FLUORESCENCE SPECTROSCOPY

Fluorescence is a sensitive technique that, although started as an analytical tool, is used more and more for the study of molecular interactions in vitro and in cells; in fact, it is nowadays capable of detection of single molecules on a routine basis. The main five parameters measured in fluorescence spectroscopy are:excitation spectrum, emission spectrum, decay times, quantum yield and anisotropy (or polarization). The description of the fluorescence measurable parameters is best understood with the introduction of the Perrin–Jablonski diagram, which is a quantum mechanics representation of the energy levels of a molecular structure. The absorption probability of a photon in each electronic level is described within the framework of quantum mechanics. A variety of research instruments is available for the measurement of the general and specific parameters of the fluorescence. Dedicated instruments are utilized for the measurements in specific immunoassays (polarimeters), in drug discovery (microwell plates and microarrays), cell sorting (cytofluorometers), and genome sequencing.