These three are discussed as though interchangeable more often than any other set in this field. They are not, and substituting one for another changes what an experiment measures.
What each one is
NAD+ is the coenzyme itself. Present in every living cell, central to redox reactions, and consumed as a substrate by sirtuins, PARPs and CD38.
NMN, nicotinamide mononucleotide, is one step upstream. It is converted to NAD+ by NMNAT enzymes.
NR, nicotinamide riboside, is a further step upstream. It is phosphorylated to NMN by NRK enzymes, then converted to NAD+.
So the sequence is NR to NMN to NAD+, with an enzymatic step at each transition.
Why the distinction matters in an assay
If you add NAD+ to a system, you are adding the coenzyme. If you add NMN or NR, you are adding a precursor and depending on the conversion machinery being present, functional and unsaturated in whatever system you are working in.
That is a large assumption in an isolated preparation and a smaller one in intact cells. In a cell free system with no NMNAT activity, adding NMN accomplishes very little.
There is also a transport question. NAD+ itself does not readily cross intact cell membranes, which is one reason precursor work exists at all.
Choosing for a protocol
| Working with | Usually specify | Because |
|---|---|---|
| Isolated enzymes, cell free assays | NAD+ | No conversion machinery present |
| Isolated mitochondria | NAD+ | Direct redox participation is the measurement |
| Intact cells, precursor studies | NMN or NR | Transport and conversion are part of the question |
| Salvage pathway work | Depends on which step | The pathway step defines the substrate |
Read the protocol you are following carefully. Papers do not always distinguish clearly, and a methods section saying only “NAD” is ambiguous.
Handling differences
NAD+ is refrigerated at 2C to 8C rather than frozen, which catches people out because most compounds in a peptide catalogue are frozen and everything arriving in one box tends to go the same way.
It is freely water soluble and dissolves immediately. Protect it from light and moisture, and keep the vial sealed until use.
The oxidised and reduced forms
A second distinction worth being precise about. NAD+ is the oxidised form, NADH the reduced form. The ratio between them is a standard readout of cellular redox state.
What is supplied here is the oxidised form. A protocol specifying NADH needs the reduced form, and the two are not substitutable.
What we supply
NAD+ in a 1000mg vial, CAS 53-84-9. The larger format exists because NAD+ is typically used at higher quantities than the peptides in this catalogue, and repeated small orders create a traceability problem across a long protocol.
NMN and NR are not currently in the catalogue. If your protocol needs one, ask and we will quote against your specification.