fluorescence

fluorescence /flu·o·res·cence/ (-ens) the property of emitting light while exposed to light, the wavelength of the emitted light being longer than that of the absorbed light.fluores´cent

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fluo·res·cence (fl-rsns, flô-)

n.

1. The emission of electromagnetic radiation, especially of visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued.

2. The property of emitting such radiation.

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fluo·rescent adj.

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fluorescence

[floo͡res′əns]

Etymology: L, flux, a discharge

the emission of light of one wavelength by a substance when it is exposed to electromagnetic radiation of a shorter wavelength. Fluorescent substances that emit visible light appear luminous. fluoresce, v.

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fluorescence [floo͡-res´ens]

the property of emitting light while exposed to light, the wavelength of the emitted light being longer than that of the absorbed light.

fluorescence microscopy the use of a fluorescence microscope to identify microorganisms or specific tissue constituents that have been stained with a fluorochrome or a fluorochrome-labeled substance (such as an antibody to a tissue antigen). A fluorescent antibody test can be used in place of time-consuming culture methods for identifying bacteria. See also immunofluorescence.

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fluorescence,

n the emission of light of a particular wavelength by a substance upon absorption of ele-ctromagnetic radiation of a shorter wavelength.

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fluorescence (flres´ns),

n the emission of radiation of a particular wavelength by certain substances as the result of absorption of radiation of a shorter wavelength.

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fluorescence

the property of emitting light while exposed to light, the wavelength of the emitted light being longer than that of the absorbed light.

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fluorescence-activated cell sorter (FACS)

an instrument for analysis (FACscan) and separating mixed populations of cells after labeling individual cell-specific surface antigens with fluorescent antibody. The individual cells in droplets are passed through a laser beam; the droplet is deflected into one of two or more collection vessels depending upon which fluorescent antibody is bound to its surface. Two or more different fluorescent antibodies are used.

fluorescence microscopy

the use of techniques for conjugating antibodies with fluorescent dyes in order to identify specific microorganisms or tissue constituents using a fluorescence microscope. Fluorescent antibody (FA) techniques can be used in place of time-consuming culture methods for identifying bacteria and viruses. There are two major types of FA techniques, direct and indirect, both of which are based on the antigen-antibody reaction in which the antibody attaches itself to its specific antigen.

In the direct fluorescent antibody (DFA) method, the antibody is bound to the antigen, for example, a bacterial cell in a smear, and cannot be easily removed by elution (washing). The antibody remains attached to the cell after all other serum proteins have been washed away. Since the antibody has been rendered fluorescent by conjugation with fluorescein or another dye, the outline of the bacterial cell that it coats can readily be seen with a special microscope.

In the indirect method (IFA), the specific antibody is allowed to react with the antigen. The slide is then washed and treated with a labeled antibody to the specific antibody. For example, if the specific antibody was raised in a rabbit, it is then treated with fluorescein-labeled anti-rabbit globulin, which results in a combination of this labeled antibody with the rabbit immunoglobulin already attached to the antigen.

Fluorescent antibody studies have been used in the detection of numerous bacterial, viral, fungal and protozoan infections and in the identification and localization of many tissue antigens.

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fluorescence

Property of a substance that, when illuminated absorbs light of a given wavelength and re-emits it as radiations of a longer wavelength. Example: fluorescein. See Draper's law; Wood's light; lumi-nescence.