Natural abundance solution 13C NMR studies of a phototropin with photoinduced polarization.
Strongly spin-polarized 13C NMR lines have been observed upon photoexcitation of FMN-binding LOV domains from the blue-light receptor phototropin. Their origin can be rationalized in terms of intermediate radical-pair spin chemistry. Due to hyperfine-selective branching into singlet and triplet products of different lifetime, nuclear spin polarization builds up on nuclei that possess high electron-spin density in the radical state. By examining point-mutated LOV domains of phototropin, spin-polarized 13C NMR signals in emission arising from 13C nuclei at natural abundance in the apoprotein can be unambiguously assigned to a tryptophan residue that is located at a distance of about 14 A from the FMN cofactor and that undergoes photoinduced electron transfer to the flavin. This demonstrates the potential of photo-CIDNP in unraveling reactive intermediates in protein function.
Eisenreich
Wolfgang
W
Technische Universität München, Lehrstuhl für Biochemie, Lichtenbergstr. 4, 85747 Garching, Germany. wolfgang.eisenreich@ch.tum.de
Joshi
Monika
M
Weber
Stefan
S
Bacher
Adelbert
A
Fischer
Markus
M
D002247:Carbon Isotopes; D056931:Cryptochromes; D005420:Flavoproteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010777:Photochemistry
D002247:Carbon Isotopes; D056931:Cryptochromes; D005420:Flavoproteins