Effect of the Solvent Environment on the Spectroscopic Properties and Dynamics of the Lowest Excited States of Carotenoids

Frank, Harry A.; Bautista, James A.; Josue, Jesusa S.; Pendon, Zeus; Hiller, Roger G.; Sharples, Frank P.; Gosztola, David J.; Wasielewski, Michael R.

doi:10.1021/jp000079u

Cited by 295 publications

(696 citation statements)

References 38 publications

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“…A similar dependence of spectral shape on solvent polarity was reported for several naturally occurring substituted carotenoids and assigned to the formation of an intramolecular charge transfer (ICT) state (23,27). The ICT state is thought to arise from the presence of a carbonyl moiety in conjugation with the extended -electron system; the carbonyl moiety accumulates electron density upon photoexcitation.…”

Section: -3 In Acetonesupporting

confidence: 56%

“…The ICT state is thought to arise from the presence of a carbonyl moiety in conjugation with the extended -electron system; the carbonyl moiety accumulates electron density upon photoexcitation. The ICT and S 1 states may effectively behave as one state (27) or as distinct molecular states that equilibrate rapidly upon population from the optically allowed S 2 state (28). The carotenoids in this study also feature carbonyl groups.…”

Section: -3 In Acetonementioning

confidence: 99%

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A simple artificial light-harvesting dyad as a model for excess energy dissipation in oxygenic photosynthesis

Berera

Herrero

Stokkum

et al. 2006

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

125

176

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Under excess illumination, plant photosystem II dissipates excess energy through the quenching of chlorophyll fluorescence, a process known as nonphotochemical quenching. Activation of nonphotochemical quenching has been linked to the conversion of a carotenoid with a conjugation length of nine double bonds (violaxanthin) into an 11-double-bond carotenoid (zeaxanthin). It has been suggested that the increase in the conjugation length turns the carotenoid from a nonquencher into a quencher of chlorophyll singlet excited states, but unequivocal evidence is lacking. Here, we present a transient absorption spectroscopic study on a model system made up of a zinc phthalocyanine (Pc) molecule covalently linked to carotenoids with 9, 10, or 11 conjugated carbon-carbon double bonds. We show that a carotenoid can act as an acceptor of Pc excitation energy, thereby shortening its singlet excited-state lifetime. The conjugation length of the carotenoid is critical to the quenching process. Remarkably, the addition of only one double bond can turn the carotenoid from a nonquencher into a very strong quencher. By studying the solvent polarity dependence of the quenching using target analysis of the time-resolved data, we show that the quenching proceeds through energy transfer from the excited Pc to the optically forbidden S 1 state of the carotenoid, coupled to an intramolecular charge-transfer state. The mechanism for excess energy dissipation in photosystem II is discussed in view of the insights obtained on this simple model system. artificial photosynthesis ͉ carotenoid ͉ nonphotochemical quenching ͉ photoprotection ͉ xanthophyll cycle

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Section: -3 In Acetonesupporting

confidence: 56%

Section: -3 In Acetonementioning

confidence: 99%

A simple artificial light-harvesting dyad as a model for excess energy dissipation in oxygenic photosynthesis

Berera

Herrero

Stokkum

et al. 2006

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

125

176

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“…The spectra of Chl a and Chl b in ethanol were shifted between 4 and 7 nm to account for the small effect of environment on the Chl peak positions and to align the spectra better with the absorption maxima of the CP26 complexes. The dashed lines represent the absorption spectra of the various xanthophylls (Xanth) taken in ethanol and shifted by between 18 and 22 nm to accommodate the large spectral shift associated with the change in polarizability of the medium (40,41). No changes in the overall line shapes of the spectra of the xanthophylls were required to simulate the absorption or excitation profiles of the CP26 complexes because it has been demonstrated that for xanthophylls lacking carbonyl functional groups, no effect on the width or vibronic structure is associated with changes in solvent environment (41).…”

Section: Resultsmentioning

confidence: 99%

“…The dashed lines represent the absorption spectra of the various xanthophylls (Xanth) taken in ethanol and shifted by between 18 and 22 nm to accommodate the large spectral shift associated with the change in polarizability of the medium (40,41). No changes in the overall line shapes of the spectra of the xanthophylls were required to simulate the absorption or excitation profiles of the CP26 complexes because it has been demonstrated that for xanthophylls lacking carbonyl functional groups, no effect on the width or vibronic structure is associated with changes in solvent environment (41). For the control sample, the xanthophyll line shape was constructed from a sum of the absorption spectra of lutein, neoxanthin, and violaxanthin in a 2/1/1 molar ratio consistent with the xanthophyll composition of the reconstituted CP26 complex ( Table 1).…”

Section: Resultsmentioning

confidence: 99%

Photochemical Behavior of Xanthophylls in the Recombinant Photosystem II Antenna Complex, CP26

et al. 2001

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The steady state absorption and fluorescence spectroscopic properties of the xanthophylls, violaxanthin, zeaxanthin, and lutein, and the efficiencies of singlet energy transfer from the individual xanthophylls to chlorophyll have been investigated in recombinant CP26 protein overexpressed in Escherichia coli and then refolded in vitro with purified pigments. Also, the effect of the different xanthophylls on the extents of static and dynamic quenching of chlorophyll fluorescence has been investigated. Absorption, fluorescence, and fluorescence excitation demonstrate that the efficiency of light harvesting from the xanthophylls to chlorophyll a is relatively high and insensitive to the particular xanthophyll that is present. A small effect of the different xanthophylls is observed on the extent of quenching of Chl fluorescence. The data provide the precise wavelengths of the absorption and fluorescence features of the bound pigments in the highly congested spectral profiles from these light-harvesting complexes. This information is important in assessing the mechanisms by which higher plants dissipate excess energy in light-harvesting proteins.Light-harvesting pigment-protein complexes in higher plants and algae possess a means of thermally dissipating photon energy absorbed, but not used, in photosynthesis. The process is known as nonphotochemical quenching (NPQ) 1 and offers a short-term protective response to changes in incident light energy irradiance (1-3). Dissipation of excess energy in light-harvesting proteins from photosynthetic systems can be measured quantitatively by observing the extent to which fluorescence from chlorophyll (Chl) a bound in the complexes is affected by different chemical and physical conditions (4-11). NPQ is known to be associated with acidification of the thylakoid lumen and correlated with the enzymatic interconversion of violaxanthin and zeaxanthin in the xanthophyll cycle (12, 13). What is not clear, however, is precisely how the interconversion of the pigments in the xanthophyll cycle is associated with thermal dissipation. Two basic hypotheses for the involvement of the xanthophylls have been presented in the literature: direct quenching and indirect quenching.The direct quenching model invokes specific energy states of xanthophyll molecules in the process of quenching (1,(13)(14)(15). Optical spectroscopic investigations of carotenoids and xanthophylls have shown that the energies of the lowest excited (S 1 ) states of some of these molecules may be sufficiently low to quench Chl excited states, thus providing a means of regulating the flow of energy in the antenna (16)(17)(18)(19). Determinations of the S 1 excited state energies of violaxanthin and zeaxanthin suggest that although the direct route of quenching of excited states of Chl a by these molecules is energetically feasible, the energy difference between the S 1 states of zeaxanthin and violaxanthin is not large enough to account for the magnitude of differential quenching associated with these pigments an...

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“…This effect has been attributed to the presence of an intramolecular charge transfer (ICT) state that acts in conjunction with the lowest excited singlet state S 1 (13). In PCP the dominant energy transfer pathway from peridinin to Chl-a is via this S 1 /ICT state, whose lifetime is Ϸ2.5 ps in the PCP complex, corresponding to an efficiency of 80% for this preferred route (14)(15)(16).…”

mentioning

confidence: 99%

Identification of a single peridinin sensing Chl- a excitation in reconstituted PCP by crystallography and spectroscopy

Schulte

Niedzwiedzki

Birge

et al. 2009

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

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The peridinin-chlorophyll a-protein (PCP) of dinoflagellates is unique among the large variety of natural photosynthetic lightharvesting systems. In contrast to other chlorophyll protein complexes, the soluble PCP is located in the thylakoid lumen, and the carotenoid pigments outnumber the chlorophylls. The structure of the PCP complex consists of two symmetric domains, each with a central chlorophyll a (Chl-a) surrounded by four peridinin molecules. The protein provides distinctive surroundings for the pigment molecules, and in PCP, the specific environment around each peridinin results in overlapping spectral line shapes, suggestive of different functions within the protein. One particular Per, Per-614, is hypothesized to show the strongest electronic interaction with the central Chl-a. We have performed an in vitro reconstitution of pigments into recombinant PCP apo-protein (RFPCP) and into a mutated protein with an altered environment near Per-614. Steady-state and transient optical spectroscopic experiments comparing the RFPCP complex with the reconstituted mutant protein identify specific amino acid-induced spectral shifts. The spectroscopic assignments are reinforced by a determination of the structures of both RFPCP and the mutant by x-ray crystallography to a resolution better than 1.5 Å. RFPCP and mutated RFPCP are unique in representing crystal structures of in vitro reconstituted light-harvesting pigment-protein complexes.light harvesting ͉ peridinin ͉ protein crystallography ͉ refolding ͉ transient absorption spectroscopy M any naturally occurring light-harvesting pigment-protein complexes use chlorophyll (Chl) to collect incoming photons, and most of these systems rely on carotenoids to supplement light-capture in the spectral region of maximal solar irradiance from 420 to 550 nm. Carotenoids function as energy donors in many different natural antenna systems and operate with an efficiency that ranges from 30% to nearly 100%. Carotenoids also fulfill a crucial photoprotective role that preserves the structural and functional integrity of the photosynthetic apparatus. A detailed knowledge of the controlling features of energy transfer in natural light-harvesting systems is critical for designing efficient artificial mimics (1).Structural determinations of several antenna complexes have lead to theoretical treatments of the photophysical processes undergone by the bound pigments and which control photosynthetic light harvesting (2). An effective approach to explore light-harvesting is mutagenesis of specific residues in conjunction with pigment substitutions or incorporations, as shown for the bacterial LH2 complex (3,4). This approach has also been applied to the membrane-bound light-harvesting complex II (LHCII) from higher plants, for which a robust in vitro reconstitution system has been developed (5). While high-resolution x-ray-derived structures exist for both native LH2 (6-8) and LHCII (9, 10), three-dimensional (3D) crystallization of modified complexes has not been possible, although 2D cry...

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Effect of the Solvent Environment on the Spectroscopic Properties and Dynamics of the Lowest Excited States of Carotenoids

Cited by 295 publications

References 38 publications

A simple artificial light-harvesting dyad as a model for excess energy dissipation in oxygenic photosynthesis

A simple artificial light-harvesting dyad as a model for excess energy dissipation in oxygenic photosynthesis

Photochemical Behavior of Xanthophylls in the Recombinant Photosystem II Antenna Complex, CP26

Identification of a single peridinin sensing Chl- a excitation in reconstituted PCP by crystallography and spectroscopy

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