Propidium

Propidium is a fluorescent dye used in biological and medical research to stain nucleic acids, particularly DNA. It is a member of the phenanthridinium family of dyes and is often used in flow cytometry and fluorescence microscopy to visualize cell viability and apoptosis. Propidium iodide (PI) is the most commonly used form of propidium, which binds to DNA and emits a red fluorescence when excited by light in the blue or ultraviolet range. This property makes it useful for identifying dead or dying cells, as the cell membrane becomes permeable to PI, allowing it to enter and bind to DNA. Propidium is also used in molecular biology for gel electrophoresis to visualize DNA fragments. Its use requires caution due to potential toxicity and the need for proper disposal of waste containing the dye.