organism. In the mutants WA A679 and YA B659 significant changes of the spectral features in the (3P700P700), the (P700+·–P700) absorbance difference and in the (P700+·–P700) CD difference spectra are induced. The results indicate structural differences among PS I from higher plants, algae, and cyanobacteria and give further insight into specific protein-cofactor interactions contributing to the optical spectra.

  • hydrogen bonding to P700 site directed mutagenesis of threonine a739 of photosystem i in chlamydomonas reinhardtii
    Biochemistry, 2002
    Co-Authors: Heike Witt, Eberhard Schlodder, Enrica Bordignon, Donatella Carbonera, Christian Teutloff, Jens Niklas, Simon Kohler, Andreas Labahn, Wolfgang Lubitz
    Abstract:

    The primary electron donor P700 of photosystem I is a dimer comprised of chlorophyll a (PB) and chlorophyll a‘ (PA). PA is involved in a hydrogen bond network with several surrounding amino acid residues and a nearby water molecule. To investigate the influence of hydrogen bond interactions on the properties of P700, the threonine at position A739, which donates a putative hydrogen bond to the 131-keto group of PA, was replaced with valine, histidine, and tyrosine in Chlamydomonas reinhardtii using site-directed mutagenesis. Growth of the mutants was not impaired. (i) The (P700+• − P700) FTIR difference spectra of the mutants lack a negative band at 1634 cm-1 observed in the wild-type spectrum and instead exhibit a new negative band between 1658 and 1672 cm-1 depending on the mutation. This band can therefore be assigned to the 131-keto group of PA which is upshifted to higher frequencies upon removal of the hydrogen bond. (ii) The main bleaching band in the Qy region of the (P700+• − P700) and (3P700 − P...

Gary Hastings - One of the best experts on this subject based on the ideXlab platform.

  • mutation of the putative hydrogen bond donor to P700 of photosystem i
    Biochemistry, 2004
    Co-Authors: Yajing Li, Ruili Wang, Velautham Sivakumar, Gary Hastings, Marie Gabrielle Lucas, Tatyana A Konovalova, Brian D Abbott, Fraser Macmillan, Alexander Petrenko, Feifei Gu
    Abstract:

    The primary electron donor of photosystem I (PS1), called P700, is a heterodimer of chlorophyll (Chl) a and a'. The crystal structure of photosystem I reveals that the chlorophyll a' (PA) could be hydrogen- bonded to the protein via a threonine residue, while the chlorophyll a (PB) does not have such a hydrogen bond. To investigate the influence of this hydrogen bond on P700, PsaA-Thr739 was converted to alanine to remove the H-bond to the 13 1 -keto group of the chlorophyll ain Chlamydomonas reinhardtii . The PsaA-T739A mutant was capable of assembling active PS1. Furthermore the mutant PS1 contained approximately one chlorophyll amolecule per reaction center, indicating that P 700 was still a Chl a/a' heterodimer in the mutant. However, the mutation induced several band shifts in the visible P 700 + - P700 absorbance difference spectrum. Redox titration of P700 revealed a 60 mV decrease in the P700/P700 + midpoint potential of the mutant, consistent with loss of a H-bond. Fourier transform infrared (FTIR) spectroscopy indicates that the ground state of P 700 is somewhat modified by mutation of ThrA739 to alanine. Comparison of FTIR difference band shifts upon P700 + formation in WT and mutant PS1 suggests that the mutation modifies the charge distribution over the pigments in the P700 + state, with 14-18% of the positive charge on PB in WT being relocated onto PA in the mutant. 1 H-electron-nuclear double resonance (ENDOR) analysis of the P700 + cation radical was also consistent with a slight redistribution of spin from the P B chlorophyll to PA, as well as some redistribution of spin within the P B chlorophyll. High-field electron paramagnetic resonance (EPR) spectroscopy at 330-GHz was used to resolve the g-tensor of P700 + , but no significant differences from wild-type were observed, except for a slight decrease of anisotropy. The mutation did, however, provoke changes in the zero-field splitting parameters of the triplet state of P 700 ( 3 P700), as determined by EPR. Interestingly, the mutation-induced change in asymmetry of P700 did not cause an observable change in the directionality of electron transfer within PS1.

  • ftir difference spectroscopy in combination with isotope labeling for identification of the carbonyl modes of P700 and P700 in photosystem i
    Biophysical Journal, 2004
    Co-Authors: Ruili Wang, Velautham Sivakumar, Wade T Johnson, Gary Hastings
    Abstract:

    Room temperature, light induced (P700+-P700) Fourier transform infrared (FTIR) difference spectra have been obtained using photosystem I (PS I) particles from Synechocystis sp. PCC 6803 that are unlabeled, uniformly 2H labeled, and uniformly 15N labeled. Spectra were also obtained for PS I particles that had been extensively washed and incubated in D2O. Previously, we have found that extensive washing and incubation of PS I samples in D2O does not alter the (P700+-P700) FTIR difference spectrum, even with ∼50% proton exchange. This indicates that the P700 binding site is inaccessible to solvent water. Upon uniform 2H labeling of PS I, however, the (P700+-P700) FTIR difference spectra are considerably altered. From spectra obtained using PS I particles grown in D2O and H2O, a (1H-2H) isotope edited double difference spectrum was constructed, and it is shown that all difference bands associated with ester/keto carbonyl modes of the chlorophylls of P700 and P700+ downshift 4–5/1–3 cm−1 upon 2H labeling, respectively. It is also shown that the ester and keto carbonyl modes of the chlorophylls of P700 need not be heterogeneously distributed in frequency. Finally, we find no evidence for the presence of a cysteine mode in our difference spectra. The spectrum obtained using 2H labeled PS I particles indicates that a negative difference band at 1698 cm−1 is associated with at least two species. The observed 15N and 2H induced band shifts strongly support the idea that the two species are the 131 keto carbonyl modes of both chlorophylls of P700. We also show that a negative difference band at ∼1639 cm−1 is somewhat modified in intensity, but unaltered in frequency, upon 2H labeling. This indicates that this band is not associated with a strongly hydrogen bonded keto carbonyl mode of one of the chlorophylls of P700.

  • mutation induced modulation of hydrogen bonding to P700 studied using ftir difference spectroscopy
    Biochemistry, 2003
    Co-Authors: Ruili Wang, Velautham Sivakumar, Yajing Li, Kevin Redding, Gary Hastings
    Abstract:

    Site-directed mutagenesis in combination with Fourier transform infrared difference spectroscopy has been used to study how hydrogen bonding modulates the electronic and physical organization of P700, the primary electron donor in photosystem I. Wild-type PS I particles from Chlamydomonas reinhardtii and a mutant in which ThrA739 is changed to alanine (TA(A739) mutant) were studied. ThrA739 is thought to provide a hydrogen bond to the chlorophyll-amolecule of P700 (the two chlorophylls of P700 (P700 + ) will be called PA and PB (PA + and PB + )). The mutation considerably alters the (P700 + - P700) FTIR difference spectra. However, we were able to describe all of the mutation induced changes in the difference spectra in terms of difference band assignments that were proposed recently (Hastings, G., Ramesh, V. M., Wang, R., Sivakumar, V. and Webber, A. (2001) Biochemistry 40, 12943-12949). Upon comparison of mutant and wild type (P700 + -P700) FTIR difference spectra, it is shown that (1) the 13 3 ester carbonyl modes of PA and PB are unaltered upon mutation of ThrA739 to alanine. (2) The 13 3 ester carbonyl modes of PA + /PB + upshift/downshift upon mutation. These oppositely directed shifts indicate that the mutation modifies the charge distribution over the pigments in the P700 + state, with charge on PB being relocated onto PA. We also show that the 13 1 keto carbonyl mode of PB/PB + is unaltered/ downshifted upon mutation, as is expected for the above-described mutation induced charge redistribution in P700 + . Although the 13 3 ester carbonyl modes of the chlorophylls of P700 in the ground state are unaltered upon mutation, the 13 1 keto carbonyl mode of PA upshifts upon mutation, as does the 13 1 keto carbonyl mode of PA + . For P700 in the ground state, bands that we associate with HisA676/HisB656 upshift/downshift upon mutation. For the P700 + state, bands that we associate with HisA676/HisB656 also upshift/downshift upon mutation. These observations are also consistent with the notion that the mutation leads to the charge on PB + being relocated onto PA + . In addition, we suggest that a hydrogen bond to the 13 1 keto carbonyl of PA is still present in the TA(A739) mutant, probably mediated through an introduced water molecule.

  • primary donor photo oxidation in photosystem i a re evaluation of P700 P700 fourier transform infrared difference spectra
    Biochemistry, 2001
    Co-Authors: Gary Hastings, Velautham Sivakumar, V M Ramesh, Ruilli Wang, Andrew N Webber
    Abstract:

    Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been used to study the photo-oxidation of the primary electron donor (P700) in PS I particles from Chlamydomonas reinhardtii and Synechocystis sp. PCC 6803. To aid in the interpretation of the spectra, PS I particles from a site-directed mutant of C. reinhardtii, in which the axial histidine ligand (HisA676) was changed to serine, were also studied. A high-frequency (3300−2600 cm-1) electronic transition is observed for all PS I particles, demonstrating that P700 is dimeric. The electronic band is, however, species-dependent, indicating some differences in the electronic structure of P700 and/or P700+ in C. reinhardtii and Synechocystis sp. 6803. For PS I particles from C. reinhardtii, substitution of HisA676 with serine has little effect on the ester carbonyl modes of the chlorophylls of P700. However, the keto carbonyl modes are considerably altered. Comparison of (P700+ − P700) FTIR difference spectra obtained using PS I partic...

  • Primary donor photo-oxidation in photosystem I: a re-evaluation of (P700(+) - P700) Fourier transform infrared difference spectra.
    Biochemistry, 2001
    Co-Authors: Gary Hastings, Velautham Sivakumar, V M Ramesh, Ruilli Wang, Andrew N Webber
    Abstract:

    Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been used to study the photo-oxidation of the primary electron donor (P700) in PS I particles from Chlamydomonas reinhardtii and Synechocystis sp. PCC 6803. To aid in the interpretation of the spectra, PS I particles from a site-directed mutant of C. reinhardtii, in which the axial histidine ligand (HisA676) was changed to serine, were also studied. A high-frequency (3300−2600 cm-1) electronic transition is observed for all PS I particles, demonstrating that P700 is dimeric. The electronic band is, however, species-dependent, indicating some differences in the electronic structure of P700 and/or P700+ in C. reinhardtii and Synechocystis sp. 6803. For PS I particles from C. reinhardtii, substitution of HisA676 with serine has little effect on the ester carbonyl modes of the chlorophylls of P700. However, the keto carbonyl modes are considerably altered. Comparison of (P700+ − P700) FTIR difference spectra obtained using PS I partic...

Jacques Breton - One of the best experts on this subject based on the ideXlab platform.

  • FTIR Studies of the Primary Electron Donor, P700
    Photosystem I, 2020
    Co-Authors: Jacques Breton
    Abstract:

    Summary Over the last two decades FTIR difference spectroscopy has emerged as a prominent technique to investigate the electronic structure and the bonding interactions of P700, the primary electron donor of photosystem I. In this chapter, the advances in the field during this period are reviewed and discussed in the light of the structural model of P700 derived from X-ray crystallography. The effect on the FTIR difference spectra of mutations of the axial ligands of the chlorophyll molecules in P700 as well as of amino acid residues in hydrogen bonding interaction with the carbonyl groups of P700 is analyzed. The results of both global and selective isotope labeling studies are

  • ftir spectroscopy of synechocystis 6803 mutants affected on the hydrogen bonds to the carbonyl groups of the psaa chlorophyll of P700 supports an extensive delocalization of the charge in P700
    Biochemistry, 2004
    Co-Authors: Maria Pantelidou, Parag R Chitnis, Jacques Breton
    Abstract:

    : P700, the primary electron donor of photosystem I is an asymmetric dimer made of one molecule of chlorophyll a' (P(A)) and one of chlorophyll a (P(B)). While the carbonyl groups of P(A) are involved in hydrogen-bonding interactions with several surrounding amino acid side chains and a water molecule, P(B) does not engage in hydrogen bonding with the protein. Light-induced FTIR difference spectroscopy of the photooxidation of P700 has been combined with site-directed mutagenesis in Synechocystis sp. PCC 6803 to investigate the influence of these hydrogen bonds on the structure of P700 and P700(+). When the residue Thr A739, which donates a hydrogen bond to the 9-keto C=O group of P(A), is changed to Phe, a differential signal at 1653(+)/1638(-) cm(-1) in the P700(+)/P700 FTIR difference spectrum upshifts by approximately 30-40 cm(-1), as expected for the rupture of the hydrogen bond or, at least, a strong decrease of its strength. The same upshift is also observed in the FTIR spectrum of a triple mutant in which the residues involved in the three main hydrogen bonds to the 9-keto and 10a-carbomethoxy groups of P(A) have been changed to the symmetry-related side chains present around P(B). In addition, the spectrum of the triple mutant shows a decrease of a differential signal around 1735 cm(-1) and the appearance of a new signal around 1760 cm(-1). This is consistent with the perturbation of a bound 10a-ester C=O group that becomes free in the triple mutant. All of these observations support the assignment scheme proposed previously for the carbonyls of P700 and P700(+) [Breton, J., Nabedryk, E., and Leibl, W. (1999) Biochemistry 38, 11585-11592] and therefore reinforce our previous conclusions that the positive charge in P700(+) is largely delocalized over P(A) and P(B).

  • the two histidine axial ligands of the primary electron donor chlorophylls P700 in photosystem i are similarly perturbed upon P700 formation
    Biochemistry, 2002
    Co-Authors: Jacques Breton, Wu Xu, Bruce A Diner, Parag R Chitnis
    Abstract:

    : The extent of delocalization of the positive charge in the oxidized dimer of chlorophyll (Chl) constituting P700, the primary electron donor of photosystem I (PSI), has been investigated by analyzing the perturbation upon P700(+) formation of infrared (IR) vibrational modes of the two His axial ligands of the two P700 Chl molecules. Fourier transform IR (FTIR) difference spectra of the photooxidation of P700 in PSI core complexes isolated from Synechocystis sp. PCC 6803 isotopically labeled either globally with (15)N or more specifically with (13)C on all the His residues reveal isotopic shifts of a differential signal at 1102/1108 cm(-)(1). This signal is assigned to a downshift upon P700(+) formation of the predominantly C(5)-Ntau imidazole stretching mode of His residue(s). The amplitude of this signal is reduced by approximately half in FTIR spectra of Synechocystis mutants in which His PsaB 651, the axial ligand to one of the two Chl molecules in P700, is replaced by Cys, Gln, or Leu. These observations provide further evidence that the positive charge in P700(+) is essentially delocalized over the two Chl molecules, in agreement with a previous FTIR study in which the frequency of the vibrational modes of the 9-keto and 10a-ester C=O groups of the two Chl's in P700, P700(+), and (3)P700 were firmly established for the first time [Breton, J., et al. (1999) Biochemistry 38, 11585-11592]. Only limited perturbations of the amplitude and frequency of the 9-keto and 10a-ester C=O bands of the P700 Chl are elicited by the mutations. On the basis of comparable mutational studies of the primary electron donor in purple bacteria, these perturbations are attributed to small molecular rearrangements of the Chl macrocycle and substituents caused by the repositioning of the P700 dimer in the new protein cavity generated by the mutations. It is proposed that the perturbation of the FTIR spectra upon mutation of a His axial ligand of the P700 Chl recently reported in Chlamydomonas reinhardtii [Hastings, G., et al. (2001) Biochemistry 40, 12943-12949] can be explained by the same effect without the need for a new assignment of the C=O bands of P700. The distribution of charge/spin in P700(+) and (3)P700 determined by FTIR spectroscopy is discussed in relation with the contrasting interpretations derived from recent magnetic resonance experiments.

  • FTIR study of the primary electron donor of photosystem I (P700) revealing delocalization of the charge in P700(+) and localization of the triplet character in (3)P700.
    Biochemistry, 1999
    Co-Authors: Jacques Breton, Eliane Nabedryk, Winfried Leibl
    Abstract:

    The effect of global 15N or 2H labeling on the light-induced P700+/P700 FTIR difference spectra has been investigated in photosystem I samples from Synechocystis at 90 K. The small isotope-induced frequency shifts of the carbonyl modes observed in the P700+/P700 spectra are compared to those of isolated chlorophyll a. This comparison shows that bands at 1749 and 1733 cm-1 and at 1697 and 1637 cm-1, which upshift upon formation of P700+, are candidates for the 10a-ester and 9-keto CO groups of P700, respectively. A broad and relatively weak band peaking at 3300 cm-1, which does not shift upon global labeling or 1H−2H exchange, is ascribed to an electronic transition of P700+, indicating that at least two chlorophyll a molecules (denoted P1 and P2) participate in P700+. Comparisons of the 3P700/P700 FTIR difference spectrum at 90 K with spectra of triplet formation in isolated chlorophyll a or in RCs from photosystem II or purple bacteria identify the bands at 1733 and 1637 cm-1, which downshift upon format...

  • ftir study of the primary electron donor of photosystem i P700 revealing delocalization of the charge in P700 and localization of the triplet character in 3 P700
    Biochemistry, 1999
    Co-Authors: Jacques Breton, Eliane Nabedryk, Winfried Leibl
    Abstract:

    The effect of global 15N or 2H labeling on the light-induced P700+/P700 FTIR difference spectra has been investigated in photosystem I samples from Synechocystis at 90 K. The small isotope-induced frequency shifts of the carbonyl modes observed in the P700+/P700 spectra are compared to those of isolated chlorophyll a. This comparison shows that bands at 1749 and 1733 cm-1 and at 1697 and 1637 cm-1, which upshift upon formation of P700+, are candidates for the 10a-ester and 9-keto CO groups of P700, respectively. A broad and relatively weak band peaking at 3300 cm-1, which does not shift upon global labeling or 1H−2H exchange, is ascribed to an electronic transition of P700+, indicating that at least two chlorophyll a molecules (denoted P1 and P2) participate in P700+. Comparisons of the 3P700/P700 FTIR difference spectrum at 90 K with spectra of triplet formation in isolated chlorophyll a or in RCs from photosystem II or purple bacteria identify the bands at 1733 and 1637 cm-1, which downshift upon format...

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  • effect of the P700 pre oxidation and point mutations near a0 on the reversibility of the primary charge separation in photosystem i from chlamydomonas reinhardtii
    Biochimica et Biophysica Acta, 2010
    Co-Authors: Wojciech Giera, Andrew N Webber, V M Ramesh, Ivo H M Van Stokkum, Rienk Van Grondelle, Krzysztof Gibasiewicz
    Abstract:

    Abstract Time-resolved fluorescence studies with a 3-ps temporal resolution were performed in order to: (1) test the recent model of the reversible primary charge separation in Photosystem I (Muller et al., 2003; Holwzwarth et al., 2005, 2006), and (2) to reconcile this model with a mechanism of excitation energy quenching by closed Photosystem I (with P700 pre-oxidized to P700 + ). For these purposes, we performed experiments using Photosystem I core samples isolated from Chlamydomonas reinhardtii wild type, and two mutants in which the methionine axial ligand to primary electron acceptor, A 0 , has been change to either histidine or serine. The temporal evolution of fluorescence spectra was recorded for each preparation under conditions where the “primary electron donor,” P700, was either neutral or chemically pre-oxidized to P700 + . For all the preparations under study, and under neutral and oxidizing conditions, we observed multiexponential fluorescence decay with the major phases of ∼ 7 ps and ∼ 25 ps. The relative amplitudes and, to a minor extent the lifetimes, of these two phases were modulated by the redox state of P700 and by the mutations near A 0 : both pre-oxidation of P700 and mutations caused slight deceleration of the excited state decay. These results are consistent with a model in which P700 is not the primary electron donor, but rather a secondary electron donor, with the primary charge separation event occurring between the accessory chlorophyll, A, and A 0 . We assign the faster phase to the equilibration process between the excited state of the antenna/reaction center ensemble and the primary radical pair, and the slower phase to the secondary electron transfer reaction. The pre-oxidation of P700 shifts the equilibrium between the excited state and the primary radical pair towards the excited state. This shift is proposed to be induced by the presence of the positive charge on P700 + . The same charge is proposed to be responsible for the fast A + A 0 −  → AA 0 charge recombination to the ground state and, in consequence, excitation quenching in closed reaction centers. Mutations of the A 0 axial ligand shift the equilibrium in the same direction as pre-oxidation of P700 due to the up-shift of the free energy level of the state A + A 0 − .

  • species specific differences of the spectroscopic properties of P700 analysis of the influence of non conserved amino acid residues by site directed mutagenesis of photosystem i from chlamydomonas reinhardtii
    Journal of Biological Chemistry, 2003
    Co-Authors: Heike Witt, N. V. Karapetyan, Enrica Bordignon, Donatella Carbonera, Jan P Dekker, Christian Teutloff, Andrew N Webber, Wolfgang Lubitz, Eberhard Schlodder
    Abstract:

    Abstract We applied optical spectroscopy, magnetic resonance techniques, and redox titrations to investigate the properties of the primary electron donor P700 in photosystem I (PS I) core complexes from cyanobacteria (Thermosynechococcus elongatus, Spirulina platensis, and Synechocystis sp. PCC 6803), algae (Chlamydomonas reinhardtii CC2696), and higher plants (Spinacia oleracea). Remarkable species-specific differences of the optical properties of P700 were revealed monitoring the (3P700P700) and (P700+·–P700) absorbance and CD difference spectra. The main bleaching band in the Qy region differs in peak position and line width for the various species. In cyanobacteria the absorbance of P700 extends more to the red compared with algae and higher plants which is favorable for energy transfer from red core antenna chlorophylls to P700 in cyanobacteria. The amino acids in the environment of P700 are highly conserved with two distinct deviations. In C. reinhardtii a Tyr is found at position PsaB659 instead of a Trp present in all other organisms, whereas in Synechocystis a Phe is found instead of a Trp at the homologous position PsaA679. We constructed several mutants in C. reinhardtii CC2696. Strikingly, no PS I could be detected in the mutant YW B659 indicating steric constraints unique to this organism. In the mutants WA A679 and YA B659 significant changes of the spectral features in the (3P700P700), the (P700+·–P700) absorbance difference and in the (P700+·–P700) CD difference spectra are induced. The results indicate structural differences among PS I from higher plants, algae, and cyanobacteria and give further insight into specific protein-cofactor interactions contributing to the optical spectra.

  • primary donor photo oxidation in photosystem i a re evaluation of P700 P700 fourier transform infrared difference spectra
    Biochemistry, 2001
    Co-Authors: Gary Hastings, Velautham Sivakumar, V M Ramesh, Ruilli Wang, Andrew N Webber
    Abstract:

    Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been used to study the photo-oxidation of the primary electron donor (P700) in PS I particles from Chlamydomonas reinhardtii and Synechocystis sp. PCC 6803. To aid in the interpretation of the spectra, PS I particles from a site-directed mutant of C. reinhardtii, in which the axial histidine ligand (HisA676) was changed to serine, were also studied. A high-frequency (3300−2600 cm-1) electronic transition is observed for all PS I particles, demonstrating that P700 is dimeric. The electronic band is, however, species-dependent, indicating some differences in the electronic structure of P700 and/or P700+ in C. reinhardtii and Synechocystis sp. 6803. For PS I particles from C. reinhardtii, substitution of HisA676 with serine has little effect on the ester carbonyl modes of the chlorophylls of P700. However, the keto carbonyl modes are considerably altered. Comparison of (P700+ − P700) FTIR difference spectra obtained using PS I partic...

  • Primary donor photo-oxidation in photosystem I: a re-evaluation of (P700(+) - P700) Fourier transform infrared difference spectra.
    Biochemistry, 2001
    Co-Authors: Gary Hastings, Velautham Sivakumar, V M Ramesh, Ruilli Wang, Andrew N Webber
    Abstract:

    Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been used to study the photo-oxidation of the primary electron donor (P700) in PS I particles from Chlamydomonas reinhardtii and Synechocystis sp. PCC 6803. To aid in the interpretation of the spectra, PS I particles from a site-directed mutant of C. reinhardtii, in which the axial histidine ligand (HisA676) was changed to serine, were also studied. A high-frequency (3300−2600 cm-1) electronic transition is observed for all PS I particles, demonstrating that P700 is dimeric. The electronic band is, however, species-dependent, indicating some differences in the electronic structure of P700 and/or P700+ in C. reinhardtii and Synechocystis sp. 6803. For PS I particles from C. reinhardtii, substitution of HisA676 with serine has little effect on the ester carbonyl modes of the chlorophylls of P700. However, the keto carbonyl modes are considerably altered. Comparison of (P700+ − P700) FTIR difference spectra obtained using PS I partic...