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Richard J Cogdell - One of the best experts on this subject based on the ideXlab platform.
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origin of the two bands in the b800 ring and their involvement in the energy transfer network of allochromatium vinosum
Journal of Physical Chemistry Letters, 2018Co-Authors: Richard J Cogdell, M Schroter, Marcelo J P Alcocer, Oliver Kuhn, Donatas ZigmantasAbstract:Bacterial photosynthesis features robust and adaptable energy-harvesting processes in which light-harvesting proteins play a crucial role. The peripheral light-harvesting complex of the purple bacterium Allochromatium vinosum is particularly distinct, featuring a double peak structure in its B800 absorption band. Two hypotheses—not necessarily mutually exclusive—concerning the origin of this splitting have been proposed; either two distinct B800 Bacteriochlorophyll site energies are involved, or an excitonic dimerization of Bacteriochlorophylls within the B800 ring takes place. Through the use of two-dimensional electronic spectroscopy, we present unambiguous evidence that excitonic interaction shapes the split band. We further identify and characterize all of the energy transfer pathways within this complex by using a global kinetic fitting procedure. Our approach demonstrates how the combination of two-dimensional spectral resolution and self-consistent fitting allows for extraction of information on li...
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Strategies to enhance the excitation energy-transfer efficiency in a light-harvesting system using the intra-molecular charge transfer character of carotenoids
Faraday Discussions, 2017Co-Authors: Nao Yukihira, Yuko Sugai, Masazumi Fujiwara, Kazuhiko Sakaguchi, Shigeo Katsumura, Daisuke Kosumi, Richard J Cogdell, Alastair T. Gardiner, Hideki HashimotoAbstract:Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (∼95%) energy-transfer from fucoxanthin to chlorophyll a in the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to Bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin into a light-harvesting complex 1 from the purple photosynthetic bacterium, Rhodospirillum rubrum G9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to Bacteriochlorophyll a when they are bound to the light-harvesting 1 apo-proteins.
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Photoprotection Mechanism of Light-Harvesting Antenna Complex from Purple Bacteria
Journal of Physical Chemistry B, 2016Co-Authors: Daisuke Kosumi, Tomoko Horibe, Mitsuru Sugisaki, Richard J Cogdell, Hideki HashimotoAbstract:Photosynthetic light-harvesting apparatus efficiently capture sunlight and transfer the energy to reaction centers, while they safely dissipate excess energy to surrounding environments for a protection of their organisms. In this study, we performed pump–probe spectroscopic measurements with a temporal window ranging from femtosecond to submillisecond on the purple bacterial antenna complex LH2 from Rhodobacter sphaeroides 2.4.1 to clarify its photoprotection functions. The observed excited state dynamics in the time range from subnanosecond to microsecond exhibits that the triplet–triplet excitation energy transfer from Bacteriochlorophyll a to carotenoid takes place with a time constant of 16.7 ns. Furthermore, ultrafast spectroscopic data suggests that a molecular assembly of Bacteriochlorophyll a in LH2 efficiently suppresses a generation of triple Bacteriochlorophyll a.
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the dependence of excitation energy transfer pathways on conjugation length of carotenoids in purple bacterial photosynthetic antennae
Physica Status Solidi B-basic Solid State Physics, 2011Co-Authors: Satoshi Maruta, Daisuke Kosumi, Tomoko Horibe, Mitsuru Sugisaki, Richard J Cogdell, Ritsuko Fujii, Hideki HashimotoAbstract:Ultrafast excited state dynamics of carotenoids in solution and bound to pigment–protein complexes have been investigated by femtosecond pump-probe spectroscopic measurements. Possible excitation energy transfer (EET) pathways between carotenoids and Bacteriochlorophylls and their efficiency depend strongly on the conjugation length of carotenoids. In the case of Rhodobacter sphaeroides 2.4.1, dual EET channels from carotenoid to Bacteriochlorophyll (S2 Qx and S1 Qy) upon excitation of carotenoid were observed. In the case of Rhodospirillum rubrum S1, on the other hand, the EET pathway of S1 Qy upon excitation of carotenoid was closed, whereas reverse energy transfer from Bacteriochlorophyll to carotenoid was clearly observed upon excitation of Bacteriochlorophyll. The role of carotenoids in the light-harvesting complexes is discussed in terms of their conjugation length.
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bacteriochlorin protein interactions in native b800 b850 b800 deficient and b800 bchla p reconstituted complexes from rhodopseudomonas acidophila strain 10050
FEBS Letters, 1999Co-Authors: Andrew Gall, Bruno Robert, Niall J Fraser, M C Bellissentfunel, Hugo Scheer, Richard J CogdellAbstract:Recently, a method which allows the selective release and removal of the 800 nm absorbing Bacteriochlorophyll a (B800) molecules from the LH2 complex of Rhodopseudomonas acidophila strain 10050 has been described [Fraser, N.J. (1999) Ph.D. Thesis, University of Glasgow, UK]. This procedure also allows the reconstitution of empty binding sites with the native pigment Bchla(p), esterified with phytol. We have investigated the Bacteriochlorophylla-protein interactions in native, B800 deficient (or B850) and in B8110-Bacteriochlorophylla(p)-reconstituted LH2 complexes by resonance Raman spectroscopy. We present the first direct structural evidence which shows that the reconstituted pigments are correctly bound within their binding pockets.
Mette Miller - One of the best experts on this subject based on the ideXlab platform.
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Bacteriochlorophyll organization and energy transfer kinetics in chlorosomes from Chloroflexus aurantiacus depend on the light regime during growth.
Photosynthesis research, 1996Co-Authors: Raymond P. Cox, Tomas Gillbro, Mette MillerAbstract:We have used measurements of fluorescence and circular dichroism (CD) to compare chlorosome-membrane preparations derived from the green filamentous bacterium Chloroflexus aurantiacus grown in continuous culture at two different light-intensities. The cells grown under low light (6 μmol m−2 s−1) had a higher ratio of Bacteriochlorophyll (BChl) c to BChl a than cells grown at a tenfold higher light intensity; the high-light-grown cells had much more carotenoid per Bacteriochlorophyll.
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antenna complexes from green photosynthetic bacteria
1995Co-Authors: John M Olson, Mette MillerAbstract:Green photosynthetic bacteria contain unique peripheral antenna complexes known as chiorosomes. Chiorosome complexes are optimized for light collection at low levels. The chlorosome is composed of large amounts of pigment and relatively little protein. The pigments consist principally of bacteriochiorophylls c, d or e plus carotenoids, along with small amounts of Bacteriochlorophyll a. The Bacteriochlorophylls c, d or e are organized into pigment oligomers with relatively little or no involvement of protein in determining the pigment arrangement. The Bacteriochlorophyll a is associated with a protein as a pigment-protein complex. Additional membrane-associated antenna complexes are energy transfer intermediates between the chlorosome and the reaction center. These include the Fenna-Matthews-Olson protein in the green sulfur bacteria, and integral membrane antenna complexes similar to the purple bacterial LHI complex in the green nonsulfur bacteria. The green sulfur bacteria antenna system is regulated by redox potential, so that excitations are efficiently quenched at high redox potentials and never reach the reaction center. This regulation is mediated by quinone molecules that are localized in the chiorosome complex and is thought to protect the cell from light-induced superoxide formation under conditions of transient oxygen exposure.
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Incorporation of exogenous long-chain alcohols into Bacteriochlorophyll c homologs by Chloroflexus aurantiacus
Archives of Microbiology, 1995Co-Authors: Kim Lambertsen Larsen, Mette Miller, Raymond P. CoxAbstract:Chloroflexus aurantiacus grown in batch culture took up exogenous alcohols and incorporated these into Bacteriochlorophyll c as the esterifying alcohol. It was possible to change the distribution of the naturally occurring homologs of Bacteriochlorophyll c esterified with phytol, hexadecanol, and octadecanol by adding the appropriate alcohol. The corresponding homolog then made up at least 60% of the cellular Bacteriochlorophyll c. It was also possible to obtain novel Bacteriochlorophyll homologs not found in detectable amounts in control cells by adding fatty alcohols with short chains (C10, C12) or long chains (C20). These changes in Bacteriochlorophyll composition had no detectable effects on the spectral properties of the chlorosomes.
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energy transfer kinetics in chlorosomes from chloroflexus aurantiacus studies using picosecond absorbance spectroscopy
Biochimica et Biophysica Acta, 1991Co-Authors: Mette Miller, Raymond P. Cox, Tomas GillbroAbstract:We have investigated energy transfer in chlorosome preparations from the green photosynthetic bacterium Chloroflexus aurantiacus using picosecond absorbance spectroscopy. The observed energy transfer kinetics were similar in preparations obtained with the detergent Miranol and the chaotropic agent NaSCN. The results can be interpreted by a simple model in which energy transfer from Bacteriochlorophyll c in the chlorosome to Bacteriochlorophyll a -795 or a -808 takes 10 ps, and further transfer from these components takes 30 ps. Annihilation studies suggested that the excitation energy was restricted to a domain of about 30 Bacteriochlorophyll c molecules. Time-resolved anisotropy decay measurements were also made and the results were used to make some structural predictions about the relative orientations of the various chromophores.
Tomas Gillbro - One of the best experts on this subject based on the ideXlab platform.
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Bacteriochlorophyll organization and energy transfer kinetics in chlorosomes from Chloroflexus aurantiacus depend on the light regime during growth.
Photosynthesis research, 1996Co-Authors: Raymond P. Cox, Tomas Gillbro, Mette MillerAbstract:We have used measurements of fluorescence and circular dichroism (CD) to compare chlorosome-membrane preparations derived from the green filamentous bacterium Chloroflexus aurantiacus grown in continuous culture at two different light-intensities. The cells grown under low light (6 μmol m−2 s−1) had a higher ratio of Bacteriochlorophyll (BChl) c to BChl a than cells grown at a tenfold higher light intensity; the high-light-grown cells had much more carotenoid per Bacteriochlorophyll.
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energy transfer kinetics in chlorosomes from chloroflexus aurantiacus studies using picosecond absorbance spectroscopy
Biochimica et Biophysica Acta, 1991Co-Authors: Mette Miller, Raymond P. Cox, Tomas GillbroAbstract:We have investigated energy transfer in chlorosome preparations from the green photosynthetic bacterium Chloroflexus aurantiacus using picosecond absorbance spectroscopy. The observed energy transfer kinetics were similar in preparations obtained with the detergent Miranol and the chaotropic agent NaSCN. The results can be interpreted by a simple model in which energy transfer from Bacteriochlorophyll c in the chlorosome to Bacteriochlorophyll a -795 or a -808 takes 10 ps, and further transfer from these components takes 30 ps. Annihilation studies suggested that the excitation energy was restricted to a domain of about 30 Bacteriochlorophyll c molecules. Time-resolved anisotropy decay measurements were also made and the results were used to make some structural predictions about the relative orientations of the various chromophores.
Jonathan S Lindsey - One of the best experts on this subject based on the ideXlab platform.
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red and near infrared fluorophores inspired by chlorophylls consideration of practical brightness in multicolor flow cytometry and biomedical sciences
Reporters Markers Dyes Nanoparticles and Molecular Probes for Biomedical Applications X, 2018Co-Authors: Masahiko Taniguchi, Rui Liu, Jonathan S LindseyAbstract:Demands in flow cytometry for increased multiplexing (for detection of multiple antigens) and brightness (for detection of rare entities) require new fluorophores (i.e., “colors”) with spectrally distinct fluorescence outside the relatively congested visible spectral region. Flow cytometry fluorophores typically must function in aqueous solution upon bioconjugation and ideally should exhibit a host of photophysical features: (i) strong absorption, (ii) sizable Stokes shift, (iii) modest if not strong fluorescence, and (iv) narrow fluorescence band. Tandem dyes have long been pursued to achieve a large effective Stokes shift, increased brightness, and better control over the excitation and emission wavelengths. Here, the attractive photophysical features of chlorophylls and Bacteriochlorophylls – Nature’s chosen photoactive pigments for photosynthesis – are described with regards to use in flow cytometry. A chlorophyll (or Bacteriochlorophyll) constitutes an intrinsic tandem dye given the red (or near-infrared) fluorescence upon excitation in the higher energy ultraviolet (UV) or visible absorption bands (due to rapid internal conversion to the lowest energy state). Synthetic (bacterio)chlorins are available with strong absorption (near-UV molar absorption coefficient e(λ exc ) ~10 5 M -1 cm -1 ), modest fluorescence quantum yield (Φf = 0.05–0.30), and narrow fluorescence band (10–25 nm) tunable from 600–900 nm depending on synthetic design. The “relative practical brightness” is given by intrinsic brightness [e(λ exc ) x Φ f ] times η f , the fraction of the fluorescence band that is captured by an emission filter in a multicolor experiment. The spectroscopic features of (bacterio)chlorins are evaluated quantitatively to illustrate practical brightness for this novel class of fluorophores in a prospective 8-color panel.
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construction of the bacteriochlorin macrocycle with concomitant nazarov cyclization to form the annulated isocyclic ring analogues of Bacteriochlorophyll a
Journal of Organic Chemistry, 2017Co-Authors: Shaofei Zhang, Jonathan S LindseyAbstract:Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 131-oxo and 132-carbomethoxy substituents. Herein, a general route to stable, synthetic Bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CH2Cl2, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin–carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb(OTf)3, CH3CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrro...
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Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll a
2017Co-Authors: Shaofei Zhang, Jonathan S LindseyAbstract:Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 131-oxo and 132-carbomethoxy substituents. Herein, a general route to stable, synthetic Bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CH2Cl2, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin–carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb(OTf)3, CH3CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrrole sites, ring A) and 132 carboalkoxy groups (R = Me or Et) were constructed in 37–61% yield from the hydrobilin analogues. The BC half and AD half are available in five and eight steps, respectively, from the corresponding pyrrole-2-carboxaldehyde and unsaturated ketone. The bacteriochlorins exhibit absorption spectra typical of bacteriopheophytins (free base Bacteriochlorophylls), with a strong near-infrared absorption band (707–751 nm)
Hideki Hashimoto - One of the best experts on this subject based on the ideXlab platform.
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Strategies to enhance the excitation energy-transfer efficiency in a light-harvesting system using the intra-molecular charge transfer character of carotenoids
Faraday Discussions, 2017Co-Authors: Nao Yukihira, Yuko Sugai, Masazumi Fujiwara, Kazuhiko Sakaguchi, Shigeo Katsumura, Daisuke Kosumi, Richard J Cogdell, Alastair T. Gardiner, Hideki HashimotoAbstract:Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (∼95%) energy-transfer from fucoxanthin to chlorophyll a in the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to Bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin into a light-harvesting complex 1 from the purple photosynthetic bacterium, Rhodospirillum rubrum G9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to Bacteriochlorophyll a when they are bound to the light-harvesting 1 apo-proteins.
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Photoprotection Mechanism of Light-Harvesting Antenna Complex from Purple Bacteria
Journal of Physical Chemistry B, 2016Co-Authors: Daisuke Kosumi, Tomoko Horibe, Mitsuru Sugisaki, Richard J Cogdell, Hideki HashimotoAbstract:Photosynthetic light-harvesting apparatus efficiently capture sunlight and transfer the energy to reaction centers, while they safely dissipate excess energy to surrounding environments for a protection of their organisms. In this study, we performed pump–probe spectroscopic measurements with a temporal window ranging from femtosecond to submillisecond on the purple bacterial antenna complex LH2 from Rhodobacter sphaeroides 2.4.1 to clarify its photoprotection functions. The observed excited state dynamics in the time range from subnanosecond to microsecond exhibits that the triplet–triplet excitation energy transfer from Bacteriochlorophyll a to carotenoid takes place with a time constant of 16.7 ns. Furthermore, ultrafast spectroscopic data suggests that a molecular assembly of Bacteriochlorophyll a in LH2 efficiently suppresses a generation of triple Bacteriochlorophyll a.
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the dependence of excitation energy transfer pathways on conjugation length of carotenoids in purple bacterial photosynthetic antennae
Physica Status Solidi B-basic Solid State Physics, 2011Co-Authors: Satoshi Maruta, Daisuke Kosumi, Tomoko Horibe, Mitsuru Sugisaki, Richard J Cogdell, Ritsuko Fujii, Hideki HashimotoAbstract:Ultrafast excited state dynamics of carotenoids in solution and bound to pigment–protein complexes have been investigated by femtosecond pump-probe spectroscopic measurements. Possible excitation energy transfer (EET) pathways between carotenoids and Bacteriochlorophylls and their efficiency depend strongly on the conjugation length of carotenoids. In the case of Rhodobacter sphaeroides 2.4.1, dual EET channels from carotenoid to Bacteriochlorophyll (S2 Qx and S1 Qy) upon excitation of carotenoid were observed. In the case of Rhodospirillum rubrum S1, on the other hand, the EET pathway of S1 Qy upon excitation of carotenoid was closed, whereas reverse energy transfer from Bacteriochlorophyll to carotenoid was clearly observed upon excitation of Bacteriochlorophyll. The role of carotenoids in the light-harvesting complexes is discussed in terms of their conjugation length.
