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 pKa, and as "green" feedstock for synthesis of custom fluorophores.

中文翻译：

---

具有碱性 pK a 的生物源荧光比率 pH 指示剂的表征

利用生物体作为荧光团的来源减轻了荧光产品有机合成中对石油原料的需求，而内生真菌为天然荧光产品提供了有希望的途径。我们报告了从沙松中分离的内生真菌的 pH 响应荧光团的表征。使用荧光显微镜测量活生物体的内源性荧光。光谱的计算解释是用时间相关的密度泛函理论方法完成的。实验和理论预测光谱的结合使用揭示了天然产物 5-甲基蜜蜡的 pH 平衡和光激发互变异构化。该产品显示出作为独立 pH 指示荧光团、碱性 pKa 和“绿色”的前景