TB-500 (synthetic thymosin β4): what it is, how it is supplied, and how to choose a research supplier

"TB-500" is a trade name, not a sequence. On the research market it most often designates full-length synthetic thymosin β4 — 43 amino acids, about 4,963 Da, with an acetylated N-terminus that starts Ac-Ser-Asp-Lys-Pro (Ac-SDKP) — and some vendors sell a shorter fragment of the same protein under the same name. Thymosin β4 itself is a small actin-binding protein found in most cell types.

Two objects therefore circulate under one label, and only the certificate of analysis tells them apart:

• Full-length synthetic thymosin β4 — 43 residues, about 4,963 Da. The usual meaning of "TB-500" on batch COAs from independent laboratories.
• A fragment of thymosin β4 — a shorter synthetic segment of the same protein, with a correspondingly lower mass, sold by some vendors under the same name.

The mass on the batch COA is what identifies a given lot: compare it with the sequence and mass stated on the product page before ordering. In the catalog, TB-500 is a research reagent: a sealed vial of lyophilized powder with a lot number and a certificate of analysis. Research use only. Not for human or veterinary use.

Most pages that rank for "TB-500" are clinics, sports-governance notices and video explainers. None of them describes the object a laboratory receives. What matters at the bench is the product, and the product has a short list of properties that can be checked.

If a listing gives no sequence, no mg quantity and no verifiable COA, it is a reseller — not a research supply.

Research TB-500 comes as a white lyophilized (freeze-dried) powder in a glass vial closed with a rubber septum and an aluminum crimp cap. The label states the compound, the net quantity in milligrams, the lot number and the words "research use only".

The catalog offers three sizes — 10 mg, 20 mg and 30 mg — and the price per milligram is listed for each. The live table at the top of this page is read directly from the catalog, so the prices shown there are the prices in force today. See TB-500 in the catalog for availability.

What "10 mg" means on the label

The number is the net mass of TB-500 powder filled into the vial, and it is the quantity the certificate of analysis refers to. Ten milligrams of a lyophilized peptide is a small amount of material: it sits at the bottom of a 3 mL vial as a thin white cake or film, sometimes barely visible against the glass. That is normal for the size and is not a short fill.

Acetate salt and peptide content

Synthetic peptides are usually isolated as an acetate salt and carry some bound water. A careful COA distinguishes purity (the share of peptide among peptide-like material, from the HPLC trace) from peptide content (the share of the powder mass that is peptide rather than counter-ion and water). Both numbers are legitimate; they are simply not the same number. The difference is explained in HPLC purity: what "> 99 %" means.

For a peptide sold under a trade name, like TB-500, a usable certificate carries:

• The laboratory's name and a verifiable identifier. Independent labs (Janoshik is the reference for this market) give each test a number that anyone can look up on the lab's site. A PDF that cannot be looked up is not a certificate.
• The lot number — identical to the lot number printed on the vial you receive.
• HPLC purity as a measured percentage with the chromatogram. Text that says "≥ 98 %" without a trace is a claim, not a measurement.
• Mass confirmation by mass spectrometry: the observed mass matches the sequence stated on the product page — about 4,963 Da for full-length thymosin β4, less for a fragment.
• The date of the test. A certificate several months old describes a lot that has probably sold through.
• A photograph of the tested vial wearing the supplier's own label. A COA showing a bare vial was issued to the manufacturer and says nothing about what this supplier bottled.

The full checklist, with examples of what a doctored certificate looks like, is in how to read a peptide COA.

TB-500 is stable as a lyophilized powder when it is kept cold, dark and dry. The catalog's storage line for the sealed vial:

• Temperature: −20 °C for long-term storage; a refrigerator (2–8 °C) is acceptable for short periods.
• Light: keep the vial in its box or in an opaque container.
• Moisture: the powder is hygroscopic. Let a cold vial reach room temperature before removing it from its bag, so no condensation forms on the glass.
• Shelf life: 24 months from the fill date for a sealed vial stored as above.

Shipping at ambient temperature for a few days does not degrade the sealed powder; that is why research peptides ship without cold packs. The general rules, size by size, are in lyophilized peptides: storage and shelf life.

"Buy TB-500" returns clinics, offshore resellers and a handful of research suppliers. To sort them, ask six questions of the product page — not of the marketing.

1. Is there a batch COA from a named independent lab, and can it be verified on the lab's site? No verifiable COA = no purchase.
2. Does the COA show the supplier's own label? A manufacturer's certificate, re-used by a reseller, does not cover what was re-bottled or re-labeled.
3. Does the mass on the COA match the sequence and mass stated on the product page? The single most useful check for a compound sold under a trade name.
4. Does the supplier ship domestically, from US stock, in a few days? Long international transit is where vials get lost, heated or seized.
5. Does the page describe the product only — composition, purity, storage — with "research use only" stated plainly? A supplier that publishes usage content is a supplier that is easy to shut down; that risk transfers to the buyer whose order is in transit.
6. Is the price at or above the market, not far below it? Third-party testing costs several hundred dollars per lot. A price far under the market is a price that did not pay for testing.

The wider checklist — payment, packaging, what to do if a parcel is stopped — is in where to buy research peptides in the US.

TB-500 and BPC-157

The two peptides are often searched together. They are unrelated molecules: BPC-157 is a 15-residue peptide of a different sequence, sold in the same 10/20/30 mg sizes. Its own guide is the BPC-157 buying guide.

The price of research TB-500 depends on three things: the size of the vial, whether a third-party test was paid for the lot, and where it ships from. Synthesis cost per milligram is far higher for a 43-residue peptide than for a tripeptide like GHK-Cu, which is why a 10 mg vial of TB-500 costs more than a 100 mg vial of GHK-Cu. The catalog table at the top of this page shows the current price per vial and per milligram for each size.

What the price includes at OXpeptides: a sealed, labeled vial from a tested lot, the batch COA, tracked domestic shipping, and a replacement if a parcel arrives damaged. What it never includes: anything other than the reagent itself.

See TB-500 in the catalog →