What is TB-500's actual molecular weight?

889.0 Da. The commonly quoted 4.9 kDa is full thymosin beta-4, the 43-residue parent protein — a 5.6-fold error.

Is BPC-157 in clinical trials?

Yes — a Phase 2 in hamstring strain, NCT07437547, recruiting with 120 participants and primary completion February 2027.

Can either be quantified at 280 nm?

No. Neither contains an aromatic residue, so there is no usable absorbance there.

GLOW (Blend)

The Two Repair-Literature Components

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-234 cited sources

BPC-157 is a fifteen-residue peptide at 1419.5 Da with a large preclinical literature and a recruiting Phase 2 trial. TB-500 is a seven-residue fragment at 889.0 Da — not 4.9 kDa, which is full thymosin beta-4 and a common 5.6-fold error.

Key facts

BPC-157: 1419.5 Da, C62H98N16O22
BPC-157 sequence: GEPPPGKPADDAGLV
BPC-157 trial: Phase 2 recruiting, NCT07437547
TB-500: 889.0 Da, seven residues
Common TB-500 error: 4.9 kDa — that is thymosin β4
Shared feature: Neither has cysteine or methionine

BPC-157's position

Fifteen residues at 1419.5 Da, dominated by four prolines and three glycines. It has the largest preclinical repair literature of the three components, and — unusually for this catalogue — a recruiting Phase 2 trial, NCT07437547, in hamstring strain with 120 participants and primary completion in February 2027.

TB-500 and the mass everyone gets wrong

TB-500 is a seven-residue acetylated fragment at 889.0 Da. The figure 4.9 kDa is frequently quoted for it, and that is full thymosin beta-4 — the 43-residue parent protein. The error is 5.6-fold, which is the largest single numerical mistake corrected on this site.

Research material referenced

GLOW 70mg — third-party HPLC tested

View — £59.99

The fragment question TB-500 carries

Many of the findings cited for TB-500 were generated with thymosin beta-4, not the fragment. A seven-residue piece of a 43-residue protein is not guaranteed to reproduce the parent's behaviour, and the read-across is often made without being flagged. This is the same caution KPV and its parent hormone require.

What they share chemically

Neither contains cysteine, methionine or an aromatic residue. That means no disulfide chemistry, no +16 Da oxidation satellite, and no usable absorbance at 280 nm for quantification. Chemically robust and analytically awkward — and, importantly here, both are unreactive toward the blend's copper.

Why they appear together

Overlapping research literatures in tissue repair and cell migration. That overlap is the rationale for combining them, and it is a rationale about subject area rather than about any demonstrated interaction between the two compounds.

Extended research context

The GLOW (Blend) deep dive

Deep dive: the copper question, and why this particular set of partners answers it

Copper is redox-active and catalyses oxidation. In protein chemistry this is well established - trace copper accelerates thiol oxidation, disulfide scrambling and methionine oxidation, which is why chelating agents appear in so many formulation buffers. So putting a copper complex in a vial with two other peptides is a fair thing to interrogate rather than wave through. Copper attacks two residues in particular: cysteine, whose free thiol is the most readily oxidised side chain in the standard set, and methionine, whose thioether becomes the sulfoxide at plus 16 daltons. Now look at what is actually in the vial. BPC-157 is Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val - no cysteine, no methionine. TB-500 is an acetylated seven-residue fragment with the same absence. The reaction copper would catalyse has no substrate present. That is a real finding rather than a reassurance, because it would not have held for many other combinations: glutathione is defined by a free thiol that oxidises in air with no catalyst at all, and IGF-1 LR3 carries three disulfide bonds whose correct pairing copper would actively disrupt. Neither belongs in a vial with GHK-Cu. This set does.

Deep dive: a blend takes the fixed ratio without the single profile

There are three ways to combine compounds and they are genuinely different propositions. Separate vials, each used independently. A blend, combined at manufacture. Or one molecule engineered to hit several targets, as retatrutide does across three receptors. The real advantage of the third is not that it hits several targets - it is that it has ONE pharmacokinetic profile. Retatrutide's three activities cannot fall out of step with each other because absorption, distribution and clearance apply to all three at once, and that is why the field pursues multi-agonism despite how hard the chemistry is. A blend buys none of that. Three peptides in one vial remain three peptides with three masses, three solubilities, three stabilities and three clearance behaviours; combining them changes the packaging, not the pharmacology. What it does cost is the ratio, which is fixed at manufacture - reconstituting in a different volume moves all three concentrations together and never their relationship. So a blend carries the inflexibility of a multi-agonist without the simplification that justifies it. What it offers instead is convenience: fewer vials, fewer reconstitutions, fewer transfers, less material lost to surfaces at each step. That is a real benefit and it is a practical one, not a pharmacological one.

Deep dive: why a blend cannot answer the question it invites

Blends invite the word synergy, so it is worth being precise about what that word means. Not that a combination works - that a combination produces MORE than its components produce independently. Two compounds each giving one unit of effect, combined giving two, is additive and entirely unremarkable. Three units would be synergy. Demonstrating it requires each component alone at the concentration present in the combination, the combination itself, and matched conditions throughout; without the individual arms there is no baseline to exceed, so a combination result on its own can never establish synergy however large it is. Here is the structural problem: those individual arms need the components separately at known concentrations, and a fixed-ratio blend whose per-component split is not stated supplies neither. The experiment that would test the claim cannot be designed from the product that prompts it. The honest position is not that synergy has been ruled out for this combination - it is that no published work addresses this combination at all, which is a different and more accurate statement. The rationale for putting these three together is overlapping research literatures in collagen, repair and cell migration, and that is a reasonable basis for a product without being evidence that the compounds interact.

Research applications

▸Combined connective tissue and matrix research protocols
▸Collagen synthesis and remodelling model systems
▸Comparative work on single compounds versus fixed combinations
▸Copper peptide coordination chemistry
▸Co-lyophilisation and multi-component formulation methodology
▸Cell migration and wound model research

Handling checklist

✓Verify GHK-Cu against 402.92 Da (CID 71587328), not 340.38 - that is free GHK
✓Verify BPC-157 against 1419.5 Da and TB-500 against 889.0 Da, not 4.9 kDa
✓Expect per-component certification - a single purity figure for a blend is a category error
✓Note the per-component mass split is not stated; no molar calculation is possible without it
✓Store lyophilised, cold, dry and protected from light - the copper complex governs
✓Reconstitute gently down the vial wall; uneven dissolution is expected and needs time, not shaking
✓Expect no disulfide or +16 Da oxidation species - no component carries cysteine or methionine

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Quoting 340.38 Da for the GHK-Cu component

Fix: That is free GHK without copper, CID 73587. The complex is 402.92 Da, CID 71587328 - a 15% difference.

✗ Quoting 4.9 kDa for the TB-500 component

Fix: That is full thymosin beta-4, the 43-residue parent protein. TB-500 is a seven-residue fragment at 889.0 Da - a 5.6-fold error.

✗ Expecting a single purity figure for the blend

Fix: With three intended compounds the other two are neither impurities nor the analyte. Each component must be verified separately before blending.

✗ Shaking to help an unevenly dissolving cake

Fix: Components of different size and solubility dissolve at different rates. Shaking creates interfaces where peptides aggregate irreversibly. Swirl and wait.

✗ Reading a blend as evidence the components act together

Fix: No published work addresses this combination. The rationale is overlapping research areas, which is not evidence of interaction.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

What is TB-500's actual molecular weight?: 889.0 Da. The commonly quoted 4.9 kDa is full thymosin beta-4, the 43-residue parent protein — a 5.6-fold error.
Is BPC-157 in clinical trials?: Yes — a Phase 2 in hamstring strain, NCT07437547, recruiting with 120 participants and primary completion February 2027.
Can either be quantified at 280 nm?: No. Neither contains an aromatic residue, so there is no usable absorbance there.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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