LL-37 Testing | Identity & Purity Check

What LL-37 is

LL-37 is the 37-residue C-terminal fragment of human cathelicidin (hCAP18), named for the two leucines that start its sequence. It is strongly cationic — rich in lysine and arginine — and folds into an amphipathic helix, which makes it both interesting and awkward: it sticks to glass and plastic, it aggregates at high concentration, and it is a long synthesis with plenty of opportunity for deletion sequences and oxidation at its methionine residues. At roughly 4.5 kDa it is among the larger peptides on the research market, and it is priced accordingly, so an underfilled or degraded vial is an expensive one. LL-37 is not an approved drug; material sold as a research chemical carries no regulated manufacturing or identity guarantee.

Why get your LL-37 independently tested

Sequence integrity on a long synthesis: 37 residues by solid-phase chemistry means truncations and deletion sequences that elute close to the parent peak. Chromatographic purity as area percent reports how much of the material is the full-length target.
Oxidation: LL-37 carries methionines that oxidise on storage, appearing as earlier-eluting shoulders. Purity and the chromatogram make that degradation visible rather than hidden in a gross weight.
Adsorptive loss and short fill: a cationic, amphipathic peptide loses mass to surfaces at every step of manufacture and fill. The net-peptide assay reports what is actually in the vial in milligrams, against a reference standard, so a fill that looked right by weight is checked by content.
Substitution risk on a costly compound: an expensive long peptide is a target for replacement with something cheaper. Identity by retention-time and UV-spectral match against a certified LL-37 standard confirms the vial holds LL-37.

What we measure on LL-37

Every LL-37 certificate reports identity (retention-time and UV-spectral match against a certified LL-37 reference standard), chromatographic purity as area percent, and net-peptide content in milligrams per vial, by reversed-phase HPLC with diode-array detection at 214 nm. Sample handling is adapted to the peptide's stickiness so the assay reflects the vial, not the vial's losses to our glassware.

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; a standard may need to be sourced before analysis, which can affect turnaround. KMD Analytical is an independent laboratory. We do not perform mass spectrometry, sterility, endotoxin, heavy-metal, or residual-solvent testing, and we do not measure antimicrobial activity.

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.

LL-37 testing — FAQ

Is LL-37 harder to test than a small peptide?

Somewhat. It is long, cationic, and adsorbs to surfaces, so sample preparation has to account for that or the assay under-reports. Identity by retention time is a clean match against the standard; purity resolves oxidised and truncated species as separate peaks. It is a routine compound for us, with handling that respects its chemistry.

Can you detect oxidised LL-37?

Oxidation at methionine produces species that separate from the parent under reversed-phase conditions and show as additional peaks, which lower the reported area-percent purity. The chromatogram printed on the certificate shows them. We do not assign which residue oxidised — that would need mass spectrometry.

Do you test the peptide's antimicrobial activity?

No. We report identity, purity, and milligrams of peptide per vial by HPLC-UV. Biological activity is outside our scope, and we say so plainly.

Test your LL-37 →Verify a certificate Pricing & turnaround

LL-37 (Cathelicidin) Testing & Verification