TB-500 vs Thymosin Beta-4: what is the difference?

Thymosin Beta-4 is a naturally occurring 43-amino-acid actin-binding protein. TB-500, as listed by Ascend Research, is a synthetic peptide corresponding to a fragment of it, with the sequence Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH. The two names are often used loosely, and not always consistently between sources, so the reliable way to know what a listing supplies is to check the stated sequence and the mass on the documentation. This guide sets out the difference and what to look for.

TB-500 and Thymosin Beta-4 at a glance

The TB-500 listing states CAS 77591-33-4 and a white lyophilised powder.

Why are there two names?

Thymosin Beta-4 is the name of the protein as it appears in the scientific literature. TB-500 is a name that came into use for synthetic material related to it. Sources do not all use the name the same way: some apply it to the full-length protein and others to a shorter fragment. That is why the name alone is not enough to identify the material.

The Ascend Research listing removes the ambiguity by stating the sequence. It supplies the seven-residue fragment, not the 43-amino-acid protein.

What do “Ac” and “OH” mean in the sequence?

They describe the two ends of the peptide. “Ac” means the first residue carries an acetyl group at the N-terminus. “OH” means the last residue ends in a free acid at the C-terminus. Both are part of the compound’s identity and both contribute to its mass.

How can you tell which material is supplied?

Do not rely on the product name alone. Check three things:

• Sequence. The listing or certificate should state it. For TB-500 as listed here it is Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH.
• Mass. The mass spectrometry result on the certificate of analysis should be consistent with the stated sequence. A seven-residue fragment has a far smaller mass than a 43-amino-acid protein, so the two cannot be mistaken for one another on a mass result.
• Batch. The batch number on the certificate should match the vial label.

For more on reading the documents, see how to read a peptide certificate of analysis.

Which listings contain TB-500?

The difference between premixed and separate-vial formats is covered in peptide blends vs separate vials. Batch documents are on the COAs page, and related materials are listed under peptide fragments.

Frequently asked questions

Is TB-500 the same as Thymosin Beta-4?

No. Thymosin Beta-4 is the full 43-amino-acid protein. TB-500, as listed by Ascend Research, is a shorter synthetic fragment of it.

What is the sequence of TB-500?

The Ascend Research listing states the sequence Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, a seven-residue acetylated fragment.

What is the CAS number for TB-500?

The Ascend Research TB-500 listing states CAS 77591-33-4.

How many amino acids are in Thymosin Beta-4?

Forty-three.

What vial sizes of TB-500 are listed?

Ascend Research lists TB-500 in 5mg and 10mg vials as a lyophilised powder.

All Ascend Research products are sold strictly for laboratory research use only. They are not for human or animal use, and nothing in this article is medical advice.

The Ascend Research team