Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

Niedzwiedzki, Dariusz M.; Fuciman, Marcel; Kobayashi, Masayuki; Frank, Harry A.; Blankenship, Robert E.

doi:10.1007/s11120-011-9692-7

Cited by 18 publications

(14 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5; Table 2) reveals the individual carotenoid-to-BChl energy transfer efficiencies of each of the carotenoids bound in the complexes. The data show clearly that all of the carotenoids transfer singlet state energy to BChl a with efficiencies less than or equal to *40 % which is consistent with previous reports on LH2 complexes containing carotenoid chromophores having N C 11 (Cong et al 2008;Niedzwiedzki et al 2011a;Noguchi et al 1990). The low energy transfer efficiencies of these carotenoids can be attributed to a number of factors including a low energy S 1 state of the carotenoid relative to the S 1 energy of BChl a (Cong et al 2008).…”

Section: Carotenoid-to-bchl Energy Transfersupporting

confidence: 91%

“…6 Photosynth Res internal conversion. The shape of the strong positive visible band in this third DADS contains features that can be attributed to N = 11 (rhodopin) and N = 12 (rhodovibrin or anhydrorhodovibrin) carotenoid chromophores which are known from previous work (Niedzwiedzki et al 2007(Niedzwiedzki et al , 2011a to have room temperature S 1 lifetimes of *4.3 ps (N = 11) and *2.2 ps (N = 12) which are within the experimental error of the lifetimes obtained from the present kinetic analysis. The fourth and fifth DADS components in the visible region (green and black dashed traces in the panels labeled VIS in Fig.…”

Section: Global Analysis Of Transient Absorption Datasupporting

confidence: 85%

“…6), the 605 nm band is dominant. Based on the red-shift expected when the N value of an open-chain carotenoid is increased by one (Niedzwiedzki et al 2007(Niedzwiedzki et al , 2011a, the 605 nm feature can be assigned to an N = 12 carotenoid, which in the present case would be a combination of rhodovibrin and anhydrorhodovibrin, both of which are present in substantial amounts in these complexes (Table 1; Fig. 2).…”

Section: Transient Absorption (Ta) Spectroscopymentioning

confidence: 71%

See 2 more Smart Citations

Spectral heterogeneity and carotenoid-to-bacteriochlorophyll energy transfer in LH2 light-harvesting complexes from Allochromatium vinosum

et al. 2015

Self Cite

View full text Add to dashboard Cite

Photosynthetic organisms produce a vast array of spectral forms of antenna pigment-protein complexes to harvest solar energy and also to adapt to growth under the variable environmental conditions of light intensity, temperature, and nutrient availability. This behavior is exemplified by Allochromatium (Alc.) vinosum, a photosynthetic purple sulfur bacterium that produces different types of LH2 light-harvesting complexes in response to variations in growth conditions. In the present work, three different spectral forms of LH2 from Alc. vinosum, B800-820, B800-840, and B800-850, were isolated, purified, and examined using steady-state absorption and fluorescence spectroscopy, and ultrafast time-resolved absorption spectroscopy. The pigment composition of the LH2 complexes was analyzed by high-performance liquid chromatography, and all were found to contain five carotenoids: lycopene, anhydrorhodovibrin, spirilloxanthin, rhodopin, and rhodovibrin. Spectral reconstructions of the absorption and fluorescence excitation spectra based on the pigment composition revealed significantly more spectral heterogeneity in these systems compared to LH2 complexes isolated from other species of purple bacteria. The data also revealed the individual carotenoid-to-bacteriochlorophyll energy transfer efficiencies which were correlated with the kinetic data from the ultrafast transient absorption spectroscopic experiments. This series of LH2 complexes allows a systematic exploration of the factors that determine the spectral properties of the bound pigments and control the rate and efficiency of carotenoid-to-bacteriochlorophyll energy transfer.

show abstract

Section: Carotenoid-to-bchl Energy Transfersupporting

confidence: 91%

Section: Global Analysis Of Transient Absorption Datasupporting

confidence: 85%

Section: Transient Absorption (Ta) Spectroscopymentioning

confidence: 71%

See 1 more Smart Citation

Spectral heterogeneity and carotenoid-to-bacteriochlorophyll energy transfer in LH2 light-harvesting complexes from Allochromatium vinosum

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Ultrafast optical spectroscopy is a powerful approach that allows direct time-domain observations of ET processes and has been widely applied to the study of isolated LH complexes (6,(10)(11)(12) and membranes (13)(14)(15) of purple bacteria.…”

Section: Introductionmentioning

confidence: 99%

Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

Lüer

Carey

Henry

et al. 2015

Biophysical Journal

View full text Add to dashboard Cite

Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.

show abstract

“…Consequently, it is not straightforward to predict how spheroidenone should perform in the LH2 protein in comparison with carotenoids with the same nominal conjugation N but comprising only C=C bonds. The S 1 (2 1 A g − ) state of spheroidenone lies in the 12,800–13,000 cm −1 range (Cong et al 2008 ; Zigmantas et al 2004 ), only marginally higher than the S 1 (2 1 A g − ) state energy of open-chain carotenoids with N = N C=C = 11 such as lycopene or rhodopin (12,400–12,800 cm −1 ) (Billsten et al 2002 ; Niedzwiedzki et al 2011b ). If energetic considerations are of paramount importance for energy transfer, a substantial difference in Φ Car→BChl among these carotenoids is not expected.…”

Section: Introductionmentioning

confidence: 99%

New insights into the photochemistry of carotenoid spheroidenone in light-harvesting complex 2 from the purple bacterium Rhodobacter sphaeroides

et al. 2016

Self Cite

View full text Add to dashboard Cite

Light-harvesting complex 2 (LH2) from the semi-aerobically grown purple phototrophic bacterium Rhodobacter sphaeroides was studied using optical (static and time-resolved) and resonance Raman spectroscopies. This antenna complex comprises bacteriochlorophyll (BChl) a and the carotenoid spheroidenone, a ketolated derivative of spheroidene. The results indicate that the spheroidenone-LH2 complex contains two spectral forms of the carotenoid: (1) a minor, “blue” form with an S2 (11Bu+) spectral origin band at 522 nm, shifted from the position in organic media simply by the high polarizability of the binding site, and (2) the major, “red” form with the origin band at 562 nm that is associated with a pool of pigments that more strongly interact with protein residues, most likely via hydrogen bonding. Application of targeted modeling of excited-state decay pathways after carotenoid excitation suggests that the high (92%) carotenoid-to-BChl energy transfer efficiency in this LH2 system, relative to LH2 complexes binding carotenoids with comparable double-bond conjugation lengths, derives mainly from resonance energy transfer from spheroidenone S2 (11Bu+) state to BChl a via the Qx state of the latter, accounting for 60% of the total transfer. The elevated S2 (11Bu+) → Qx transfer efficiency is apparently associated with substantially decreased energy gap (increased spectral overlap) between the virtual S2 (11Bu+) → S0 (11Ag−) carotenoid emission and Qx absorption of BChl a. This reduced energetic gap is the ultimate consequence of strong carotenoid–protein interactions, including the inferred hydrogen bonding.

show abstract

Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum

Cited by 18 publications

References 54 publications

Spectral heterogeneity and carotenoid-to-bacteriochlorophyll energy transfer in LH2 light-harvesting complexes from Allochromatium vinosum

Spectral heterogeneity and carotenoid-to-bacteriochlorophyll energy transfer in LH2 light-harvesting complexes from Allochromatium vinosum

Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

New insights into the photochemistry of carotenoid spheroidenone in light-harvesting complex 2 from the purple bacterium Rhodobacter sphaeroides

Contact Info

Product

Resources

About