UV Fluorescence Polarization as a Means to Investigate Protein Conformational and Mass Change Using Intrinsic Tryptophan Fluorescence in Conjunction with UV-capable Polarizers

Fluorescence polarization (FP) is a fluorescence detection technique that is based on the observation that fluorescent molecules, when excited by plane polarized light, will emit plane polarized light. In solution, proteins are free to rotate, thus the plane of polarized light emitted can change based on the fluorescence lifetime of the fluorophore in question and the extent of rotation the molecule undergoes during that time frame. The molecule’s rotational speed is influenced by solution viscosity, absolute temperature, molecular volume and the gas constant. If one keeps viscosity and temperature constant, then the key variable for rotational speed differences is molecular volume or to a first approximation, molecular weight.