Photoconversion in the red fluorescent protein from the sea anemone Entacmaea quadricolor. Is cis-trans isomerization involved?

Davey C. Loos, Satoshi Habuchi*, Cristina Flors, Jun Ichi Hotta, Jörg Wiedenmann, G. Ulrich Nienhaus, Johan Hofkens

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Proteins from the family of the green fluorescent protein (GFP) are presently extensively used in molecular and cellular biology. Recent studies suggest that isomerization of the chromophore occurs upon excitation and is involved in nonradiative deactivation. Using Raman spectroscopy, we report on photoinduced cis-trans isomerization in the red fluorescent protein eqFP611 from the sea anemone Entacmaea quadricolor. The crystal structure of eqFP611 shows that the chemical structure of the chromophore, p-hydroxybenzylidene-imidazolinone with an extended π-conjugated system, is nearly identical to the chromophore of other red fluorescent proteins such as DsRed and HcRed. However, the chromophore of eqFP611 has a trans configuration whereas the chromophore of DsRed has a cis configuration. Upon irradiation with 532-nm light, the absorption of eqFP611 peaking at 559 nm diminished, and concomitantly a drastic decrease in the quantum yield of fluorescence as well as more complex decay kinetics was observed. Upon irradiation, changes in the Raman spectrum of eqFP611 were observed, and the relative intensities and peak positions of the irradiated eqFP611 showed striking similarity with the peaks in the Raman spectrum of DsRed. These observations are tentatively interpreted as trans-to-cis isomerization of the chromophore taking place upon irradiation together with the opening of new, nonradiative pathways.

Original languageEnglish (US)
Pages (from-to)6270-6271
Number of pages2
JournalJournal of the American Chemical Society
Issue number19
StatePublished - May 17 2006

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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