Fluorescence and phosphorescence of tryptophan in peptides of different length and sequence

To interpret accurately protein fluorescence and phosphorescence, it is essential to achieve a better understanding of the luminescence properties of tryptophan (Trp, or W) in peptides. In published literature data on luminescence of peptides of varied length are scarce. This article describes studi...

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Bibliographic Details
Published in:Journal of photochemistry and photobiology. B, Biology Biology, 2016-04, Vol.157, p.120-128
Main Authors: Radotić, Ksenija, Melø, Thor Bernt, Leblanc, Roger M., Yousef, Yaser A., Naqvi, K. Razi
Format: Article
Language:English
Subjects:
Luminescence
Peptides
Peptides - chemistry
Phosphorescence
Spectrometry, Fluorescence
Steady state fluorescence
Time resolved fluorescence
Tryptophan
Tryptophan - chemistry
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Summary:To interpret accurately protein fluorescence and phosphorescence, it is essential to achieve a better understanding of the luminescence properties of tryptophan (Trp, or W) in peptides. In published literature data on luminescence of peptides of varied length are scarce. This article describes studies of fluorescence and phosphorescence properties of the eight Trp-containing synthetic peptides: WAK, AWK, SWA, KYLWE, AVSWK, WVSWAK, WAKLAWE, and AVSWAKLARE. The aim was to investigate which factors influence the fluorescence yield and phosphorescence-spectra and lifetimes. Absorption spectra, room temperature fluorescence emission and corresponding excitation spectra and time-resolved phosphorescence spectra (77K) have been recorded; the dependence of the fluorescence quantum yield on the specific peptide and its variation with the wavelength of excitation has been studied. The changes in fluorescence yield and shape of phosphorescence spectra are explained in terms of internal electron and proton transfer. The structured phosphorescence spectrum originates from proton transfer occurring upon excitation of Trp, while electron transfer gives rise to a non-structured luminescence spectrum. There is also electron transfer from higher vibronic S1 states. In the peptides there is higher probability of electron transfer than in Trp alone. The obtained data are interpreted in light of the peptides' sequence, length and conformation. [Display omitted] •All peptides and Trp show double exponential decay of fluorescence and luminescence.•Both short and long fluorescence lifetimes increase with peptide length.•Peptides' luminescence spectrum contains a structured and a non-structured component.•Unstructured and structured spectrum decay with short and long lifetime respectively.•Amplitudes of long fluorescence lifetime and short luminescence lifetime are similar.
ISSN:1011-1344
1873-2682
DOI:10.1016/j.jphotobiol.2016.02.011