NAD+ — nicotinamide adenine dinucleotide — is a coenzyme found in every living cell, not a peptide, and the largest fill in the range at 500mg. It is the molecule that carries electrons in the redox reactions cells use to turn nutrients into ATP, and it is also the substrate for two families of enzymes, the sirtuins and the PARPs, that are involved in DNA repair, gene regulation and the cell's stress responses. Its levels fall with age, which is what drew ageing research to it. It is commonly researched for its role in mitochondrial energy metabolism, in those sirtuin and PARP pathways, and in longevity and metabolic models. Supplied as 500mg of freeze-dried powder per vial, for reconstitution with bacteriostatic water; store at 2–8°C.