YO-PRO-1

YO-PRO-1 (Oxazole yellow) is a carbocyanine monomer and DNA green fluorescent dye that is not permeable to normal animal cell membranes but is permeable to the cell membranes of apoptotic and necrotic cells. YO-PRO-1 is commonly used for the detection of apoptosis and necrosis. YO-PRO-1 has a high affinity for DNA and is essentially non-fluorescent when not bound to DNA. When apoptosis occurs, the permeability of the cell membrane changes. YO-PRO-1 can enter apoptotic cells and bind to DNA and emit bright green fluorescence. Therefore, YO-PRO-1 is often used together with propidium iodide (PI) to analyze and identify apoptotic and necrotic cells.