Reactions of excited-state cytochrome c derivatives. Delayed fluorescence and phosphorescence of zinc, tin, and metal-free cytochrome c at room temperature

Dixit, Bhavna; Moy, Vincent T.; Vanderkooi, Jane M.

doi:10.1021/bi00304a035

Cited by 39 publications

(52 citation statements)

References 15 publications

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“…The time course of fluorescence decay of the Zn-NIR excited at 424 nm was measured with a Spex energy-modulated spectrofluorimeter, using fluorescein as a standard. This process is the fastest observed in this study, with a time constant of 2.4 ns, and its rate constant agrees well with that measured for Zn-cytochrome c [9]. Flash-induced absorbance changes after excitation at 532 nm are shown in Figure 3.…”

Section: Dynamic Absorption and Fluorescencesupporting

confidence: 89%

“…Zn-containing porphyrins can be photoexcited to populate a long-lived triplet state [9], which may be able to transfer an Abbreviations used : NIR, nitrite reductase ; apo-NIR, recombinant NIR lacking the d 1 -haem ; Zn-NIR, recombinant NIR in which the d 1 -haem has been replaced with Zn-protoporphyrin IX (each monomer contains one Fe c-haem and one Zn-porphyrin) ; ANS, 1-anilino-8-naphthalenesulphonate ; eT, electron transfer. Time constants are defined as the reciprocal of the rate constants ; notice that all processes observed in this study are first order.…”

Section: Introductionmentioning

confidence: 99%

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Electron transfer in zinc-reconstituted nitrite reductase from Pseudomonas aeruginosa

Bellelli

Brzezinski

Arese

et al. 1996

Biochemical Journal

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1. The catalytic cycle of the haem-containing nitrite reductase (NIR) from Pseudomonas aeruginosa involves electron transfer between the two prosthetic groups of the enzyme, the c-haem and the d1-haem; this reaction was shown to be slow by stopped-flow analysis. The recombinant enzyme, expressed in Pseudomonas putida, contains the c-haem but no d1-haem; we have reconstituted this protein with Zn-protoporphyrin IX in the place of the d1-haem. 2. Photoexcitation of Zn-NIR is followed by electron transfer from the triplet excited state of the Zn-porphyrin to the oxidized c-haem, with a rate constant of 7 x 10(5) s-1; since the intermediate with reduced c-haem is not significantly populated, we conclude that the back reaction is probably as fast. 3. Even taking into account that in the native NIR the driving force is close to zero, the rate constant for the c-->d1 electron transfer, estimated from our experiments, is still much higher than that observed by stopped flow (k = 0.3 s-1) using reduced azurin as the electron donor. This finding may be a direct kinetic indication that reduction of the d1-haem is associated with a substantial reorganization of the co-ordination of the metal, as shown by spectroscopy of the oxidized and reduced NIR.

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Section: Dynamic Absorption and Fluorescencesupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Electron transfer in zinc-reconstituted nitrite reductase from Pseudomonas aeruginosa

Bellelli

Brzezinski

Arese

et al. 1996

Biochemical Journal

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“…The heme group in these proteins is not covalently linked to the protein which enables the removal of the heme b molecule from the binding pocket (Teale 1959) and replacement with light-active porphyrins (McGourty et al 1987;Petersonkennedy et al 1984;Simolo et al 1984). Upon light excitation ZnPP forms a triplet state with near unity efficiency (Ut = 0.9) which is long lived (s * 14 ms) (Sudha et al 1984;Zemel and Hoffman 1981). This has been utilized to study long-range electrontransfer reactions, such as those between proteins.…”

Section: Metal-substituted Porphyrinsmentioning

confidence: 99%

Designing photosystem II: molecular engineering of photo-catalytic proteins

Conlan

2008

Photosynth Res

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Biological photosynthesis utilizes membrane-bound pigment/protein complexes to convert light into chemical energy through a series of electron-transfer events. In the unique photosystem II (PSII) complex these electron-transfer events result in the oxidation of water to molecular oxygen. PSII is an extremely complex enzyme and in order to exploit its unique ability to convert sunlight into chemical energy it will be necessary to make a minimal model. Here we will briefly describe how PSII functions and identify those aspects that are essential in order to catalyze the oxidation of water into O(2), and review previous attempts to design simple photo-catalytic proteins and summarize our current research exploiting the E. coli bacterioferritin protein as a scaffold into which multiple cofactors can be bound, to oxidize a manganese metal center upon illumination. Through the reverse engineering of PSII and light driven water splitting reactions it may be possible to provide a blueprint for catalysts that can produce clean green fuel for human energy needs.

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“…porphyrin cation radical, Zncyt + , was monitored at 676 nm, where the difference in absorbance between Zncyt + and 3 Zncyt is the greatest. 80,84,85 The concentration of Zncyt was 3.0 (JM in experiments done at pH 7.00 and 5.0 PM in those done at pH 2.0 or in the presence of urea. The concentration of the triplet state, 3 Zncyt, depended on the excitation power and was ca.…”

Section: Methodsmentioning

confidence: 97%

“…Another criterion of purity was that the rate constant & d for the natural decay of3 Zncyt be less than 110 s -1 . The concentration of Zncyt was determined on the basis of its molar absorptivity: e = 243 mM -1 cm -1 at 423 nm 80. The metal-free form of cytochrome c is porphyrin cytochrome c, designated H 2 cyt.…”

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confidence: 99%

Electron-transfer reactivity of metalloproteins in folded, partially unfolded, and completely unfolded forms

Tremain

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Fittings of Kinetic Data 44 Results 45 Characterization of (Un)folded Forms of Zncyt by Absorption Spectroscopy 45 Equilibrium Unfolding of Zncyt 45 Characterization of (Un)folded Forms of Zncyt by Circular Dichroism Spectroscopy 45 Characterization of (Un)folded Forms of Zncyt by Natural Decay of the Triplet State 46 Conformational Transitions Between (Un)folded Forms of Zncyt 47 V Oxidative Quenching of 3 Zncyt by Inorganic Complexes and Cyt(HI) 49 Discussion 51 Structure and Reactivity of (Un)folded Forms of Cyt(III) and Zncyt Absorption and Circular Dichroism Spectra of (Un)folded Forms of Zncyt 51 Natural Decay of the Triplet State of Zncyt in Different (Un)folded Forms 53 Reactivity of 3 Zncyt in the Five (Un)folded Forms 54 (A) Role of Electrostatic Interactions 54 (B) Partial Unfolding of Zncyt: The Molten-Globule Form

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Reactions of excited-state cytochrome c derivatives. Delayed fluorescence and phosphorescence of zinc, tin, and metal-free cytochrome c at room temperature

Cited by 39 publications

References 15 publications

Electron transfer in zinc-reconstituted nitrite reductase from Pseudomonas aeruginosa

Electron transfer in zinc-reconstituted nitrite reductase from Pseudomonas aeruginosa

Designing photosystem II: molecular engineering of photo-catalytic proteins

Electron-transfer reactivity of metalloproteins in folded, partially unfolded, and completely unfolded forms

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