What is ?

01

What the name refers to

Thymosin beta-4 is a 43-amino-acid protein. It was isolated from calf thymus and fully sequenced in 1981, when it was still thought to be a thymic hormone.

is a trade name, not a scientific one. In the analytical literature it means a synthetic copy of residues 17–23 of thymosin beta-4 with an acetyl group on the N-terminus (Ac-LKKTETQ). That seven-residue stretch is the part of the protein that binds actin.

Some research suppliers use the same name for full-length synthetic thymosin beta-4. Seven amino acids and 43 are very different molecules, so read the identity result on your lot’s certificate of analysis: the measured mass shows which one the vial contains.

Sources: [1] PNAS · 1981 · [4] Journal of Chromatography A · 2012 · [5] Journal of Chromatography B · 2024

02

What thymosin beta-4 does in cells

Actin is the protein that builds a cell’s internal scaffolding. In 1991, researchers showed that thymosin beta-4 is identical to Fx, a peptide that binds single actin molecules one to one and stops them from joining into filaments.

A 1992 study found that it holds most of the unassembled actin in resting white blood cells. Because it is abundant in many cell types, papers describe it as a major regulator of actin assembly.

Sources: [2] Journal of Biological Chemistry · 1991 · [3] Journal of Cell Biology · 1992

03

What researchers have studied

The protein and its fragments have a mostly preclinical literature:

• Blood-vessel development, including a 2007 study of coronary vessels in mice.
• Cell migration, which analytical papers tie to the 17–23 stretch the fragment copies.
• Tendon repair in rats, in a 2026 study that tested it alone and combined with .
• Metabolism of the acetylated fragment, mapped in human serum in vitro and in rats in 2024.

The 2024 study noted that the biological effects of the fragment itself had not been documented. Most findings come from the full-length protein, so check which molecule a paper used before comparing it with a vial.

These are observations in laboratory models. They are not evidence about any use in people.

Sources: [6] Annals of the New York Academy of Sciences · 2007 · [4] Journal of Chromatography A · 2012 · [7] Joint Diseases and Related Surgery · 2026 · [5] Journal of Chromatography B · 2024

04

vs

They are often sold and studied together, but they are unrelated molecules. comes from thymosin beta-4, an actin-binding protein found in most cells; is a 15-residue fragment of a protein described in gastric juice.

Prism Labs sells each on its own and together as the . Side by side: vs .

05

Where else it appears

It is one of three peptides in and one of four in .

06

How it is supplied and stored

ships as a lyophilized (freeze-dried) powder in 5 mg or 10 mg vials. The powder is stable at room temperature in transit. For lab use it is reconstituted with bacteriostatic water such as .

For a vial, concentration is content divided by volume: 10 mg in 2 mL gives 5 mg per mL. The reconstitution calculator handles other combinations.

For storage before and after reconstitution, see how to store lyophilized peptides.

07

How to verify a batch

Every lot has its own certificate of analysis from an independent lab. Read three results separately:

• Identity: confirms the expected compound was detected.
• Purity: the share of the measured material that is the intended compound.
• Content: the amount measured, compared with the label.

Then match the lot number on your vial or bottle to the report, and use the report’s verification link to confirm it with the testing lab. Step by step: how to read a peptide COA.