Time-resolved resonance Raman spectroscopy of carotenoids in Triton X-100 micellar solution

Conn, P F; Haley, Joseph L.; Lambert, C.; Truscott, T. George; Parker, Anthony W.

doi:10.1039/ft9938901753

Cited by 5 publications

(6 citation statements)

References 16 publications

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“…The triplet state resonance Raman spectra of 77DH and SEPT (see Figures and ) in methanol display marked differences to the respective ground state spectra, which is consistent with previous observations in resonance Raman studies of other carotenoids . However, the most striking observation is the difference between the 3 77DH* and 3 SEPT* spectra which contrasts with the relative similarity of the ground state spectra.…”

Section: Resultssupporting

confidence: 87%

“…Both ground state spectra exhibit similarities with the resonance Raman spectrum of β-carotene reported previously …”

Section: Resultssupporting

confidence: 79%

“…Thus, in the case of β-carotene, the central bond (15, 15‘) in the ground state is a double bond, while in the triplet state, it is a single bond. Consequently, the resonance Raman spectra of carotenoid triplet states exhibit additional bands and different intensity profiles (see below) compared to those of the respective ground state spectra …”

Section: Resultsmentioning

confidence: 99%

“…Resonance Raman spectroscopy has provided structural information on the ground, excited singlet, and triplet states of carotenoids, − all of which have strong electronic absorption bands in the visible region. However, the principal electronic absorption bands of carotenoid radical cations are located in the less accessible near-infrared region (750−950 nm), and consequently, resonance Raman studies have been limited by the availability of sensitive near-infrared detectors.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Carotenoid Radical Cations and Triplet States by Laser Flash Photolysis and Time-Resolved Resonance Raman Spectroscopy: Observation of Competitive Energy and Electron Transfer

et al. 1996

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The first nanosecond time-resolved resonance Raman study of carotenoid radical cations is reported for the polyenes septapreno-β-carotene and 7,7‘-dihydro-β-carotene. In addition, previously unreported resonance Raman spectra of the ground and triplet states of these molecules are reported. The radical cations were generated following electron transfer quenching of triplet 1-nitronaphthalene in methanol and Triton X-100 micelles. The quenching of triplet 1-nitronaphthalene by these carotenoids involves solvent-dependent competition between energy transfer and electron transfer, and for both carotenoids, estimates are given for the efficiencies of these two processes in methanol and hexane. The resonance Raman spectra of septapreno-β-carotene ground and triplet states are consistent with spectra reported previously for other carotenoids. However, the resonance Raman spectrum of the triplet state of 7,7‘-dihydro-β-carotene displays an intensity profile not found in the triplet spectra of other carotenoids. In addition, the resonance Raman spectrum of the radical cation of 7,7‘-dihydro-β-carotene is quite distinct from that of septapreno-β-carotene. These observations are attributed to differences in electronic structure arising from septapreno-β-carotene having an odd number of conjugated double bonds while 7,7‘-dihydro-β-carotene, unusually, has an even number.

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Section: Resultssupporting

confidence: 87%

“…Both ground state spectra exhibit similarities with the resonance Raman spectrum of β-carotene reported previously …”

Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigation of Carotenoid Radical Cations and Triplet States by Laser Flash Photolysis and Time-Resolved Resonance Raman Spectroscopy: Observation of Competitive Energy and Electron Transfer

et al. 1996

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“…Indeed, as extensively documented in the literature (see, for example, refs. [31][32][33], the C=C stretching frequency has consistently been reported to be sensitive to the conjugation length and configuration (cis/trans) of the carotenoid molecule, as well as to the polarizability of their environment, none of which is expected to change upon formation of the triplet (4,34). This "triplet-sharing" mechanism would lead to a decreased electron population in the antibonding π* orbital of the carotenoid, thereby resulting in a smaller downshift of the ν 1 a band.…”

Section: Resultsmentioning

confidence: 99%

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

Kish

Méndez-Hernández

et al. 2017

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

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In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet-triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.artificial photosynthesis | photoprotection | DFT calculations | triplet-triplet energy transfer | resonance Raman P hotoprotection is central to the maintenance of photosynthesis. Under certain circumstances, chlorophyll excited triplet states may form from intersystem crossing and from electron-hole recombination reactions in reaction centers. Chlorophyll triplet species can sensitize the formation of singlet oxygen, a deleterious reactive oxygen species (1). In photosynthetic complexes, this sensitization reaction is precluded by sufficiently rapid transfer of the triplet excited state from chlorophyll (Chl) or bacteriochlorophyll (BChl) to carotenoid molecules. The triplet states of carotenoids involved in photoprotection are well below the energy of singlet oxygen and therefore do not sensitize singlet oxygen. This quenching reaction reduces the lifetime of the Chl or BChl triplet state by many orders of magnitude (1) and renders it kinetically incompetent to sensitize singlet oxygen. Moreover, carotenoids can quench singlet oxygen directly in the event that it is inadvertently formed.In the light-harvesting (LH) proteins from most (anoxygenic) purple bacteria, triplet-triplet energy transfer (T-TET) from BChl to carotenoid molecules occurs on the nanosecond timescale (2, 3). By contrast, in light-harvesting complexes (LHCs) from...

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ChemInform Abstract: Timeresolved Resonance Raman Spectroscopy of Carotenoids in Triton X‐ 100 Micellar Solution.

et al. 1993

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Time-resolved resonance Raman spectroscopy of carotenoids in Triton X-100 micellar solution

Cited by 5 publications

References 16 publications

Investigation of Carotenoid Radical Cations and Triplet States by Laser Flash Photolysis and Time-Resolved Resonance Raman Spectroscopy: Observation of Competitive Energy and Electron Transfer

Investigation of Carotenoid Radical Cations and Triplet States by Laser Flash Photolysis and Time-Resolved Resonance Raman Spectroscopy: Observation of Competitive Energy and Electron Transfer

Triplet–triplet energy transfer in artificial and natural photosynthetic antennas

ChemInform Abstract: Timeresolved Resonance Raman Spectroscopy of Carotenoids in Triton X‐ 100 Micellar Solution.

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