Propidium iodide (or PI) is a
fluorescent
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...
intercalating agent
In biochemistry, intercalation is the insertion of molecules between the planar bases of deoxyribonucleic acid (DNA). This process is used as a method for analyzing DNA and it is also the basis of certain kinds of poisoning.
There are several ...
that can be used to
stain cells and
nucleic acids
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...
. PI binds to DNA by intercalating between the bases with little or no sequence preference. When in an aqueous solution, PI has a fluorescent excitation maximum of 493 nm (blue-green), and an emission maximum of 636 nm (red). After binding DNA, the
quantum yield The quantum yield (Φ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system.
Applications
Fluorescence spectroscopy
The fluorescence quantum yield is defined as the ratio of the numb ...
of PI is enhanced 20-30 fold, and the excitation/emission maximum of PI is shifted to 535 nm (green) / 617 nm (orange-red). Propidium iodide is used as a DNA stain in
flow cytometry to
evaluate cell viability or DNA content in
cell cycle analysis, or in microscopy to visualize the nucleus and other DNA-containing organelles. Propidium Iodide is not membrane-permeable, making it useful to differentiate
necrotic
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
,
apoptotic
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes incl ...
and healthy cells based on membrane integrity. PI also binds to
RNA, necessitating treatment with nucleases to distinguish between RNA and DNA staining.
PI is widely used in fluorescence staining and visualization of the plant cell wall.
See also
*
Viability assay
A viability assay is an assay that is created to determine the ability of organs, cells or tissues to maintain or recover a state of survival. Viability can be distinguished from the all-or-nothing states of life and death by the use of a quanti ...
*
Vital stain A vital stain in a casual usage may mean a stain that can be applied on living cells without killing them. Vital stains have been useful for diagnostic and surgical techniques in a variety of medical specialties. In supravital staining, living cells ...
*
SYBR Green I
SYBR Green I (SG) is an asymmetrical cyanine dye used as a nucleic acid stain in molecular biology. The SYBR family of dyes is produced by Molecular Probes Inc., now owned by Thermo Fisher Scientific. SYBR Green I binds to DNA. The resulting DN ...
*
Ethidium bromide
Ethidium bromide (or homidium bromide, chloride salt homidium chloride) is an intercalating agent commonly used as a fluorescent tag ( nucleic acid stain) in molecular biology laboratories for techniques such as agarose gel electrophoresis. It ...
References
{{DEFAULTSORT:Propidium Iodide
Flow cytometry
DNA-binding substances
Iodides
Phenanthridine dyes
Staining dyes