Thymosin Beta-4

What Thymosin Beta-4 is, structurally

Thymosin Beta-4 is a forty-three residue peptide at 4963.44 g/mol, among the largest compounds in this catalogue.

The most important thing to establish is what it is not. This catalogue also carries TB-500, a seven-residue fragment corresponding to positions 17 to 23 of this molecule, sold separately at 889.02 g/mol under a different CAS. The two differ by over four thousand mass units and thirty-six residues. A weight near 889 describes the fragment; 4963 describes this compound. Confusing them is the likeliest error involving either.

Neither the sequence nor the formula is recorded for this product, so the observations below derive from the registered formula and the deposited structure.

Fifty-six nitrogens across forty-three residues means forty-three backbone amides and thirteen from side chains, so under a third of residues carry nitrogen beyond the backbone. That is a low proportion for this length, indicating a composition weighted toward acidic and small residues rather than basic ones.

The single sulfur has been identified rather than assumed. The deposited structure shows a thioether, which is a methionine, and no S-S bond. So no cysteine is present, no disulfide is possible, and no reducing agent is needed. Worth confirming rather than inferring on a chain long enough to accommodate a bridge.

The peptide is water soluble, though no quantitative figure is quoted here.

Reconstitution and handling

Sterile water is the default solvent, and with no metal centre present PBS or an appropriate assay buffer are equally suitable. Add diluent slowly down the inside wall of the vial and swirl gently. Do not vortex: a forty-three residue chain has real conformational structure, and shear with foaming at the air-liquid interface is the most efficient way to aggregate it. Allow time rather than agitating.

No reducing agent should be added, since there is no sulfur chemistry for one to act on.

Adsorption matters more here than for a short peptide, since a molecule this size presents far more binding surface and losses at low concentration can be substantial. Low-protein-binding tubes are worth using rather than merely considering.

This is laboratory preparation chemistry, not dosing, administration, or protocol guidance of any kind.

Storage and stability

Store the lyophilized solid at -20 degrees C, sealed, desiccated and protected from light, and let a cold vial reach room temperature before opening. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze for longer storage.

Aliquot before the first freeze and treat that as a requirement. A chain long enough to fold can misfold and aggregate on repeated cycling, and aggregation is not reversed by warming. On a short peptide that advice is precautionary; here it addresses the likeliest failure mode.

The chemical liabilities are few. The methionine oxidises to a sulfoxide on air exposure, adding sixteen mass units, unambiguous with no cysteine competing. A chain this long will contain residues capable of the usual hydrolytic rearrangements, but without the sequence this page will not name positions.

The dominant risk is physical rather than chemical, and it is one mass spectrometry cannot report. A non-covalent aggregate dissociates under electrospray conditions, so a spectrum will show a normal monomer while the vial holds material that has aggregated.

These are storage conditions for the material, not dosing or administration guidance.

How Thymosin Beta-4 is tested

Reversed-phase HPLC establishes chromatographic purity as area percent, with detection near 214 nm. Whether 280 nm is usable depends on aromatic content the formula alone cannot settle.

Size changes what a purity figure means. On a short peptide a deleted residue is a large proportional mass change that separates cleanly; on forty-three residues it alters the mass by roughly two percent and may barely shift retention, so the same percentage represents a more demanding separation.

Mass spectrometry confirms identity, and here it does something more valuable: it distinguishes this compound from its own fragment beyond any ambiguity. A molecular ion near 4963 is this peptide; one near 889 is TB-500. Four thousand mass units is not a resolution question, so any analytical record reporting the wrong one of those two figures has the wrong compound rather than an impure sample.

Methionine oxidation appears at plus sixteen. Aggregation is assessed by size-exclusion chromatography rather than by mass.

These describe general methodology, not a claim about any particular batch.

Handling FAQ

Is this the same as TB-500? No. TB-500 is a seven-residue fragment of this molecule, positions 17 to 23, carried separately in this catalogue at 889.02 g/mol under its own CAS number. This compound is the full forty-three residue peptide at 4963.44. The two are different products and the mass difference between them is unmistakable.

Does this contain a disulfide bridge? No. The formula carries one sulfur, and a bridge requires two. Its deposited structure confirms that sulfur is a methionine thioether with no S-S bond anywhere, so no reducing agent is needed at any stage.

Full specifications for Thymosin Beta-4.