Fragment vs full-length identity diagram
Two different molecules share the shop name “TB-500.” Full-length thymosin β4 is a 43-residue actin-binding peptide, commonly indexed as CAS 77591-33-4. BioLabs Research lists TB-500 as a fragment reagent: N-acetyl LKKTETQ (Ac-LKKTETQ), CAS 885340-09-2. Those are not interchangeable identities on a purchase order or a lot COA.
Vendors sometimes print “TB-500” while the certificate still cites the full Tβ4 registry number. For laboratory purchasing, that mismatch is a documentation failure: the mass on the certificate must match the sequence printed on the vial label. If the paper says 77591-33-4 against a heptapeptide fragment carton, request corrected lot paper before the material is booked into inventory.
This note is an identity walkthrough for catalog buyers — how to read the two CAS numbers, what MS should confirm, and how our storefront listing differs from intact thymosin β4. It is not a protocol, dosing guide, or clinical claim.
Laboratory identity check — matching label sequence to lot paper
In practice, purchasing teams compare three fields: (1) the sequence or fragment string on the label, (2) the CAS or registry line on the COA, and (3) the observed intact mass (or fragment mass) reported by the testing lab. Agreement across those three is what makes the lot usable for comparative models. Disagreement means the SKU name alone is not enough.
Side by side
| This catalog’s TB-500 | Thymosin β4 (full) | |
|---|---|---|
| CAS | 885340-09-2 | 77591-33-4 (commonly indexed) |
| Identity line | Ac-LKKTETQ | 43-aa Tβ4 (SDKP… at the N-terminus in the native protein) |
| What MS must match | heptapeptide fragment mass | ~4963 Da class (salt form aside) |
| Storefront role | Fragment listing on this catalog | Intact Tβ4 is not this SKU |
A COA that quotes 77591-33-4 against a fragment vial is the wrong paper. Intact mass vs the sequence on the label is the check. Thymosin alpha-1 is a third, unrelated peptide: 28-residue N-acetyl Tα1.
We do not invent HPLC area% on this page. Purity-related numbers, when issued, live on the lot certificate for that batch. We also do not frame this reagent as an injury, recovery, or human-use protocol — laboratory reagent listing only.
Keep labels distinct — fragment listing vs full-length Tβ4
Next steps for buyers: open the TB-500 catalog page, confirm Ac-LKKTETQ / CAS 885340-09-2, and request lot documentation if your SOP requires it. Related reading: TB-500 research note and Lot COA, not a purity percentage.
References
- Catalog identity for this site’s TB-500 SKU: CAS 885340-09-2, Ac-LKKTETQ, as printed on the product spec strip. Confirm observed mass on the lot COA.
- Thymosin β4 (full-length) is a separate 43-residue protein; do not copy that sequence onto a fragment listing.