Primary Reactions 2.4 CHEMILUMINESCENCE Flashcards
the emission of light from a substance as it returns from an electronically excited state to ground state.
Luminescence
Forms of luminescence, differing in the way the excited state is reached. e.g.,
● _________ is simply fluorescence; excitation is initiated by a light at a particular wavelength.
● _________ is characterized by the use of a bioluminescent compound, such as luciferin and firefly luciferase (Photinus pyralis)
● ________is light produced by a chemical reaction.
Photoluminescence
Bioluminescence
Chemiluminescence
Principle:
_______ relies on the reaction of NO with ozone. The chemical oxidation of NO by ozone yields nitrogen dioxide in an excited state. Relaxation from this excited state produces distinctive light emission (chemiluminescence) that is directly proportional to NO concentration.
Chemiluminescence
________ – are compounds that undergo a chemical reaction and form an unstable derivative. Upon return to the ground state, they release energy in the form of visible light. The light is measured by a luminometer and light intensity is related directly to the concentration of the reactants.
Chemiluminescent Label
Common Chemiluminescent labels used –
- Luminol
- Acridium esters
- Peroxalates
- Ruthenium derivatives
- Dioxetanes
______ is an organic compound
● When oxidized, emits light– a phenomenon known as ________
Luminol
chemiluminescence
_______ is a property in which a substance is undergoing a chemical reaction and releasing energy in the form of lights
○ Example: firefly and glowsticks
○ Produce chemical that, when exposed to other substances that catalyze the reaction, produce a glow
● Formula: C8H7N3O2
● Discovered in the late 19th century
Chemiluminescence
➢ This labelling can be used for both __________assays because the labels can be attached to either antigen or antibody.
➢ Labelling involves the oxidation of an organic compound by an _____, i.e Hydrogen peroxide, Hypochlorite or oxygen: light is emitted from the excited product formed in oxidation reaction.
➢ _______ the temperature of the reaction speeds up and releases more light, however, the light ______ long.
➢ The reaction of luciferin with ATP in the presence of the enzyme _____ is a well-known example of chemiluminescence. This reaction occurs within fireflies to produce their light, characterized as bioluminescence.
heterogeneous and homogeneous
oxidant
Increasing; doesn’t last
luciferase
– competitive and sandwich formats are often used.
Homogeneous Assays
_____ - for smaller analytes such as:
a. therapeutic drugs
b. steroid hormones
Competitive Format
_______ - for longer analytes such as protein hormones
Sandwich Format
_________ is used by forensic scientists to solve crimes. In this case, luminol and hydrogen peroxide are used. The iron from the blood acts as a catalyst and reacts with the luminol and hydrogen peroxide to produce blue light for about 30 seconds.
Chemiluminescence
Advantages of Chemiluminescence:
- Has excellent ________comparable to EIA and RIA. Some assays are reported to be in the range of attamoles (10-18 mol) to zeptamoles (10-21 mol).
- _____, very little reagent is used.
- Reagents are stable and relatively ______.
- Has relatively _____ of detection.
- Detection system basically consist of ________, which are simple and relatively inexpensive.
sensitivity Inexpensive non-toxic high speed photomultiplier tubes
Disadvantage:
______ may be obtained if there is lack of precision in the injection of ____or if some biologic materials, i.e., ______ cause quenching of light emission.
False results
H2O2
urine or plasma
Uses:
- Hormones: Insulin, thyroxin, testosterone, progesterone
- Vitamin: vit B 12
- Tumor markers: bone morphogenic protein-2, carcino embryonic antigen (CEA), alpha fetoprotein (AFP)
- Human beta chorionic gonadotropin
- C-reactive protein
- Tumor necrosis factor
