TB-500

What TB-500 is, structurally

TB-500 is a seven-residue peptide with an acetylated N-terminus and a free C-terminal acid. It corresponds to residues 17 to 23 of the larger protein Thymosin Beta-4 and is supplied as that fragment alone.

That distinction is the most important thing on this page, because the parent is a separate product here with entirely different specifications. Thymosin Beta-4 is forty-three residues at roughly 4963 g/mol under CAS 77591-33-4; TB-500 is seven residues at 889.02 under CAS 885340-08-9. Any specification, certificate or calculation quoting a weight near 4963 describes the parent, not this compound.

The formula reconciles with the sequence on three independent counts, worth doing given that confusion. Ten nitrogens: seven backbone amides, one per lysine side chain, one for the glutamine amide, the acetyl contributing none. Thirty-eight carbons: two for the acetyl plus six, six, six, four, five, four and five across the residues. Fourteen oxygens: the acetyl carbonyl, six backbone carbonyls, two for the terminal acid, two threonine hydroxyls, two on the glutamate and one on the glutamine. All three match exactly.

Charge is close to balanced. Two lysines contribute positives, the glutamate side chain and the terminal acid contribute negatives, and the acetylated N-terminus contributes nothing, no longer being a free amine. The peptide is polar and water soluble, though no quantitative figure is quoted here. There is no cysteine, no methionine and no aromatic residue anywhere in the sequence.

Reconstitution and handling

Sterile water is the default solvent, and with no metal centre present PBS or an assay buffer are equally suitable. Add diluent down the vial wall, swirl gently, and let it clarify. Vortexing adds foaming and nothing else.

No reducing agent is needed. The formula contains no sulfur, so there is nothing for one to act on.

Keep preparations near neutral. The glutamine at the C-terminal position is the one residue here with a meaningful chemical liability, and alkaline conditions accelerate it.

Adsorption is worth allowing for at low concentration, with low-protein-binding tubes reducing measured loss. A small, roughly charge-balanced peptide with no aromatic surface has limited affinity for polypropylene, so this is modest rather than pressing.

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

Storage and stability

Store the lyophilized powder at -20 degrees C, sealed, desiccated and protected from light, and let a cold vial warm before opening. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze rather than thawing repeatedly.

The liability profile is narrow. No cysteine to oxidise, no methionine to form a sulfoxide, no tryptophan to photo-oxidise, no aspartate to isomerise. The acetylated N-terminus also removes the free amine an exopeptidase works from and the diketopiperazine route open to short peptides with an unblocked terminus.

What remains is the glutamine at position seven. It deamidates to glutamate, turning a neutral side chain acidic and adding roughly one mass unit. Slower than asparagine deamidation, but the fastest route this sequence offers, and it needs water, so the solid is largely protected while solutions are not. Warmth and alkaline pH accelerate it.

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

How TB-500 is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. With no aromatic residue there is no absorbance at 280 nm, so detection sits near 214 nm. The peptide is short and polar, so it retains weakly on standard C18.

Area percent is a chromatographic measure rather than peptide content by weight. Solid-phase synthesis delivers a salt, commonly trifluoroacetate or acetate, and on an 889 g/mol peptide with two basic sites that counter-ion is a proportionally large share of the vial contents.

Mass spectrometry confirms identity and, more valuably here, distinguishes the fragment from its parent unambiguously. An ion near 889 is this compound; one near 4963 is Thymosin Beta-4. No resolution issue arises, the two differing by over four thousand mass units. An analytical record reporting the higher figure for a product labelled TB-500 has the wrong compound, not an impure one.

Glutamine deamidation adds about one mass unit, resolvable on ordinary instrumentation at 889, unlike the same modification on a larger peptide where it hides inside the isotope envelope.

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

Handling FAQ

Is this the same as Thymosin Beta-4? No, and the difference is large rather than subtle. TB-500 is a seven-residue fragment at 889.02 g/mol; Thymosin Beta-4 is the forty-three residue parent at roughly 4963, carried separately under a different CAS. A figure near 4963 always refers to the parent.

Does this need protection from air? Not particularly. The formula contains no sulfur and no tryptophan, so the oxidation routes that make air exposure matter on other peptides are absent. pH and temperature matter more here, because the one real liability is deamidation of the C-terminal glutamine.

Full specifications for TB-500.