Femtosecond spectroscopy of photosynthetic light-harvesting systems

Current Opinion in Structural Biology

Volumn 7, Issue 5, 1997, Pages 738-748

  Fleming, Graham R ^a   Grondelle, Rienk Van ^b  

^a UNIVERSITY OF CALIFORNIA   (United States)

^b VU UNIVERSITY AMSTERDAM   (Netherlands)

Author keywords

[No Author keywords available]

Indexed keywords

BACTERIOCHLOROPHYLL; CAROTENOID; CHLOROPHYLL;

CYANOBACTERIUM; ELECTRON TRANSPORT; ENERGY TRANSFER; HIGHER PLANT; NONHUMAN; PHOTOSYNTHESIS; PHOTOSYSTEM I; PHOTOSYSTEM II; PHOTOTROPHIC BACTERIUM; PRIORITY JOURNAL; PROTEIN STRUCTURE; REVIEW; SPECTROSCOPY; TIME;

EID: 0030780277     PISSN: 0959440X     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0959-440X(97)80086-3     Document Type: Article

References (86)

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16. Beekman LMP, Steffen M, Stokkum IHM, van Olsen JD, Hunter CN, Boxer SG, van Grondelle R. Characterization of the light harvesting antennas of photosynthetic purple bacteria by Stark spectroscopy. 1. LH1 antenna complex and the B820 subunit from Rhodospirillum rubrum. J Phys Chem. 1997; The response of the optical absorption spectrum to an externally applied electrical field (Stark effect) is measured for LH1, the B820 dimeric subunit of LH1, and the reconstituted LH1 of purple photosynthetic bacteria. The Stark effect for LH1 is strongly reminiscent of that measured for the special pair of the purple bacterial reaction center, it is dominated by a large change in polarizability between ground and excited states - most probably due to the mixing of charge transfer states into the lower excited states of a dimeric subunit of LH1. of special interest.
17. -1. The general trends observable in the CD spectrum of LH2 are tentatively explained. The calculations predict strong CD features at ~790 nm which await experimental verification. of outstanding interest.
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22. Wu HM, Savikhin S, Reddy NRS, Jankowiak R, Cogdell RJ, Struve WS, Small GJ. Ferntosecond and hole-burning studies of B800's excitation energy relaxation dynamics in the LH2 antenna complex of Rhodopseudomonas acidophila (strain 10050). J Phys Chem. 100:1996;12022-12033 The transfer of excitation energy in the LH2 complex of Rps. acidophila is studied using holeburning and femtosecond laser spectroscopy. B800→B850 energy transfer is observed to occur with monophasic kinetics with a time constant ranging from 1.6 ps (19K) to 1.1 ps (130K), while holeburning at 4.2K yields 1.8 ps. Holeburning with applied pressure shows no effect on the energy transfer rate. Together with the weak temperature dependence, this suggests that the B800 emission overlaps with a weak vibronic band of B850. Time-domain and holeburning spectroscopy show that there is an additional relaxation channel for B800 excitations when the excitation is to the blue of the B800 band. Two possible processes, intra-B800 transfer and coupling with the quasi degenerate upper exciton manifold of B850, are discussed. of outstanding interest.
23. Wu HM, Reddy NRS, Cogdell RJ, Muenke C, Michel H, Small GJ. A comparison of the LH2 antenna complex of three purple bacteria by hole-burning and absorption spectroscopies. Mol Cryst Liq Cryst. 291:1996;163-173 The LH2 complexes of Rps. acidophila, Rb. sphaeroides and Rs. molischianum are investigated using holeburning. B800→B850 energy transfer at 4.2K takes 1.9 ps, very similar to the time constant observed for the same process in the other species. The absorption spectra of Rs. molischianum and Rps. acidophila undergo a dramatic redshift and thermal narrowing upon cooling from room temperature to 4.2K; for LH2 of Rb. sphaeroides, these effects are much smaller. This is interpreted as a smaller excitonic coupling in the latter species. of special interest.
24. Van Mourik F, Visschers RW, van Grondelle R. Energy transfer and aggregate size effects in the inhomogeneously broadened core light-harvesting complex of Rhodobacter sphaeroides. Chem Phys Lett. 193:1992;1-7.
25. Monshouwer RM, Visschers RW, van Mourik F, Freiberg A, van Grondelle R. Low-temperature absorption and site-selected fluorescence of the light-harvesting antenna of Rhodopseudomonas viridis. Evidence for heterogeneity. Biochim Biophys Acta. 1229:1995;373-380.
26. Alden RG, Johnson E, Nagarajan V, Parson WW, Law CJ, Cogdell RJ. Calculations of spectroscopic properties of the LH2 bacteriochlorophyll-protein antenna complex from Rhodopseudomonas acidophila. J Phys Chem B. 101:1997;4667-4680 This paper describes the calculation of absorption and CD spectra of a photosynthetic bacterial antenna complex based on the crystal structure of the LH2 complex from Rps. acidophila. Molecular orbitals for the three different BChl structures in the complex are obtained by semiempirical quantum mechanical calculations. Exciton and charge transfer interactions are introduced at the level of configuration interactions. Absorption bandshapes are treated with vibronic parameters as obtained from holeburning experiments, whereas inhomogeneous broadening is included by a Monte Carlo method. Calculations reproduce the measured absorption and CD spectra. The results support the idea that excitations are rather delocalized in LH2. of outstanding interest.
27. Koolhaas MHC, van der Zwan G, Frese RN, van Grondelle R. The red shift of the zero-crossing in the CD spectra of the LH2 antenna complex of Rhodopseudomonas acidophila: a structure based study. J Phys Chem. 1997; The published crystal structure of LH2 of Rps. acidophila is used to calculate absorption and CD spectra of the complex. It is shown that the relative position of the CD zero crossing with respect to the absorption maximum is an important parameter that is rather sensitive to structural changes. It is demonstrated that the experimentally observed CD spectrum can only be explained if the whole ring is considered and if the α-polypeptide and β-polypeptide BChls are allowed to have different excitation energies. of outstanding interest.
28. Leupold D, Stiel H, Teuchner K, Nowak F, Sandner W, Ücker B, Scheer H. Size enhancement of transition dipoles to one and two-exciton bands in a photosynthetic antenna. Phys Rev Lett. 77:1996;4675-4678 From a measurement of the nonlinear absorption, the differential absorption density spectrum, and the fluorescence for LH2 from Rb. sphaeroides, the dipole moments associated with the ground state→one-exciton and one-exciton→two-exciton transition are estimated to be 25.5 D and 21.5 D, respectively. These values are seen as an indication that in LH2 the exciton is delocalized over 16±4 BChl molecules, corresponding to the full physical length of the circular aggregate. of outstanding interest.
29. Novoderezhkin VI, Razjivin AP. Exciton dynamics in circular aggregates: application to antenna of photosynthetic purple bacteria. Biophys J. 68:1995;1089-1100.
30. van Grondelle R, Dekker JP, Gillbro T, Sundström V. Energy transfer and trapping in photosynthesis. Biochim Biophys Acta. 1187:1994;1-65.
31. van Grondelle R, aiKramer HJM, Rijgersberg CP. Energy transfer in the B800-850-carotenoid light-harvesting complex of various mutants of Rhodopseudomonas sphaeroides and of Rhodopseudomonas capsulatus. Biochim Biophys Acta. 682:1982;208-215.
32. Trautman JK, Shreve AP, Violette CA, Frank HA, Owens TG, Albrecht AC. Femtosecond dynamics of energy transfer in B800-850 light-harvesting complexes of Rhodobacter sphaeroides. Proc Natl Acad Sci USA. 87:1990;215-219.
33. Laan H, Schmidt Th, Visschers RW, Visscher KJ, van Grondelle R, Völker S. Energy transfer in the B800-850 antenna complex of the purple bacterium Rhodobacter sphaeroides: a study by spectral hole-burning. Chem Phys Lett. 170:1990;231-238.
34. Monshouwer R, Ortiz de Zarate I, van Mourik F, van Grondelle R. Low-intensity pump - probe spectroscopy on the B800 to B850 transfer in the light harvesting 2 complex of Rhodobacter sphaeroides. Chem Phys Lett. 246:1995;341-346.
35. Hess S, Åkesson E, Cogdell RJ, Pullerits T, Sundström V. Energy transfer in spectrally inhomogeneous light-harvesting pigment-protein complexes of purple bacteria. Biophys J. 69:1995;2211-2225.
36. Joo T, Jia Y, Yu J-Y, Jonas DM, Fleming GR. Dynamics in isolated bacterial light harvesting antenna (LH2) of Rhodobacter sphaeroides at room temperature. J Phys Chem. 100:1996;2399-2409 Transient absorption, transient grating and photon echoes are measured on the B800 band of LH2 of Rb. sphaeroides using 30 fs pulses. B800→B850 energy transfer occurs in 800fs. The three-pulse photon echo peak shift experiment identifies important contributions to the B800 lineshape and thereby the dynamics of the system involved: low-frequency intramolecular vibrations; ultrafast bath (solvent plus protein) responses; and static inhomogeneity on a timescale longer than the energy transfer time. The transient absorption is observed to decay nonexponentially. The authors argue that the fast phase is vibrational relaxation within the B800 band. of outstanding interest.
37. Ma Y-Z, Cogdell RJ, Gillbro T. Energy transfer and exciton annihilation in the B800-850 antenna complex of the photosynthetic bacterium Rhodopseudomonas acidophila (strain 10050). A transient femtosecond absorption study. J Phys Chem B. 101:1997;1087-1095 This paper describes femtosecond pump - probe experiments on LH2 of Rps. acidophila. At room temperature, B800→B850 energy transfer is ~0.8 ps; at 77K, ~1.3 ps. Anisotropy kinetics measured within B800 band indicate that relaxation within the B800 band is wavelength dependent. A fast depolarization time of 210 fs observed at 77K is thought to originate from exciton relaxation. From a dramatic energy dependence of the B800 kinetics, it is speculated that several high-lying excitonic states of B850 exist that show good spectral overlap with the B800 band and thus could serve as excellent acceptors for the energy transfer from B800 to B850. of special interest.
38. Monshouwer R, van Grondelle R. Excitations and excitons in bacterial light-harvesting complexes. Biochim Biophys Acta. 1275:1996;70-75 The localization versus delocalization of excitations in bacterial light-harvesting complexes is discussed. It is argued that a 'ring-of-dimers' model is adequate to explain most of the spectroscopic and time-resolved data. Furthermore, two-colour pump - probe experiments in the B800 band of Rb. sphaeroides reveal 'blue-to-red' energy transfer on a timescale of 400fs within the B800 band. of outstanding interest.
39. Bakker JGC, van Grondelle R, den Hollander WTF. Trapping, loss and annihilation of excitations in a photosynthetic system. II. Experiments with the purple bacteria Rhodospirillum rubrum and Rhodopseudomonas capsulatus. Biochim Biophys Acta. 725:1983;508-518.
40. Sundström V, van Grondelle R, Bergström H, Åkesson E, Gillbro T. Excitation-energy transport in the bacteriochlorophyll antenna systems of Rhodospirillum rubrum and Rhodobacter sphaeroides studied by low-intensity picosecond absorption spectroscopy. Biochim Biophys Acta. 851:1986;431-446.
41. van Grondelle R, Bergström H, Sundström V, Gillbro T. Energy transfer within the bacteriochlorophyll antenna of purple bacteria at 77K studied by picosecond absorption recovery. Biochim Biophys Acta. 894:1987;313-326.
42. Bradforth SE, Jiminez R, van Mourik F, van Grondelle R, Fleming GR. Excitation transfer in the core light-harvesting complex (LH-1) of Rhodobacter sphaeroides: an ultrafast fluorescence depolarization and annihilation study. J Phys Chem. 99:1995;16179-16191.
43. -1 yields an average delocalization length of ~5 molecules in the middle of the band. of outstanding interest.
44. Visser HM, Somsen OJG, van Mourik F, Lin S, van Stokkum IHM, van Grondelle R. Direct observation of sub-picosecond equilibration of excitation energy in the light-harvesting antenna of Rhodospirillum rubrum. Biophys J. 69:1995;1083-1099.
45. -1. of outstanding interest.
46. Chachisvilis M, Pullerits T, Jones MR, Hunter CN, Sundström V. Vibrational dynamics in the light harvesting complexes of the photosynthetic bacterium Rhodobacter sphaeroides. Chem Phys Lett. 224:1994;345-351.
47. Jean JM, Fleming GR. Competition between energy and phase relaxation in electronic curve crossing processes. J Chem Phys. 103:1995;2092-2101.
48. Pullerits T, Chachisvilis M, Sundström V. Exciton delocalization length in the B850 antenna of Rhodobacter sphaeroides. J Phys Chem. 100:1996;10787-10792 Excitation transfer dynamics in LH2 of Rb. sphaeroides is investigated using transient absorption spectroscopy. In LH2, the anisotropy decays in 130 fs, whereas the isotropic decay occurs in 70 fs. For a ninefold symmetric ring, with the orientation of the transition dipoles as in LH2, a factor of 3 between the two time constants is expected. As this is not observed, the authors conclude that the energy migration is (partially) coherent. From an analysis of the transient absorption difference spectrum, they conclude that the excitation is delocalized over 4±2 monomers. of special interest.
49. Chachisvilis M, Kühn O, Pullerits T, Sundström V. Excitons in photosynthetic purple bacteria. Wavelike motion or incoherent hopping? J Phys Chem. 1997; From a comparison of isotropic and anisotropic pump probe signals measured for LH1 and LH2 of Rb. sphaeroides, the anisotropy decay is observed to be always about twofold slower. Modeling using a hopping model predicts a much more dramatic difference between isotropic and anisotropy decays. As a consequence, the authors believe that the excitation transfer is partly coherent. From a fit of the pump - probe spectrum, they conclude that the delocalization length is ~4 BChls and is not strongly dependent on temperature. of special interest.
50. Monshouwer R, Abrahamsson M, van Mourik F, van Grondelle R. Superradiance and exciton delocalisation in bacterial photosynthetic light-harvesting systems. J Phys Chem. 1997; The radiative rate of LH1 and LH2 of Rb. sphaeroides are measured as a function of temperature. For LH2, the radiative rate is about threefold larger compared with that of monomeric BChl a and is independent of temperature. LH1 is very similar to LH2 at room temperature, but the radiative rate increases about 2.4-fold upon lowering the temperature to 4K. The results are interpreted in terms of a model that includes both the coupling between all the pigments and the inhomogeneous broadening and suggests that the ratio between coupling and inhomogeneous broadening is ~2. The results suggest that in LH2 the excitation is rather localized at all temperatures. The degree of delocalization in LH1 may be somewhat larger, certainly at low temperature. of outstanding interest.
51. Nagarajan V, Alden RG, Williams JC, Parson WW. Ultrafast exciton relaxation in the B850 antenna complex of Rhodobacter sphaeroides. Proc Natl Acad Sci USA. 93:1996;13774-13779 The femtosecond response of LH2 of Rb. sphaeroides at room temperature is measured. The authors observe a 35 fs relaxation phase in absorption and emission spectra of the excited state, and a 20 fs anisotropy decay. They ascribe these dynamics to interlevel relaxation and dephasing, respectively, of extensively delocalized exciton states of the circular bacteriochlorophyll aggregate. of special interest.
52. Leegwater JA. Coherent versus incoherent energy transfer and trapping in photosynthetic antenna complexes. J Phys Chem. 100:1996;14403-14409 A model is described which has an arbitrary ratio of homogeneous broadening versus interaction energy. This allows the study of the crossover from hopping dynamics to exciton dynamics. For the survival time, the hopping approach is shown to yield a surprisingly accurate estimate, even when the dynamics is excitonic. For LH1, it is estimated that the excitation is, on the average, delocalized over two dimers. The excitation is localized by phonons. of special interest.
53. Meier T, Chernyak V, Mukamel S. Multiple exciton coherence sizes in photosynthetic antenna complexes viewed by pump - probe spectroscopy. J Phys Chem. 1997; From an analysis of the pump - probe signal from the LH2 light-harvesting antenna of purple bacteria, the localization size is determined to be 15 at 4.2K. The analysis of the difference in frequency between positive and negative peaks in the pump - probe spectrum yields an estimate for the exciton mean free path (or the exciton dephasing lengthscale) of ~ 11. of outstanding interest.
54. Jimenez R, van Mourik F, Fleming GR. Three pulse echo peak shift measurements on LH1 and LH2 complexes of Rhodobacter sphaeroides: a nonlinear spectroscopic probe of energy transfer. J Phys Chem. 1997; Three pulse photon echo peak shift measurements are performed on the B875 and B850 bands of detergent-isolated LH1 and LH2 complexes at room temperature. The peak shifts are much larger and decay much faster than those typically observed for dye molecules in solution. The peak shift decay is simulated on the basis of the optical frequency correlation function, M(t), which includes contributions from rapid fluctuations of the protein, vibrational motion and energy transfer. The 90 fs and 130 fs exponential components in M(t) observed for LH1 and LH2, respectively, are ascribed to energy transfer. A simulation based on a model that assumes hopping in a ring of dimers, with each dimer randomly selected from an inhomogeneous distribution, explains the results. of outstanding interest.
55. 2 subunit of LH1, and on its reaggregated form, B873. In B820, the timescale of the Stokes' shift is sub 50 fs, as reflected by a shift of the nuclear wavepacket and a fast component in the anisotropy decay. In similar experiments on reassociated B873, the anisotropy is observed to decay from 0.24 to 0.07 with two time constants: 70 fs and 400 fs. The authors suggest that, following fast scattering, the excitation transfer proceeds between states of dimeric subunits. of special interest.
56. Yu J-Y, Nagasawa Y, van Grondelle R, Fleming GR. Three pulse echo peak shift measurements on B820 subunit of LH1 of Rhodospirillum rubrum. Chem Phys Lett. 1997; This paper describes the measurement cf the three pulse photon echo peak shift for the LH1 subunit, B820, a protein bound BChl dimer. The major difference between B820 and LH1 is the absence of the 100 fs exponential phase that was ascribed to energy transfer in LH1 and is now present as a nondecaying component. The experiment strongly supports the idea that, in LH1, the excitation is also localized on a BChl dimer. of outstanding interest.
57. Shreve AP, Trautman JK, Frank HA, Owens TG, Albrecht AC. Femtosecond energy-transfer processes in the B800-850 light-harvesting complex of Rhodobacter sphaeroides 2.4.1. Biochim Biophys Acta. 1058:1991;280-288.
58. + state. of special interest.
59. 1 state to B800 in ~ 0.5 ps. of outstanding interest.
60. Freiberg A, Godik VI, Pullerits T, Timpmann K. Directed picosecond excitation transport in purple photosynthetic bacteria. Chem Phys. 128:1988;227-235.
61. Zhang FG, van Grondelle R, Sundström V. Pathways of energy flow through the light-harvesting antenna of the photosynthetic purple bacterium Rhodobacter sphaeroides. Biophys J. 61:1992;911-920.
62. Hess S, Chachisvilis M, Timpmann K, Jones MR, Fowler GJC, Hunter CN, Sundström V. Temporally and spectrally resolved subpicosecond energy transfer within LH2 and from LH2 to LH1 in photosynthetic purple bacteria. Proc Natl Acad Sci USA. 92:1995;12333-12337.
63. Nagarajan V, Parson WW. Excitation energy transfer between the B850 and B875 antenna complexes of Rhodobacter sphaeroides. Biochemistry. 36:1997;2300-2306 In membrane of Rb. sphaeroides, energy transfer from B850 (LH2) to B875 (LH1) proceeds with two time constants, 4.6 ps and 26.3 ps, but a significant fraction of the excitations remain in B850 for considerably longer times. The fast step is ascribed to hopping from LH2 to LH1, the slow step to migration within the LH2 pool. Back transfer from LH1 to LH2 could not be detected. of special interest.
64. Beekman LMP, van Mourik F, Jones MR, Visser HM, Hunter CN, van Grondelle R. Trapping kinetics in mutants of the photosynthetic purple bacterium Rhodobacter sphaeroides: influence of the charge separation rate and consequences for the rate-limiting step in the light-harvesting process. Biochemistry. 33:1994;3143-3147.
65. Pullerits T, Sundström V. Photosynthetic light-harvesting pigment - proteins: toward understanding how and why. Acc Chem Res. 29:1996;381-389 The energy transfer and trapping dynamics in photosynthetic purple bacteria is reviewed: a model is proposed for the LH2-LH1 association based on the measured LH2→LH1 energy transfer time of 3.3 ps at room temperature. Modeling this step gives a 3 nm distance of closest approach between the LH2 and LH1 rings. of outstanding interest.
66. Eads DD, Castner EW Jr, Alberte RS, Mets L, Fleming GR. Direct observation of energy transfer in a photosynthetic membrane: chlorophyll b to chlorophyll a transfer in LHCII. J Phys Chem. 93:1990;8271-8275.
67. Kwa SLS, van Amerongen H, Lin S, Dekker JP, van Grondelle R, Struve WS.
68. Bittner T, Irrgang KD, Renger G, Wasielewski MR. Ultrafast excitation energy transfer and exciton - exciton annihilation processes in isolated light harvesting complexes of Photosystem II (LHCII) from spinach. J Phys Chem. 98:1994;11821-11826.
69. Du M, Xie X, Mets L, Fleming GR. Direct observation of ultrafast energy-transfer processes in light-harvesting complex II. J Phys Chem. 98:1994;4736-4741.
70. Pålsson LO, Spangfort MD, Gulbinas V, Gillbro T. Ultrafast chlorophyll β-chlorophyll a excitation energy transfer in the isolated light harvesting complex, LHCII, of green plants. Implications for the organization of chlorophylls. FEBS Lett. 339:1994;134-138.
71. Visser HM, Kleima FJ, van Stokkum IHM, van Grondelle R, van Amerongen H. Probing the many energy-transfer processes in the photosynthetic light-harvesting complex II at 77K using energy-selective sub-picosecond transient absorption spectroscopy. Chem Phys. 210:1996;297-312 The ultrafast energy transfer dynamics in LHCII is measured using transient absorption spectroscopy. Three phases in the Chl b→Chl a energy transfer are resolved: 200 fs, 600 fs and ~ 5 ps, with relative amplitude ratios of 40%, 40% and 20%, respectively. In the trimer, all the energy transfer occurs to the major red absorbing species at 676 nm. Measurements of singlet - singlet and singlet - triplet annihilation suggest that intermonomer energy transfer occurs on a timescale of 10-20 ps. of outstanding interest.
72. Connelly JP, Müller MG, Hucke M, Gatzen G, Mullineaux CW, Ruban AV, Horton P, Holzwarth AR. Ultrafast spectroscopy of trimeric light-harvesting complex II from higher plants. J Phys Chem B. 101:1997;1902-1909 These authors perform a highly sensitive transient absorption experiment to resolve all three phase in the Chl b→Chl a energy transfer and find time constants of 175 fs, 600 fs and ~ 5 ps. Furthermore, they conclude from their data that, probably, the 175ffs component partly reflected energy transfer between 'blue' and 'red' Chl bs. of special interest.
73. Trinkunas G, Connelly JP, Müller MG, Valkunas L, Holzwarth AR. A model for the excitation dynamics in the light-harvesting complex II from higher plants. J Phys Chem B. 1997;. in press.
74. Giuffra E, Cugini D, Croce R, Bassi R. Reconstitution and pigment-binding properties of recombinant CP29. Eur J Biochem. 238:1996;112-120 This paper describes the reconstitution of the minor chlorophyll a/b-binding protein CP29, overexpressed in Escherichia coli. The recombinant pigment-protein shows biochemical and spectroscopic properties identical to the native CP29 complex, with a Chl a: Chl b ratio of three. Also other stoichiometries yielded stable complexes. of special interest.
75. Peterman EJG, Monshouwer R, van Stokkum IHM, van Grondelle R, van Amerongen H. Ultrafast singlet excitation transfer from carotenoids to chlorophylls via different pathways in light-harvesting complex II of higher plants. Chem Phys Lett. 264:1997;279-284 Energy transfer from the xanthophylls to the chlorophylls is studied in trimeric LHCII at 77K. No evidence for direct energy transfer from the xanthophylls to Chl b is found, whereas efficient xanthophyll to Chl a energy transfer occurs in 220 fs. With preferential violaxanthin excitation (514 nm) relative to lutein excitation (500 nm), energy transfer to Chl as absorbing at ~ 670 nm is more pronounced, compared with transfer to Chl as absorbing at ~ 676 nm. Following 514 nm excitation, the transfer from 670 to 676 nm occurs in 2.1 ps. of outstanding interest.
76. Connelly JP, Müller MG, Bassi R, Croce R, Holzwarth AR. Femtosecond transient absorption study of carotenoid to chlorophyll energy transfer in the light-harvesting complex II of Photosystem II. Biochemistry. 36:1997;281-287 Energy transfer from the xanthophylls to the chlorophylls is studied in LHCII trimers from Arabidopsis thaliana at room temperature. At 475 and 490 nm excitation, energy transfer is mainly from xanthophyll to Chl b. of outstanding interest.
77. Holzwarth AR, Schatz G, Brock H, Bittersmann E. Energy transfer and charge separation kinetics in Photosystem I. Part 1: Picosecond transient absorption and fluorescence study of cyanobacterial Photosystem I particles. Biophys J. 64:1993;1813-1822.
78. Hastings G, Hoshina S, Webber AN, Blankenship RE. Universality of energy and electron transfer processes in Photosystem I. Biochemistry. 34:1995;15512-15522.
79. Du M, Xie X, Jia Y, Mets L, Fleming GR. Direct observation of ultrafast energy transfer in PS1 core antenna. Chem Phys Lett. 201:1993;535-542.
80. Goberts B, van Amerongen H, Monshouwer R, Kruip J, Rögner M, van Grondelle R, Dekker JP. Polarized site-selection spectroscopy of isolated Photosystem 1 particles. Biochim Biophys Acta. 1188:1994;75-85.
81. Pålsson LO, Dekker JP, Schlodder E, Monshouwer R, van Grondelle R. Polarized site-selective fluorescence spectroscopy of the long-wavelength emitting chlorophylls in isolated Photosystem I particles of Synechococcus elongatus. Photosynth Res. 48:1996;239-246 Isolated trimeric PS1 complexes of Synechococcus elongatus have been studied in absorption and polarized fluorescence. Two types of long wavelength pigments are distinguished: C708 and C719. Their contribution to the absorption spectrum corresponds to ~ 4-5 C708 and 5-6 C719 per P700. From low-temperature energy-selective polarized fluorescence experiments, it is concluded that at ultra low temperatures C708 still is able to transfer excitation energy to C719 and furthermore that energy transfer among C719s occurs. of special interest.
82. Valkunas L, Liuolia V, Dekker JP, van Grondelle R. Description of energy migration and trapping in Photosystem I by a model with two distance scaling parameters. Photosynth Res. 43:1995;149-154.
83. Kumazaki S, Ikegami I, Yoshihara K. Excitation and electron transfer from selectively excited primary donor chlorophyll (P700) in a Photosystem I reaction center. J Phys Chem A. 101:1997;597-604 Primary processes in a Photosystem 1 reaction center are studied using subpicosecond fluorescence upconversion. In these enriched reaction centers there are ~ 14 Chl as per P700. The 1 ps fluorescence anisotropy decay following selective P700 excitation is ascribed to equilibration between P700 and the surrounding antenna Chls. In the isotropic fluorescence decay, at least two components can be distinguished: 2.2 ps (35%) and 15 ps (55%). The fast and slow phases are interpreted in terms of charge separation before and after full equilibration of the excited state, respectively. From kinetic modeling, the intrinsic time constant for charge separation from P700 is concluded to be < 4 ps. of special interest.
84. Trinkunas G, Holzwarth AR. Kinetic modeling of exciton migration in photosynthetic systems. 3. Application of genetic algorithms to simulations of excitation dynamics in three-dimensional Photosystem I core antenna/reaction center complexes. Biophys J. 71:1996;351-364 This paper describes calculations of energy transfer and trapping in Photosystem 1 using a genetic algorithm. Various 3D models for the pigment arrangement and the corresponding energy transfer dynamics are tested for Photosystem 1. It is concluded that: the red pigments never are close to P700; the red pigments are also never far away from P700 and tend to cluster; the charge separation time is shorter than 1.2 ps; and the total energy transfer time within the main antenna pool is < 1 ps. of special interest.
85. -1. of outstanding interest.
86. 700. Biochemistry. 36:1997;2898-2907 Time-resolved absorption and fluorescence spectroscopy are used to investigate the energy and electron transfer processes in the detergent-isolated Photosystem I core particles from the site directed mutant of Chlamydamonas reinhardtii with the His656 of PsaB replaced by asparagine. There is no indication that the mutation affects the spectral distribution in the antenna; however, the excited state lifetime increases from ~ 30 ps to ~ 65 ps. It is proposed that the excited state decay is limited by charge separation. of outstanding interest.