page_title: Fluorescent tag
section_title: Fluorescent labels
hierarchical_section_title: Fluorescent tag / Methods for tracking biomolecules / Fluorescent labels
caption_attribution_description: Green Fluorescent Protein (GFP). Produced from PDB: 1EMA, rendered in PyMOL.
context_page_description: In molecular biology and biotechnology, a fluorescent tag, also known as a fluorescent label or fluorescent probe, is a molecule that is attached chemically to aid in the 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.
context_section_description: Of the various methods of labeling biomolecules, fluorescent labels are advantageous in that they are highly sensitive even at low concentration and non-destructive to the target molecule folding and function.
  Green fluorescent protein is a naturally occurring fluorescent protein from the jellyfish Aequorea victoria that is widely 
  used to tag proteins of interest.  GFP emits a photon in the green region of the light spectrum when excited by the absorption of light.  The chromophore consists of an oxidized tripeptide -Ser^65-Tyr^66-Gly^67 located within a β barrel.  GFP catalyzes the oxidation and
  only requires molecular oxygen.  GFP has been modified by changing the wavelength of light absorbed to include other colors of fluorescence.  YFP or yellow fluorescent protein, BFP or blue fluorescent protein, and CFP or cyan fluorescent protein are examples of GFP variants.  These variants are produced by the genetic engineering of the GFP gene.
  Synthetic fluorescent probes can also be used as fluorescent labels.  Advantages of these labels include a smaller size with more variety in color.  They can be used to tag proteins of interest more selectively by various methods including chemical recognition-based labeling, such as utilizing metal-chelating peptide tags, and biological recognition-based labeling utilizing enzymatic reactions.  However, despite their wide array of excitation and emission wavelengths as well as better stability, synthetic probes tend to be toxic to the cell and so are not generally used in cell imaging studies.
  Fluorescent labels can be hybridized to mRNA to help visualize interaction and activity, such as mRNA localization. An antisense strand labeled with the fluorescent probe is attached to a single mRNA strand, and can then be viewed during cell development to see the movement of mRNA within the cell.
caption: GFP structure
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