BPC-157 vs TB-500: what the labels actually denote

BPC-157 and TB-500 are the two most-requested sequences in the research peptide catalogue, and they are routinely compared as though the choice were a matter of preference. For a laboratory the useful comparison is narrower and more concrete: what each name denotes chemically, how well-defined that identity is, and what a supplier can actually prove about the powder in the vial.

That last point separates them more than anything else. One of these labels maps to a single, unambiguous sequence. The other is used across the market for at least two different molecules. Nothing on this page is usage, preparation, dosing or outcome guidance — materials are supplied for laboratory research only and are not for human or veterinary consumption.

Identity at a glance

Why BPC-157 is the easier identity to verify

BPC-157 is a synthetic pentadecapeptide with the sequence GEPPPGKPADDAGLV. Because that sequence is fixed, everything downstream is checkable arithmetic: the molecular formula follows from the residues, the average mass follows from the formula, and a mass-spectrometry result on the batch either agrees with that calculated mass or it does not. A certificate quoting an observed mass near 1419.5 g/mol, alongside an RP-HPLC purity figure, is a self-consistent claim a reviewer can check without trusting the vendor.

Proline-rich sequences like this one are also comparatively well-behaved in synthesis and storage terms — there is no methionine, cysteine or tryptophan in the chain, which are the residues most readily oxidised. The practical consequence for a buyer is that impurity profiles tend to be dominated by synthesis-related species (deletion and truncation sequences) rather than degradation products, and those are exactly what an RP-HPLC chromatogram is good at showing. The mechanics are covered in how research peptides are made.

Why “TB-500” needs more scrutiny

TB-500 is a trade name rather than a chemical identifier, and the market has never fully settled what it denotes. It is most often used for an acetylated seven-residue fragment corresponding to residues 17–23 of thymosin β4 (Ac-LKKTETQ, roughly 0.9 kDa). It is also widely used for the full-length 43-residue thymosin β4 protein, which is around 4.9 kDa — more than five times the mass. Intermediate constructs with flanking residues exist too.

These are different materials at every level that matters analytically: different formulae, different masses, different chromatographic behaviour, different impurity profiles. A purity percentage tells you nothing about which one you have, because purity is a statement about homogeneity, not identity — the distinction is set out in RP-HPLC vs mass spectrometry.

This is why we publish no CAS number, formula or theoretical mass for TB-500 on the product page. Asserting a single identifier for a name that is used across multiple constructs would be a claim we could not stand behind. What the batch certificate carries instead is the observed mass for that lot, which resolves the question empirically.

Where labs specify one or the other

At material level the two behave differently in ways that shape how a laboratory writes its specification, independent of any downstream application:

• Reference and method work. A fixed sequence with a registered CAS number is the easier material to cite in a method, to re-order against, and to compare across suppliers. BPC-157 is straightforward here; TB-500 requires the construct to be pinned down in the specification itself, not just by name.
• Analytical planning. A ~1.4 kDa peptide and a ~4.9 kDa protein are not interchangeable inputs to a chromatographic or mass-spectrometric method. Column choice, gradient and charge-state envelope all differ, so the construct has to be known before the method is written.
• Batch comparability. Where a programme spans several orders, the risk with an ambiguous label is receiving a different construct on a later lot. Ordering against a stated construct — and checking each batch certificate — is the control. See bulk research peptides in the UK.
• Storage assumptions. Both are supplied lyophilised and stored at −20 °C protected from light, but degradation pathways depend on the residues actually present, so they are not automatically equivalent. Background in lyophilised peptide storage.

We do not publish comparative claims about what either material does, in people or in any other system. That is not modesty about the science; it is the line that keeps a research-use-only supply lawful, as explained in what “research use only” means in the UK.

What NorthScientific publishes for each

Both sequences are supplied as lyophilised powder in crimp-sealed vials. Where an identifier is database-verifiable, as with BPC-157, it appears on the datasheet; where a name is ambiguous, as with TB-500, we state the format and do not assert an identifier we cannot stand behind. NorthScientific does not currently publish independent third-party analysis for the material it holds.

Full pricing and the rest of the range are on the catalogue. Questions about chemistry, batches or certificates go to info@northscientific.co.uk; questions about use in people will not be answered, by anyone here, ever.

Materials referenced: BPC-157 · TB-500 · BPC-157 + TB-500 blend · full catalogue