title: Ultraviolet fluorescence of coelenteramide and coelenteramide-containing fluorescent proteins. Experimental and theoretical study.
abstract: Coelenteramide-containing fluorescent proteins are products of bioluminescent reactions of marine coelenterates. They are called 'discharged photoproteins'. Their light-induced fluorescence spectra are variable, depending considerably on external conditions. Current work studies a dependence of light-induced fluorescence spectra of discharged photoproteins obelin, aequorin, and clytin on excitation energy. It was demonstrated that photoexcitation to the upper electron-excited states (260-300nm) of the discharged photoproteins initiates a fluorescence peak in the near UV region, in addition to the blue-green emission. To characterize the UV fluorescence, the light-induced fluorescence spectra of coelenteramide (CLM), fluorophore of the discharged photoproteins, were studied in methanol solution. Similar to photoproteins, the CLM spectra depended on photoexcitation energy; the additional peak (330nm) in the near UV region was observed in CLM fluorescence at higher excitation energy (260-300nm). Quantum chemical calculations by time depending method with B3LYP/cc-pVDZ showed that the conjugated pyrazine-phenolic fragment and benzene moiety of CLM molecule are responsible for the additional UV fluorescence peak. Quantum yields of CLM fluorescence in methanol were 0.028±0.005 at 270-340nm photoexcitation. A conclusion was made that the UV emission of CLM might contribute to the UV fluorescence of the discharged photoproteins. The study develops knowledge on internal energy transfer in biological structures - complexes of proteins with low-weight aromatic molecules.
authors.affiliation: Institute of Biophysics SB RAS, Akademgorodok 50/50, Krasnoyarsk 660036, Russia.
authors.forename: Roza R
authors.initials: RR
authors.lastname: Alieva
authors.affiliation: Institute of Physics SB RAS, Akademgorodok 50/38, Krasnoyarsk, 660036, Russia; Siberian Federal University, Svobodny Prospect 79, Krasnoyarsk 660041, Russia.
authors.forename: Felix N
authors.initials: FN
authors.lastname: Tomilin
authors.affiliation: Siberian Federal University, Svobodny Prospect 79, Krasnoyarsk 660041, Russia.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Kuzubov
authors.affiliation: Institute of Physics SB RAS, Akademgorodok 50/38, Krasnoyarsk, 660036, Russia; Siberian Federal University, Svobodny Prospect 79, Krasnoyarsk 660041, Russia.
authors.forename: Sergey G
authors.initials: SG
authors.lastname: Ovchinnikov
authors.affiliation: Institute of Biophysics SB RAS, Akademgorodok 50/50, Krasnoyarsk 660036, Russia; Siberian Federal University, Svobodny Prospect 79, Krasnoyarsk 660041, Russia. Electronic address: n_qdr@yahoo.com.
authors.forename: Nadezhda S
authors.initials: NS
authors.lastname: Kudryasheva
mesh_terms: D044482:Benzeneacetamides / Q000737:chemistry*; D008164:Luminescent Proteins / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D008958:Models, Molecular; D011487:Protein Conformation; D011719:Pyrazines / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D044482:Benzeneacetamides; D008164:Luminescent Proteins; D011719:Pyrazines; C542661:coelenteramide; D000432:Methanol
keywords: Aequorin; B3LYP; Coelenteramide; Discharged photoproteins; Excitation energy; Fluorescence; Fluorescent protein; Obelin