Essential tools for life science research
Tocris offers a broad range of fluorescent reagents, to facilitate the visualization of sub-cellular components in live and fixed cells with high sensitivity and selectivity. The product range includes fluorescent probes, dyes and indicators.
Fluorescent Imaging Target Files
Characteristics of Fluorescent Compounds
Fluorescent compounds are generally small organic molecules (although they may also be peptides or proteins) that absorb light radiation of a specific wavelength and emit radiation at a longer wavelength (lower energy). The compounds cease to emit radiation immediately, when the incident radiation stops. Fluorescent compounds have a maximum excitation and emission wavelength, measured in nanometers, and the difference between the two is known as the Stokes shift. The ratio of the number of photons emitted to the number absorbed is an indicator of the efficiency of the fluorescence process and is known as the quantum yield. How strongly a fluorescent compound absorbs radiation is known as the extinction coefficient, and links the amount of radiation of a given wavelength absorbed to the molar concentration of the compound. Another useful parameter to take into account is the lifetime, which corresponds to the average time (measured in picoseconds) that the compound spends in an excited state before emitting a photon and returning to the ground state.