Picosecond time-resolved fluorescence of phycobiliproteins: Subunits of phycocyanin from Mastigocladus laminosus

Fischer, Richard W.; Gottstein, J.; Scheer, Hugo; Geiselhart, P.; Schneider, Siegfried

doi:10.1016/1011-1344(90)80003-g

Cited by 11 publications

(7 citation statements)

References 27 publications

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“…The experimental measurement of the observed fluorescence lifetimes of the chromophores suffers from the fact that apc, containing a single chromophore, shows a multiexponential fluorescence decay from its excited state. [23][24][25] The decay is dominated by a single component that accounts for about 90% of the observed intensity; nevertheless, assigning the lifetimes of the chromophores to single values is an approximation. On the other hand, direct calculation of the intrinsic fluorescence lifetimes from eq 7 relies on the assumption that the ground and excited electronic states of the chromophores have the same vibrational structure.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Calculated and Experimentally Resolved Rate Constants for Excitation Energy Transfer in C-Phycocyanin. 1. Monomers

et al. 1995

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Rate constants for excitation energy transfer in the light-harvesting protein, C-phycocyanin (PC), in the monomeric aggregation state, isolated from the cyanobacterium Synechococcus sp. PCC 7002, are calculated using Forster theory and compared with the results of time-resolved fluorescence measurements. In addition to the relative distances and orientations between chromophores, obtained from the crystal structure of PC, the Forster calculations require spectroscopic resolution of several properties of the chromophore types ( $1 5 5 , aS4, p 8 4 ) found in PC monomers, including absorption and fluorescence spectra, molar absorptivities, fluorescence quantum yields, and fluorescence lifetimes. The resolution of the first two properties, the chromophore absorption and fluorescence spectra, was described in a previous paper [Debreczeny et al. J. Phys. Chem. 1993, 97, 9852-98621. The assignments of the energy-transfer rate constants in PC monomers are confirmed here by time-resolved fluorescence anisotropy measurements of the PC monomers isolated from both the wild-type and a mutant strain (cpcBKZ55S) whose PC is missing the P I 5 5 chromophore. These fluorescence anisotropy measurements also allow one to extract the angles between the transition dipoles of the chromophores within the p l 5 5 -p 8 4 (34') and a 8 4 -p S 4 (27') chromophore pairs. The values of the inverse of the sum of the forward and back calculated Forster rate constants for energy transfer within the p l 5 5 -p 8 4 , ~8~-/ & 4 , and p 1 5 5 -a 8 4 chromophore pairs are 49, 158, and 890 ps, respectively, and are in excellent agreement with the experimentally measured values. It is concluded that the Forster model of resonant energy transfer in the weak coupling limit successfully describes the dominant energy-transfer processes in this protein in the monomeric state.

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Section: Discussionmentioning

confidence: 99%

Comparison of Calculated and Experimentally Resolved Rate Constants for Excitation Energy Transfer in C-Phycocyanin. 1. Monomers

et al. 1995

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“…The phycocyanobilin S 1 state exhibits a 1.2-ns lifetime in isolated R subunits of C-phycocyanin. 24 Note that the THB spectra exhibit regions of net ESA in the 14 700-and 19 000-cm -1 regions.…”

Section: Methodsmentioning

confidence: 98%

Protein-Matrix Solvation Dynamics in the α Subunit of C-Phycocyanin

1996

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We have used femtosecond transient hole-burning (THB) spectroscopy to study single-chromophore dynamics at room temperature in the R subunit of C-phycocyanin, a cyanobacterial light-harvesting protein. The R subunit contains a single phycocyanobilin (open-chain tetrapyrrole) chromophore. A reasonable description of the THB spectra requires the presence of a broad excited-state absorption (ESA) line shape underlying the entire photobleaching/stimulated emission (PB/SE) region. The time evolution of the THB spectrum involves line broadening on the 100-200-fs time scale and a <100-fs time scale dynamic Stokes shift of the SE component. We suggest that the dynamic Stokes shift can be attributed to transient solvation by the protein matrix. The solvent correlation function, C(t), exhibits a sub-100-fs component that describes 90% of the total C(t) response, with the remaining 10% of response occurring on a much longer time scale than the longest delay employed in these experiments (10 ps). We assign the ultrafast decay component of C(t) to an inertial, librational response of the protein matrix. The slower component probably involves a diffusive, collective protein-matrix response.

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“…For reference, 'imaginary' bands in the heterohexameric (c@)~ or heterodimeric (cu@, sedimentation range were also retrieved, and checked in the same way. Native molecular weight markers were heterohexameric PC ((a&: 112.2 kDa), its dimeric subunits (CY~Z 36 kDa, p2: 38.8 kDa [21,25]), myoglobin (horse heart, Sigma, 17.5 kDa) and cytochrome c (horse heart, Sigma, 12.4 kDa).…”

Section: Characterization Of the Modification Productsmentioning

confidence: 99%

“…Some main features of excited state kinetics have been modelled by Fijrster transfer [13], but there is experimental 119, 201 and theoretical 113, 17, 181 evidence for exciton coupling, in particular among the proximate a-84 and 884 chromophores of different (Crp), heterodimer ("monomer") units within the heterohexamers or heterododecamers. There are also several reports on more complicated excited state kinetics which are unaccounted for by the simple model, and which have been taken as evidence for microheterogeneity [17,18,21,221. In order to investigate the role of individual chromophores in the process, we have begun to modify distinct chromophores within energy transferring chromophore ensembles.…”

Section: C-phycocyaninmentioning

confidence: 99%

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Dissociating effect of chromophore modifications on C-phycocyanin heterohexamers

Fischer

Scheer

1992

Journal of Photochemistry and Photobiology B: Biology

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The bilin chromophores of the a or /3 subunit of C-phycocyanin (PC) from Mastigocladus laminosus were modified, and subsequently recombined with the respective complementary unmodified chromophores. The modifications consisted of photobleaching (350 nm) or reversible reduction of the verdin-to rubin-type chromophore(s). Recombination led to heterodimers (a& but the heterohexameric aggregation state (a& could not be obtained with the modified chromophores. Autoxidation of the reduced a-84 chromophore in such a hybrid, which occurred on standing under aerobic conditions, induced reaggregation to heterohexamers. Chemical re-oxidation of the reduced chromophores did not produce reaggregation, and it was not promoted by a 22 kDa linker peptide fragment (Gottschalk et al., Photochem. Photobiol., 54 (1991) 283), which in unmodified samples stabilized heterohexameric aggregates. Binding of the mercurial p-chloromercury-benzenesulphonate to the single free cysteine of PC near (approximately 0.4 nm) the 884 chromophore had only a moderately destabilizing effect on the heterohexamer (a&. It was concluded that the intact chromophore structure is an important factor determining the quaternary structure of biliproteins. The tendency of heterohexamer destabilization is related to the situation in phycoerythrocyanin, where photoisomerization of the violobilin chromophore of the a subunit near the heterodimer-heterodimer contact region is also responsible for aggregate destabilization (Siebzehnriibl et al., Photochem. Photobiol., 46 (1989) 753).

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Picosecond time-resolved fluorescence of phycobiliproteins: Subunits of phycocyanin from Mastigocladus laminosus

Cited by 11 publications

References 27 publications

Comparison of Calculated and Experimentally Resolved Rate Constants for Excitation Energy Transfer in C-Phycocyanin. 1. Monomers

Comparison of Calculated and Experimentally Resolved Rate Constants for Excitation Energy Transfer in C-Phycocyanin. 1. Monomers

Protein-Matrix Solvation Dynamics in the α Subunit of C-Phycocyanin

Dissociating effect of chromophore modifications on C-phycocyanin heterohexamers

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