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Roger G. Hiller - One of the best experts on this subject based on the ideXlab platform.
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unveiling the excited state energy transfer pathways in Peridinin chlorophyll a protein by ultrafast multi pulse transient absorption spectroscopy
Biochimica et Biophysica Acta, 2017Co-Authors: Kipras Redeckas, Roger G. Hiller, Donatas Zigmantas, Vladislava Voiciuk, Mikas VengrisAbstract:Time-resolved multi-pulse methods were applied to investigate the excited state dynamics, the interstate couplings, and the excited state energy transfer pathways between the light-harvesting pigments in Peridinin-chlorophyll a-protein (PCP). The utilized pump-dump-probe techniques are based on perturbation of the regular PCP energy transfer pathway. The PCP complexes were initially excited with an ultrashort pulse, resonant to the S0 → S2 transition of the carotenoid Peridinin. A portion of the Peridinin-based emissive intramolecular charge transfer (ICT) state was then depopulated by applying an ultrashort NIR pulse that perturbed the interaction between S1 and ICT states and the energy flow from the carotenoids to the chlorophylls. The presented data indicate that the Peridinin S1 and ICT states are spectrally distinct and coexist in an excited state equilibrium in the PCP complex. Moreover, numeric analysis of the experimental data asserts ICT → Chl-a as the main energy transfer pathway in the photoexcited PCP systems.
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Light Harvesting by Carotenoids: Peridinin-Chlorophyll-Protein (PCP) from Amphidinium carterae Structural Relation to Proteins with Globin Fold
2016Co-Authors: Eckllard Hofmann, Roger G. Hiller, Wolfram Welte, Kay Diederichs, Fakultiit Fur Biologie, Universitiit KonstanzAbstract:Dinoflagellates contribute a major part of the plankton on earth. We have recently solved by x-ray crystallography [1] at 2.oA resolution the structure of Peridinin-chlorophyll-protein (PCP), a water-soluble Iight-harvesting complex. which has a blue-green absorbing carotenoid as its main pigment, and is present in most photosynthetic dinoflagellates. PCP forms a flat non· crystallographic trimer, which we believe is the photosynthetically active fonn. The PCP polypeptide (312 residues) has the shape of the hull of a ship (Fig. I) enclosing two lipid, eight Peridinin and two chlorophyll a molecules. Each monomer is composed of a pseudosymmetry-related N · and C-terminal half of eight helices each adopting a peculiar topology which we found to be similar to lhe globin fold (2). The structural basi
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Structural Basis of Light Harvesting by Carotenoids: Peridinin-Chlorophyll-Protein from
2016Co-Authors: Amphidinium Carterae, Frank P Sharples, Roger G. Hiller, Wolfram Welte, Eckhard Hofmann, Pamela M Wrench, Kay DiederichsAbstract:Peridinin-chlorophyll-protein, a water-soluble light-harvesting complex that has a blue-green absorbing carotenoid as its main pigment, is present in most photosynthetic dinoflagellates. Its high-resolution (2.0 angstrom) x-ray structure reveals a noncrystal-lographic trimer in which each polypeptide contains an unusual jellyroll fold of the a-helical amino- and carboxyl-terminal domains. These domains constitute a scaffold with pseudo-twofold symmetry surrounding a hydrophobic cavity filled by two lipid, eight Peridinin, and two chlorophyll a molecules. The structural basis for efficient excitonic energy transfer from Peridinin to chlorophyll is found in the clustering of Peridinins around the chlorophylls at van der Waals distances. Table 1. Crystallographic data. Data collection: Native1 and derivative data (5 IllM K2 PtCI4, 1-day soak) were collected on a rotating anode source (CuKa, 40 kV, 100 mA) with a STOE (Darmstadt, Germany) imaging plate detector. Native2 was collected at the BW7B wiggler bealllline at DESY on a 30-cm MARresearch (Hamburg, Germany) image plate. All data were processed with XDS (26). Phasing: Six heavy-atom binding sites were found using SHELXS (27) in Patterson search mode, and four additional sites were found by inspection of difference Fourier maps. Refinement of heavy-atom parameters wa
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Conservation of Spin Polarization during Triplet–Triplet Energy Transfer in Reconstituted Peridinin–Chlorophyll–Protein Complexes
2016Co-Authors: Marilena Di Valentin, Roger G. Hiller, Stefano Ceola, Enrico Salvadori, Claudia Tait, Hugo Scheer, Donatella CarboneraAbstract:Peridinin–chlorophyll–protein (PCP) complexes, where the N-terminal domain of native PCP from Amphidinium carterae has been reconstituted with different chlorophyll (Chl) species, have been investigated by time-resolved EPR in order to elucidate the details of the triplet–triplet energy transfer (TTET) mechanism. This spectroscopic approach exploits the concept of spin conservation during TTET, which leads to recognizable spin-polarization effects in the observed time-resolved EPR spectra. The spin polarization produced at the acceptor site (Peridinin) depends on the initial polarization of the donor (chlorophyll) and on the relative geometric arrangement of the donor–acceptor spin axes. A variation of the donor triplet state properties in terms of population probabilities or triplet spin axis directions, as produced by replacement of chlorophyll a (Chl a) with non-native chlorophyll species (ZnChl a and BacterioChl a) in the reconstituted complexes, is unambiguously reflected in the polarization pattern of the carotenoid triplet state. For the first time, in the present investigation spin-polarization conservation has been shown to occur among natural cofactors in protein complexes during the TTET process. Proving the validity of the assumption of spin conservation adopted in the EPR spectral analysis, the results reinforce the hypothesis that in PCP proteins Peridinin 614, according to X-ray nomenclature (Hofmann, E.; et al. Science 1996, 272, 1788–1791), is the carotenoid of election in the photoprotection mechanism based on TTET
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x ray structure of the high salt form of the Peridinin chlorophyll a protein from the dinoflagellate amphidinium carterae modulation of the spectral properties of pigments by the protein environment
Biochemistry, 2009Co-Authors: Tim Schulte, Frank P Sharples, Roger G. Hiller, Eckhard HofmannAbstract:Light-harvesting complexes have evolved into very different structures but fulfill the same function, efficient harvesting of solar energy. In these complexes, pigments are fine-tuned and properly arranged to gather incoming photons. In the photosynthetic dinoflagellate Amphidinium carterae, two variants of the soluble light-harvesting complex PCP have been found [main form PCP (MFPCP) and high-salt PCP (HSPCP)], which show small variations in their pigment arrangement and tuning mechanisms. This feature makes them ideal models for studying pigment-protein interactions. Here we present the X-ray structure of the monomeric HSPCP determined at 2.1 A resolution and compare it to the structure of trimeric MFPCP. Despite the high degree of structural similarity (rmsd C(alpha)-C(alpha) of 1.89 A), the sequence variations lead to a changed overall pigment composition which includes the loss of two carotenoid molecules and a dramatic rearrangement of the chlorophyll phytol chains and of internal lipid molecules. On the basis of a detailed structural comparison, we favor a macrocycle geometry distortion of the chlorophylls rather than an electrostatic effect to explain energetic splitting of the chlorophyll a Q(y) bands [Ilagan, R. P. (2006) Biochemistry 45, 14052-14063]. Our analysis supports their assignment of Peridinin 611* as the single blue-shifted Peridinin in HSPCP but also highlights another electrostatic feature due to glutamate 202 which could add to the observed binding site asymmetry of the 611*/621* Peridinin pair.
Harry A Frank - One of the best experts on this subject based on the ideXlab platform.
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Structural Tuning of Quantum Decoherence and Coherent Energy Transfer in Photosynthetic Light Harvesting
2018Co-Authors: Jerome D. Roscioli, Harry A Frank, Soumen Ghosh, Amy M. Lafountain, Warren F. BeckAbstract:Photosynthetic organisms capture energy from solar photons by constructing light-harvesting proteins containing arrays of electronic chromophores. Collective excitations (excitons) arise when energy transfer between chromophores is coherent, or wavelike, in character. Here we demonstrate experimentally that coherent energy transfer to the lowest-energy excitons is principally controlled in a light-harvesting protein by the temporal persistence of quantum coherence rather than by the strength of vibronic coupling. In the Peridinin–chlorophyll protein from marine dinoflagellates, broad-band two-dimensional electronic spectroscopy reveals that replacing the native chlorophyll a acceptor chromophores with chlorophyll b slows energy transfer from the carotenoid Peridinin to chlorophyll despite narrowing the donor–acceptor energy gap. The formyl substituent on the chlorophyll b macrocycle hastens decoherence by sensing the surrounding electrostatic noise. These findings demonstrate how quantum coherence enhances the efficiency of energy transfer despite being very short lived in light-harvesting proteins at physiological temperatures
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Quantum Coherent Excitation Energy Transfer by Carotenoids in Photosynthetic Light Harvesting
2017Co-Authors: Jerome D. Roscioli, Harry A Frank, Soumen Ghosh, Amy M. Lafountain, Warren F. BeckAbstract:It remains an open question whether quantum coherence and molecular excitons created by delocalization of electronic excited states are essential features of the mechanisms that enable efficient light capture and excitation energy transfer to reaction centers in photosynthetic organisms. The Peridinin–chlorophyll a protein from marine dinoflagellates is an example of a light-harvesting system with tightly clustered antenna chromophores in which quantum coherence has long been suspected, but unusually it features the carotenoid Peridinin as the principal light absorber for mid-visible photons. We report that broad-band two-dimensional electronic spectroscopy indeed reveals the initial presence of exciton relaxation pathways that enable transfer of excitation from Peridinin to chlorophyll a in
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Excitation Energy Transfer by Coherent and Incoherent Mechanisms in the Peridinin–Chlorophyll a Protein
2017Co-Authors: Soumen Ghosh, Harry A Frank, Michael M. Bishop, Jerome D. Roscioli, Amy M. Lafountain, Warren F. BeckAbstract:Excitation energy transfer from Peridinin to chlorophyll (Chl) a is unusually efficient in the Peridinin–chlorophyll a protein (PCP) from dinoflagellates. This enhanced performance is derived from the long intrinsic lifetime of 4.4 ps for the S2 (11Bu+) state of Peridinin in PCP, which arises from the electron-withdrawing properties of its carbonyl substituent. Results from heterodyne transient grating spectroscopy indicate that S2 serves as the donor for two channels of energy transfer: a 30 fs process involving quantum coherence and delocalized Peridinin–Chl states and an incoherent, 2.5 ps process initiated by dynamic exciton localization, which accompanies the formation of a conformationally distorted intermediate in 45 fs. The lifetime of the S2 state is lengthened in PCP by its intramolecular charge-transfer character, which increases the system–bath coupling and slows the torsional motions that promote nonradiative decay to the S1 (21Ag–) state
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Femtosecond Heterodyne Transient Grating Studies of Nonradiative Deactivation of the S2 (11Bu+) State of Peridinin: Detection and Spectroscopic Assignment of an Intermediate in the Decay Pathway
2016Co-Authors: Soumen Ghosh, Harry A Frank, Michael M. Bishop, Jerome D. Roscioli, Amy M. Lafountain, Warren F. BeckAbstract:Femtosecond heterodyne transient grating spectroscopy was employed to investigate the nonradiative decay pathway from the S2 (11Bu+) state to the S1 (21Ag–) state of Peridinin in methanol solution. Just as previously observed by this laboratory for β-carotene in benzonitrile, the real (absorption) and imaginary (dispersion) components of the transient grating signal obtained with Fourier transform spectral interferometry from Peridinin exhibit ultrafast responses indicating that S2 state decays in 12 fs to produce an intermediate state, Sx. The excited state absorption spectrum from the Sx state of Peridinin, however, is found to be markedly blue-shifted from that of β-carotene because it makes a substantial contribution to the signal observed with 40 fs, 520 nm pulses. The results of a global target analysis and numerical simulations using nonlinear response functions and the multimode Brownian oscillator model support the assignment of Sx to a displaced conformation of the S2 state rather than to a vibrationally excited (or hot) S1 state. The Sx state in Peridinin is assigned to a structure with a distorted conjugated polyene backbone moving past an activation-energy barrier between planar and twisted structures on the S2 potential surface. The lengthened lifetime of the Sx state of Peridinin in methanol, 900 ± 100 fs, much longer than that typically observed for carotenoids lacking carbonyl substituents, ∼150 fs, can be attributed to the slowing of torsional motions by solvent friction. In Peridinin, the system–bath coupling is significantly enhanced over that in β-carotene solution most likely due to the intrinsic intramolecular charge transfer character it derives from the electron withdrawing nature of the carbonyl substituent. An important additional implication is that the Sx state, and the distorted structures reached subsequently along the torsional gradient on the S2 potential surface, may serve as the principal excitation energy transfer donors to chlorophyll a in the Peridinin–chlorophyll a protein from dinoflagellates
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Torsional Dynamics and Intramolecular Charge Transfer in the S2 (11Bu+) Excited State of Peridinin: A Mechanism for Enhanced Mid-Visible Light Harvesting
2016Co-Authors: Soumen Ghosh, Harry A Frank, Michael M. Bishop, Amy M. Lafountain, Jerome D. Roscioli, Jason K. Gurchiek, Warren F. BeckAbstract:Of the carotenoids known in photosynthetic organisms, Peridinin exhibits one of the highest quantum efficiencies for excitation energy transfer to chlorophyll (Chl) a acceptors. The mechanism for this enhanced performance involves an order-of-magnitude slowing of the S2 (11Bu+) → S1 (21Ag–) nonradiative decay pathway compared to carotenoids lacking carbonyl substitution. Using femtosecond transient grating spectroscopy with optical heterodyne detection, we have obtained the first evidence that the nonradiative decay of the S2 state of Peridinin is promoted by large-amplitude torsional motions. The decay of an intermediate state termed Sx, which we assign to a twisted form of the S2 state, is substantially slowed by solvent friction in Peridinin due to its intramolecular charge transfer (ICT) character
Donatella Carbonera - One of the best experts on this subject based on the ideXlab platform.
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Conservation of Spin Polarization during Triplet–Triplet Energy Transfer in Reconstituted Peridinin–Chlorophyll–Protein Complexes
2016Co-Authors: Marilena Di Valentin, Roger G. Hiller, Stefano Ceola, Enrico Salvadori, Claudia Tait, Hugo Scheer, Donatella CarboneraAbstract:Peridinin–chlorophyll–protein (PCP) complexes, where the N-terminal domain of native PCP from Amphidinium carterae has been reconstituted with different chlorophyll (Chl) species, have been investigated by time-resolved EPR in order to elucidate the details of the triplet–triplet energy transfer (TTET) mechanism. This spectroscopic approach exploits the concept of spin conservation during TTET, which leads to recognizable spin-polarization effects in the observed time-resolved EPR spectra. The spin polarization produced at the acceptor site (Peridinin) depends on the initial polarization of the donor (chlorophyll) and on the relative geometric arrangement of the donor–acceptor spin axes. A variation of the donor triplet state properties in terms of population probabilities or triplet spin axis directions, as produced by replacement of chlorophyll a (Chl a) with non-native chlorophyll species (ZnChl a and BacterioChl a) in the reconstituted complexes, is unambiguously reflected in the polarization pattern of the carotenoid triplet state. For the first time, in the present investigation spin-polarization conservation has been shown to occur among natural cofactors in protein complexes during the TTET process. Proving the validity of the assumption of spin conservation adopted in the EPR spectral analysis, the results reinforce the hypothesis that in PCP proteins Peridinin 614, according to X-ray nomenclature (Hofmann, E.; et al. Science 1996, 272, 1788–1791), is the carotenoid of election in the photoprotection mechanism based on TTET
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triplet triplet energy transfer in Peridinin chlorophyll a protein reconstituted with chl a and chl d as revealed by optically detected magnetic resonance and pulse epr comparison with the native pcp complex from amphidinium carterae
Biochimica et Biophysica Acta, 2009Co-Authors: Marilena Di Valentin, Roger G. Hiller, Giancarlo Agostini, Stefano Ceola, Giorgio M Giacometti, Enrico Salvadori, Donatella CarboneraAbstract:The triplet state of the carotenoid Peridinin, populated by triplet-triplet energy transfer from photoexcited chlorophyll triplet state, in the reconstituted Peridinin-Chlorophyll a-protein, has been investigated by ODMR (Optically detected magnetic resonance), and pulse EPR spectroscopies. The properties of Peridinins associated with the triplet state formation in complexes reconstituted with Chl a and Chl d have been compared to those of the main-form Peridinin-chlorophyll protein (MFPCP) isolated from Amphidinium carterae. In the reconstituted samples no signals due to the presence of chlorophyll triplet states have been detected, during either steady state illumination or laser-pulse excitation. This demonstrates that reconstituted complexes conserve total quenching of chlorophyll triplet states, despite the biochemical treatment and reconstitution with the non-native Chl d pigment. Zero field splitting parameters of the Peridinin triplet states are the same in the two reconstituted samples and slightly smaller than in native MFPCP. Analysis of the initial polarization of the photoinduced Electron-Spin-Echo detected spectra and their time evolution, shows that, in the reconstituted complexes, the triplet state is probably localized on the same Peridinin as in native MFPCP although, when Chl d replaces Chl a, a local rearrangement of the pigments is likely to occur. Substitution of Chl d for Chl a identifies previously unassigned bands at approximately 620 and approximately 640 nm in the Triplet-minus-Singlet (T-S) spectrum of PCP detected at cryogenic temperature, as belonging to Peridinin.
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spectroscopic properties of the Peridinins involved in chlorophyll triplet quenching in high salt Peridinin chlorophyll a protein from amphidinium carterae as revealed by optically detected magnetic resonance pulse epr and pulse endor spectroscopies
Biochimica et Biophysica Acta, 2008Co-Authors: Marilena Di Valentin, Giancarlo Agostini, Stefano Ceola, Giorgio M Giacometti, Enrico Salvadori, Donatella CarboneraAbstract:Abstract The photoexcited triplet state of the carotenoid Peridinin in the high-salt Peridinin–chlorophyll a -protein (HSPCP) of the dinoflagellate Amphidinium carterae was investigated by ODMR (optically detected magnetic resonance), pulse EPR and pulse ENDOR spectroscopies. The properties of Peridinins associated to the triplet state formation in HSPCP were compared to those of Peridinins involved in triplet state population in the main-form Peridinin–chlorophyll protein (MFPCP), previously reported. In HSPCP no signals due to the presence of chlorophyll triplet state have been detected, during either steady-state illumination or laser-pulse excitation, meaning that Peridinins play the photo-protective role with 100% efficiency as in MFPCP. The general spectroscopic features of the Peridinin triplet state are very similar in the two complexes and allow drawing the conclusion that the triplet formation pathway and the triplet localization in one specific Peridinin in each subcluster are the same in HSPCP and MFPCP. However some significant differences also emerged from the analysis of the spectra. Zero field splitting parameters of the Peridinin triplet states are slightly smaller in HSPCP and small changes are also observed for the hyperfine splittings measured by pulse ENDOR and assigned to the β-protons belonging to one of the two methyl groups present in the conjugated chain, ( a iso = 10.3 MHz in HSPCP vs a iso = 10.6 MHz in MFPCP). The differences are explained in terms of local distortion of the tails of the conjugated chains of the Peridinin molecules, in agreement with the conformational data resulting from the X-ray structures of the two complexes.
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pulse endor and density functional theory on the Peridinin triplet state involved in the photo protective mechanism in the Peridinin chlorophyll a protein from amphidinium carterae
Biochimica et Biophysica Acta, 2008Co-Authors: Marilena Di Valentin, Giancarlo Agostini, Stefano Ceola, Giorgio M Giacometti, Alexander Angerhofer, Orlando Crescenzi, Vincenzo Barone, Donatella CarboneraAbstract:Abstract The photoexcited triplet state of the carotenoid Peridinin in the Peridinin–chlorophyll a–protein of the dinoflagellate Amphidinium carterae has been investigated by pulse EPR and pulse ENDOR spectroscopies at variable temperatures. This is the first time that the ENDOR spectra of a carotenoid triplet in a naturally occurring light-harvesting complex, populated by energy transfer from the chlorophyll a triplet state, have been reported. From the electron spin echo experiments we have obtained the information on the electron spin polarization dynamics and from Mims ENDOR experiments we have derived the triplet state hyperfine couplings of the α- and β-protons of the Peridinin conjugated chain. Assignments of β-protons belonging to two different methyl groups, with aiso = 7.0 MHz and aiso = 10.6 MHz respectively, have been made by comparison with the values predicted from density functional theory. Calculations provide a complete picture of the triplet spin density on the Peridinin molecule, showing that the triplet spins are delocalized over the whole π-conjugated system with an alternate pattern, which is lost in the central region of the polyene chain. The ENDOR investigation strongly supports the hypothesis of localization of the triplet state on one Peridinin in each subcluster of the PCP complex, as proposed in [Di Valentin et al. Biochim. Biophys. Acta 1777 (2008) 186–195]. High spin density has been found specifically at the carbon atom at position 12 (see Fig. 1B), which for the Peridinin involved in the photo-protective mechanism is in close contact with the water ligand to the chlorophyll a pigment. We suggest that this ligated water molecule, placed at the interface between the chlorophyll–Peridinin pair, is functioning as a bridge in the triplet–triplet energy transfer between the two pigments.
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identification by time resolved epr of the Peridinins directly involved in chlorophyll triplet quenching in the Peridinin chlorophyll a protein from amphidinium carterae
Biochimica et Biophysica Acta, 2008Co-Authors: Marilena Di Valentin, Giancarlo Agostini, Stefano Ceola, Enrico Salvadori, Donatella CarboneraAbstract:The mechanism of triplet-triplet energy transfer in the Peridinin-chlorophyll-protein (PCP) from Amphidinium carterae was investigated by time-resolved EPR (TR-EPR). The approach exploits the concept of spin conservation during triplet-triplet energy transfer, which leads to spin polarization conservation in the observed TR-EPR spectra. The acceptor (Peridinin) inherits the polarization of the donor (chlorophyll) in a way which depends on the relative geometrical arrangement of the donor-acceptor couple. Starting from the initially populated chlorophyll triplet state and taking the relative positions among Chls and Peridinins from the X-ray structure of PCP, we calculated the expected triplet state polarization of any Peridinin in the complex. Comparison with the experimental data allowed us to propose a path for triplet quenching in the protein. The Peridinin-chlorophyll pair directly involved in the triplet-triplet energy transfer coincides with the one having the shortest center to center distance. A water molecule, which is coordinated to the central Mg atom of the Chl, is also placed in close contact with the Peridinin. The results support the concept of localization of the triplet state mainly in one specific Peridinin in each of the two pigment subclusters related by a pseudo C2 symmetry.
Robert E Blankenship - One of the best experts on this subject based on the ideXlab platform.
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excited state properties of the central cis isomer of the carotenoid Peridinin
Archives of Biochemistry and Biophysics, 2018Co-Authors: Dariusz M Niedzwiedzki, Robert E BlankenshipAbstract:The central-cis isomer of the carotenoid Peridinin, presumably 13-cis, was separated and studied with spectroscopic methods including static absorption, fluorescence and femtosecond time-resolved absorption. The investigations exposed differences in the photophysical properties of this isomer in respect to all-trans Peridinin. Steady-state absorption spectroscopy revealed the presence of an additional weak absorption band at the long wavelength tail of the main S0 → S2 transition. Modelling of the hypothetical vibronic progression of the S0 → S1 electronic transition demonstrated that this weak band can be associated with a higher (0-2) vibronic band of the transition and that lower vibronic bands have negligible intensities due to a large displacement between the S0 and S1 states energy curves as also suggested by the spectral shape of steady-state fluorescence emission. Transient absorption studies demonstrated that the lifetime of the S1 state of the central-cis isomer is shorter compared to the all-trans counterpart by 6-16%, depending on the polarity of the solvent. On the other hand, molecular isomerization negligibly affects the lifetime of intramolecular charge transfer (ICT), which for both isomers is ∼10 ps in the polar solvent methanol.
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spectroscopic properties of the chlorophyll a chlorophyll c 2 Peridinin protein complex acppc from the coral symbiotic dinoflagellate symbiodinium
Photosynthesis Research, 2014Co-Authors: Dariusz M Niedzwiedzki, Jing Jiang, Robert E BlankenshipAbstract:Femtosecond time-resolved transient absorption spectroscopy was performed on the chlorophyll a–chlorophyll c 2–Peridinin-protein-complex (acpPC), a major light-harvesting complex of the coral symbiotic dinoflagellate Symbiodinium. The measurements were carried out on the protein as well on the isolated pigments in the visible and the near-infrared region at 77 K. The data were globally fit to establish inter-pigment energy transfer paths within the scaffold of the complex. In addition, microsecond flash photolysis analysis was applied to reveal photoprotective capabilities of carotenoids (Peridinin and diadinoxanthin) in the complex, especially the ability to quench chlorophyll a triplet states. The results demonstrate that the majority of carotenoids and other accessory light absorbers such as chlorophyll c 2 are very well suited to support chlorophyll a in light harvesting. However, their performance in photoprotection in the acpPC is questionable. This is unusual among carotenoid-containing light-harvesting proteins and may explain the low resistance of the acpPC complex against photoinduced damage under even moderate light conditions.
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low temperature spectroscopic properties of the Peridinin chlorophyll a protein pcp complex from the coral symbiotic dinoflagellate symbiodinium
Journal of Physical Chemistry B, 2013Co-Authors: Dariusz M Niedzwiedzki, Jing Jiang, Robert E BlankenshipAbstract:The spectroscopic properties of the Peridinin–chlorophyll a–protein (PCP) from the coral symbiotic dinoflagellate Symbiodinium have been characterized by application of various ultrafast optical spectroscopies including femto- and nanosecond time-resolved absorption and picosecond time-resolved fluorescence (TRF) at 77 K. Excited state properties of Peridinin and Chl a and their intramolecular interaction characteristics have been obtained from global fitting analysis and directed kinetic modeling of the data sets and compared to their counterparts known for the PCP from Amphidinium carterae. The lifetimes of the excited state of Peridinin show close agreement with those known for the counterpart PCP, demonstrating that molecular interactions have the same characteristics in both complexes. More variances have been recorded for the excited state properties of Chl a including elongation of both the intramolecular energy transfer time between Chl’s within the pair in the protein monomer and the excited stat...
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spectroscopic properties of the main form and high salt Peridinin chlorophyll a proteins from amphidinium carterae
Biochemistry, 2004Co-Authors: Robielyn P Ilagan, Frank P Sharples, Roger G. Hiller, Robert E Blankenship, Sumie Shima, Robert R Birge, Alexander N Melkozernov, Su Lin, Harry A FrankAbstract:The main-form (MFPCP) and high-salt (HSPCP) Peridinin-chlorophyll a proteins from the dinoflagellate Amphidinium carterae were investigated using absorption, fluorescence, fluorescence excitation, two-photon, and fast-transient optical spectroscopy. Pigment analysis has demonstrated previously that MFPCP contains eight Peridinins and two chlorophyll (Chl) a molecules, whereas HSPCP has six Peridinins and two Chl a molecules (Sharples, F. P., et al. (1996) Biochim. Biophys. Acta 1276, 117- 123). Absorption spectra of the complexes were recorded at 10 K and analyzed in the 400-600 nm region by summing the individual 10 K spectra of Chl a and Peridinin recorded in 2-MTHF. The absorption spectral profiles of the complexes in the Qy region between 650 and 700 nm were fit using Gaussian functions. The absorption and fluorescence spectra from both complexes exhibit several distinguishing features that become evident only at cryogenic temperatures. In particular, at low temperatures the Q y transitions of the Chls bound in the HSPCP complex are split into two well-resolved bands. Fluorescence excitation spectroscopy has revealed that the Peridinin-to-Chl a energy transfer efficiency is high (>95%). Transient absorption spectroscopy has been used to measure the rate of energy transfer between the two bound Chls which is a factor of 2.9 slower in HSPCP than in MFPCP. The kinetic data are interpreted in terms of the Forster mechanism describing energy transfer between weakly coupled, spatially fixed, donor- acceptor Chl a molecules. The study provides insight into the molecular factors that control energy transfer in this class of light-harvesting pigment-protein complexes.
Tomas Polivka - One of the best experts on this subject based on the ideXlab platform.
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triplet triplet energy transfer from chlorophylls to carotenoids in two antenna complexes from dinoflagellate amphidinium carterae
Biochimica et Biophysica Acta, 2016Co-Authors: Zuzana Kvicalova, Tomas Polivka, Eckhard Hofmann, Petro Khoroshyy, David Bína, Radek Litvín, Jan Alster, Jakub PšenčíkAbstract:Room temperature transient absorption spectroscopy with nanosecond resolution was used to study quenching of the chlorophyll triplet states by carotenoids in two light-harvesting complexes of the dinoflagellate Amphidinium carterae: the water soluble Peridinin-chlorophyll protein complex and intrinsic, membrane chlorophyll a-chlorophyll c2-Peridinin protein complex. The combined study of the two complexes facilitated interpretation of a rather complicated relaxation observed in the intrinsic complex. While a single carotenoid triplet state was resolved in the Peridinin-chlorophyll protein complex, evidence of at least two different carotenoid triplets was obtained for the intrinsic light-harvesting complex. Most probably, each of these carotenoids protects different chlorophylls. In both complexes the quenching of the chlorophyll triplet states by carotenoids occurs with a very high efficiency (~100%), and with transfer times estimated to be in the order of 0.1ns or even faster. The triplet-triplet energy transfer is thus much faster than formation of the chlorophyll triplet states by intersystem crossing. Since the triplet states of chlorophylls are formed during the whole lifetime of their singlet states, the apparent lifetimes of both states are the same, and observed to be equal to the carotenoid triplet state rise time (~5ns).
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spectroscopy of the Peridinin chlorophyll a protein insight into light harvesting strategy of marine algae
Archives of Biochemistry and Biophysics, 2007Co-Authors: Tomas Polivka, Roger G. Hiller, Harry A FrankAbstract:An important component of the photosynthetic apparatus is a light-harvesting system that captures light energy and transfers it efficiently to the reaction center. Depending on environmental conditions, photosynthetic antennae have adopted various strategies for this function. Peridinin-chlorophyll-a protein (PCP) represents a unique situation because, unlike other antenna systems which have a preponderance of chlorophyll, it has the carotenoid, Peridinin, as its major pigment. The key structural feature of Peridinin is a conjugated carbonyl group. Owing to the presence of this group, an intramolecular charge-transfer excited state is formed in Peridinin which exhibits different excited state spectra and dynamics depending on the polarity of the environment. The charge-transfer state also facilitates energy transfer between Peridinin and chlorophyll-a in PCP. This review summarizes results of spectroscopic investigations of PCP in the past few years, emphasizing the specific light-harvesting strategy developed by marine photosynthetic organisms utilizing carbonyl-containing carotenoids in their antenna complexes.
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energy transfer in the major intrinsic light harvesting complex from amphidinium carterae
Biochemistry, 2006Co-Authors: Villy Sundström, Tomas Polivka, Donatas Zigmantas, Ivo H M Van Stokkum, Rienk Van Grondelle, Roger G. HillerAbstract:Carbonyl carotenoids are important constituents of the antenna complexes of marine organisms. These carotenoids possess an excited state with a charge-transfer character (intramolecular charge transfer state, ICT), but many details of the carotenoid to chlorophyll energy transfer mechanisms are as yet poorly understood. Here, we employ femtosecond transient absorption spectroscopy to study energy transfer pathways in the intrinsic light-harvesting complex (LHC) of dinoflagellates, which contains the carbonyl carotenoid Peridinin. Carotenoid to chlorophyll energy transfer efficiency is about 90% in the 530-550 nm region, where the Peridinin S2 state transfers energy with an efficiency of 25-50%. The rest proceeds via the S1/ICT channel, and the major S1/ICT-mediated energy transfer pathway utilizes the relaxed S1/ICT state and occurs with a time constant of 2.6 ps. Below 525 nm, the overall energy transfer efficiency drops because of light absorption by another carotenoid, diadinoxanthin, that contributes only marginally to energy transfer. Instead, its role is likely to be photoprotection. In addition to the Peridinin-Chl-a energy transfer, it was shown that energy transfer also occurs between the two chlorophyll species in LHC, Chl-c2, and Chl-a. The time constant characterizing the Chl-c2 to Chl-a energy transfer is 1.4 ps. The results demonstrate that the properties of the S1/ICT state specific for carbonyl carotenoids is the key to ensure the effective harvesting of photons in the 500-600 nm region, which is of vital importance to underwater organisms.
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effect of a conjugated carbonyl group on the photophysical properties of carotenoids
Physical Chemistry Chemical Physics, 2004Co-Authors: Donatas Zigmantas, Frank P Sharples, Roger G. Hiller, Villy Sundström, Harry A Frank, Tomas PolivkaAbstract:Effects of introducing a carbonyl group into the conjugation system of carotenoids were studied for four naturally occurring carotenoids: Peridinin, fucoxanthin, siphonaxanthin and spheroidenone. The conjugated carbonyl group affects energetics and dynamics of all these carotenoids in a similar way, although the magnitude of the changes depends strongly on the carotenoid structure. Firstly, presence of a carbonyl group considerably narrows the S1/ICT–S2 gap, and this effect does not depend on polarity. The S1/ICT energies of carotenoids were measured by recording S1/ICT–S2 spectral profiles in the near-infrared region and the resulting energies were 16100 cm−1 for Peridinin, 16520 cm−1 for fucoxanthin and 16610 cm−1 for siphonaxanthin. Narrowing of the S1/ICT–S2 gap has important consequences for functionality of these carotenoids in light-harvesting systems of oceanic organisms, since while the S2 state is red-shifted to capture green light, the S1/ICT state is still high enough to transfer energy to chlorophyll. The S1/ICT energy of spheroidenone was determined to be 13000 cm−1. Secondly the carbonyl group introduces some polarity-dependent effects: (1) polarity-induced change of the S1/ICT lifetime. When changing from nonpolar to polar solvent, the S1/ICT lifetime is changed from 160 to 8.5 ps for Peridinin, from 60 to 30 ps for fucoxanthin, from 60 to 20 ps for fucoxanthin, while for the longer carotenoid spheroidenone the S1/ICT lifetime remains 6 ps regardless of solvent polarity. This effect is explained in terms of stabilization of charge-transfer character of both ground and excited states. (2) stabilization of the charge-transfer character in polar solvents is also demonstrated by appearance of new polarity-induced bands in the transient absorption spectra. (3) polarity-induced changes of the ground state are manifested by asymmetric broadening of the absorption spectrum accompanied by a loss of vibrational structure.
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carotenoid to chlorophyll energy transfer in the Peridinin chlorophyll a protein complex involves an intramolecular charge transfer state
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Donatas Zigmantas, Roger G. Hiller, Villy Sundström, Tomas PolivkaAbstract:Carotenoids are, along with chlorophylls, crucial pigments involved in light-harvesting processes in photosynthetic organisms. Details of carotenoid to chlorophyll energy transfer mechanisms and their dependence on structural variability of carotenoids are as yet poorly understood. Here, we employ femtosecond transient absorption spectroscopy to reveal energy transfer pathways in the Peridinin-chlorophyll-a-protein (PCP) complex containing the highly substituted carotenoid Peridinin, which includes an intramolecular charge transfer (ICT) state in its excited state manifold. Extending the transient absorption spectra toward near-infrared region (600-1800 nm) allowed us to separate contributions from different low-lying excited states of Peridinin. The results demonstrate a special light-harvesting strategy in the PCP complex that uses the ICT state of Peridinin to enhance energy transfer efficiency.