Carotenoids are crucial for photosynthesis, playing key roles in light harvesting and photoprotection. In this study, spheroidene and bacteriochlorophyll a (Bchl a) were reconstituted into the chromatophores of the carotenoidless mutant Rhodobacter sphaeroides R26.1, resulting in the preparation of high-quality LH2 complexes. Global and target analyses of transient absorption data revealed that incorporating B800 Bchl a significantly enhances excitation energy transfer (EET) efficiency from carotenoids to Bchl a. EET predominantly occurs from the carotenoid S2 state, with additional pathways from the S1 state observed in native LH2. Unique relaxation dynamics were identified, including the generation of the carotenoid S* state in reconstituted LH2 with both spheroidene and B800 Bchl a and the formation of the carotenoid T1 state in reconstituted LH2. These findings underscore the critical influence of pigment composition and spatial organization on energy transfer mechanisms. They provide valuable insights into the molecular interplay that governs excitation energy transfer in photosynthetic light-harvesting systems.

Department of Applied Chemistry for Environment Graduate School of Science and Technology Kwansei Gakuin University 1 Gakuen Uegahara Sanda 669 1330 Japan

Institute of Microbiology Czech Academy of Sciences 379 81 Trebon Czech Republic

School of Molecular Biosciences University of Glasgow Glasgow G12 8QQ UK

Zobrazit více v PubMed

Young A., Britton G. Carotenoids in Photosynthesis; Chapman & Hall, London, UK, 1993

Green B.R., Parson W.W. Light-Harvesting Antennas in Photosynthesis. Kluwer Academic Publishers; Dordrecht, The Netherlands: 2003.

Stange C. Carotenoids in Nature: Biosynthsis, Regulatuion and Fuction. Springer; Cham, Switzerland: 2016.

Blankenship R.E., Madigan M.T., Bauer C.E. Anoxygenic Photosynthetic Bacteria. Kluwer Academic Publishers; Dordrecht, The Netherlands: 1995.

Hunter C.N., Daldal F., Thurnauer M.C., Beatty J.T. The Purple Photosynthetic Bacteria. Springer; Dordrecht, The Netherlands: 2009.

Blankenship R.E. Molecular Mechanisms of Photosynthesis. Wiley; Oxford, UK: 2002. DOI

Roszak A.W., Howard T.D., Southall J., Gardiner A.T., Law C.J., Isaacs N.W., Cogdell R.J. Crystal structure of the RC-LH1 core complex from Rhodopseudomonas palustris. Science. 2003;302:1969–1972. doi: 10.1126/science.1088892. PubMed DOI

Qian P., Siebert C.A., Wang P., Canniffe D.P., Hunter C.N. Cryo-EM structure of the Blastochloris viridis LH1-RC complex at 2.9 Å. Nature. 2018;556:203–208. doi: 10.1038/s41586-018-0014-5. PubMed DOI

Yu L.-J., Ma F. Recent Progress on the LH1-RC Complexes of Purple Photosynthetic Bacteria. In: Wang Q., editor. Microbial Photosynthesis. Springer; Dordrecht, The Netherlands: 2020.

Tani K., Kanno R., Ji X.C., Hall M., Yu L.J., Kimura Y., Madigan M.T., Mizoguchi A., Humbel B.M., Wang-Otomo Z.Y. Cryo-EM Structure of the Photosynthetic LH1-RC Complex from Rhodospirillum rubrum. Biochemistry. 2021;60:2483–2491. doi: 10.1021/acs.biochem.1c00360. PubMed DOI

Mcdermott G., Prince S.M., Freer A.A., Hawthornthwaitelawless A.M., Papiz M.Z., Cogdell R.J., Isaacs N.W. Crystal-Structure of an Integral Membrane Light-Harvesting Complex from Photosynthetic Bacteria. Nature. 1995;374:517–521. doi: 10.1038/374517a0. DOI

Koepke J., Hu X., Muenke C., Schulten K., Michel H. The crystal structure of the light-harvesting complex II (B800-850) from Rhodospirillum molischianum. Structure. 1996;4:581–597. doi: 10.1016/S0969-2126(96)00063-9. PubMed DOI

Gardiner A.T., Naydenova K., Castro-Hartmann P., Nguyen-Phan T.C., Russo C.J., Sader K., Hunter C.N., Cogdell R.J., Qian P. The 2.4 Å cryo-EM structure of a heptameric light-harvesting 2 complex reveals two carotenoid energy transfer pathways. Sci. Adv. 2021;7:eabe4650. doi: 10.1126/sciadv.abe4650. PubMed DOI PMC

Qian P., Swainsbury D.J.K., Croll T.I., Castro-Hartmann P., Divitini G., Sader K., Hunter C.N. Cryo-EM Structure of the Rhodobacter sphaeroides Light-Harvesting 2 Complex at 2.1 A. Biochemistry. 2021;60:3302–3314. doi: 10.1021/acs.biochem.1c00576. PubMed DOI PMC

Hunter C.N. Anoxygenic Photosynthetic Bacteria. Advances in Photosynthesis and Respiration; Kluwer; Dordrecht, The Netherlands: 2004. Genetic Manipulation of the Antenna Complexes of Purple Bacteria; pp. 473–501.

Renger G. Primary Processes of Photosynthesis—Part 1, Priciples and Apparatus. RSC Publishing; Cambridge, UK: 2008.

Landrum J.T.E. Carotenoids: Physical, Chemical, and Biological Functions and Properties. 1st ed. CRC Press; Boca Raton, FL, USA: 2009. DOI

Kispert L.D., Focsan A.L. Chemistry of Carotenoid Radicals and Complexes. World Scietific; Singapore: 2024. DOI

Spezia R., Knecht S., Mennucci B. Excited state characterization of carbonyl containing carotenoids: A comparison between single and multireference descriptions. Phys. Chem. Chem. Phys. 2017;19:17156–17166. doi: 10.1039/C7CP02941A. PubMed DOI

Akimoto S., Yamazaki I., Sakawa T., Mimuro M. Temperature Effects on Excitation Relaxation Dynamics of the Carotenoid β-Carotene and Its Analogue β-Apo-8‘-carotenal, Probed by Femtosecond Fluorescence Spectroscopy. J. Phys. Chem. A. 2002;106:2237–2243. doi: 10.1021/jp0125653. DOI

Niedzwiedzki D.M., Sullivan J.O., Polívka T., Birge R.R., Frank H.A. Femtosecond Time-Resolved Transient Absorption Spectroscopy of Xanthophylls. J. Phys. Chem. B. 2006;110:22872–22885. doi: 10.1021/jp0622738. PubMed DOI

Tavan P., Schulten K. The low-lying electronic excitations in long polyenes: A PPP-MRD-CI study. J. Chem. Phys. 1986;85:6602–6609. doi: 10.1063/1.451442. DOI

Sashima T., Nagae H., Kuki M., Koyama Y. A new singlet-excited state of all-trans-spheroidene as detected by resonance-Raman excitation profiles. Chem. Phys. Lett. 1999;299:187–194. doi: 10.1016/S0009-2614(98)01278-0. DOI

Polívka T., Sundström V. Ultrafast dynamics of carotenoids excited states - From solution to natural and artificial systems. Chem. Rev. 2004;104:2021–2071. doi: 10.1021/cr020674n. PubMed DOI

Lang H.P., Hunter C.N. The relationship between carotenoid biosynthesis and the assembly of the light-harvesting LH2 complex in Rhodobacter sphaeroides. Biochem. J. 1994;298:197–205. doi: 10.1042/bj2980197. PubMed DOI PMC

Scheer H. Wiley Encyclopedia of Chemical Biology. John Wiley & Sons, Inc.; Hoboken, NJ, USA: 2008. Chlorophylls and Carotenoids, Chemistry of; pp. 1–11. DOI

Koyama Y., Rondonuwu F.S., Fujii R., Watanabe Y. Light-harvesting function of carotenoids in photo-synthesis: The roles of the newly found 11Bu− state. Biopolymers. 2004;74:2–18. doi: 10.1002/bip.20034. PubMed DOI

Kosumi D., Maruta S., Horibe T., Fujii R., Sugisaki M., Cogdell R.J., Hashimoto H. Ultrafast Energy-Transfer Pathway in a Purple-Bacterial Photosynthetic Core Antenna, as Revealed by Femtosecond Time-Resolved Spectroscopy. Angew. Chem. Int. Ed. 2011;50:1097–1100. doi: 10.1002/anie.201003771. PubMed DOI

Burke M., Land E.J., McGarvey D.J., Truscott T.G. Carotenoid triplet state lifetimes. J. Photochem. Photobil. B. 2000;59:132–138. doi: 10.1016/S1011-1344(00)00150-0. PubMed DOI

Papagiannakis E., van Stokkum I.H.M., van Grondelle R., Niederman R.A., Zigmantas D., Sundström V., Polívka T. A near-infrared transient absorption study of the excited-state dynamics of the carotenoid spirilloxanthin in solution and in the LH1 complex of Rhodospirillum rubrum. J. Phys. Chem. B. 2003;107:11216–11223. doi: 10.1021/jp034931j. DOI

Papagiannakis E., Das S.K., Gall A., van Stokkum I.H.M., Robert B., van Grondelle R., Frank H.A., Kennis J.T.M. Light harvesting by carotenoids incorporated into the B850 light-harvesting complex from Rhodobacter sphaeroides R-26.1: Excited-state relaxation, ultrafast triplet formation, and energy transfer to bacteriochlorophyll. J. Phys. Chem. B. 2003;107:5642–5649. doi: 10.1021/jp027174i. DOI

Rondonuwu F.S., Watanabe Y., Fujii R., Koyama Y. A first detection of singlet to triplet conversion from the 11Bu− to the 31Ag state and triplet internal conversion from the 31Ag to the 13Bu state in carotenoids: Dependence on the conjugation length. Chem. Phys. Lett. 2003;376:292–301. doi: 10.1016/S0009-2614(03)00983-7. DOI

Koyama Y., Kakitani Y. Mechanisms of carotenoid-to-bacteriochlorophyll energy transfer in the light harvesting antenna complexes 1 and 2: Dependence on the conjugation length of carotenoids. In: Grimm B., Porra R.J., Rüdiger W., Scheer H., editors. Chlorophylls and Bacteriochlorophylls. Springer; Dordrecht, The Netherlands: 2006.

Koyama Y., Kakitani Y., Watanabe Y. Photophysical Properties and Light-Harvesting and Photoprotective Functions of Carotenloids in Bacterial Photosynthesis: Structural Selections. In: Renger G., editor. Primary Processes of Photosynthesis—Part 1: Principles and Apparatus. RSC Publishing; Cambridge, UK: 2008. pp. 151–201.

Nakagawa K., Suzuki S., Fujii R., Gardiner A.T., Cogdell R.J., Nango M., Hashimoto H. Probing the effect of the binding site on the electrostatic behavior of a series of carotenoids reconstituted into the light-harvesting 1 complex from purple photosynthetic bacterium Rhodospirillum rubrum detected by stark spectroscopy. J. Phys. Chem. B. 2008;112:9467–9475. doi: 10.1021/jp801773j. PubMed DOI

Akahane J., Rondonuwu F.S., Fiedor L., Watanabe Y., Koyama Y. Dependence of singlet-energy transfer on the conjugation length of carotenoids reconstituted into the LH1 complex from Rhodospirillum rubrum G9+ Chem. Phys. Lett. 2004;393:184–191. doi: 10.1016/j.cplett.2004.06.021. DOI

Yamamoto M., Horibe T., Nishisaka Y., Suzuki S., Kozaki M., Fujii R., Doe M., Nango M., Okada K., Hashimoto H. Reassociation of All-trans-3,4-Dihydroanhydrorhodovibrin with LH1 Subunits Isolated from Rhodospirillum rubrum: Selective Binding of All-trans Isomer from Mixture of cis- and trans-Isomers. Bull. Chem. Soc. Jpn. 2013;86:121–128. doi: 10.1246/bcsj.20120230. DOI

Kakitani Y., Fujii R., Hayakawa Y., Kurahashi M., Koyama Y., Harada J., Shimada K. Selective Binding of Carotenoids with a Shorter Conjugated Chain to the LH2 Antenna Complex and Those with a Longer Conjugated Chain to the Reaction Center from Rubrivivax gelatinosus. Biochemistry. 2007;46:7302–7313. doi: 10.1021/bi602485x. PubMed DOI

Macpherson A.N., Arellano J.B., Fraser N.J., Cogdell R.J., Gillbro T. Efficient Energy Transfer from the Carotenoid S2 State in a Photosynthetic Light-Harvesting Complex. Biophys. J. 2001;80:923–930. doi: 10.1016/S0006-3495(01)76071-7. PubMed DOI PMC

Snellenburg J.J., Laptenok S.P., Seger R., Mullen K.M., van Stokkum I.H.M. Glotaran: A Java-Based Graphical User Interface for the R Package TIMP. J. Stat. Softw. 2012;49:1–22. doi: 10.18637/jss.v049.i03. DOI

Hashimoto H., Uragami C., Yukihira N., Horiuchi K., Cogdell R.J. Chapter One—Ultrafast laser spectroscopic studies on carotenoids in solution and on those bound to photosynthetic pigment-protein complexes. In: Wurtzel E.T., editor. Methods in Enzymology. Volume 674. Academic Press; Cambridge, MA, USA: 2022. pp. 1–51. PubMed

Niedzwiedzki D.M., Dilbeck P.L., Tang Q., Martin E.C., Bocian D.F., Hunter C.N., Holten D. New insights into the photochemistry of carotenoid spheroidenone in light-harvesting complex 2 from the purple bacterium Rhodobacter sphaeroides. Photosynth. Res. 2017;131:291–304. doi: 10.1007/s11120-016-0322-2. PubMed DOI PMC

Niedzwiedzki D.M., Swainsbury D.J.K., Hunter C.N. Carotenoid-to-(bacterio)chlorophyll energy transfer in LH2 antenna complexes from Rba. sphaeroides reconstituted with non-native (bacterio)chlorophylls. Photosynth. Res. 2020;144:155–169. doi: 10.1007/s11120-019-00661-6. PubMed DOI PMC

Kosumi D., Horibe T., Sugisaki M., Cogdell R.J., Hashimoto H. Photoprotection Mechanism of Light-Harvesting Antenna Complex from Purple Bacteria. J. Phys. Chem. B. 2016;120:951–956. doi: 10.1021/acs.jpcb.6b00121. PubMed DOI

Polívka T., Niedzwiedzki D., Fuciman M., Sundström V., Frank H.A. Role of B800 in carotenoid-bacteriochlorophyll energy and electron transfer in LH2 complexes from the purple bacterium Rhodobacter sphaeroides. J. Phys. Chem. B. 2007;111:7422–7431. doi: 10.1021/jp071395c. PubMed DOI

Kosumi D., Maruta S., Fujii R., Kanemoto K., Sugisaki M., Hashimoto H. Ultrafast excited state dynamics of monomeric bacteriochlorophyll a. Phys. Status Solidi C. 2011;8:92–95. doi: 10.1002/pssc.201000684. DOI

Uragami C., Sato H., Yukihira N., Fujiwara M., Kosumi D., Gardiner A.T., Cogdell R.J., Hashimoto H. Photoprotective mechanisms in the core LH1 antenna pigment-protein complex from the purple photosynthetic bacterium, Rhodospirillum rubrum. J. Photochem. Photobiol. A Chem. 2020;400:112628. doi: 10.1016/j.jphotochem.2020.112628. DOI

Cohen-Bazire G., Sistrom W.R., Stanier R.Y. Kinetic studies of pigment synthesis by non-sulfur purple bacteria. J. Cell. Comp. Physiol. 1957;49:25–68. doi: 10.1002/jcp.1030490104. PubMed DOI

Davidson E., Cogdell R.J. Reconstitution of carotenoids into the light-harvesting pigment-protein complex from the carotenoidless mutant of Rhodopseudomonas sphaeroides R26. Biochim. Biophys. Acta—Bioenerg. 1981;635:295–303. doi: 10.1016/0005-2728(81)90028-1. PubMed DOI

Fujii R., Onaka K., Kuki M., Koyama Y., Watanabe Y. The 2Ag− energies of all-trans-neurosporene and spheroidene as determined by fluorescence spectroscopy. Chem. Phys. Lett. 1998;288:847–853. doi: 10.1016/S0009-2614(98)00376-5. DOI

Saga Y., Hirota K. Determination of the Molar Extinction Coefficients of the B800 and B850 Absorption Bands in Light-harvesting Complexes 2 Derived from Three Purple Photosynthetic Bacteria Rhodoblastus acidophilus, Rhodobacter sphaeroides, and Phaeospirillum molischianum by Extraction of Bacteriochlorophyll a. Anal. Sci. 2016;32:801–804. doi: 10.2116/analsci.32.801. PubMed DOI

Nishizawa E., Koyama Y. The T1 Raman spectra of bacteriochlorophyll a: Changes in the bond orders of the conjugated macrocycle upon triplet excitation. Chem. Phys. Lett. 1990;172:317–322. doi: 10.1016/0009-2614(90)85411-5. DOI