522
Chemiluminescence and Bioluminescence, Analysis by
Electrochemiluminescence
Light emission that occurs in electrochemical reactions.
Homogeneous Assay
An assay (e.g. immunoassay or nucleic acid hybridization assay) that does not require a
separation step.
Immunoassay
An assay that uses specifc antibodies or labeled antibodies to detect an antigen
(the analyte).
Luciferase
The generic name For an enzyme that catalyzes a bioluminescent reaction.
Luciferin
The generic name For the substrate oF a luciFerase.
Luminometer
An instrument For detecting and measuring light emission.
Nucleic Acid Hybridization Assay
An assay that utilizes the specifc recognition oF a nucleic acid probe or labeled nucleic
acid probe For a complementary sequence on the target nucleic acid.
Photoprotein
A tightly bound protein–luciFerin complex that can be activated to produce light.
¥
Bioluminescent (BL) and chemiluminescent (CL) reactions are used as analytical
detection tools in immunoassay, protein and nucleic acid blotting, nucleic acid
sequencing, and hybridization assays, and in reporter gene studies. In a BL or
CL assay, the intensity or the total light emission is measured and related to
the concentration oF the unknown analyte. Light is measured quantitatively using
a luminometer (photomultiplier tube or charge-coupled device) as a detector or
qualitatively by means oF photographic or X-ray flm. The main advantages oF
these reactions are simplicity and an analytical sensitivity capable oF obtaining
results From minute amounts oF analyte [attomole–zeptomole (10
18
–10
21
mol)
range]. In immunoassay and nucleic acid hybridization tests, these reactions or
their components are used in two ways: as labels and as detection systems
For labels oF other types (e.g. enzymes). Acridinium esters, acridinium sulFonyl
carboxamides, isoluminol derivatives, the photoprotein aequorin, and luciFerases
From the frefly, marine bacteria,
Vargula
(Formerly
Cypridina
), and
Renilla
are
the principal luminescent labels. CL and BL detection schemes have been
developed For assaying alkaline phosphatase, glucose oxidase, glucose 6-phosphate
dehydrogenase, horseradish peroxidase, and xanthine oxidase labels. In addition,
simple homogeneous assays are possible with CL acridinium ester and isoluminol
labels, as well as with glucose 6-phosphate dehydrogenase labels. CL and BL reactions
previous page 1196 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online next page 1198 Encyclopedia of Molecular Cell Biology and Molecular Medicine read online Home Toggle text on/off