TB-500 peptide: technical data sheet (sequence, mass, CAS, form, COA, sizes)

"TB-500" is a trade name.

It designates a synthetic peptide made from the sequence of thymosin β4 (Tβ4), a 43-residue protein present in the cytosol of most cell types, where it binds monomeric actin.

The name does not specify which part of Tβ4 was synthesized, and two different objects circulate under it.

The heptapeptide Ac-LKKTETQ is the segment of Tβ4 that binds actin, identified in the cell-free work of the early 1990s.

It is the object described on the TB-500 product page and in this sheet. The mass on the certificate of analysis is what tells a buyer which of the two objects went into a given vial. Research use only.

Not for human or veterinary use.

Listings spell the name several ways: TB-500, TB500, "TB-500 acetate", "Tβ4 (17-23)", "thymosin beta-4 fragment".

The spelling carries no information; the sequence, the mass and the CAS number do. A listing that gives none of the three has not said what it sells, whatever it calls it.

The numbers below are those of the catalog entry, with the CAS number checked against the PubChem record.

Seven residues is short. On a reverse-phase column the heptapeptide and the 15-residue BPC-157 elute at different retention times, which is how the two are told apart on the single chromatogram of the BPC-157 + TB-500 vial.

A synthetic peptide leaves preparative HPLC in a solution that contains trifluoroacetic acid from the mobile phase.

Reputable manufacturers exchange that counter-ion for acetate before freeze-drying, so what arrives in the vial is the acetate salt of Ac-LKKTETQ plus a few percent of bound water.

Two consequences follow for anyone reading a label:

• Purity and peptide content are two numbers. HPLC purity (the share of peptide among peptide-like material) can read 99 % while peptide content (the share of the powder's mass that is peptide rather than acetate and water) reads 85 to 90 %. Both are legitimate. A certificate reports the first; a good one also reports the second. The difference is explained in HPLC purity: what 99 % means.
• Ten milligrams is a thin cake. In a 3 mL vial, 10 mg of a freeze-dried heptapeptide sits as a white film at the bottom, sometimes barely visible against the glass. That is the normal appearance of the fill, not a short vial.

Lyophilization removes the water by sublimation from the frozen solution, which leaves the peptide as a porous solid that dissolves in seconds and, sealed and cold, keeps for two years.

The process and its limits are described in lyophilized peptides: storage and shelf life.

Further reading: DSIP data sheet and Wolverine peptide.

For a peptide sold under a trade name, the certificate does two jobs. It says which object is in the vial (identity) and how clean it is (purity). A complete TB-500 certificate carries:

1. Identity and quantity. The compound found, named by the laboratory, and the mg measured. If a lab adds mass spectrometry as an option: about 889.0 g/mol (M+H⁺ near 890) for Ac-LKKTETQ, about 4,963 for full-length Tβ4.
2. HPLC purity, as a measured percentage: one dominant peak, and the small peaks that always accompany a synthetic peptide (deletion sequences, a de-acetylated fraction, oxidized variants).
3. The laboratory's name and a verifiable test number. Janoshik Analytical is the reference laboratory of this market; its reports can be looked up on its site.
4. The lot number with its task number and verification key, the test date, and a photograph of the tested vial wearing the supplier's own label.

The OXpeptides Janoshik reports (Retatrutide and GHK-Cu) are in the COA library; the TB-500 product page sets out the sequence, the vial sizes and the live price.

A certificate is read field by field in how to read a peptide COA, and the number at the top of a laboratory page is checked against the laboratory itself as described in how to read a Janoshik test report.

Further reading: ARA-290 sequence and COA.

TB-500 is supplied as a lyophilized powder in a sealed 3 mL borosilicate vial with a bromobutyl septum and an aluminum crimp cap, in three fills:

The catalog card at the top of this page reads the live price of each single-peptide size. Prices, the supplier checklist and the "buy" side of the question are in the TB-500 buying guide.

Further reading: BPC-157 buying guide, KLOW, BPC-157 + TB-500 + GHK-Cu + KPV and where to buy research peptides in Europe.

• Sealed vial: −20 °C, protected from light and moisture. Shelf life 24 months from the fill date.
• Condensation: let a cold vial reach room temperature before it leaves its bag, so water condenses on the bag and not on the septum.
• Shipping: a few days at ambient temperature do not degrade the sealed powder, which is why the vial ships without a cold pack.

The heptapeptide has no cysteine and no methionine, the two residues most prone to oxidation, and no aspartate-glycine pair prone to rearrangement, which makes it one of the more stable short peptides in the catalog as a dry solid.

Repeated warming and cooling of a sealed vial does no measurable harm to that solid. The risk is water.

A septum pierced while the glass is still cold pulls in condensation, and a wet cake degrades in weeks where a dry one keeps for two years.

Search the trade name in a scientific database and nothing comes back. The literature is written about thymosin β4, the protein, and about its actin-binding segment.

Two papers anchor the chemistry. Safer, Elzinga and Nachmias (1991) showed in a cell-free system that thymosin β4 is the actin-sequestering peptide of the cytosol.

Goldstein and Kleinman (2005) reviewed the protein and located the actin-binding segment at residues 17 to 23, the LKKTETQ sequence the catalog's TB-500 reproduces. Both are listed below with their DOI.

What a buyer takes from that: a listing that gives a sequence, a formula, a mass and a CAS number describes an object that can be checked against the literature and against an independent laboratory report.

A listing that gives only the trade name describes nothing.

Thymosin β4 is a 43-residue protein, N-acetylated, with an average mass of about 4,963 Da.

Inside it, the stretch from residue 17 to residue 23 reads Leu-Lys-Lys-Thr-Glu-Thr-Gln.

The first six of these, LKKTET, are known in the literature as the actin-binding motif of the β-thymosins, and that is why the fragment was made on its own.

"TB-500" is the market name for a synthetic version of that fragment, acetylated at its N-terminus: Ac-LKKTETQ, 889.0 g/mol.

The trouble is that the same name is also used for full-length synthetic thymosin β4. The two products differ by a factor of more than five in mass, and a vial labelled only "TB-500" does not say which one it holds.

The mass on the certificate settles it. A lot of Ac-LKKTETQ is confirmed near 889; a lot without the acetyl group shows about 42 Da less; a full-length product shows a mass in the thousands.

Electrospray mass spectrometry rarely shows the molecule as a single neutral mass.

It shows ions carrying one or more protons, and the laboratory converts them back to the molecular mass. For Ac-LKKTETQ (C₃₈H₆₈N₁₀O₁₄), the numbers to expect are:

• Monoisotopic mass: about 888.5 Da (every atom as its lightest isotope).
• [M+H]⁺: about 889.5, the singly charged ion.
• [M+2H]²⁺: about 445.3, the doubly charged ion; with two lysines, this peptide picks up a second proton easily.
• Average mass: 889.0 g/mol, the figure used to weigh the powder.

A certificate that writes "MS: conforms" without any number is weaker than one that prints the observed mass. Ask for the number, then compare it with the list above.

A difference of about 42 Da points to the non-acetylated fragment; a difference of 16 Da can mean an oxidised impurity; a figure in the thousands means another product altogether.

The HPLC side of the same certificate is read as for any peptide: one main peak, its share of the total area, the wavelength used. The method is explained in how to read a peptide COA.

TB-500 is often listed next to BPC-157, alone or in a blend.

The two have nothing in common chemically: fifteen residues against seven, a proline-rich chain against a lysine-rich one, about 1,419 against 889 g/mol.

They are compared line by line in BPC-157 vs TB-500, and the vial holding both is described in the wolverine peptide blend. Research use only. Not for human or veterinary use.

A short peptide leaves little room for error, and the few defects that occur have clear signatures on the certificate:

• A missing residue (a deletion during synthesis): a mass lower by the weight of one amino acid, for example about 128 Da for a lysine or 129 Da for a glutamic acid.
• A missing acetyl group: about 42 Da less, the non-acetylated fragment.
• A converted glutamine: the C-terminal glutamine can deamidate slowly to glutamic acid, about 1 Da more, a shoulder next to the main peak.
• Counter-ion and water: not impurities but weight in the powder, which the net peptide content accounts for.

Each of these is visible to a laboratory that runs both HPLC and mass spectrometry on the lot, and invisible on a certificate that prints only a purity percentage.