Fluorescence kinetics of emission from a small finite volume of a biological system |
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| Authors: | AJ Dagen RR Alfano BA Zilinskas CE Swenberg |
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| Institution: | Institute for Ultrafast and Lasers, Department of Physics, The City College, New York 10031, USA;Department of Biochemistry and Microbiology, Cook College, Rutgers University, New Brunswick, New Jersey 08903, USA;Radiation Sciences Department, Armed Forces Radiobiology Research Institute, Bethesda, Maryland 20814, USA |
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| Abstract: | The fluorescence decay, apparent quantum yield and transmission from chromophores constrained to a microscopic volume using a single picosecond laser excitation were measured as a function of incident intensity. The β subunit of phycoeryhthrin aggregate isolated from the photosynthetic antenna system of Nostoc sp. was selected since it contains only four chromophores in a volume of less than 5.6×104 Å3. The non-exponential fluorescence decay profiles were intensity independent for the intensity range studied (5 × 1013 - 2 × 1015 photon cm?2 per pulse). The apparent decrease in the relative fluorescence quantum yield and increase of the relative transmission with increasing excitation intensity is attributed to the combined effects of ground state depletion and upper excited state absorption. Evidence suggests that exciton annihilation is absent within isolated β subunits. |
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