Fluorescence Polarisation

Molecules in solution excited with polarized light emit light that is also polarized. Due to molecular movement (brownian motion, molecular rotation), the polarization of the emitted light decreases ("depolarization"), the size of the effect depends on molecular properties (fluorescence lifetime, volume) and the environment (viscosity/ temperature). Molecular interactions cause a volume increase of a fluorescence labeled target that can be used to determine the affinity (equilibrium dissociation constant, KD) of an interaction with a ligand. For measuring FP, we use a Spark fluorescence microplate reader (Tecan, https://lifesciences.tecan.com/multimode-plate-reader).