Fluorescence occurs when a fluorophore, such as fluorescein, absorbs light at one wavelength and emits it at another. Chemifluorescent reactions produce the fluorophore by chemical conversion of a fluorogenic substrate. Both types of fluorescent detection systems require an external light source, usually a laser.
Chemiluminescence is caused by a chemical reaction whose products glow without external stimulation. In many biological applications, an enzyme, linked to a detection antibody, catalyzes this reaction. Some chemiluminescent systems are based on the formation of peroxides by horseradish peroxidase, such as Piscataway, NJ-based Amersham Biosciences' ECL Plus™ reagent. Other systems use dioxetane substrates and alkaline phosphatase, such as Foster City, Calif.-based Applied Biosystems' CDP-Star® reagent.1 Though chemiluminescent systems do not require a light source, exposures can be long, sometimes exceeding one hour.
A number of instruments perform chemiluminescence detection in addition to fluorescence and UV/visible modes, profiting from the increased dynamic range and linearity of ...
