Photometric Detection of Nicotinamide Adenine Dinucleotides

was first discovered by Arthur Harden and William Youndin in 1906. It plays key roles as a carrier of electrons and a participant in metabolic redox reactions, as well as in cell signaling. There are two forms of this coenzyme in cells, the non-phosphorylated form NAD + and the phosphorylated form NADP + . These two related coenzymes have similar chemistry, but perform different roles in metabolism. When both coenzymes are being discussed, they are referred to collectively as NAD(P) + .