What is a Radioimmunoassay?
- separation of a protein (from a mixture) using the specificity of antibody - antigen binding.
- Quantation using radioactivity
what is an Enzyme-linked immunosorbent assay?
- the molecules is detected by antibodies that have been made against it.
- Quantitation by the same antibodies coupled to an enzyme (eg: an enzymes that produces a colored products from a colorless substrate)
- uses an enzyme linked to an antibody or antigen as a marker for the detection of a specific protein
How does ELISA work?
- the sample with an unknown ammount of antigen is immobilized on a solid support either specifically or non-specifically.
- the detection antibody is then added, forming a complex with the antigen
what are the characteristics of the Enzymes for ELISA?
- high specific activity, not reduced by conjugation
- stability and solubility
- simple and sensitive
activity constant under test conditions
Advantages of ELISA (8)
- sensitive assay
- equipment widely available
- no radiation hazards
- reagents are cheap with long shelf life
- adaptable to automation and high speed
- qualitative and quantitative
- reproducible
- can be used on most types of biological samples such as plasma, serum, urine and cell extracts.
Disadvantages of ELISA? (2)
- enzyme activity may be affected by plasma constituents
2. Homogenous ELISA is not as sensitive as radioimmunoassay
what is a bevel?
a slanted opening at the end of a needle
what is the gauge of a needle?
the number that indicates the diameter of the lumen/bore.
- the higher the guage the smaller the lumen
what is the lumen/bore of a needle?
the circular hollow space inside the needle
what are Vacuum collection tubes?
glass or plastic tubes sealed with a partial vacuum inside by rubber stoppers. the air pressure inside the tube is negative and thus when a needle is inserted into the tube, the fluid inside is drawn out due to this pressure difference.
A red top indicates?
collection of serum
A light blue top indicates?
additive - sodium citrate
A pink top indicates?
additive - EDTA
A green top indicates?
one of the following: sodium heparin, lithium, heparin or ammonium heparin.
A grey top indicates?
additive:
potassium oxalate and sodium fluoride or lithium iodacetate and heparin
A black top indicates?
buffered sodium citrate
A brown/tan top indicates?
additive: sodium heparin or K2 EDTA
A yellow top indicates?
sodium polyanethol sulfonate
