Fluorescent labeling

In molecular biology and biotechnology, a fluorescent tag, also known as a label or probe, is a molecule that is attached chemically to aid in the labeling and detection of a biomolecule such as a protein, antibody, or amino acid. Generally, fluorescent tagging, or labeling, uses a reactive derivative of a fluorescent molecule known as a fluorophore. The fluorophore selectively binds to a specific region or functional group on the target molecule and can be attached chemically or biologically. Various labeling techniques such as enzymatic labeling, protein labeling, and genetic labeling are widely utilized. Ethidium bromide, fluorescein and green fluorescent protein are common tags. The most commonly labelled molecules are antibodies, proteins, amino acids and peptides which are then used as specific probes for detection of a particular target.

The development of methods to detect and identify biomolecules has been motivated by the ability to improve the study of molecular structure and interactions. Before the technology of fluorescent labeling, radioisotopes were used to detect and identify molecular compounds. Since then, safer methods have been developed that involve the use of fluorescent dyes or fluorescent proteins as tags or probes as a means to label and identify biomolecules. Although fluorescent tagging in this regard has only been recently utilized, the discovery of fluorescence has been around for a much longer time.

Sir George Stokes developed the Stokes Law of Fluorescence in 1852 which states that the wavelength of fluorescence emission is greater than that of the exciting radiation. Richard Meyer then termed fluorophore in 1897 to describe a chemical group associated with fluorescence. Since then, Fluorescein was created as a fluorescent dye by Adolph von Baeyer in 1871 and the method of staining was developed and utilized with the development of fluorescence microscopy in 1911.

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