NADP is sold as four different things under four different CAS numbers: the free acid (53-59-8), the monosodium salt (1184-16-3), the disodium salt (24292-60-2), and the reduced tetrasodium salt (2646-71-1). All four carry the same coenzyme activity per mole of NADP(H); what differs is how much sodium they bring into your reaction, how fast they dissolve, and how much of the weighed powder is actually coenzyme. This article is a decision path through that choice.
1. The four forms side by side
| Form | CAS | Formula | MW (anhydrous) | Na per mole |
|---|---|---|---|---|
| NADP free acid | 53-59-8 | C21H28N7O17P3 | 743.4 | 0 |
| NADP monosodium | 1184-16-3 | C21H27N7NaO17P3 | 765.4 | 1 |
| NADP disodium | 24292-60-2 | C21H26N7Na2O17P3 | 787.4 | 2 |
| NADPH tetrasodium (reduced) | 2646-71-1 | C21H26N7Na4O17P3 | 833.3 | 4 |
| NADPH free acid (reduced) | 53-57-6 | C21H30N7O17P3 | 745.4 | 0 |
The molecular weight spread is not cosmetic: from free acid to tetrasodium salt the same molar quantity of coenzyme is 12% heavier. A protocol transferred from one salt to another on a weight basis will be 12% off in molar terms.
2. How much sodium you are actually adding
Sodium load scales with the coenzyme concentration, and at the concentrations used in cell-free reactions it is usually modest – but the arithmetic is worth doing before blaming an enzyme for losing activity.
| Coenzyme concentration | Free acid | Monosodium | Disodium | Tetrasodium (NADPH) |
|---|---|---|---|---|
| 0.1 mM | 0 mM Na+ | 0.1 mM | 0.2 mM | 0.4 mM |
| 1 mM | 0 | 1 mM | 2 mM | 4 mM |
| 10 mM | 0 | 10 mM | 20 mM | 40 mM |
Where coenzyme is used catalytically with a regeneration system – the normal industrial pattern – the concentration is typically in the 0.1-1 mM range and the sodium contribution is small next to the buffer itself. The salt form becomes a real variable in three situations: a high coenzyme concentration, a reaction already at high ionic strength, and an enzyme with a genuinely low sodium tolerance. In those cases the monosodium or free acid is worth asking for by name.
3. Dissolution behaviour
| Form | Dissolution | Solution pH tendency | Practical note |
|---|---|---|---|
| Free acid | Slowest; may need gentle warming and stirring | Acidic – needs neutralising | Best for stock solutions you will titrate yourself |
| Monosodium | Good | Slightly acidic | The compromise option |
| Disodium | Fastest of the oxidised forms | Near neutral | Standard commercial choice; also available as a 75% min solution |
| Tetrasodium (NADPH) | Fast | Alkaline | Watch the pH shift in an unbuffered system |
A slow-dissolving free acid is not a quality defect – it is what the free acid does. If your process has a fixed dissolution window, specify the salt form that fits the window rather than trying to make the free acid behave like the disodium salt.
4. Where the sodium question actually bites
- High-ionic-strength buffers. If the buffer is already at several hundred millimolar, adding the smallest possible counter-ion load keeps headroom for other components.
- Sodium-sensitive enzymes. Some kinases, membrane-associated enzymes and certain metal-dependent oxidoreductases lose activity well below the sodium concentrations that a typical assay buffer would reach. Check the enzyme datasheet before blaming the coenzyme.
- Analytical methods with a conductivity or ion-balance specification. In IVD reagents the sodium figure may be part of the method validation.
- Downstream isolation. Where the product is sensitive to salt load, the counter-ion is part of the impurity profile, not just a formulation detail.
5. Comparing prices across salt forms
| Step | What to do | Why |
|---|---|---|
| 1 | Convert price per kg to price per mole | MW ranges 743.4 to 833.3 across the oxidised and reduced forms |
| 2 | Correct for assay | A 98% lot delivers 98% of the coenzyme you are paying for; a 95% lot delivers 95% |
| 3 | Correct for water content | These materials are hygroscopic; water is not coenzyme |
| 4 | Add dose-level costs | Free acid may need extra pH adjustment; solution may cost more to ship |
A NADP disodium at a given price per kilogram is not comparable to a NADP free acid at the same price per kilogram: you are buying 787.4 g of material per mole in one case and 743.4 g in the other, and the cheaper-looking option can be the dearer one per mole of coenzyme.
6. Choosing, in one table
| Your situation | Choose |
|---|---|
| Standard biocatalysis with a regeneration system, no special constraints | NADP disodium (24292-60-2), powder or 75% solution |
| Buffer already high in salt, or enzyme sensitive to Na+ | NADP monosodium (1184-16-3) or free acid (53-59-8) |
| You need a sodium-free reference standard | NADP free acid (53-59-8) |
| You need the reduced coenzyme, fast dissolution, standard ionic strength | NADPH tetrasodium (2646-71-1) |
| You need the reduced coenzyme with no sodium at all | NADPH free acid (53-57-6) |
| Direct dosing into a bioreactor, no dissolution step | NADP disodium 75% min aqueous solution |
7. What to put on the purchase order
- CAS plus salt form – both, because the CAS alone can be misread and the salt form alone is ambiguous.
- Assay and its basis: dry basis HPLC, or in-solution for the aqueous grade. The two are not comparable.
- Water content for powder lots; concentration and pH for solution lots.
- Endotoxin and microbial limits if the material enters a cell-based or IVD process – not stated unless requested.
- Shipping temperature, agreed up front: 2-8 °C for solution, -20 °C option for powder held long term.
8. Packaging and supply
Powder ships in foil-lined bags or drums with an inner liner, and solution in HDPE drums or flexibags sized to your batch, so that the pack is consumed rather than stored half-used. Each lot carries a certificate of analysis and a safety data sheet; the assay method statement and third-party testing are available on request. Cold-chain and documentation requirements are quoted with the material – tell us the regulatory framework your incoming goods specification follows and the quotation will be built on that basis rather than adjusted afterwards.
Related reading
- The nicotinamide coenzyme family: NAD, NADH, NADP and NADPH explained on one page
- NAD in three forms: aqueous solution, biotransformation grade and food grade
- NADH: stability, diagnostic assays and biocatalytic use
Products in this family
- NADP free acid (CAS 53-59-8) – assay 98% min
- NADP monosodium salt (CAS 1184-16-3) – assay 98% min
- NADP disodium salt (CAS 24292-60-2) – 75% min solution and 98% min powder
- NADPH free acid (CAS 53-57-6) – assay 98% min
- NADPH tetrasodium salt (CAS 2646-71-1) – assay 95% min
PolyBlueChem supplies NADP free acid (53-59-8), NADP monosodium (1184-16-3), NADP disodium (24292-60-2), NADPH free acid (53-57-6) and NADPH tetrasodium (2646-71-1), with per-batch COA and SDS and FOB/CIF delivery. Tell us the salt form, assay basis, quantity and destination and we will quote the exact grade.