TB-500 (Thymosin Beta-4): A Research Reference
TB-500 (Thymosin Beta-4): A Research Reference
TB-500 is among the largest peptides commonly held in research supply, and that size is the single most useful fact about it from an analytical standpoint. Almost everything distinctive about how the compound is synthesised, separated, detected and verified follows from its molecular weight. This reference covers its chemical identity and what a peptide of this scale demands of the laboratory.
The scope is chemistry and analytical method. No use of any kind is described.
Chemical identity
TB-500 carries CAS registry number 885340-08-9. Its molecular formula is C212H350N56O78S, corresponding to a molecular weight of approximately 4,963.49 g/mol. It is catalogued under the orthographic variants TB-500 and TB500, and in relation to Thymosin Beta-4.
It is worth noting that this formula and this molecular weight are mutually consistent: summing the atomic weights of C212H350N56O78S gives 4,963.5, matching the stated figure. That agreement is a small but genuine check — a specification where the formula and the quoted mass disagree indicates an error in one of them.
At an average residue mass of roughly 110 g/mol, a molecular weight near 4,963 implies a chain of approximately forty-five residues. This places TB-500 firmly in the large-peptide category, several times the size of compounds such as Ipamorelin or the short bioregulators.
What the formula reveals
A molecular formula carries more information than its molecular weight alone, and two features of this one are directly relevant to handling.
A single sulfur atom. In a peptide, sulfur occurs only in methionine and cysteine. One sulfur means one such residue. Where that residue is a methionine, it introduces the most likely single modification to appear in aged material: oxidation to the sulfoxide, adding 16 g/mol. Against a parent mass near 4,963 that is a small relative shift, but it is readily detectable by mass spectrometry and it is not reversible.
A high nitrogen and oxygen count. Fifty-six nitrogens and seventy-eight oxygens against 212 carbons indicates a sequence rich in polar and charged residues rather than hydrophobic ones. Highly polar peptides of this size tend to be sensitive to mobile-phase composition in reversed-phase chromatography and can adsorb variably to container and column surfaces, which is one reason method conditions belong on a Certificate of Analysis alongside the result.
Synthesis at this scale
Assembling a peptide of roughly forty-five residues requires roughly forty-four sequential coupling steps by solid-phase synthesis. Each is an opportunity for incomplete reaction, and the probability of a perfectly assembled chain falls with every additional step even at high individual coupling efficiency.
The practical consequence is that the impurity profile of a large peptide is inherently more complex than that of a short one. Deletion sequences — chains missing one or more residues — are the dominant class, and a chain missing a single residue from a 4,963 g/mol parent is chemically very similar to it. Such species elute close to the target rather than as cleanly separated peaks, so a chromatogram typically shows a cluster around the main peak rather than a few discrete impurities.
Mass spectrometric behaviour
Peptides of this size behave differently in the mass spectrometer from small ones. Electrospray ionisation of a large, highly charged molecule generally produces a series of multiply charged ions rather than a single dominant species, and the observed mass-to-charge values must be deconvoluted to recover the true molecular weight.
Resolving a single-residue deletion against a parent near 4,963 Da also demands more of the instrument than resolving one against a small peptide. A missing glycine, for instance, shifts the mass by only 57 g/mol — around one percent of the total. Adequate resolution is therefore a prerequisite rather than an assumption, and this is part of why LC-MS is run alongside chromatographic purity determination rather than either standing alone.
Analytical verification
Research-grade TB-500 is typically specified at greater than 98% purity by HPLC, with identity confirmed by LC-MS. Reading such a specification, several elements carry weight beyond the headline figure.
- The observed mass against the theoretical 4,963.49 g/mol, and whether it was obtained by deconvolution of multiple charge states.
- The chromatographic method, including column and gradient, given the resolution demands described above.
- The detection wavelength used for the purity determination.
- A batch identifier that can be matched to a marking on the vial.
Batch specificity matters particularly for large peptides. Because so many coupling steps are involved, run-to-run variation has more scope to express itself than in a short synthesis, and a purity figure from a previous batch is a weak guide to the current one.
Physical form and storage chemistry
TB-500 is supplied as a lyophilised powder, white to off-white, in a sealed glass research vial. Freeze-drying removes the water required for hydrolysis, which for a chain of this length is significant simply because there are so many peptide bonds available to hydrolyse.
The sulfur-containing residue makes oxygen exclusion the other relevant consideration, and the integrity of the vial seal addresses both concerns at once.
Corix Labs supplies TB-500 5mg and TB-500 10mg as lyophilised research preparations, and in combination with BPC-157 as a pre-blended single vial and a twin vial pack of two separate preparations.
Corix Labs publishes analytical documentation for its research materials. See third-party testing reports for further detail on how batches are verified.
All materials referenced in this article are supplied strictly for laboratory research and analytical use. They are not licensed medicines and are not sold for use in humans or animals. Nothing in this article constitutes guidance on administration, preparation for use, or any clinical, therapeutic, diagnostic or cosmetic application.
