Pure North Peptides Journal · Compendium
LL-37: cathelicidin antimicrobial-peptide research notes
Published 2024-10-18 · Pure North Peptides Editorial · Canada
Short answer. LL-37 is the 37-residue cleavage fragment of human cathelicidin antimicrobial protein hCAP-18. The amphipathic α-helix is investigated in in-vitro membrane-disruption and antimicrobial-pathway research. LL-37 is not currently stocked in the Pure North Peptides catalog — email us to ask about future availability.
Sequence and structure
LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES — 37 residues, mass 4493.34 Da. Adopts an amphipathic α-helix in membrane-mimetic environments, with hydrophobic residues clustering on one face and cationic residues on the other. The amphipathicity drives the membrane-perturbing activity that defines the cathelicidin class.
Synthesis challenges
LL-37 is one of the harder peptides on a research catalog to synthesize cleanly:
- Aggregation in synthesis: the long hydrophobic stretches drive coupling-step interruptions; double-couplings on residues 12–18 are routine.
- Aspartimide formation: the Asp-Gly motif at positions 26–27 is aspartimide-prone; synthesis cocktails should include 0.1 M HOBt to suppress.
- HPLC retention: high hydrophobicity means LL-37 elutes late on standard C18 gradients; columns benefit from extended conditioning between injections.
Reference-grade quality criteria
- RP-HPLC purity ≥ 99% at 220 nm.
- ESI-MS at 4493.34 Da ± 0.5 Da.
- Aspartimide content < 1.5% (key impurity for this sequence).
- Net peptide content ≥ 80% by AAA.
- Endotoxin < 0.5 EU/mg.
Reconstitution
LL-37 is moderately surface-active and adheres to plastic. Reconstitute in bacteriostatic water at 1 mg/mL or higher; lower concentrations show measurable loss to pipette tips. Use low-binding tubes for aliquots. Stable 14 days at 2–8 °C; longer storage as −80 °C aliquots with single freeze-thaw protocol.
LL-37 is not currently in the Pure North Peptides catalog. Email purenorthpeptides@proton.me if you would like to be notified if it is added in the future, or browse the current catalog →
Frequently asked questions
Is LL-37 hard to make?
Relative to short research peptides, yes — the long hydrophobic stretches and aspartimide-prone Asp-Gly motif require attentive synthesis. Reference-grade lots typically run higher than $50 CAD per 10 mg vial.
What is LL-37's mass?
Theoretical 4493.34 Da. ESI-MS confirmation should fall within 0.5 Da on a competent COA.
Why is aspartimide content tracked?
The Asp-Gly motif at positions 26–27 is prone to forming aspartimide during synthesis. Reference-grade material should report < 1.5% aspartimide impurity.
How does LL-37 differ from KPV?
LL-37 is a 37-residue cathelicidin with direct membrane-disruption activity. KPV is a 3-residue α-MSH fragment with cytokine-pathway effects. Different mechanism, different size class.
Where to source LL-37 in Canada?
LL-37 is not currently stocked in the Pure North Peptides catalog. Email purenorthpeptides@proton.me to ask about future availability.
Disclaimer: All Pure North Peptides products are supplied for laboratory research use only. They are not approved by Health Canada as drugs. See our research-use declaration for full terms.