TB-500 Peptide: Thymosin Beta-4, the LKKTETQ Fragment and the Research

What is TB-500?

TB-500, also written tb500, is the name research suppliers use for peptides derived from thymosin beta-4. The catch is that suppliers don’t all mean the same molecule.

Some sell full-length thymosin beta-4, all 43 amino acids. Others sell a synthetic seven-residue piece of it, and analytical chemists who examined TB-500 product found exactly that fragment (Esposito et al., 2012).

So the first question about any TB-500 vial isn’t what it does. It’s what’s inside, and the answer changes everything that follows from it.

Thymosin beta-4, the parent peptide

Thymosin beta-4 is a small protein found in cells throughout the body. Its mature form is 43 amino acids long, with an acetyl group on the first residue (UniProt P62328).

Its day job is handling actin, the protein that builds a cell’s internal scaffold. Thymosin beta-4 is the main actin-sequestering molecule in animal cells, holding actin units in reserve until the cell needs them (Goldstein et al., 2005).

That link to cell movement is why it entered repair research. A wound only closes when cells crawl into it, and crawling depends on actin.

Our thymosin beta-4 research guide goes deeper on the full-length protein.

Where the LKKTETQ fragment comes from

Inside thymosin beta-4 sits a seven-amino-acid stretch, LKKTETQ, at positions 17 to 23. Researchers describe it as the protein’s active site for actin binding, cell migration and wound healing (Ho et al., 2012).

Ho and colleagues reported that the key ingredient of TB-500 is LKKTETQ with an acetyl group added to the front end, and they published a mass-spectrometry method for identifying it (Ho et al., 2012).

Esposito and colleagues reached the same answer from the other direction. They identified Ac-LKKTETQ in a TB-500 product, then synthesized it to confirm the match (Esposito et al., 2012).

Full-length or fragment: two very different molecules

TB-500 forms compared

A gap of more than 4,000 Da is impossible to miss. Any mass spectrum shows it. A certificate of analysis that reports mass should make the form obvious at a glance.

The research gap matters just as much. Findings for full-length thymosin beta-4 can’t simply be credited to a seven-residue fragment, even one cut from its active region.

What does TB-500 research show?

Most of the animal evidence behind the TB-500 name comes from full-length thymosin beta-4. In rats, it accelerated the healing of full-thickness skin wounds (Malinda et al., 1999).

The fragment’s own record is much thinner. The best-documented work on Ac-LKKTETQ is analytical: identifying it in products and building methods to detect it (Esposito et al., 2012; Ho et al., 2012).

What the evidence covers

TB-500 in the Wolverine stack

Researchers most often pair TB-500 with BPC-157, a synthetic 15-residue peptide its developers derived from a gastric juice protein. Its studies use rat tendon, muscle and ligament injuries. The pairing has its own name, explained in the guide to the Wolverine stack.

They share a research theme, repair, and very little chemistry. BPC-157 was derived from a gastric protein and is known for stability, while thymosin beta-4 is known for binding actin.

The BPC-157 peptide guide covers its rat studies and the FDA’s 2026 review. A three-compound option, BPC-157, TB-500 and GHK-Cu, is the BPC-157, TB-500 and GHK-Cu recovery research protocol.

Is TB-500 FDA approved?

No. Neither full-length thymosin beta-4 nor the Ac-LKKTETQ fragment is approved by the FDA for any use. Both are research chemicals, sold for lab use.

Reading a TB-500 certificate of analysis

Labels vary. Mass spectra don’t, so it falls to the certificate to settle identity, and four lines on it matter more than the rest.

• Which form. The certificate should name full-length thymosin beta-4 or the Ac-LKKTETQ fragment, not just “TB-500.”
• Measured mass. Expect about 4,963 Da for the full peptide or about 889 Da for the fragment.
• HPLC purity, reported as the main peak’s share of the sample.
• Lot number, so the paperwork can be tied to one specific vial.

Check the TB-500 research peptide page and the published certificates of analysis for the form and measured mass of each lot. It’s also part of the BPC-157 and TB-500 Wolverine blend.

Storing TB-500 in the lab

Both forms ship dry. Unopened vials stay cold, dry and dark, at the temperature the lot’s certificate gives.

Log the form. Two experiments labeled TB-500 may not have used the same molecule.

TB-500: the name versus the molecule

TB-500 is a supplier name for thymosin beta-4 products, and it covers two different molecules: the 43-amino-acid protein and its seven-residue Ac-LKKTETQ fragment. Mass spectrometry separates them instantly.

The animal research, such as faster wound healing in rats, is mostly about the full protein. Check which form a vial holds before linking it to any of that work.

TB-500 questions researchers ask

What is TB-500?

TB-500 is a research-market name for thymosin beta-4 products. It can mean the full 43-amino-acid peptide or a synthetic seven-residue fragment, Ac-LKKTETQ, from its actin-binding region. It’s sold for laboratory research only.

Is TB-500 the same as thymosin beta-4?

Sometimes. One supplier’s TB-500 is the full 43-residue protein, while analyses of TB-500 product found only Ac-LKKTETQ, a seven-residue fragment. The certificate of analysis should state which form a vial holds.

What is Ac-LKKTETQ?

It’s an acetylated copy of amino acids 17 to 23 of thymosin beta-4, the segment linked to actin binding. Two analytical chemistry groups identified it as the key ingredient of TB-500 products in 2012.

How do you tell full thymosin beta-4 from the TB-500 fragment?

By mass spectrometry. Full-length thymosin beta-4 weighs about 4,963 Da and the Ac-LKKTETQ fragment about 889 Da, so the two can’t be confused on a mass spectrum.

Does Spartan publish a COA for TB-500?

Spartan publishes certificates of analysis by lot on its COA page. For TB-500, check that the certificate names the form, reports a measured mass near 4,963 or 889 Da, and gives HPLC purity and a matching lot number.

How was the TB-500 fragment identified?

In 2012, two analytical chemistry groups examined TB-500 product by liquid chromatography and mass spectrometry. Both found Ac-LKKTETQ. Esposito’s group then synthesized the fragment as a reference standard, which confirmed the match beyond doubt.

Is TB-500 FDA approved?

No. Neither full-length thymosin beta-4 nor the Ac-LKKTETQ fragment is approved by the FDA for any use. Both are research compounds sold for laboratory work only.

What does TB-500 do in animal studies?

Most animal data are for full-length thymosin beta-4, which accelerated skin wound healing in rats. Published work on the seven-residue fragment is mostly analytical, so results for the full peptide shouldn’t be assumed for it.