Fluorophore

A fluorophore-labeled human cell.

A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different (but equally specific) wavelength. The amount and wavelength of the emitted energy depend on both the fluorophore and the chemical environment of the fluorophore. This technology has particular importance in the field of biochemistry and protein studies, eg. in immunofluorescence and immunohistochemistry.^[1]

Fluorescein isothiocyanate (FITC), a reactive derivative of fluorescein, has been one of the most common fluorophores chemically attached to other, non-fluorescent molecules to create new fluorescent molecules for a variety of applications. Other historically common fluorophores are derivatives of rhodamine (TRITC), coumarin, and cyanine.^[2] Newer generations of fluorophores such as the Alexa Fluors and the DyLight Fluors are generally more photostable, brighter, and less pH-sensitive than other standard dyes of comparable excitation and emission.^{[1] [3] [4]}

Size

The size of the fluorophore might sterically hinder the tagged molecule:

• quantum dot: 2-10 nm (diameter), 100-100,000 atoms
• protein: Green fluorescent protein (GFP) 26 kDa
• small molecule: fluorescein: about 20 atoms

Families

Fluorophores can be attached to protein to specific functional groups, such as

• amino groups (succinimide, Isothiocyanate, hydrazine)
• carboxyl groups (Carbodiimide)
• thiol (maleimide, acetyl bromide)
• azide (via click chemistry)

or non-specificately (Glutaraldehyde).

These fluorophores are either quantum dots or small molecules. The former a fluorescent semiconductor nanoparticles. The latter molecules which fluoresce thanks to delocalized electrons which can jump a band and stabilize the energy absorbed, hence most fluorophores are aromatic, a propriety that can arise is that when polar molecules stabilize one resonance structure more over the other the dye is sensitive to the environment's polarity (solvatochromic), hence called environmentally sensitive.

Common dye families are:

• Alexa Fluor (invitrogen)
• cyanine and merocyanine
• BODIPY (invitrogen)
• Atto (sigma)
• Fluorescein derivatives
• Rhodamine derivatives
• naphtalene derivatives (Dansyl and Prodan derivatives)
• Pyridyloxazole, Nitrobenzoxadiazole and Benzoxadiazole derivatives
• Coumarin derivatives
• Pyrene derivatives
• Oregon green, eosin, texas red, Cascade blue, Nile red etc

See also

• Dark quencher
• Category:Fluorescent dyes
• Fluorescence recovery after photobleaching (FRAP) - an application for quantifying mobility of molecules in lipid bilayers.
• Fluorescence in the life sciences

References

External links

• The Database of fluorescent dyes
• Table of fluorochromes