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FLUORESCENCE QUANTUM YIELDS OF 124‐kDa PHYTOCHROME FROM OAT UPON EXCITATION WITHIN DIFFERENT ABSORPTION BANDS
Author(s) -
Colombano Claudio G.,
Braslavsky Silvia E.,
Holzwarth Alfred R.,
Schaffner Kurt
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01749.x
Subject(s) - quantum yield , fluorescence , chromophore , excited state , absorption (acoustics) , avena , phytochrome , chemistry , excitation , etiolation , relaxation (psychology) , analytical chemistry (journal) , photochemistry , materials science , atomic physics , physics , optics , red light , biology , botany , biochemistry , quantum mechanics , chromatography , neuroscience , composite material , enzyme
— A fluorescence quantum yield (emission at650–850 nm) of π= (2.3 ± 0.3)10 −3 was measured for the red‐absorbing form (Pr) of 124‐kDa phytochrome from etiolated oat seedlings ( Avena sativa ) upon excitation in the Soret band at Λ exc = 380 nm. The small difference between this value and the previously determined quantum yield with Λ exc = 640 nm, π= (3.5 ± 0.4)10 −3 is attributed to a blue‐absorbing emitter responsible for the “anomalous” or “blue” emission of the chromoprotein in the region from ca. 400 to 550 nm. The absorption of Pr at 380 nm is consequently somewhat lower than that measured directly from the spectrum. Processes from upper excited states of the Pr phytochromobilin‐derived chromophore other than rapid relaxation to the emitting state are not important. A quantum yield of Φ ' 1.2 times 10 −3 is estimated for the blue fluorescence. The proportion of the blue emitters relative to Pr appears to be relatively high.