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

Noel Boens; Luc D. Janssens; Luc Van Dommelen; Frans C. De Schryver; Jacques Gallay

doi:10.1117/12.58201

1 April 1992 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 deuterium isotope effect

Noel Boens, Luc D. Janssens, Luc Van Dommelen, Frans C. De Schryver, Jacques Gallay

Author Affiliations +

Proceedings Volume 1640, Time-Resolved Laser Spectroscopy in Biochemistry III; (1992) https://doi.org/10.1117/12.58201
Event: OE/LASE '92, 1992, Los Angeles, CA, United States

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.

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Noel Boens, Luc D. Janssens, Luc Van Dommelen, Frans C. De Schryver, and Jacques Gallay "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 deuterium isotope effect", Proc. SPIE 1640, Time-Resolved Laser Spectroscopy in Biochemistry III, (1 April 1992); https://doi.org/10.1117/12.58201

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