title: Carotenoid-to-Bacteriochlorophyll Energy Transfer in the LH1-RC Core Complex of a Bacteriochlorophyll b Containing Purple Photosynthetic Bacterium Blastochloris viridis.
abstract: Carotenoid-to-bacteriochlorophyll energy transfer has been widely investigated in bacteriochlorophyll (BChl) a-containing light harvesting complexes. Blastochloris viridis utilizes BChl b, whose absorption spectrum is more red-shifted than that of BChl a. This has implications on the efficiency and pathways of carotenoid-to-BChl energy transfer in this organism. The carotenoids that comprise the light-harvesting reaction center core complex (LH1-RC) of B. viridis are 1,2-dihydroneurosporene and 1,2-dihydrolycopene, which are derivatives of carotenoids found in the light harvesting complexes of several BChl a-containing purple photosynthetic bacteria. Steady-state and ultrafast time-resolved optical spectroscopic measurements were performed on the LH1-RC complex of B. viridis at room and cryogenic temperatures. The overall efficiency of carotenoid-to-bacteriochlorophyll energy transfer obtained from steady-state absorption and fluorescence measurements were determined to be ∼27% and ∼36% for 1,2-dihydroneurosporene and 1,2-dihydrolycopene, respectively. These results were combined with global fitting and target analyses of the transient absorption data to elucidate the energetic pathways by which the carotenoids decay and transfer excitation energy to BChl b. 1,2-Dihydrolycopene transfers energy to BChl b via the S2 → Qx channel with kET2 = (500 fs)(-1) while 1,2-dihydroneurosporene transfers energy via S1→ Qy (kET1 = (84 ps)(-1)) and S2 → Qx (kET2 = (2.2 ps)(-1)) channels.
authors.affiliation: Department of Biology, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.|Department of Chemistry, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.|Photosynthetic Antenna Research Center, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.
authors.forename: Nikki Cecil M
authors.initials: NC
authors.lastname: Magdaong
authors.affiliation: Photosynthetic Antenna Research Center, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.
authors.forename: Dariusz M
authors.initials: DM
authors.lastname: Niedzwiedzki
authors.affiliation: Department of Biology, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.
authors.forename: Carrie
authors.initials: C
authors.lastname: Goodson
authors.affiliation: Department of Biology, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.|Department of Chemistry, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.|Photosynthetic Antenna Research Center, Washington University in Saint Louis , One Brookings Drive, St. Louis, Missouri 63130 United States.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001429:Bacteriochlorophylls / Q000737:chemistry*; D002338:Carotenoids / Q000737:chemistry*; D004735:Energy Transfer; D041921:Hyphomicrobiaceae / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D010788:Photosynthesis; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; C107900:bacteriochlorophyll b; D002338:Carotenoids