FRETsensors

FRET sensors are molecular tools used to detect and quantify specific biological events or molecules. FRET stands for Förster Resonance Energy Transfer, a biophysical process where energy is transferred non-radiatively from an excited donor fluorophore to an acceptor fluorophore. This energy transfer is highly dependent on the distance and orientation between the two fluorophores, typically occurring efficiently when they are within 10 nanometers of each other.

A FRET sensor typically consists of a donor fluorophore and an acceptor fluorophore linked by a molecular recognition element. This element is designed to change its conformation or undergo a change in proximity between the donor and acceptor upon binding to a target analyte or experiencing a specific environmental condition. For instance, if the recognition element undergoes a conformational change that brings the donor and acceptor closer together, FRET efficiency increases, leading to a detectable change in fluorescence emission. Conversely, if they move further apart, FRET efficiency decreases.

The change in FRET efficiency can be measured by monitoring the fluorescence of the donor and acceptor. Typically, exciting the donor fluorophore and observing a decrease in its emission and a concomitant increase in the acceptor's emission indicates FRET. The ratio of acceptor emission to donor emission, or other related metrics, provides a quantitative measure of the FRET efficiency and thus the biological event of interest.

FRET sensors have found widespread applications in studying protein-protein interactions, enzyme activity, changes in ion concentrations (like calcium), nucleic acid binding, and cellular signaling pathways. Their ability to report on molecular events in real-time and in living cells makes them invaluable for biological research and the development of diagnostic tools.