Ultrafast fluorescence dynamics of tryptophan in the proteins monellin and IIAGlc.
The complete time-resolved fluorescence of tryptophan in the proteins monellin and IIA(Glc) has been investigated, using both an upconversion spectrophotofluorometer with 150 fs time resolution and a time-correlated single photon counting apparatus on the 100 ps to 20 ns time scale. In monellin, the fluorescence decay displays multiexponential character with decay times of 1.2 and 16 ps, and 0.6, 2.2, and 4.2 ns. In contrast, IIA(Glc) exhibited no component between 1.2 ps and 0.1 ns. For monellin, surprisingly, the 16 ps fluorescence component was found to have positive amplitude even at longer wavelengths (e.g., 400 nm). In conjunction with quantum mechanical simulation of tryptophan in monellin, the experimental decay associated spectra (DAS) and time-resolved emission spectra (TRES) indicate that this fluorescence decay time should be ascribed to a highly quenched conformer. Recent models (Peon, J.; et al. Proc. Natl.Acad. Sci. U.S.A. 2002, 99, 10964) invoked exchange-coupled relaxation of protein water to explain the fluorescence decay of monellin.
Xu
Jianhua
J
Optical Spectroscopy Section, Laboratory of Biophysical Chemistry, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1412, USA.
Toptygin
Dmitri
D
Graver
Karen J
KJ
Albertini
Rebecca A
RA
Savtchenko
Regina S
RS
Meadow
Norman D
ND
Roseman
Saul
S
Callis
Patrik R
PR
Brand
Ludwig
L
Knutson
Jay R
JR
D029968:Escherichia coli Proteins / Q000737:chemistry*; D007700:Kinetics; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D014364:Tryptophan / Q000737:chemistry*
D029968:Escherichia coli Proteins; D010940:Plant Proteins; C032242:crr protein, E coli; C002541:monellin protein, Dioscoreophyllum cumminsii; D014364:Tryptophan; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System