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 (in water). The major derivatives are
fluorescein isothiocyanate (FITC) and, in
oligonucleotide synthesis,
6-FAM phosphoramidite.
Biosciences In cellular biology, the
isothiocyanate derivative of fluorescein is often used to label and track
cells in
fluorescence microscopy applications (for example,
flow cytometry). Additional biologically active molecules (such as
antibodies) may also be attached to fluorescein, allowing biologists to target the fluorophore to specific proteins or structures within cells. This application is common in
yeast display. Fluorescein can also be conjugated to
nucleoside triphosphates and incorporated into a
probe enzymatically for
in situ hybridisation. The use of fluorescein amidite, shown below right, allows one to
synthesize labeled
oligonucleotides for the same purpose. Yet another technique termed
molecular beacons makes use of synthetic fluorescein-labeled oligonucleotides. Fluorescein-labelled probes can be imaged using
FISH, or targeted by
antibodies using
immunohistochemistry. The latter is a common alternative to
digoxigenin, and the two are used together for labelling two genes in one sample. Intravenous or oral fluorescein is used in
fluorescein angiography in research and to diagnose and categorize vascular disorders including retinal disease,
macular degeneration,
diabetic retinopathy, inflammatory intraocular conditions, and intraocular
tumors. It is also being used increasingly during surgery for
brain and spine tumors. Diluted fluorescein dye has been used to localise multiple muscular ventricular septal defects during open heart surgery and confirm the presence of any residual defects. spacecraft releases dye into the water, to aid location after
splashdown, June 1965.
Earth sciences Fluorescein is used as a rather conservative
flow tracer in hydrological
tracer tests to help in understanding of water flow of both
surface waters and
groundwater. The dye can also be added to
rainwater in environmental testing simulations to aid in locating and analyzing any water leaks, and in Australia and New Zealand as a
methylated spirit dye. As fluorescein solution changes its color depending on concentration, it has been used as a tracer in evaporation experiments. One of its more recognizable uses was in the
Chicago River, where fluorescein was the first substance used to dye the river green on
St. Patrick's Day in 1962. In 1966, environmentalists forced a change to a vegetable-based dye to protect local wildlife. Fluorescein dye solutions, typically 15% active, are commonly used as an aid to leak detection during
hydrostatic testing of
subsea oil and gas pipelines and other subsea infrastructure. Leaks can be detected by divers or
ROVs carrying an ultraviolet light.
Plant science Fluorescein has often been used to track water movement in
groundwater to study water flow and observe areas of contamination or obstruction in these systems. The
fluorescence that is created by the dye makes problem areas more visible and easily identified. A similar concept can be applied to plants because the dye can make problems in plant vasculature more visible. In
plant science, fluorescein, and other fluorescent dyes, have been used to monitor and study
plant vasculature, particularly the
xylem, which is the main water transportation pathway in plants. This is because fluorescein is xylem-mobile and unable to cross
plasma membranes, making it particularly useful in tracking water movement through the xylem. Fluorescein can be introduced to a plant's veins through the roots or a cut stem. The dye is able to be taken up into the plant the same way as water and moves from the roots to the top of the plant due to a transpirational pull. The fluorescein that has been taken up into the plant can be visualized under a
fluorescent microscope. == See also ==