title: Up-converted fluorescence from photosynthetic light-harvesting complexes linearly dependent on excitation intensity.
abstract: Weak up-converted fluorescence related to bacteriochlorophyll a was recorded from various detergent-isolated and membrane-embedded light-harvesting pigment-protein complexes as well as from the functional membranes of photosynthetic purple bacteria under continuous-wave infrared laser excitation at 1064 nm, far outside the optically allowed singlet absorption bands of the chromophore. The fluorescence increases linearly with the excitation power, distinguishing it from the previously observed two-photon excited fluorescence upon femtosecond pulse excitation. Possible mechanisms of this excitation are discussed.
authors.affiliation: Institute of Physics, University of Tartu, Ravila 14c, 51011, Tartu, Estonia. Kristjan.Leiger@ut.ee.
authors.forename: Kristjan
authors.initials: K
authors.lastname: Leiger
authors.affiliation: Institute of Physics, University of Tartu, Ravila 14c, 51011, Tartu, Estonia. arvi.freiberg@ut.ee.|Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51014, Tartu, Estonia. arvi.freiberg@ut.ee.
authors.forename: Arvi
authors.initials: A
authors.lastname: Freiberg
mesh_terms: D025541:Bacteriochlorophyll A / Q000737:chemistry / Q000378:metabolism; D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism; D005292:Ferricyanides / Q000737:chemistry; D005453:Fluorescence; D007834:Lasers; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D017785:Photons; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D025541:Bacteriochlorophyll A; D005292:Ferricyanides; D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids; C028033:potassium ferricyanide
keywords: Bacteriochlorophyll a; Delayed fluorescence; Fluorescence; Triplet–triplet annihilation; Two-photon excitation; Two-step excitation