Cyclopropyl Substituents Transform the Viscosity-Sensitive BODIPY Molecular Rotor into a Temperature Sensor.

A quantitative fluorescent probe that responds to changes in temperature is highly desirable for studies of biological environments, particularly . Here, we report new cell-permeable fluorescence probes based on the BODIPY moiety that respond to environmental temperature. The new probes were developed on the basis of a well-established BODIPY-based viscosity probe by functionalization with cyclopropyl substituents at α and β positions of the BODIPY core.

Time-Resolved Fluorescence Anisotropy of a Molecular Rotor Resolves Microscopic Viscosity Parameters in Complex Environments.

Understanding viscosity in complex environments remains a largely unanswered question despite its importance in determining reaction rates in vivo. Here, time-resolved fluorescence anisotropy imaging (TR-FAIM) is combined with fluorescent molecular rotors (FMRs) to simultaneously determine two non-equivalent viscosity-related parameters in complex heterogeneous environments. The parameters, FMR rotational correlation time and lifetime, are extracted from fluorescence anisotropy decays, which in heterogeneous environments show dip-and-rise behavior due to multiple dye populations.