Two water-soluble two-photon fluorescence probes for ratiometric imaging endogenous SO2 derivatives in mitochondria.

Rational and convenient design water-soluble two-photon excited fluorescence (TPEF) probes for monitoring SO 2 derivatives with specificity at subcellular level remain a challenge. Herein, two low molecular weight, ratiometric fluorescence probes, bearing α, β-unsaturated benzoindolium moiety ( EIM and EIS) , are designed for monitoring endogenously SO 2 derivatives in mitochondria using two-photon microscopy (TPM). The two probes not only showed >100 nm blue-shift emission with two well-resolved bands upon addition of HSO 3 − /SO 3 2− , but also displayed rapid response, high selectivity and sensitivity for monitoring and quantifying HSO 3 − /SO 3 2− over other species in living cells. Further studies indicated that probes EIM and EIS can highly discern HSO 3 − /SO 3 2− with two different nucleophilic addition mechanisms, respectively, just by structural fine-tuning, which were confirmed by both theoretical calculation and experimental technique. It is suggested that probes EIM / EIS with two-photon absorption property in the NIR region, large Stocks shift, high selectivity and signal ratio, are promising molecular tool for bisulfite/sulfite biology. [ABSTRACT FROM AUTHOR]