quenching

1. The process of extinguishing, removing, or diminishing a physical property such as heat or light; e.g., the cooling of a hot metal rapidly by plunging it into water or oil. 2. In beta liquid scintillation counting, the shifting of the energy spectrum from a true to a lower energy; it is caused by a variety of interfering materials in the counting solution, including foreign chemicals and coloring agents. 3. The process of stopping a chemical or enzymatic reaction. [M. E. quenchen, fr. O.E. acwencan]

- fluorescence q. a technique used in investigations dealing with binding of antigens (haptens) by purified antibodies, applicable in cases in which the bound antigen (hapten) absorbs (quenches) light emitted during fluorescence of protein (antibody) excited by ultraviolet light.

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quench·ing (kwenchґing) 1. extinguishing, suppressing, or diminishing a physical property, as the rapid chilling of a hot metal by plunging it into cold liquid. 2. in biochemistry, decrease of fluorescence from an excited molecule by interference that reduces the fluorescence intensity, such as deexcitation of the fluorescent molecule by collision with other molecules, absorption of fluorescent emission by the surrounding medium, or a decrease or shift in wavelength of fluorescence due to chemical interaction of the fluorescent molecule with other molecules. 3. in liquid scintillation counting, interference with generation or propagation of light energy from the sample, decreasing the counting efficiency of the detector. 4. the termination of secondary and subsequent ionizations in a detector to give it time to become sensitive again.