PT - JOURNAL ARTICLE AU - John O. Onukwufor AU - Adam J. Trewin AU - Timothy M. Baran AU - Anmol Almast AU - Thomas H. Foster AU - Andrew P. Wojtovich TI - Quantification of reactive oxygen species production by the red fluorescent proteins KillerRed, SuperNova and mCherry AID - 10.1101/777417 DP - 2019 Jan 01 TA - bioRxiv PG - 777417 4099 - http://biorxiv.org/content/early/2019/09/20/777417.short 4100 - http://biorxiv.org/content/early/2019/09/20/777417.full AB - Fluorescent proteins can generate reactive oxygen species (ROS) upon absorption of photons via type I and II photosensitization mechanisms. The red fluorescent proteins KillerRed and SuperNova are phototoxic proteins engineered to generate ROS and are used in a variety of biological applications. However, their relative quantum yields and rates of ROS production are unclear, which has limited the interpretation of their effects when used in biological systems. We cloned and purified KillerRed, SuperNova, and mCherry - a related red fluorescent protein not typically considered a photosensitizer - and measured the superoxide (O2 •-) and singlet oxygen (1O2) quantum yields with irradiation at 561 nm. The formation of the O2 •--specific product 2-hydroxyethidium (2-OHE+) was quantified via HPLC separation with fluorescence detection. Relative to a reference photosensitizer, Rose Bengal, the O2 •- quantum yield (ΦO2 •-) of SuperNova was determined to be 0.00150, KillerRed was 0.00097, and mCherry 0.00120. At an excitation fluence of 916.5 J/cm2 and matched absorption at 561 nm, SuperNova, KillerRed and mCherry made 3.81, 2.38 and 1.65 μM O2 •-/min, respectively. Using the probe Singlet Oxygen Sensor Green (SOSG), we ascertained the 1O2 quantum yield (Φ1O2) for SuperNova to be 0.0220, KillerRed 0.0076, and mCherry 0.0057. These photosensitization characteristics of SuperNova, KillerRed and mCherry improve our understanding of fluorescent proteins and are pertinent for refining their use as tools to advance our knowledge of redox biology.2-OHE+2-hydroxyethidiumCALIChromophore assisted light inactivationDHE+DihydroethidiumE+EthidiumO2•-Superoxide1O2Singlet oxygenΦQuantum yieldΦO2•-Superoxide quantum yieldΦ1O2Singlet oxygen quantum yieldROSReactive oxygen speciesSOSGSinglet oxygen sensor greenSODSuperoxide dismutaseXXanthineXOXanthine oxidase