Thymosin Beta-4 Testing | Full-Length Tβ4

What Thymosin Beta-4 (full-length) is

Thymosin beta-4 (Tβ4) is the natural 43-amino-acid actin-sequestering peptide found in nearly every human cell, N-terminally acetylated, with an average molecular weight near 4,960 g/mol. It is the parent molecule of TB-500: TB-500 as usually sold is only residues 17–23 of this sequence (the acetylated heptapeptide Ac-LKKTETQ, ~889 g/mol). The two are chemically distinct — a full-length vial is roughly five and a half times the mass per molecule, carries a different charge and hydrophobicity, and elutes at a different retention time — so a certificate written against the TB-500 standard says nothing reliable about a full-length vial, and vice versa. Market labels blur the line constantly: vials sold as 'TB-500', 'TB4' or 'thymosin beta-4' can contain either molecule. The sequence has no tryptophan or tyrosine, so it is quantified at 214 nm; the 280 nm trace is blank by design. It is a research chemical and is not an FDA-approved drug; as a lyophilized powder, nothing about its identity, purity or content can be judged by eye.

Why get your Thymosin Beta-4 (full-length) independently tested

Fragment vs. full-length substitution: the single most common problem with this compound is receiving the 889 g/mol TB-500 fragment in a vial labelled thymosin beta-4, or the reverse. Retention-time and UV-spectral comparison against the full-length reference standard shows which molecule is actually in the vial.
Net peptide content vs. label mass: a 43-residue peptide carries proportionally more counter-ion (TFA or acetate) and water than a short fragment, so the dry weight on the label routinely overstates the peptide present. The assay reports milligrams of peptide per vial, not milligrams of powder.
Synthesis-related impurities: a 43-mer made by solid-phase synthesis accumulates deletion, truncation and incomplete-deprotection sequences that elute close to the main peak; a methionine at position 6 adds an oxidation-prone site. Purity by area percent separates a clean lot from one padded with near-neighbours.
Identity for an expensive, low-volume peptide: full-length Tβ4 costs several times what the fragment does, which is exactly the incentive for substitution. An independent identity match is the only way to know the premium bought the longer molecule.

What we measure on Thymosin Beta-4 (full-length)

Every full-length thymosin beta-4 certificate reports three results by reversed-phase HPLC with UV/diode-array detection at 214 nm: identity (retention-time plus UV-spectral match to a full-length Tβ4 reference standard — never the TB-500 fragment standard), chromatographic purity as area percent, and net-peptide assay in milligrams of peptide per vial. We do not perform mass spectrometry, sterility, or endotoxin testing.

Every result is issued as a certificate of analysis you — or anyone you forward it to — can verify cryptographically. Reporting identity, purity, and milligram content is the point: a vial can be pure and still underfilled, so we report all three. More on purity vs. net-peptide content and how to read a peptide COA.

Our scope — stated plainly

Testing is RP-HPLC-UV against a certified reference standard and establishes identity, chromatographic purity, and net peptide content — not sterility, safety, or fitness for any use. Full-length Tβ4 is a less-common compound and its reference standard is sourced to order, so turnaround can be longer than for the core panel; we confirm the timeline before you ship. A vial that turns out to be the TB-500 fragment is reported as such.

KMD is an independent RP-HPLC-UV lab. We do not run LC-MS / mass-spec, sterility, endotoxin, or heavy-metal testing. If your job needs a capability we don't have, we'll say so.

Thymosin Beta-4 (full-length) testing — FAQ

Is this the same test as TB-500?

No. TB-500 is the 7-residue fragment (residues 17–23) of thymosin beta-4; this page is the full 43-residue peptide. They run against different reference standards and elute at different retention times, so pick the compound that matches your label. If you are not sure which one you bought, tell us and we will check the vial against both.

My vial just says 'TB4' or 'thymosin beta-4' — which do I order?

Order it as Thymosin Beta-4 (full-length) if the supplier describes a 43-amino-acid peptide or a molecular weight around 4,900–5,000 g/mol; order TB-500 if it lists Ac-LKKTETQ or a weight near 889 g/mol. If the label says nothing either way, tell us before you order and we will check the vial against both standards — we never guess which molecule a bare 'thymosin beta-4' means.

Why is the 280 nm trace empty on my certificate?

Full-length thymosin beta-4 contains no tryptophan or tyrosine, the residues that absorb at 280 nm, so a flat 280 nm trace is expected. Identity, purity and content are all read at 214 nm, where the peptide backbone absorbs.

Do you confirm the sequence or the acetyl group by mass spec?

No. We use RP-HPLC-UV, which establishes identity by retention-time and UV-spectral match to a reference standard, not by molecular mass. We do not run LC-MS or any mass-spectrometric methods.

Test your Thymosin Beta-4 (full-length) →Verify a certificate Pricing & turnaround

Thymosin Beta-4 (Full-Length Tβ4) Testing & Verification