The inherent fluorescent properties of nucleosides, nucleotides, and nucleic acids are limited, and thus the need has arisen for fluorescent labeling of these molecules for a variety of analytical applications. This review traces the analytical ancestry of fluorescent labeling of nucleosides, nucleotides, and nucleic acids, with an emphasis on the first to publish or patent. The scope of labeling includes (a) direct labeling by covalent labeling of nucleic acids with a fluorescent label or noncovalent binding or intercalation of a fluorescent dye to nucleic acids and (b) indirect labeling via covalent attachment of a secondary label to a nucleic acid, and then binding this to a fluorescently labeled ligand binder. An alternative indirect strategy involves binding of a nucleic acid to a nucleic acid binder molecule (e.g., antibody, antibiotic, histone, antibody, nuclease) that is labeled with a fluorophore. Fluorescent labels for nucleic acids include organic fluorescent dyes, metal chelates, carbon nanotubes, quantum dots, gold particles, and fluorescent minerals. Fluorescently labeled nucleosides, nucleotides, and nucleic acids are important types of reagents for biological assay methods and underpin current methods of chromosome analysis, gel staining, DNA sequencing and quantitative PCR. Although these methods use predominantly organic fluorophores, new types of particulate fluorophores in the form of nanoparticles, nanorods, and nanotubes may provide the basis of a new generation of fluorescent labels and nucleic acid detection methods.
