DNA-Binding Fluorophores

The first cyanine dye, named cyanine because of its blue color, was serendipitously synthesized by C.H.G. Williams as early as 1856. Since the end of the 19th century, the class of cyanine dyes have dominated the field of photography as photosensitizers and are unrivalled even today. The maximum absorption of cyanine dyes depends on the length of the conjugated chain and the nature of the heterocyclic moieties. Today dyes are available whose absorptions span a broad range of the visible spectrum. They typically have several hundredfold enhancements in fluorescence upon binding DNA and a quantum yield in bound state of at least 0.1. Fluorescent probes have replaced radioisotopes as labels of nucleic acids. They have important advantages in being nonhazardous and stable upon storage. Moreover, some dyes have different fluorescence in free and bound state, which opens for probing in homogeneous solution, eliminating the need to separate bound and free probes.