Fluorophores

Abstract

Fluorescence probes represent the most important area of fluorescence spectroscopy. The wavelength and time resolution required of the instruments is determined by the spectral properties of the fluorophores. Furthermore, the information available from the experiments is determined by the properties of the probes. Only probes with non-zero anisotropies can be used to measure rotational diffusion, and the lifetime of the fluorophore must be comparable to the timescale of interest in the experiment. Only probes that are sensitive to pH can be used to measure pH. And only probes with reasonably long excitation and emission wavelengths can be used in tissues, which display autofluorescence at short excitation wavelengths. Thousands of fluorescent probes are known, and it is not practical to describe them all. This chapter contains an overview of the various types of fluorophores, their spectral properties, and applications. Fluorophores can be broadly divided into two main classes—intrinsic and extrinsic. Intrinsic fluorophores are those that occur naturally. These include the aromatic amino acids, NADH, flavins, derivatives of pyridoxyl, and chlorophyll. Extrinsic fluorophores are added to the sample to provide fluorescence when none exists, or to change the spectral properties of the sample. Extrinsic fluorophores include dansyl, fluorescein, rho-damine, and numerous other substances.