Fluorescent coelenteramide-containing protein as a color bioindicator for low-dose radiation effects

The study addresses the application of fluorescent coelenteramide-containing proteins as color bioindicators for radiotoxicity evaluation. Biological effects of chronic low-dose radiation are under investigation. Tritiated water (200 MBq/L) was used as a model source of low-intensive ionizing radiation of beta type. 'Discharged obelin,' product of bioluminescent reaction of marine coelenterate Obelia longissimi, was used as a representative of the coelenteramide-containing proteins. Coelenteramide, fluorophore of discharged obelin, is a photochemically active molecule; it produces fluorescence forms of different color. Contributions of 'violet' and 'blue-green' forms to the visible fluorescence serve as tested parameters. The contributions depend on the coelenteramide's microenvironment in the protein, and, hence, evaluate distractive ability and toxicity of radiation. The protein samples were exposed to beta radiation for 18 days, and maximal dose accumulated by the samples was 0.28 Gy, being close to a tentative limit of a low-dose interval. Increase of relative contribution of 'violet' fluorescence under exposure to the beta irradiation was revealed. High sensitivity of the protein-based test system to low-dose ionizing radiation (to 0.03 Gy) was demonstrated. The study develops physicochemical understanding of radiotoxic effects. Graphical abstract Coelenteramide-containing protein (discharged obelin) changes fluorescence color under exposure to low-dose ionizing radiation of tritium.