title: Ultra-broadband 2D electronic spectroscopy of carotenoid-bacteriochlorophyll interactions in the LH1 complex of a purple bacterium.
abstract: We investigate the excitation energy transfer (EET) pathways in the photosynthetic light harvesting 1 (LH1) complex of purple bacterium Rhodospirillum rubrum with ultra-broadband two-dimensional electronic spectroscopy (2DES). We employ a 2DES apparatus in the partially collinear geometry, using a passive birefringent interferometer to generate the phase-locked pump pulse pair. This scheme easily lends itself to two-color operation, by coupling a sub-10 fs visible pulse with a sub-15-fs near-infrared pulse. This unique pulse combination allows us to simultaneously track with extremely high temporal resolution both the dynamics of the photoexcited carotenoid spirilloxanthin (Spx) in the visible range and the EET between the Spx and the B890 bacterio-chlorophyll (BChl), whose Qx and Qy transitions peak at 585 and 881 nm, respectively, in the near-infrared. Global analysis of the one-color and two-color 2DES maps unravels different relaxation mechanisms in the LH1 complex: (i) the initial events of the internal conversion process within the Spx, (ii) the parallel EET from the first bright state S2 of the Spx towards the Qx state of the B890, and (iii) the internal conversion from Qx to Qy within the B890.
authors.affiliation: CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Maiuri
authors.affiliation: CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133, Italy.
authors.forename: Julien
authors.initials: J
authors.lastname: Réhault
authors.affiliation: Glasgow Biomedical Research Centre, IBLS, University of Glasgow, 126 Place, Glasgow G12 8TA, Scotland, United Kingdom.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Carey
authors.affiliation: Glasgow Biomedical Research Centre, IBLS, University of Glasgow, 126 Place, Glasgow G12 8TA, Scotland, United Kingdom.
authors.forename: Kirsty
authors.initials: K
authors.lastname: Hacking
authors.affiliation: Dipartimento di Chimica "G. Ciamician," Università di Bologna, Via Selmi 2, IT-40126 Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Garavelli
authors.affiliation: Madrid Institute for Advanced Studies, IMDEA Nanociencia, Madrid, Spain.
authors.forename: Larry
authors.initials: L
authors.lastname: Lüer
authors.affiliation: CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Polli
authors.affiliation: Glasgow Biomedical Research Centre, IBLS, University of Glasgow, 126 Place, Glasgow G12 8TA, Scotland, United Kingdom.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
authors.affiliation: CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry* / Q000378:metabolism; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D012247:Rhodospirillum rubrum / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis
chemical_list: D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids