Energy transport and trapping in a synthetic chlorophyllide substituted hemoglobin: orientation of the chlorophyll S1 transition dipole

Moog, Richard S.; Kuki, Atsuo; Fayer, M. D.; Boxer, Steven G.

doi:10.1021/bi00302a034

Cited by 84 publications

(65 citation statements)

References 42 publications

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“…The steady-state fluorescence spectrum of the isolated B875(-896) complex at 77 K [19] gives f(A), and kF = 5.6 x 107 s -I is obtained from the literature [20]. Since the solvent is mostly glycerol we have used n = 1.5 as the refractive in-dex [21]. The rate of energy transfer is kET = (37 × 10 -12 S) -1 --(650 x 10 -12 s) -1 where 650 x 10 -12 is the excited-state lifetime of BChl896 in the absence of trapping as measured in the isolated B875 complex at 77 K [22].…”

Section: Resultsmentioning

confidence: 99%

Characterization of excitation energy trapping in photosynthetic purple bacteria at 77 K

1989

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We have studied the energy-transfer dynamics in chromatophores of Rhodobacter sphaeroides and Rhodospirillum rubrum at 77 K, with functional charge separation. Using low-intensity picosecond absorption recovery, we determined that transfer between the energetically low-lying antenna component BCh1896 and the special pair of the reaction center occurs with a time constant of 37 ps in Rb. sphaeroides and 75 ps in R. rubrum. Assuming that a F6rster energy-transfer mechanism applies to the process, this allows us to estimate the distance between BCh1896 in the B875 complex and the special pair P870 in the reaction center to range between 26 and 39/~, in Rb. sphaeroides. Such a distance indicates that the BChI896 pigment and the special pair of the reaction center are at the minimum separation allowed by the size and shape of the reaction center and the light-harvesting polypeptides.

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Section: Resultsmentioning

confidence: 99%

Characterization of excitation energy trapping in photosynthetic purple bacteria at 77 K

1989

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“…9,15 The distances and orientations of the individual chromophores in the DsRed complex are now known from X-ray crystallographic data. 18 The chromophores, arbitrarily numbered 1 through 4, are assumed to couple by standard dipole-dipole Förster energy transfer.…”

Section: Discussionmentioning

confidence: 99%

Photophysics of DsRed, a Red Fluorescent Protein, from the Ensemble to the Single-Molecule Level

et al. 2001

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DsRed, a tetrameric fluorescent protein cloned from the Discosoma genus of coral, has shown promise as a longer-wavelength substitute for green fluorescent protein (GFP) mutants for in vivo protein labeling. Bulk and single-molecule studies of the recombinant protein revealed that the DsRed chromophore shows high stability against photobleaching as compared to GFP mutants. Stark modulation spectra confirm that the electronic structure of the DsRed chromophore is similar to that of GFP. However, the tetrameric nature of DsRed leads to intersubunit energy transfer, as evidenced by the molecule's unusually low fluorescence anisotropy when immobilized (0.23 ( 0.02). This value is approximately consistent with an estimate of the energy transfer rates based on preliminary crystallographic information. The fluorescence emission bleaches at a rate linear in the applied excitation intensity, implying that the cessation of emission during pumping at 532 nm is light-driven and, consistent with the tetrameric structure, several photobleaching "steps" were observed for individual complexes. Because more photons are emitted before bleaching, this study suggests that DsRed may be superior to some GFP-based labeling technologies as long as tetramerization is not an issue in physiological studies. IntroductionSingle-molecule spectroscopy (SMS) continues to play a unique role in the elucidation of the dynamics of an increasingly broad range of complex systems. 14,25 By removing the averaging inherent in ensemble measurements, SMS yields a measure of the distribution of molecular properties which is of importance in systems that display static or time-dependent heterogeneity. Concurrently, developments in fluorescence microscopy have made the observation of single molecules of biological interest possible under a wide range of experimental conditions. 26 This versatility can be exploited to examine the molecular complexity of many biological systems.One critical challenge to the application of SMS techniques to biomolecules, especially in vivo, is the introduction of a fluorophore that acts as a reporter of activity, local environment, or spatial location. While certain important proteins display useful amounts of visible fluorescence arising from native cofactors, 12 most require the attachment of an extrinsic fluorophore to serve as the probe. The genetic fusion of naturally fluorescent proteins to a protein of interest ensures a consistent 1:1 stoichiometry in the cell, without the need for external chemical reactions. While the green fluorescent protein (GFP) and its mutants have proved suitable for many applications, 22,27 the relatively high quantum yield of photobleaching (∼10× that for a rhodamine dye 16 ) leaves room for improvement in applications that require a large number of emitted photons, such as in single-molecule studies. Also, no mutant of GFP has been demonstrated to be a strong emitter at long (>550 nm) wavelengths, where the interference from endogenous fluorophores is substantially less severe.Considering th...

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“…(The authors would like to thank Prof. S.G. Boxer of Stanford University for calling attention to his analysis of the role and appropriate values to use for the refractive index in the Forster equations. Readers are referred to the informative Appendix of Moog et al [18]). Because of the dependence of the FSrster rate constants on the inverse fourth power of the refractive index, the result of this change is 159 to increase all values of the rate constants by a factor of (1.34/1.54) -4= 1.74 relative to those calculated previously.…”

Section: Methodsmentioning

confidence: 99%

Excitation transfer in C-phycocyanin. Förster transfer rate and exciton calculations based on new crystal structure data for C-phycocyanins from Agmenellum quadruplicatum and Mastigocladus laminosus

Sauer

Scheer²

1988

Biochimica et Biophysica Acta (BBA) - Bioenergetics

125

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F~rs:er mechanlsm; ExcitonCalculations of excitation tra~er rates among the chr,mmphores of C-phycocyanin using the F6rster inductive resonance transfer mechanism have been carried out using the new coordinates for the pesition and ovlentation of the dn-omophores (Schirmer, T., Bode, W. and Hubor, R. (1967) J. Mol. Biol. 196, 677-69b'). Several of the rate constants are significantly altered from the results of oor calculations using the previously published emmlinates (Sauer, K., Scheer, H. and Sauer, P. (1987) Photochem. Photoblol. 46, 427-4d0). Ill partiolllar, for the (a/~)3-trimers of Mastigoclmtm/am/Iosm or for the (al0)3-trimels or the (~8)¢hexamers of Agmn~,llmn ~adr~icatm~ the new calculations predict excited state relaxation components with exponential time constants shorter than 1 ps. In fact, some of the interactions are so strong that exeiton coupling is probably the relevant mechanism of interaction. The largest exciton energy is calculated to be about 56 an -I, for the imeracfion betweea the adjacent a84 and ~84 ehromophores of neighboring monomer units within the (a~)3.triaters or (aB)¢hexamers. An energy transfer model invoking a combination of pairwlse exciton formation followed by slower Fc~rster transfer steps is described. that transfer excitation to it with an efficiency of 95~ or greater and in a time that is much shorter than the lifetime (a few nanoseconds) of the excited state in the absence of trapping [1]. A model, known as the Pebble Mosaic Model, was developed to describe this excitation transfer process [2]. It is based on the knowledge that most photosynthetic pigments (chromophores) occur in welldefined associations with proteins and that these pigment proteins occur in organized arrays with respect to the embedded reaction centers in photosynthetically active membranes [3]. In the Pebble Mosaic Model excitation is considered to appear in collective excited states (excitons) that encompass all of the chromophores that interact with 0005-2728/88/$03.50

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Energy transport and trapping in a synthetic chlorophyllide substituted hemoglobin: orientation of the chlorophyll S1 transition dipole

Cited by 84 publications

References 42 publications

Characterization of excitation energy trapping in photosynthetic purple bacteria at 77 K

Characterization of excitation energy trapping in photosynthetic purple bacteria at 77 K

Photophysics of DsRed, a Red Fluorescent Protein, from the Ensemble to the Single-Molecule Level

Excitation transfer in C-phycocyanin. Förster transfer rate and exciton calculations based on new crystal structure data for C-phycocyanins from Agmenellum quadruplicatum and Mastigocladus laminosus

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