Four Generations of Fluorescent Labels

Fooking at the fluorescence molecules available today, there is a very wide range of fluorophores. Fluorophores can be classified by year of their introduction. The four generations of fluorescence compounds have increasingly better properties. 

1st Generation 1942 - Fluorescein and rhodamine fluorophores. Albert Coons (Coons et al., 1942) prepared the first fluorescent compound used for immunocytochemistry, fluorescein isocyanate. All organic fluorescent compounds use variations of the basic ring structure. The later derived fluorescein isothyocyanate (FITC Riggs et al., 1958) and rhodamine also photobleach very quickly and are quenched when bound to antibodies. 

2nd Generation 1993 - Cy fluorophores cyanine dyes Cy2, Cy3, Cy5 (Jackson Immuno-Research), AMCA, and Texas Red. These were more photostable (photobleached more slowly than 1st generation) and have high quantum yields. 

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