Propidium Iodide Dyes
Propidium iodide (or PI) is a fluorescent intercalator that can be used to stain cells and nucleic acids. PIs bind to DNA with little or no sequence preference by inserting between bases. When in aqueous solution, the maximum fluorescence excitation of PI is 493 nm (blue-green) and the maximum emission spectrum is 636 nm (red). After DNA binding, the quantum yield of PI increased by 20-30 times, and the excitation / emission maximum of PI moved to 535 nm (green)/617 nm (orange-red). Propidium iodide is used as a DNA stain in flow cytometry to assess cell viability or DNA content during cell cycle analysis, or when viewing the nucleus and other DNA-containing organelles under a microscope. Propidium iodide is impermeable to the membrane and can therefore be used to distinguish necrotic, apoptotic, and healthy cells based on membrane integrity. PI also binds to RNA, so it must be treated with nuclease to distinguish between RNA and DNA staining.
Introductions
The fluorescent dye PI (propidium iodide) is a nuclear staining reagent that can stain DNA. It is often used for the detection of apoptosis. It is an analog of ethidium bromide, which emits red fluorescence after embedding double-stranded DNA. Although PI cannot pass through the living cell membrane, it can stain the nucleus through the broken cell membrane. PI is often used with fluorescent probes such as Calcein-AM or FDA to stain live and dead cells simultaneously. The excitation and emission wavelengths of the PI-DNA complex are 535 nm and 615 nm, respectively.
Principle of propidium iodide staining
Propidium iodide (PI) cannot penetrate human intact live cell membranes, that is, normal cells and apoptotic cells resist PI staining under unfixed conditions, and necrotic cells can enter PI due to loss of membrane integrity. Cells bind to DNA. Based on this feature, PI staining can be used to identify dead cells. If staining live cells must be fixed before staining to increase the permeability of the cell membrane to the dye.
Applications
At present, the methods for measuring the number of living cells include optical microscope reading counting method, plate coating culture colony counting method, photoelectric turbidimetric method, maximum likelihood method, and membrane filtration method. Direct microscope counting method: A small amount of the suspension of the sample to be measured is placed on a special glass slide (also known as a bacteria counter) with a defined area and volume, and the count is directly observed under the microscope. The method is simple, fast, and intuitive, and can be used to count suspensions of yeast, bacteria, mold spores, and animal cells. The disadvantage is that the dead or alive state of the cells cannot be accurately identified, and the measured result is usually the sum of dead and live cells.
Reference:
- Stevenson, P.; et al. Comparison of isometamidium chloride and homidium bromide as prophylactic drugs for trypanosomiasis in cattle at Nguruman, Kenya. Acta Tropica. 1995, 59 (2): 257–258.
Dyes Application
- Acridine Dyes
- Alcian Blue Stain Dyes
- Alexa Fluor Dyes
- Allophycocyanin Dyes
- Anthracene Dyes
- BODIPY Dyes
- Coumarin Dyes
- Cresyl Violet Dyes
- Crystal Violet Dyes
- DAPI Dyes
- DNA Dyes Stain
- Feulgen Stain Dyes
- Fluorescein Isothiocyanate Dyes
- Fluorescent protein Dyes
- Nile Blue Dyes
- Nile Red Dyes
- Pacific Blue Dyes
- Pacific Green Dyes
- Pacific Orange Dyes
- Pyrene Dyes
- Texas Red Dyes
- Xanthene Dyes
Probe Application
