A KLOW certificate reports four molecular weights: 342.4, 403.2, 1419.5 and 4964.2 Da. Those identify KPV, GHK-Cu, BPC-157 and TB-500 — the GLOW formulation with a fourth component added.
Four components is where certificate reading stops being casual. Two of these masses sit close enough together that reading them the wrong way round leads to a wrong conclusion about whether the copper complex is intact. This post covers the decode, the specific confusion, what KPV is, and what four components in one vial costs you.
The four masses
| Mass | Component | What it is |
|---|---|---|
| 342.4 | KPV | Lys-Pro-Val, the C-terminal tripeptide of α-MSH |
| 403.2 | GHK-Cu | Gly-His-Lys complexed with copper(II) |
| 1419.5 | BPC-157 | 15-residue synthetic peptide |
| 4964.2 | TB-500 | Full-length thymosin β4, 43 residues |
The two larger masses match the single-compound certificates exactly, which is the standard cross-check — see reading a two-component blend certificate for the method.
The confusion worth avoiding
Three small numbers are in play, and two of them are nearly identical:
| Species | Approximate mass |
|---|---|
| Free GHK (no copper) | ~340 |
| KPV | 342.4 |
| GHK-Cu (with copper) | 403.2 |
Free GHK and KPV are about two daltons apart. On a certificate that lists masses without naming which component each belongs to — and many do — it is entirely possible to read 342.4 as "GHK" and conclude the copper is missing.
It is not. The copper is in the 403.2 line. The 342.4 line is a different molecule entirely.
The reliable way to read a four-component certificate is to check that all four masses are accounted for, not to match them one at a time. If you have 342.4 and 403.2, you have KPV and the copper complex. If you had only 342.4 with nothing near 403, that would be a question worth asking.
What is GHK-Cu covers why the copper adds ~63 Da and why the complex is the point.
What KPV is
KPV is lysine-proline-valine — three amino acids, residues 11–13 of α-melanocyte-stimulating hormone, which is its C-terminal end.
A three-residue peptide having a research literature at all needs explaining, and the explanation is that it is not an arbitrary tripeptide: it is the conserved C-terminal tail of a well-studied signalling hormone. Brzoska and colleagues' 2008 Endocrine Reviews survey covers α-MSH and the related tripeptides together, which is the context that makes KPV interesting rather than trivial.
α-MSH itself acts at melanocortin receptors — the same family covered in melanocortin receptors explained and relevant to PT-141. KPV's proposed activity is generally described as not requiring those receptors, which is part of why it is studied separately. Dalmasso and colleagues (2008) describe uptake via the PepT1 transporter in an intestinal model.
The KPV tripeptide certificate covers the single-compound document, and why tripeptides behave differently in solution covers the handling consequences of being this short.
What the certificate reports
| Field | Lot KLOW80-0713 |
|---|---|
| Molecular weights | 342.4, 403.2, 1419.5, 4964.2 |
| Purity (RP-HPLC, 214 nm) | 99.81% |
| Identity | LC-MS/MS |
| Endotoxin | <0.05 EU/mL |
Why the purity figure is least useful here
With four components the single area-percent number is at its least informative.
Absorbance at 214 nm comes mainly from peptide bonds. KPV has two. TB-500 has forty-two. Per molecule, TB-500 absorbs roughly twenty times more strongly. A chromatogram of this blend is dominated by the largest component regardless of how much of each is present, and the tripeptides produce small peaks even when abundant.
So: 99.81% means the four expected peaks together account for 99.81% of total absorbance. It says nothing about ratio, and visual peak size is actively misleading. Net content per component is the only line describing quantity — net peptide content vs purity and HPLC purity as area percent cover both halves of this.
The cost of four components
| Consequence | |
|---|---|
| Attribution | No observation can be assigned to any single compound |
| Ratio control | Fixed at manufacture |
| Independent testing | Not possible from this material |
| Stability | Four degradation pathways on four timescales |
| Interactions | Copper is redox-active; TB-500 has an oxidisable methionine |
The copper point is worth repeating from the GLOW article: copper(II) can participate in oxidation chemistry, and sharing solution with an oxidisable residue is a reason to keep reconstituted material cold, dark and short-lived. How long does reconstituted peptide last covers the timescales; peptide blends vs single compounds covers when the format is appropriate.
For any experiment where attribution matters, four single-compound vials are the correct purchase and a blend is the wrong one. That is a straightforward methodological point, not a quality judgement about the material.
Regulatory position
None of the four is an approved drug in any major jurisdiction. BPC-157 sits in FDA 503A Category 2; TB-500 is prohibited in sport under WADA's S2 class. All four are supplied for laboratory research only — what "research use only" means covers the limits of that designation.
Frequently asked questions
What is the difference between GLOW and KLOW?
KLOW is GLOW plus KPV. The other three components — GHK-Cu, BPC-157 and TB-500 — are the same.
Is 342.4 the GHK?
No, and this is the easy mistake. 342.4 is KPV. Free GHK is about 340, two daltons away, but the GHK in this blend is the copper complex at 403.2. Check that all four masses are present rather than matching them individually.
What does KPV stand for?
The one-letter codes of its three residues: K for lysine, P for proline, V for valine.
Why does such a short peptide have a literature?
Because it is the conserved C-terminal fragment of α-MSH, a well-studied hormone, rather than an arbitrary tripeptide.
Can I work out the ratio from the chromatogram?
No. The four components absorb very differently at 214 nm — TB-500 roughly twenty times more strongly per molecule than KPV. Peak size does not track quantity.
Should I buy the blend or the four compounds separately?
Separately, if you need to attribute an observation to a specific compound or vary one independently. The blend is a convenience format.
References
- Brzoska T, Luger TA, Maaser C, Abels C, Bohm M. Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo, and future perspectives for the treatment of immune-mediated inflammatory diseases. Endocrine Reviews 2008;29(5):581-602. doi.org/10.1210/er.2007-0027
- Pickart L, Margolina A. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. International Journal of Molecular Sciences 2018;19(7):1987. doi.org/10.3390/ijms19071987
- Dalmasso G, Charrier-Hisamuddin L, Nguyen HT, et al. PepT1-mediated tripeptide KPV uptake reduces intestinal inflammation. Gastroenterology 2008;134(1):166-78. doi.org/10.1053/j.gastro.2007.10.026
Every product mentioned is sold for laboratory research use only and is not for human or animal use. Nothing on this page describes or recommends use of the material sold here in humans or animals.
