Ratiometric biosensors based on dimerization-dependent fluorescent protein exchange

This paper reports a new strategy for the rapid and efficient generation of ratiometric fluorescent sensors for a variety of cellular processes. We have developed a versatile new class of genetically encoded fluorescent biosensor based on reversible exchange of the heterodimeric partners of green and red dimerization-dependent fluorescent proteins. We demonstrate the use of this strategy to construct both intermolecular and intramolecular ratiometric biosensors for qualitative imaging of caspase activity, Ca 2+ concentration dynamics and other second-messenger signaling activities.