PI Brite™ is a propidium iodide (PI) analog developed by AAT Bioquest to improve the brightness and fixability of propidium iodide in cells. Under the same conditions, PI Brite™ is significantly brighter and better survives cell fixation process than PI. Propidium iodide is a fluorescent intercalating agent commonly used for staining cells with compromised membranes, such as dead cells, apoptotic or fixed cells. One of the primary applications of propidium iodide is for cell viability assays. Since it only stains cells with compromised cell membranes, it is often used to distinguish between live and dead cells in a population. In addition, PI is frequently used in flow cytometry to assess the cell cycle distribution of a population of cells. It allows researchers to analyze the DNA content of individual cells and identify different phases of the cell cycle. It binds to DNA by intercalating between the bases. PI is often used for detecting and quantifying DNA in various applications, such as flow cytometry, fluorescence microscopy, and gel electrophoresis.