TB-500: structure and analysis

What it is

TB-500 is supplied here as the long-chain form: the full 43-amino-acid thymosin beta-4 sequence, an actin-sequestering peptide, rather than a short active fragment of it.

That distinction is the single most important fact about buying this compound. TB-500 is sold across this category in both forms — the complete 43-residue sequence and a much shorter fragment — and they are not the same material. Their molecular masses differ by a large margin.

At 43 residues it is the longest synthetic peptide in this catalogue, exceeded in size only by the recombinant protein IGF-1 LR3.

How it is produced

Assembled by solid-phase peptide synthesis: the chain is built one residue at a time on an insoluble resin support, then cleaved from the resin, deprotected and purified — most commonly by reversed-phase high-performance liquid chromatography. The purified material is lyophilized to a dry solid.

The impurity profile that appears on a certificate is a record of where that process was imperfect: deletion sequences from an incomplete coupling, truncated chains, and species retaining a protecting group.

Confirming identity

Mass spectrometry settles the question the product name alone cannot: whether the vial contains the full-length sequence or a fragment. The mass difference between them is large, so this is an unambiguous confirmation rather than a marginal one.

It is precisely the check a supplier without per-lot certificates cannot offer, and precisely the ambiguity a purchaser is otherwise asked to take on trust.

Analytical considerations

Forty-three coupling steps make deletion and truncation sequences the dominant impurity class, and at this length they are numerous and closely spaced in retention. Resolving them demands a well-developed gradient rather than a generic one.

Chain length also means the molecule begins to have genuine secondary structure in solution, which a pentapeptide does not. That affects chromatographic behaviour and is a reason methods for long peptides are not simply scaled-up versions of methods for short ones.

Thymosin alpha-1 shares a name and a tissue of origin with this compound and is otherwise unrelated in structure. The two belong to separate families and should not be treated as variants of one another.

What its certificate reports

A certificate for a lot of this material names the lot, names the issuing laboratory, and states for each parameter both the method used and the specification the result was measured against. Identity and purity are the two core results; net peptide content states how much of the fill weight is actually peptide.

A certificate belongs to a lot, not to a product line. When a new lot is released it is tested again, and the certificate published against it is that lot's certificate — a previous lot's result is never carried forward.

Research use only

This page describes structure and analysis. It makes no claim about what this compound does, and none should be inferred from it. Material is supplied for laboratory research use only: it is not a drug, food, dietary supplement, cosmetic or medical device, it is not for human or veterinary consumption, and no dosing, administration or reconstitution guidance is provided for any such use.