page_title: Fluorescein
section_title: Derivatives
hierarchical_section_title: Fluorescein / Derivatives
caption_attribution_description: English: Structural formulas of FITC and 6-FAM phosphoramidite
context_page_description: Fluorescein is an organic compound and dye. It is available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications.
  Fluorescein is a fluorophore commonly used in microscopy, in a type of dye laser as the gain medium, in forensics and serology to detect latent blood stains, and in dye tracing. Fluorescein has an absorption maximum at 494 nm and emission maximum of 512 nm. The major derivatives are fluorescein isothiocyanate and, in oligonucleotide synthesis, 6-FAM phosphoramidite.
  The color of its aqueous solution varies from green to orange as a function of the way it is observed: by reflection or by transmission, as can be noticed in bubble levels, for example, in which fluorescein is added as a colorant to the alcohol filling the tube in order to increase the visibility of the air bubble contained within. More concentrated solutions of fluorescein can even appear red.
  It is on the World Health Organization's List of Essential Medicines.
context_section_description: Many derivatives of fluorescein are known. Example
  fluorescein isothiocyanate 1, often abbreviated as FITC, features an isothiocyanate group (−N=C=S) substituent. FITC reacts with the amine groups of many biologically relevant compounds including intracellular proteins to form a thiourea linkage.
  succinimidyl ester modified fluorescein, i.e. NHS-fluorescein, is another common amine-reactive derivative, yielding amide adducts that are more stable than the aforementioned thioureas.
  Others: carboxyfluorescein, carboxyfluorescein succinimidyl ester, Pentafluorophenyl esters (PFP), tetrafluorophenyl esters (TFP) are other useful reagents.
  In oligonucleotide synthesis, several phosphoramidite reagents containing protected fluorescein, e.g. 6-FAM phosphoramidite 2, are used for the preparation of fluorescein-labeled oligonucleotides.
  Other green dyes include Oregon Green, Tokyo Green, SNAFL, and carboxynaphthofluorescein. These dyes, along with newer fluorophores such as Alexa 488, FluoProbes 488 and DyLight 488, have been tailored for various chemical and biological applications where higher photostability, different spectral characteristics, or different attachment groups are needed.
  The extent to which fluorescein dilaurate is broken down to yield lauric acid can be detected as a measure of pancreatic esterase activity.
caption: Fluorescein isothiocyanate and 6-FAM phosphoramidite
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