Photophysics and Photochemistry of Phytochrome

Schaffner, Kurt; Braslavsky, Silvia E.; Holzwarth, Alfred R.

doi:10.1002/9780470133453.ch4

Cited by 52 publications

(5 citation statements)

References 134 publications

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“…16 for numbering) and thus strong energetic increase of the S 0 -S 1 energy gap. An analogous observation was described for biliverdin-dimethyl-ester (BVE) in ethanol [51][52][53][54], and is expected for bilatrienes in donating solvents in general, [55] as well as via adduct formation in protein-bound forms (phytochrome [53,56] and cyanobacteriochrome [57,58]). It is noted that (i) in analogy to Ref.…”

Section: Static Fluorescence Measurements On Pcbsupporting

confidence: 63%

Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

Theiß

Grupe

Lamparter

et al. 2021

Photochem Photobiol Sci

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Deactivation processes of photoexcited (λex = 580 nm) phycocyanobilin (PCB) in methanol were investigated by means of UV/Vis and mid-IR femtosecond (fs) transient absorption (TA) as well as static fluorescence spectroscopy, supported by density-functional-theory calculations of three relevant ground state conformers, PCBA, PCBB and PCBC, their relative electronic state energies and normal mode vibrational analysis. UV/Vis fs-TA reveals time constants of 2.0, 18 and 67 ps, describing decay of PCBB*, of PCBA* and thermal re-equilibration of PCBA, PCBB and PCBC, respectively, in line with the model by Dietzek et al. (Chem Phys Lett 515:163, 2011) and predecessors. Significant substantiation and extension of this model is achieved first via mid-IR fs-TA, i.e. identification of molecular structures and their dynamics, with time constants of 2.6, 21 and 40 ps, respectively. Second, transient IR continuum absorption (CA) is observed in the region above 1755 cm−1 (CA1) and between 1550 and 1450 cm−1 (CA2), indicative for the IR absorption of highly polarizable protons in hydrogen bonding networks (X–H…Y). This allows to characterize chromophore protonation/deprotonation processes, associated with the electronic and structural dynamics, on a molecular level. The PCB photocycle is suggested to be closed via a long living (> 1 ns), PCBC-like (i.e. deprotonated), fluorescent species.

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Section: Static Fluorescence Measurements On Pcbsupporting

confidence: 63%

Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

Theiß

Grupe

Lamparter

et al. 2021

Photochem Photobiol Sci

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“…Its value was determined to kRI = 2.8 X 1Olo s-l from the condition that the quantum yield for formation of lumi-R has to be 0.5. 5 The following values could be obtained: k+ = (4 5 a formation time of 25 ps and a mean decay time of -55 ps. This is in good agreement with earlier findings for the transient pre-1~mi-R.~ Theoretical bleaching curves calculated by means of the energy level scheme used show that parts of the energy levels of lumi-R (levels 5 , 7, 9, lo) cannot be populated significantly during the 35 ps excitation pulse (k,,, k , 2 50 ps) and thus do not influence the intensity-dependent transmission behavior (processes C-F).…”

Section: Resultsmentioning

confidence: 99%

“…The first longer-lived intermediate built up within 100 ps after exciting P,. is referred to as lumi-R or I,w.4,3 The fluorescence quantum yield of the P,-species is very low (-2 X 1 O-1).4,- 5 The fluorescence decay exhibits four exponential~~,' from which only the shortest two (approximately 10 and 50 ps; depending on emission wavelength and solvent) show photochromicity6 and are therefore relevant for the phytochrome photocycle. The interpretation of this double exponential decay is presently not quite clear and different models have been discussed for the still unknown pathway from the primary excited state P,* to l~m i -R .~-" At present the following models are discussed: ( 1 ) the fluorescence decay has been interpreted in terms of heterogeneity in the P, species exhibiting different lifetime^.…”

Section: Introductionmentioning

confidence: 99%

EXCITED STATE BEHAVIOR OF PHYTOCHROME P_r

Teuchner

Schulz

Stiel

et al. 1995

Photochem & Photobiology

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The primary excited state processes of phytochrome, the plant chromoprotein responsible for most photomorphogenetic responses, are investigated by picosecond intensity‐dependent transmission measurements. At sufficient high excitation intensity (starting at photon flux densities of about 1′1025 cm−2 s−l) a moderate bleaching of the absorption is observed. For the quantitative analysis of the experimental data a rate equation system approach for the energy levels responsible for the ultrafast transformation Pr→ lumi‐R and the photon transport through the sample was utilized. The following was found for the excited state parameters of the phytochrome Pr: (1) an excited state absorption of the same order of magnitude as the ground state absorption (cross section: S̀exc= 4′10−16 cm−2 at 650 nm), (2) a fast relaxation of the higher excited singlet state on the femtosecond time scale.

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“…As the different absorption properties suggest, the order of events may be different on the pathway from Pr to Pfr, although also this well characterized reaction course is initiated by an isomerization around a double bond and must include a subsequent single bond rotation as well as the change of the hydrogen bonding partner of N24 (Scheme ). It is possible that the formation of Meta-R is not only linked to a break of a hydrogen bond to water but to a deprotonation process on N24 leading to a neutral chromophore and therefore a bleached first electronic transition . The single bond rotation occurs during the final transformation, the formation of Pfr from Meta-R .…”

Section: Discussionmentioning

confidence: 99%

Phytochrome as Molecular Machine: Revealing Chromophore Action during the Pfr → Pr Photoconversion by Magic-Angle Spinning NMR Spectroscopy

et al. 2010

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The cyanobacterial phytochrome Cph1 can be photoconverted between two thermally stable states, Pr and Pfr. The photochemically induced Pfr --> Pr back-reaction has been followed at low temperature by magic-angle spinning (MAS) NMR spectroscopy, allowing two intermediates, Lumi-F and Meta-F, to be trapped. Employing uniformly (13)C- and (15)N-labeled open-chain tetrapyrrole chromophores, all four states-Pfr, Lumi-F, Meta-F, and Pr-have been structurally characterized. In the first step, the double bond photoisomerization forming Lumi-F occurs. The second step, the transformation to Meta-F, is driven by the release of the mechanical tension. This process leads to the break of the hydrogen bond of the ring D nitrogen to Asp-207 and triggers signaling. The third step is protonically driven allowing the hydrogen-bonding interaction of the ring D nitrogen to be restored. Compared to the forward reaction, the order of events is changed, probably caused by the different properties of the hydrogen bonding partners of N24, leading to the directionality of the photocycle.

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Photophysics and Photochemistry of Phytochrome

Cited by 52 publications

References 134 publications

Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

EXCITED STATE BEHAVIOR OF PHYTOCHROME P_r

Phytochrome as Molecular Machine: Revealing Chromophore Action during the Pfr → Pr Photoconversion by Magic-Angle Spinning NMR Spectroscopy

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Photophysics and Photochemistry of Phytochrome

Cited by 52 publications

References 134 publications

Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

EXCITED STATE BEHAVIOR OF PHYTOCHROME Pr

Phytochrome as Molecular Machine: Revealing Chromophore Action during the Pfr → Pr Photoconversion by Magic-Angle Spinning NMR Spectroscopy

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EXCITED STATE BEHAVIOR OF PHYTOCHROME P_r