The Primary Photophysics of the Avena sativa Phototropin 1 LOV2 Domain Observed with Time-resolved Emission Spectroscopy

The phototropins are blue‐light receptors that base their light‐dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine in light, oxygen or voltage (LOV) domains. The primary reactions of the Avena sativa phototropin 1 L...

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Bibliographic Details
Published in:Photochemistry and photobiology 2011-05, Vol.87 (3), p.534-541
Main Authors: van Stokkum, Ivo H. M., Gauden, Magdalena, Crosson, Sean, van Grondelle, Rienk, Moffat, Keith, Kennis, John T. M.
Format: Article
Language:English
Subjects:
Aqueous solutions
Avena - chemistry
Avena - metabolism
Cold Temperature
Cysteine - metabolism
Emission spectroscopy
Flavin Mononucleotide - metabolism
Flavoproteins - chemistry
Flavoproteins - metabolism
Fluorescence
Hydrogen-Ion Concentration
Light
Low temperature
Luminescent Measurements
Models, Molecular
Oats
Photobiology
Photochemistry
Photoelectron Spectroscopy
Phototropins - chemistry
Phototropins - metabolism
Plant Proteins - chemistry
Plant Proteins - metabolism
Protein Structure, Tertiary
Proteins
Spectrometry, Fluorescence
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Summary:The phototropins are blue‐light receptors that base their light‐dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine in light, oxygen or voltage (LOV) domains. The primary reactions of the Avena sativa phototropin 1 LOV2 domain were investigated by means of time‐resolved and low‐temperature fluorescence spectroscopy. Synchroscan streak camera experiments revealed a fluorescence lifetime of 2.2 ns in LOV2. A weak long‐lived component with emission intensity from 600 to 650 nm was assigned to phosphorescence from the reactive FMN triplet state. This observation allowed determination of the LOV2 triplet state energy level at physiological temperature at 16600 cm−1. FMN dissolved in aqueous solution showed pH‐dependent fluorescence lifetimes of 2.7 ns at pH 2 and 3.9−4.1 ns at pH 3–8. Here, too, a weak phosphorescence band was observed. The fluorescence quantum yield of LOV2 increased from 0.13 to 0.41 upon cooling the sample from 293 to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K in the steady‐state emission.
ISSN:0031-8655
1751-1097
DOI:10.1111/j.1751-1097.2011.00903.x