Fluorescence is the result of a three-stage process that occurs in certain molecules (generally polyaromatic hydrocarbons or heterocycles) called fluorophores or fluorescent dyes. Fluorescent probes enable researchers to detect particular components of complex biomolecular assemblies (including live cells) with exquisite sensitivity and selectivity. Reactive fluorescent dyes are widely used to modify amino acids, peptides, proteins (in particular, antibodies), oligonucleotides, nucleic acids, carbohydrates and other biological molecules.
Available Fluorescent Labeling Dyes
Although the superior fluorescent labeling dyes such as iFluor™ dyes and Alexa Fluor® dyes have been increasingly used for the more challenging biological applications, the classic fluorescent labeling dyes are preferred for some less demanding applications due to their significantly lower costs. Among the classic labeling dyes, courmains, fluoresceins, rhodamines, and cyanines are the most common fluorephores. For example, FITC (fluorescein isothiocyanate), a fluorescein derivative is one of the most popular fluorescent labeling dyes, and predominantly used for preparing a variety of fluorescent bioconjugates. FAM, TAMRA, Texas Red®, Cy3®, Cy5® and Cy7® are also popular classic fluorescent labeling dyes used for preparing peptide and oligonucleotide conjugates.
Table 1. Classic Fluorescent Labels For Available Fluorescent Labeling Dyes
| Colour | Classic Labeling Dyes |
| Coumarin dyes and derivatives | |
| Fluorescein dyes and derivatives | |
| Rhodamine dyes and derivatives | |
| Cyanine dyes and derivatives | |
| Indocyanine Green (ICG) dyes |
