Contrasting the excited-state dynamics of the photoactive yellow protein chromophore: protein versus solvent environments.
Wavelength- and time-resolved fluorescence experiments have been performed on the photoactive yellow protein, the E46Q mutant, the hybrids of these proteins containing a nonisomerizing "locked" chromophore, and the native and locked chromophores in aqueous solution. The ultrafast dynamics of these six systems is compared and spectral signatures of isomerization and solvation are discussed. We find that the ultrafast red-shifting of fluorescence is associated mostly with solvation dynamics, whereas isomerization manifests itself as quenching of fluorescence. The observed multiexponential quenching of the protein samples differs from the single-exponential lifetimes of the chromophores in solution. The locked chromophore in the protein environment decays faster than in solution. This is due to additional channels of excited-state energy dissipation via the covalent and hydrogen bonds with the protein environment. The observed large dispersion of quenching timescales observed in the protein samples that contain the native pigment favors both an inhomogeneous model and an excited-state barrier for isomerization.
Vengris
Mikas
M
Faculty of Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
van der Horst
Michael A
MA
Zgrablic
Goran
G
van Stokkum
Ivo H M
IH
Haacke
Stefan
S
Chergui
Majed
M
Hellingwerf
Klaas J
KJ
van Grondelle
Rienk
R
Larsen
Delmar S
DS
D001426:Bacterial Proteins / Q000737:chemistry*; D055592:Biophysical Phenomena; D001703:Biophysics; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008856:Microscopy, Fluorescence / Q000379:methods*; D008956:Models, Chemical; D015233:Models, Statistical; D016011:Normal Distribution; D020283:Photoreceptors, Microbial / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman; D013997:Time Factors
D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria