Cytoskeleton research
Thymosin β4 is studied as an actin-sequestering protein; work at this level needs the full 43-residue molecule, because the actin-binding region spans more than the 17-23 fragment.
Peptide · Repair & recovery
TB-500 (Thymosin β4, full length)
Two different molecules are sold under this name. This page is the full-length 43-residue protein — 4,963 Da. The fragment is a separate product with a separate CAS.
Also known as TB-500 · Thymosin β4 · Tβ4 · thymosin beta-4
Sequence · 43 residues
AcidicBasicHydrophobicPolar
- Residues
- 43
- Molecular weight
- 4963.44
- Formula
- C212H350N56O78S
- Purity
- 99.41% HPLC
Identity data as printed on the batch certificate of analysis.
Overview
What TB-500 is
TB-500 is the full-length thymosin β4 molecule: 43 residues, acetylated on the N-terminal serine, free acid at the C-terminus, 4,963.44 g/mol. The sequence printed on the certificate is the whole protein — not a fragment of it.
That matters because the name is used for two things. The 17-23 fragment (Ac-LKKTETQ) is also sold as “TB-500”, and it weighs 889 Da — 5.6 times less than what is on this page. A quotation that says “TB-500” without a residue range or a molecular weight has not told you which molecule you are buying, and the difference is not a matter of grade.
We list both. This code, ES003, is full-length thymosin β4 at CAS 77591-33-4. The fragment is ES021, with its own CAS and its own certificate. Ask for the code, not the trade name, and the ambiguity disappears.
- Full-length 43-residue sequence printed on the certificate, with the residue range
- 99.41% by HPLC; total impurities 1.1%, largest single 0.3%
- Acetate counter-ion, content stated per batch — 1.5% on the current lot
- Peptide content 90.6%, so a 5 mg weighing holds about 4.5 mg of peptide
Identity
The record.
The identifiers your specification sheet, customs paperwork and product label all have to agree on. Where a number depends on the salt form, both are given.
- Chemical name
- N-acetyl-thymosin β4, 43 residues, C-terminal free acid
- Common name
- TB-500; thymosin β4; Tβ4
- CAS number
- 77591-33-4
- Molecular formula
- C₂₁₂H₃₅₀N₅₆O₇₈S
- Molecular weight
- 4963.44 g/mol
- Residue count
- 43 · full length, N-acetylated
- Counter-ion
- Acetate — 1.5% on the current lot
- Appearance
- White or off-white powder
- Solubility
- Soluble in water
- Water content
- ≤ 8.0% (Karl Fischer)
- Storage
- −20 ± 5 °C, sealed, protected from light
- Retest period
- 24 months from manufacture
HS codes are indicative only. Final classification is confirmed per shipment with your customs broker.
Manufacture
How it is made.
Forty-three residues is a protein by any practical measure. Yield and impurity profile both depend on how the long chain is assembled.
- 01
Solid-phase assembly
The 43-residue chain is built stepwise and acetylated on resin. At this length, each incomplete coupling leaves a sequence one residue short of the target — the hardest impurity class to separate, because it differs from the product by one amino acid.
- 02
Cleavage and deprotection
Acid cleavage releases the peptide and strips side-chain protecting groups, leaving the C-terminus as the free acid that the certificate describes.
- 03
Preparative HPLC
Gradient purification against the full-length product. The 1.1% total impurity on the current lot is the measure of how much truncation survived.
- 04
Acetate exchange and drying
Converted to the acetate and lyophilised to ≤ 8.0% water. The acetate figure is reported per batch rather than assumed — see the note below on why it varies.
Applications
Where it is used.
Supplied to laboratories working on the repair and cytoskeletal side of the catalogue. Research use only.
Comparative studies
Side-by-side work on full-length versus fragment, where having both CAS numbers, both masses and both certificates documented is the point of the comparison.
Formulation development
A 4,963 Da peptide with a defined acetate load and 90.6% peptide content — the numbers a formulator needs before calculating anything.
Specification
Release criteria.
The written limits we release against, with the method used to test each one. Batch results for the lot you receive are stated on its certificate of analysis.
| Parameter | Limit | Method |
|---|---|---|
| Appearance | White or off-white powder | Visual |
| Solubility | Soluble in water | Visual |
| Water content | ≤ 8.0% | Karl Fischer |
| Acetic acid | ≤ 15.0% | HPLC |
| Assay | 95 – 105% | In-house |
| Purity | ≥ 98.0% | HPLC |
| Total impurities | ≤ 2.0% | HPLC |
| Largest single impurity | ≤ 1.0% | HPLC |
| Peptide content | ≥ 85.0% | Nitrogen determination |
| Shelf life | 24 months from manufacture | Stability programme |
Tighter limits — for example a lower heavy-metal ceiling or a residual-solvent panel — can be quoted against your own specification wording.
HPLC · ES003
Certificate
Reading the certificate.
On this product the first question is not how pure it is, it is which molecule it is.
The residue range has to be printed
Look for 43 residues, or a sequence line that runs the full length, or a molecular weight near 4,963. A certificate carrying 889 Da is the fragment sold under the same trade name — a legitimate product, but not this one.
A low acetate figure is not a fault
The current lot carries 1.5% acetic acid, against a ≤ 15% limit. A low counter-ion content means the powder is closer to the free peptide, which changes the mass balance: peptide content is 90.6% precisely because there is little acetate and little water left.
Assay and purity answer different questions
Assay at 100% is a mass-balance figure — how much peptide is present. Purity at 99.41% is a chromatographic figure — how much of that peptide is the right sequence. Both are on this certificate; quoting either one alone understates the material.
Documentation & packaging
What ships with it.
The paperwork travels with the goods. If your QA team needs an extra declaration, ask before the order is released — some are issued per production lot and cannot be retrofitted.
Certificate of analysis
Full-length sequence, purity, impurities, acetate, water, peptide content and assay for the lot supplied.
Analytical data
HPLC chromatogram at 229 nm (Kromasil 100-3.5-C18, 15→30% over 25 min) and mass spectrometry data.
SDS & specification
Safety data sheet and the enterprise standard the batch is released against.
Sequence statement
The 43-residue sequence with the residue range and both terminal modifications, so the molecule can be matched against your reference.
| Pack size | Presentation | Typical use |
|---|---|---|
| 1–10 g | Amber vial, 10 mL | Evaluation |
| 25–50 g | Amber vial, 50 mL | Pilot scale |
| 100 g | Amber vial, 100 mL | Small commercial |
| 1 kg+ | Foil bag, quoted per order | Bulk |
Questions
Before you order.
The questions buyers actually ask about TB-500. Anything not covered here, ask directly — you will get an answer from someone technical, not a template.
Is TB-500 the same as thymosin β4?
Yes — full-length thymosin β4 is what TB-500 normally refers to, CAS 77591-33-4, 43 residues, 4,963 Da. But the trade name is also applied to the 17-23 fragment, so the name alone is not a specification.
How do I tell the full-length product from the fragment?
By mass or by residue count. Full length is 4,963.44 g/mol and 43 residues; the fragment is 889 g/mol and 7 residues. If a supplier quotes “TB-500” without either figure, ask for the certificate before you compare prices.
Why is the acetate content only 1.5%?
Because that is what this batch measured, against a ≤ 15% limit. A low figure means the lyophilised powder is close to the free peptide. It is not a deficiency — it changes the peptide content, which is why that figure is stated separately at 90.6%.
What is the peptide content for?
Weighing. At 90.6% peptide content, 5 mg of powder contains about 4.53 mg of peptide. Concentrations calculated from the label weight will be roughly 9% low, and only the certificate will tell you that.
How should it be stored?
−20 ± 5 °C, sealed and protected from light. Equilibrate to room temperature before opening so condensation does not form on the cake.
Do you supply the 17-23 fragment as well?
Yes, as a separate catalogue item (ES021) with its own CAS number and certificate. The two are not interchangeable, and we do not quote one against the other.
Related
Often quoted together.
Quotation
Ask for TB-500, by the gram.
Send the quantity, the grade you need and the destination. You will get a written quotation with lead time, packaging options and the documentation set for this material.