Fluorescent protein FRET pairs for ratiometric imaging of dual biosensors.

Fluorescence resonance energy transfer (FRET) with fluorescent proteins is a powerful method for detection of protein-protein interactions, enzyme activities and small molecules in the intracellular milieu. Aided by a new violet-excitable yellow-fluorescing variant of Aequorea victoria GFP, we developed dual FRET-based caspase-3 biosensors. Owing to their distinct excitation profiles, each FRET biosensor can be ratiometrically imaged in the presence of the other.