What is NAD+?
The first thing to say about this item is what it is not: NAD+ is not a peptide and carries no amino acid sequence. It is a dinucleotide coenzyme built from a nicotinamide mononucleotide half and an adenosine monophosphate half joined through a pyrophosphate bridge.
On record: CAS 53-84-9, molecular formula C21H27N7O14P2, molecular weight 663.43. It has no amino acid sequence because it is not a peptide; identity is confirmed by mass and by its 260 nm absorbance signature rather than by a peptide-bond assay. What can be described without them is the chemistry of the class. The nicotinamide ring accepts a hydride to give the reduced form, and the adenine chromophore gives strong ultraviolet absorbance near 260 nm.
In the published literature the oxidized and reduced forms shuttle electrons for dehydrogenase reactions across glycolysis, the citric acid cycle and oxidative phosphorylation. Separately, the oxidized form is consumed as a substrate by sirtuins, poly-ADP-ribose polymerases and CD38 in cell models. Compartment-specific pool sizes, how readily exogenous material crosses membranes intact, and how much of any effect in animal models reflects breakdown products rather than the coenzyme itself, all remain unsettled.
Reconstitution & handling
Sterile water dissolves the powder quickly and the resulting solution is mildly acidic. The coenzyme is far more stable in slightly acidic than in alkaline water, so unbuffered water is preferable to a high pH buffer. Concentration is mass over volume arithmetic against the labelled content, using the molecular weight printed on the certificate of analysis.
Storage & stability
Keep the sealed powder at -20 °C, tightly closed and desiccated, since the material is hygroscopic and absorbed moisture drives hydrolysis of the pyrophosphate linkage. Reconstituted stock should sit at 2 to 8 °C for short periods only, or be frozen in single-use aliquots, since dilute solutions lose titre faster than the dry solid. Protect from light and avoid alkaline conditions and heat, which accelerate decomposition to nicotinamide and ADP-ribose.
How it's tested
Purity is determined by reversed-phase HPLC with ultraviolet detection near 260 nm, where the chromophores absorb, rather than at the 214 and 220 nm peptide bond wavelengths used for peptides. Identity is confirmed by mass spectrometry against the theoretical mass for the coenzyme. Water content, residual solvent and principal degradation products are reported, and a lot-matched certificate of analysis is available on request.