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COMPARATIVE PHOTOCHEMICAL ANALYSIS OF HIGHLY PURIFIED 124 KILODALTON OAT and RYE PHYTOCHROMES in vitro
Author(s) -
Lagarias J. Clark,
Kelly John M.,
Cyr Karen L.,
Smith William O.
Publication year - 1987
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.1751-1097.1987.tb04729.x
Subject(s) - phytochrome , absorption (acoustics) , kilodalton , chemistry , absorption spectroscopy , fluence , analytical chemistry (journal) , chromatography , botany , red light , biology , biochemistry , optics , ion , physics , organic chemistry , gene
A direct comparison of the photochemical interconversions between red (P r ‐) and far‐red (P fr ‐) absorbing forms of highly‐purified 124 kDa oat and rye phytochromes under identical experimental conditions was performed. In two different buffer systems at 5°C, the quantum yields for the P r to P tr and P fr to P r phototransformations under constant red and far‐red illumination, φ r and φ fr respectively, were determined to be 0.152‐0.154 and 0.060‐0.065 for oat preparations and 0.172‐0.174 and 0.074‐0.078 for rye preparations. These values as well as the wavelength dependence of the photoequilibrium produced under continuous illumination throughout the visible and near‐ultraviolet spectrum were based on the absorption spectra of the two phytochrome preparations and revised molar absorption coefficients. The molar absorption coefficients were estimated by quantitative amino acid analysis and shown to be identical for the two monocot phytochromes (i.e. 132 mM −1 cm −1 at the red absorption maximum for the P r form). Because these measurements were performed under identical experimental conditions, including buffer, temperature, light fluence rate, and instrumentation, the differences observed must reflect structural features inherent to the two different monocotyledonous phytochromes.