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Photophysics of tryptophan: global analysis of the fluorescence decay surface as a function of pH, temperature, quencher concentration, excitation and emission wavelengths, timing calibration and de
Author(s): Noel Boens; Luc D. Janssens; Luc Van Dommelen; Frans C. De Schryver; Jacques Gallay
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Paper Abstract

The fluorescence decay surface of tryptophan measured over a very wide pH range (1.35 to 12.38) was analyzed in a single global analysis. It is clear that the decay components remain the same over the whole pH range. This is also confirmed by the decay-associated emission spectra. At low pH the decays are biexponential and both decay components contribute to the fluorescence up to pH 11. From about pH 7.5 onwards a third component has to be taken into account which becomes the only component at pH > 11. The decay times decrease at low pH due to quenching by H3O+. At pH > 11 the decay times decline due to quenching by OH-. Decays collected at different temperatures at neutral pH indicate that the short decay time is independent of temperature, both in H2O and D2O solution. Both decay times increase by a factor of two when H2O is replaced by D2O as solvent. The decay times and their normalized pre-exponential terms at neutral pH in H2O solution are constant as a function of excitation wavelength (from 250 to 295 nm). This indicates that the absorption spectra associated with the two ground-state species overlap completely and that the contribution of both species to the total absorption remains constant over the whole absorption spectrum.

Paper Details

Date Published: 1 April 1992
PDF: 12 pages
Proc. SPIE 1640, Time-Resolved Laser Spectroscopy in Biochemistry III, (1 April 1992); doi: 10.1117/12.58201
Show Author Affiliations
Noel Boens, Katholieke Univ. Leuven (Belgium)
Luc D. Janssens, Katholieke Univ. Leuven (Belgium)
Luc Van Dommelen, Katholieke Univ. Leuven (Belgium)
Frans C. De Schryver, Katholieke Univ. Leuven (Belgium)
Jacques Gallay, Univ. Paris-Sud (France)

Published in SPIE Proceedings Vol. 1640:
Time-Resolved Laser Spectroscopy in Biochemistry III
Joseph R. Lakowicz, Editor(s)

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