Fluorescent pH Indicators for Neutral to Near-Alkaline Conditions Based on 9‑Iminopyronin Derivatives
Horvath,, P., Sebej, P., Kovar, D., Damborsky, J., Prokop, Z., Klan, P.
ACS OMEGA 4: 5479−5485 (2019)
Monitoring enzymatic activities at pH ranges compatible with their physiological optimum using fluorescent assays is important for high-throughput screening and engineering of novel biocatalysts as well as applications in biosensing and diagnostics. However, the number of fluorescent dyes exhibiting necessary optical properties at alkaline pHs is limited. Here, we report the design, synthesis, and biochemical application of fluorescent 9-iminopyronin derivatives possessing unique and distinct emission properties to provide optimal sensitivity at neutral to near-alkaline conditions. They exist in two acid−base forms, allowing for a dual-emission ratiometric sensing with a linear response of pH between 6.0 and 8.5 and detection sensitivity of a 0.06 pH unit. Selected
fluorophores were used as the sensors for monitoring the enzymatic hydrolytic activity of a model enzyme haloalkane dehalogenase.