Quick answer
TB-500 means different thymosin beta-4 entities at different suppliers, so confirm the stated sequence, check the certificate's mass against it, and require a lot-matched CoA.
- Standalone: 10 mg vial on the TB-500 product page, ≥98% by HPLC listed
- Stack: also in the BPC-157 + TB-500 stack
- Identity: mass must agree with the stated sequence; watch for +16 Da oxidation
- Documents: CoA page
- Research use: For laboratory research use only; not for human consumption.
For laboratory research use only; not for human consumption.
What "TB-500" means, and why it matters when buying
TB-500 is the trade name used for a synthetic peptide derived from thymosin beta-4 (Tβ4), a 43-residue, roughly 4.96 kDa protein found in most cell types and associated with actin regulation. The catch for buyers is that "TB-500" is not used with one fixed meaning. Depending on the source it can refer to full-length thymosin beta-4, to an acetylated N-terminal fragment, or to the short actin-binding region (Leu-Lys-Lys-Thr-Glu-Thr-Gln, residues 17–23). Those are different molecules with very different masses, so the first question for any purchase is: which sequence does this listing claim, and does the mass on the certificate agree with it?
The V8 Peptides product page lists TB-500 as a synthetic fragment of thymosin β4 and gives the sequence as the acetylated 23-residue N-terminal fragment Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys-Phe-Asp-Lys-Ser-Lys-Leu-Lys-Lys-Thr-Glu-Thr-Gln. By simple residue-mass arithmetic, that chain would come out near 2.7 kDa, against about 4.96 kDa for the full 43-residue protein. A certificate that reports a mass inconsistent with the stated sequence should be queried before use. The compound's research background is in the TB-500 research overview.
| Entity | Residues | Approximate mass |
|---|---|---|
| Full-length thymosin beta-4 | 43 | About 4,963 Da |
| Acetylated N-terminal fragment (as listed) | 23 | About 2.7 kDa (calculated from sequence) |
| Actin-binding heptapeptide (17–23) | 7 | About 0.8 kDa |
Where to find standalone TB-500
V8 Peptides lists TB-500 as its own product: a 10 mg lyophilized vial with a purity specification of ≥98% by HPLC, on the TB-500 research vial page. It is also supplied as a component of combination products, including the BPC-157 + TB-500 research stack, the GLOW stack, and the KLOW blend covered in where to buy the KLOW Stack. Researchers who want to vary the two peptides independently can use separate vials; those who want matched documentation and reconstitution timing across both can use the stack.
What to check before buying TB-500
- Measured purity, not a marketing claim. A stated HPLC purity value (for example ≥98%) with the analytical method identified, not a bare percentage. See understanding HPLC purity.
- Confirmed identity. Mass spectrometry data showing the measured mass matches the expected sequence, not just an assumed match based on the label. See HPLC vs. mass spectrometry.
- Lot-specific documentation. A certificate of analysis tied to the exact batch in hand, not a generic reference document reused across every listing. See how to read a CoA.
- Independent verification. Third-party testing that corroborates the supplier's in-house results. See third-party testing explained.
- Honest, research-only framing. Clear labeling and storage guidance, with no clinical claims anywhere on the listing.
- Appropriate shipping and handling for a lyophilized peptide. See how research peptides are shipped.
Analytical challenges specific to TB-500
A fragment of this size and composition is lysine-rich and carries many acidic residues, so it is strongly charged and hygroscopic. Three consequences matter for documentation.
Charge states and mass spectra
A lysine-rich peptide picks up many protons in electrospray ionization and produces a broad series of multiply charged ions. A reliable report shows the deconvoluted neutral mass alongside the raw envelope, so a reader can confirm it against the calculated mass for the stated sequence. A single reported number with no spectrum is harder to trust.
Methionine oxidation
The sequence contains a methionine, which can oxidize during synthesis, storage or handling. The oxidized form is about 16 Da heavier and usually elutes slightly earlier. A shoulder or small leading peak with a +16 Da mass is the typical signature, and it is a reason to check storage history on older material.
Counter-ions and water
Because the peptide is highly charged, the lyophilized powder carries significant counter-ion mass, often acetate or trifluoroacetate. A 10 mg vial is therefore 10 mg of powder, not necessarily 10 mg of peptide. Net peptide content is measured separately from HPLC purity; for concentration planning use the calculator and adjust for the net content where it is known.
| Observation | Likely cause | What to do |
|---|---|---|
| Observed mass about 16 Da above expected | Methionine oxidation | Check storage; ask for a fresher lot |
| Observed mass far from the stated sequence | Different TB-500 entity or wrong product | Query the supplier before use |
| Early shoulder on the main HPLC peak | Oxidized or deamidated species | Request integration table |
| No lot number on the certificate | Generic document | Request a batch-specific CoA |
Why TB-500 is often paired with BPC-157
TB-500 and BPC-157 are studied together often enough, for the reasons discussed in BPC-157 vs. TB-500 and BPC-157 and TB-500 combination research, that many researchers requesting TB-500 are already running a two-peptide design. Because the two are very different sizes (BPC-157 is about 1.4 kDa), mass spectrometry separates them easily, which makes the combined product straightforward to verify. The related reconstitution notes are in BPC-157 + TB-500 blend reconstitution, and third-party testing of the pair is discussed in BPC-157 and TB-500 third-party testing.
Storage and handling after delivery
Lyophilized TB-500 should be refrigerated at 2–8 °C, frozen for long-term storage, and protected from heat, moisture and light, as the product page states. Once reconstituted, solutions degrade faster than powder, so labs typically prepare single-use aliquots and avoid repeated freeze-thaw cycles. As an example of concentration arithmetic, 10 mg in 2 mL is 5 mg/mL. See storing research peptides and how to reconstitute a lyophilized peptide.
Comparing offers like for like
When two TB-500 listings differ in price, the difference is only meaningful if the products are the same thing. Compare the stated sequence first, then the vial size, then the purity method, then the documentation. A 10 mg vial of a 23-residue fragment and a 10 mg vial of full-length thymosin beta-4 contain very different numbers of molecules, so a price per milligram says nothing about price per mole. Labs designing molar-matched experiments should convert using the mass that applies to the sequence actually supplied, which is another reason the certificate's observed mass should be recorded with the lot number. Consistency across a study matters more than any single purchase: reordering the same sequence from the same documented source keeps the variable fixed.
Red flags
- A listing that does not say which TB-500 sequence it is.
- Purity quoted with no method and no document available on request.
- A certificate with no lot number, or one identical across unrelated products.
- Listing copy that makes clinical claims instead of staying within research framing.
More patterns are collected in red flags when buying research peptides, and the full supplier framework is in choosing a peptide supplier. Batch documents are posted on the certificate of analysis page, and the TB-500 product page lists the supplied form and storage.
Where to Buy TB-500 (Thymosin Beta-4) for Research FAQ
Does V8 Peptides sell TB-500 on its own?
Yes. TB-500 is listed as a 10 mg lyophilized vial, and it is also a component of the BPC-157 + TB-500 stack and other blends.
Is TB-500 the same as thymosin beta-4?
Not necessarily. Thymosin beta-4 is a 43-residue protein of about 4.96 kDa; TB-500 is used for a synthetic fragment, and the exact sequence varies by source, so check the listing.
What sequence does the V8 Peptides listing give?
The acetylated 23-residue N-terminal fragment, Ac-SDKPDMAEIEKFDKSKLKKTETQ. A certificate's mass should be consistent with that sequence.
Why does the mass on the certificate matter so much here?
Because different entities are sold as TB-500 and their masses differ widely, mass spectrometry is the check that shows which one is in the vial.
What does a +16 Da peak mean?
Usually oxidation of the methionine residue. It is a common degradation signature and a reason to check the lot's age and storage.
Is a 10 mg vial 10 mg of peptide?
10 mg is the powder mass. Counter-ions and residual water account for part of it, so net peptide content is lower; measure it separately where concentration accuracy matters.
How should lyophilized TB-500 be stored?
Refrigerated at 2 to 8 degrees C, frozen for long-term storage, and protected from heat, moisture and light.
Why is TB-500 often bought with BPC-157?
They are frequently studied together, and a combined product keeps documentation and reconstitution timing consistent across both. They are easy to tell apart by mass.
For laboratory research use only; not for human consumption. This article is research education, not usage guidance.
References
- TB-500 research overview
- TB-500 purity testing
- How to read a CoA
- Certificate of analysis page
- TB-500 product page
- BPC-157 + TB-500 stack
Research Use Only. Supplied strictly for laboratory research and development; not for human or veterinary use, consumption, or any clinical or diagnostic purpose.