TB-500 Research Guide: Thymosin Beta-4 vs. Fragment, COA and Handling
“TB-500” is a research-market name tied to thymosin beta-4, a 43-amino-acid protein that binds actin inside cells. Labs use it in studies of actin dynamics, cell migration and tissue-repair models. The catch is that suppliers use the name for two different molecules. This page explains both, shows how to tell from a certificate of analysis which one you have, and covers handling, using FRO Peptides’ own published lot report as the example.
TB-500 vs. thymosin beta-4: two molecules, one name
| Thymosin beta-4 (full length) | TB-500 fragment | |
|---|---|---|
| Length | 43 amino acids, N-terminal acetyl | 7 amino acids, Ac-LKKTETQ |
| What it is | The complete native sequence | Positions 17-23, the actin-binding region |
| Molecular weight | ≈ 4,963 g/mol | ≈ 889 g/mol |
| Molecular formula | C212H350N56O78S | C38H68N10O14 |
| CAS number | 77591-33-4 | Varies by supplier |
Both are sold as “TB-500,” and both are legitimate research materials, but they are not interchangeable. A study designed around the full protein won’t give the same results with a seven-residue fragment that is about one-fifth its size. Before you buy, check the identity line of the COA.
FRO’s TB-500 at a glance
| Declared identity on the COA | Thymosin Beta-4 |
|---|---|
| Supplied as | Lyophilized white powder in sealed vials |
| FRO vial sizes | 2mg, 5mg, 10mg |
| FRO tested purity | 99.1% by HPLC (10mg, sample 5D9E-LGK5) |
| Measured quantity | 9.66 mg in a 10 mg vial |
Why labs study it
- Actin dynamics. Thymosin beta-4 is one of the main proteins that holds G-actin (single actin units) in reserve inside cells. The LKKTETQ region is the part that binds actin, which is why the fragment exists at all.
- Cell migration. Because actin drives how cells move, it is used in cell-culture assays that measure migration and spreading.
- Tissue-repair and angiogenesis models. Published animal and cell studies look at its effects on wound-model closure and new blood-vessel formation.
How to read a TB-500 certificate of analysis
A COA is only useful if you know what each line proves. Here is FRO’s 10mg report (AccuMark Labs, sample code 5D9E-LGK5, received 02/24/2026, published 09/07/2026) line by line:
| Test | Result | What it tells you |
|---|---|---|
| Identity | Thymosin Beta-4, conforms | The lab matched the main compound to thymosin beta-4. This is the line that tells you which “TB-500” you are looking at. |
| HPLC purity | 99.1% (spec > 98.0%) | Share of the sample that is the target peptide, measured by UV detection at 220 nm. The chromatogram shows one sharp main peak at about 5.38 minutes. The small dip near 1 minute is the solvent front, not an impurity. |
| Quantity | 9.66 mg measured in a 10 mg vial | How much peptide is actually in the vial, here about 97% of the label. Many COAs skip this line, but it is the one that catches underfilled vials. |
The full report, chromatogram included, is free to open in the TB-500 COA library. Match the code on your vial to the report.
What this report doesn’t cover
This report covers identity, HPLC purity and measured quantity. It does not include endotoxin, sterility or mass spectrometry results. For TB-500 in particular, mass spectrometry settles the full-length vs. fragment question in one measurement, because the two molecular weights (about 4,963 vs. about 889) are so far apart. FRO has additional third-party testing underway at Vanguard Laboratory, an ISO 17025 lab, and new results are added to the COA library as they come in.
Red flags on any supplier’s TB-500 COA
- No identity line, or one that just says “TB-500” without saying which molecule.
- No lot or sample code, or a code that doesn’t match the vial.
- No lab name, or a lab you can’t find.
- Purity with no chromatogram.
- No measured quantity, only the label claim.
- The same report reused across several products or years.
Storage and handling for research use
- Lyophilized powder: store frozen (−20 °C), sealed and protected from light. Let the vial reach room temperature before opening to avoid condensation.
- Reconstitution: add bacteriostatic water slowly down the vial wall and swirl gently. Don’t shake, because a 43-residue peptide is more prone to aggregation under agitation than a short one. Use the peptide reconstitution calculator to work out concentration for your protocol.
- After reconstitution: refrigerate at 2–8 °C, protect from light, and use within your protocol’s defined window.
- Avoid repeated freeze-thaw. If you need to store reconstituted material frozen, split it into single-use aliquots first.
Frequently asked questions
Is TB-500 the same as thymosin beta-4?
Sometimes. Suppliers use “TB-500” for both full-length thymosin beta-4 and the short Ac-LKKTETQ fragment. The identity line on the COA tells you which. FRO’s current 10mg report lists the identity as thymosin beta-4.
Does FRO Peptides publish a COA for TB-500?
Yes. The 10mg report from AccuMark Labs, an independent lab, is published in the COA library, chromatogram included.
What purity is FRO’s TB-500?
The current 10mg lot tested at 99.1% by HPLC, against a specification of more than 98.0%, with 9.66 mg measured in the 10 mg vial.
Can I get TB-500 and BPC-157 together?
Yes. The Wolverine Stack combines BPC-157 and TB-500 in one vial, and the Glow blend adds GHK-Cu. Each has its own lot report.
Is TB-500 from FRO for human use?
No. FRO sells TB-500 strictly for laboratory and analytical research. It is not for human or veterinary use.
View TB-500 research peptide (2mg–10mg) →
Lot report published in the COA library. Ships next business day, FedEx 2-Day.
For laboratory research use only. Not for human or veterinary use. Not a drug, food, or cosmetic under FDA regulations. Nothing on this page is medical advice.