Characterization of a Bio-sourced, Fluorescent, Ratiometric pH Indicator with Alkaline pK a

• Published in: Photochemistry and photobiology Vol. 96; no. 6; pp. 1176 - 1181
• Main Authors: Alheety, Samar, Valenti, Domenic, Mujumdar, Nirvani, Ellis, Nakita, Campiglia, Andres D, Harper, James K, Heider, Emily C
• Format: Journal Article
• Language: English
• Published: United States 01.11.2020
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.13299

Utilizing organisms as sources of fluorophores relieves the demand for petroleum feedstock in organic synthesis of fluorescent products, and endophytic fungi provide a promising vein for natural fluorescent products. We report the characterization of a pH-responsive fluorophore from an endophytic fungus isolated from sand pine. The endogenous fluorescence of the live organism was measured using fluorescence microscopy. Computational interpretation of the spectra was accomplished with time-dependent density functional theory methods. The combined use of experimental and theoretically predicted spectra revealed the pH equilibria and photoexcited tautomerization of the natural product, 5-methylmellein. This product shows promise both as a stand-alone pH-indicating fluorophore, with alkaline pK , and as "green" feedstock for synthesis of custom fluorophores.