A comparative picosecond‐resolved fluorescence study of tryptophan residues in iron‐sulfur proteins

Dorovska-Taran, Victoria; Hoek, A. van; Link, Thomas; Visser, Antonie J. W. G.; Hagen, Wilfred R.

doi:10.1016/0014-5793(94)00606-7

Cited by 10 publications

(4 citation statements)

References 26 publications

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“…The [Fe-S] cluster has a strong charge-transfer absorption band at 380 nm (13,14), which overlaps with the Trp emission. Thus, RET between Trp and the cluster is expected and has been observed in other iron-sulfur proteins (15).…”

supporting

confidence: 55%

Femtosecond dynamics of rubredoxin: Tryptophan solvation and resonance energy transfer in the protein

Zhong

Pal

Zhang

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

138

134

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We report here studies of tryptophan (Trp) solvation dynamics in water and in the Pyrococcus furiosus rubredoxin protein, including the native and its apo and denatured forms. We also report results on energy transfer from Trp to the iron-sulfur [Fe-S] cluster. Trp fluorescence decay with the onset of solvation dynamics of the chromophore in water was observed with femtosecond resolution (Ϸ160 fs; 65% component), but the emission extended to the picosecond range (1.1 ps; 35% component). In contrast, the decay is much slower in the native rubredoxin; the Trp fluorescence decay extends to 10 ps and longer, reflecting the local rigidity imposed by residues and by the surface water layer. The dynamics of resonance energy transfer from the two Trps to the [Fe-S] cluster in the protein was observed to follow a temporal behavior characterized by a single exponential (15-20 ps) decay. This unusual observation in a protein indicates that the resonance transfer is to an acceptor of a well-defined orientation and separation. From studies of the mutant protein, we show that the two Trp residues have similar energy-transfer rates. The critical distance for transfer (R 0) was determined, by using the known x-ray data, to be 19.5 Å for Trp-36 and 25.2 Å for Trp-3, respectively. The orientation factor ( 2 ) was deduced to be 0.13 for Trp-36, clearly indicating that molecular orientation of chromophores in the protein cannot be isotropic with 2 value of 2͞3. These studies of solvation and energy-transfer dynamics, and of the rotational anisotropy, of the wild-type protein, the (W3Y, I23V, L32I) mutant, and the fmetPfRd variant at various pH values reveal a dynamically rigid protein structure, which is probably related to the hyperthermophilicity of the protein.T ryptophan (Trp) is the most important fluorophore among amino acid residues for optical probing of proteins. However, Trp fluorescence is complex because of different rotamers in the ground state and the two nearly degenerate electronic states ( 1 L a , 1 L b ) with perpendicular transition moments. Accordingly, numerous studies (1-10) have focused on the lifetime, quantum yield, Stokes shift, and fluorescence anisotropy. Most of these studies were made with picosecond or nanosecond time resolution (3, 6-10). To probe the local protein dynamics, Trp solvation by neighboring soft͞rigid water molecules, or by other polar amino acid residues, must be resolved on the femtosecond time scale. Moreover, such studies are important for examining the nature of resonance energy transfer (RET) that is used for deducing distances and orientations between the Trp and quenchers in the protein (e.g., see refs. 3 and 10, and references therein).We choose the hyperthermophilic iron-sulfur protein, Pyrococcus furiosus rubredoxin (PfRd), as a prototype system (Fig. 1). The high-resolution x-ray crystallographic structures of PfRd at 0.95 Å and its formylmethionine variant (fmetPfRd) at 1.2 Å, have been recently reported (11). PfRd is a small protein of 53 amino acid residues with an iron a...

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supporting

confidence: 55%

Femtosecond dynamics of rubredoxin: Tryptophan solvation and resonance energy transfer in the protein

Zhong

Pal

Zhang

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

138

134

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“…The efficiency of the Tyr to Trp energy transfer was estimated as described by Eisinger (1969). Time-resolVed fluorescence and fluorescence anisotropy decays were measured by using the time-correlated singlephoton counting technique (Dorovska-Taran et al, 1994;Pap et al, 1993). The measuring system was able to resolve accurately fluorescence lifetimes of 30 ps.…”

Section: Methodsmentioning

confidence: 99%

Dissociation Equilibrium of Human Recombinant Interferon γ

et al. 1996

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The biologically active form of interferon gamma is a dimer composed of two noncovalently bound identical polypeptide chains of 17 kDa each. In this study, it was found that dissociation of the dimer into monomers significantly reduced the fluorescence quantum yield and the efficiency of the intermolecular Tyr to Trp radiationless energy transfer. The same process caused significant changes in the fluorescence decay and in the fluorescence anisotropy decay. The kinetic and thermodynamic parameters of the dimer-monomer equilibrium were determined by fluorescence measurements at different temperatures and by a theoretical mathematical model. Dissociation of the dimers into monomers was an endothermic process and was favored by concentrations of the protein lower than 1 microM and by increasing the temperature. It was accompanied by formation of aggregates, a slow and partially reversible process leading to inactivation of the interferon. It is suggested that certain monomeric conformers are competent for aggregation.

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“…This reveals that the energy of PVK exciton was quenched in these two blended films. Emission quenching results from two processes: Förster energy transfer [19] and exciton dissociation. [20] In PVK:Alq3 (1:1), the emission of Alq3 is relatively strong thanks to Förster energy transfer from PVK to Alq3.…”

Section: Varying the Composition Of The Active Layersmentioning

confidence: 99%

Solar cells based on the poly(N-vinylcarbazole): porphyrin: tris(8-hydroxyquinolinato) aluminium blend system*

et al. 2011

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Organic solar cells based on poly(N-vinylcarbazole) (PVK): porphyrin: tris (8-hydroxyquinolinato) aluminium (Alq3) blend p-n junction systems have been fabricated in this work. The roles of the different components in the blend system and of the amount of porphyrin have been investigated. The 5, 10, 15, 20-tetraphenylporphyrin (TPP) and 5, 10, 15, 20-tetra(o-chloro)phenylporphyrinato-copper (CuTClPP) are used in the solar cells. The results show that TPP is better than CuTCIPP in enhancing the performance of PVK:Alq3 solar cells. When the weight ratio of PVK:TPP:Alq3 is 1:1.5:1, the best performance of solar cell is obtained. The open circuit voltage (V oc) is 0.87 V, and the short circuit current (J sc) is 17.5 μA·cm−2. In the ternary bulk hereojunction system, the device may be regarded as a cascade of three devices of PVK:TPP, TPP:Alq3 and PVK:Alq3. PVK, TPP and Alq3 can improve the hole mobility, light absorption intensity and electron mobility of the ternary bulk hereojunction system, respectively.

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A comparative picosecond‐resolved fluorescence study of tryptophan residues in iron‐sulfur proteins

Cited by 10 publications

References 26 publications

Femtosecond dynamics of rubredoxin: Tryptophan solvation and resonance energy transfer in the protein

Femtosecond dynamics of rubredoxin: Tryptophan solvation and resonance energy transfer in the protein

Dissociation Equilibrium of Human Recombinant Interferon γ

Solar cells based on the poly(N-vinylcarbazole): porphyrin: tris(8-hydroxyquinolinato) aluminium blend system*

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