fluorescence

(noun)

The emission of light (or other electromagnetic radiation) by a material when stimulated by the absorption of radiation or of a subatomic particle

Related Terms

Examples of fluorescence in the following topics:

  • Fluorescent Antibodies

    • Fluorescent antibodies are antibodies that have been tagged with a fluorescent compound to facilitate their detection in the laboratory.
    • Fluorescent molecules are used as substitutes for radioisotope or enzyme labels.
    • Fluorescent techniques are very specific and sensitive, so fluorescent antibody-based techniques require a fluorescent microscope.
    • Fluorescein fluoresces an intense apple-green color when excited under fluorescent microscopy.
    • Fluorescent antibody conjugates are commonly used in immunoassays.

  • Fluorescence Microscopy

    • Fluorescence microscopy is used to study specimens that are chemically manipulated to emit light.
    • This laboratory technique employs fluorescent dyes chemically linked to antibodies to help identify unknown microorganisms.
    • This method uses the specificity of an antibody to its antigen to deliver a fluorescent dye to a target molecule.
    • A filter is used to block the heat generated from the lamp and to match the fluorescent dye labeling the specimen.
    • Fixed endothelial cells stained with fluorescent dyes.

  • Confocal Microscopy

    • Confocal microscopy is a non-invasive fluorescent imaging technique that uses lasers of various colors to scan across a specimen with the aid of scanning mirrors.
    • The biological sample to be studied is stained with antibodies chemically bound to fluorescent dyes similar to the method employed in fluorescence microscopy .
    • Unlike in conventional fluorescence microscopy where the fluorescence is emitted along the entire illuminated cone creating a hazy image, in confocal microscopy the pinhole is added to allow passing of light that comes from a specific focal point on the sample and not the other.

  • Tracking Cells with Light

    • Advanced technology enables tracking cells with light by introducing fluorescent or luminescent reporter genes into the cells' genome.
    • Examples of such reporters are the genes encoding for Green Fluorescent Protein (GFP) and luciferase, respectively.
    • Thus, only those cells in which the tagged gene is expressed, or the target proteins are produced, will fluoresce when observed under fluorescence microscopy , or bioluminesce (emit light) when luciferin, the substrate for luciferase is added.

  • DNA Sequencing Based on Sanger Dideoxynucleotides

    • Technical variations of chain-termination sequencing include tagging with nucleotides containing radioactive phosphorus for radiolabelling, or using a primer labeled at the 5' end with a fluorescent dye.
    • The later development by Leroy Hood and coworkers of fluorescently labeled ddNTPs and primers set the stage for automated, high-throughput DNA sequencing.
    • In dye-terminator sequencing, each of the four dideoxynucleotide chain terminators is labelled with fluorescent dyes, each of which emit light at different wavelengths .
    • DNA sequencers carry out capillary electrophoresis for size separation, detection and recording of dye fluorescence, and data output as fluorescent peak trace chromatograms.
    • This is an example of the output of a Sanger sequencing read using fluorescently labelled dye-terminators.

  • Interference Microscopy

    • There are three types of interference microscopy: classical, differential contrast, and fluorescence contrast.
    • Fluorescence differential interference contrast (FLIC) microscopy was developed by combining fluorescence microscopy with DIC to minimize the effects of photobleaching on fluorochromes bound to the stained specimen.
    • The same microscope is equipped to simulataneously image a specimen using DIC and fluorescence illumination.

  • The FISH Technique

    • FISH is a hybridization technology which allows the labeling of target RNAs with a fluorescent probe.
    • FISH (fluorescence in situ hybridization) is a cytogenetic technique developed by biomedical researchers in the early 1980s.
    • FISH uses fluorescent probes bind to those targets that show a high degree of sequence complementarity.
    • Describe how fluorescent in situ hybridization (FISH) is used in clinical and biomedical studies to detect and localize the presence or absence of specific DNA sequences and to identify pathogens

  • Reporter Fusions

    • Commonly used reporter genes that induce visually identifiable characteristics usually involve fluorescent and luminescent proteins.
    • Examples include the gene that encodes jellyfish green fluorescent protein (GFP), which causes cells that express it to glow green under blue light, the enzyme luciferase, which catalyzes a reaction with luciferin to produce light, and the red fluorescent protein from the gene dsRed.
    • In the case of GFP which fluorescence one can deduce that the attached protein is wherever the fluorescence is.
    • As you can see the localization of the fused protein can now be determined using fluorescent reporter fusions.

  • Purifying Proteins by Affinity Tag

    • Fluorescence tags are used to give visual readout on a protein.
    • GFP and its variants are the most commonly used fluorescence tags.
    • More advanced applications of GFP include using it as a folding reporter (fluorescent if folded, colorless if not).
    • Green fluorescent protein-tag, a protein which is spontaneously fluorescent and can be bound by nanobodies

  • Tests That Differentiate Between T Cells and B cells

    • B-lymphocytes have membrane-bound immunoglobulins that can be stained with anti-immunoglobulin labeled with fluorescent dyes and detected with a fluorescent microscope.
    • More modern techniques like flow cytometry and immunohistochemistry are commonly used and rely on the use of fluorescent antibodies.