TB-500 COA Guide: What to Check Before You Buy

TB-500 has a naming problem that makes its Certificate of Analysis more important than most: the label is used loosely across the market for both the full thymosin β4 protein (43 amino acids, ~4963 Da) and, far more commonly, the short active fragment Ac-LKKTETQ (~889 Da). Those are very different molecules — and only the COA tells you which one is in the vial.

The four checks

1. Identity — and the mass tells the story. The mass-spec section should show an observed mass near ONE of the theoretical values: ~889 Da for the Ac-LKKTETQ fragment or ~4963 Da for full-length thymosin β4. A COA that names "TB-500" but shows neither mass, or shows no mass spec at all, proves nothing about identity.

2. Purity by HPLC with the chromatogram attached. Research-grade material typically certifies ≥98% main-peak area. A typed percentage with no chromatogram — or the same chromatogram appearing across a vendor's catalog — is the recycled-cert red flag.

3. Lot number matching the vial. No match, no evidence.

4. Named third-party lab with a date. Independent, contactable, and dated within a reasonable window of the batch.

The free COA checker walks these checks interactively, and how to read a COA covers the fundamentals.

Handling notes (research context)

Lyophilized material stores cool, dry, and dark — −20°C for the long term. Reconstituted solutions refrigerate at 2–8°C and are used within an appropriate window; the reconstitution calculator handles the concentration math and the stability estimator the storage windows.