Fate of the fluorescent state of p-amido analogue of green fluorescence protein chromophore

Yi Hui Chen, Robert Sung, Kuangsen Sung

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6 Citations (Scopus)


When the wild-type green fluorescent protein (wtGFP) chromophore, p-hydroxybenzylidene-imidazolinone (p-HBDI), was modified into various analogues, its fluorescent state and relaxation pathways were also changed dramatically. In contrast to p-HBDI and its various analogues, such as the o-hydroxy analogue (o-HBDI), the o-sulfonamide analogue (o-TsABDI), the p-sulfonamide analogue (p-TsABDI) and the p-amino analogue (p-ABDI), the p-amido analogue (p-AABDI) of wtGFP chromophore displays single fluorescence and its electronic absorption and fluorescence emission do not involve a charge transfer. Its ground-state N–H acid strength (pKa) is 19.6 in DMSO, which is not very acidic, so, unlike p-TsABDI, p-AABDI does not undergo an excited-state proton transfer. Its S1 excited state decays mainly along τ torsion through the S1/S0 conical intersection with a barrier of 2.8 kcal/mol. This was confirmed by the cis-trans photoisomerization experiment, in which 47% of cis-p-AABDI was converted to its trans-form right after 20 min irradiation with 350 nm UV light.

Original languageEnglish
Pages (from-to)446-450
Number of pages5
JournalJournal of Luminescence
Publication statusPublished - 2019 Sept

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Atomic and Molecular Physics, and Optics
  • General Chemistry
  • Biochemistry
  • Condensed Matter Physics


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