MUP, free acid (4-Methylumbelliferyl phosphate, free acid) is a fluorogenic phosphatase substrate that releases the blue fluorescent dye 4-methyl-7-hydroxycoumarin. MUP free acid and its sodium salt form are the most widely used fluorogenic substrates for alkaline phosphatase detection. λEx/λEm= 360/450 nm (end product) White solid soluble in water and DMSO Store desiccated at 4°C and protect from light C10H9O6P MW: 256