Skip to content

LL-37

LL-37 (CAS 154947-66-7) is the sole human cathelicidin antimicrobial peptide (CAMP), a 37-amino acid cationic peptide with a molecular weight of approximately 4,493 Da and formula C₂₀₅H₃₄₀N₆₀O₅₃. Derived from proteolytic cleavage of the hCAP18 precursor protein, LL-37 begins with two leucine residues (hence "LL") and is expressed by neutrophils, macrophages, and epithelial cells at mucosal barriers. As a multifunctional host defense peptide, LL-37 integrates direct antimicrobial activity with immunomodulatory signaling, wound healing, and chemotaxis functions.

Technical Specifications

Property Value
CAS Number 154947-66-7
Molecular Formula C₂₀₅H₃₄₀N₆₀O₅₃
Molecular Weight ~4,493 Da
Purity ≥99% (HPLC-verified)
Appearance Lyophilized white powder
Solubility Soluble in aqueous buffers; limited water solubility
Storage -20°C (lyophilized), 2–8°C (reconstituted)

Mechanism of Action

LL-37 adopts an amphipathic α-helical structure upon contact with negatively charged microbial membranes, enabling direct membrane disruption. The cationic face of the helix (rich in arginine and lysine residues) electrostatically binds to anionic bacterial phospholipids (phosphatidylglycerol and cardiolipin), while the hydrophobic face inserts into the lipid bilayer, forming toroidal pores that dissipate the transmembrane electrochemical gradient and cause rapid microbial lysis. This membrane-targeting mechanism confers broad-spectrum activity against Gram-positive and Gram-negative bacteria, enveloped viruses, fungi, and biofilms with low propensity for resistance development. Beyond direct antimicrobial action, LL-37 binds to multiple host receptors — including FPR2/ALX, P2X7, and EGFR — to modulate immune responses. It chemoattracts neutrophils, monocytes, and CD4⁺ T-cells to sites of infection, neutralizes LPS and lipoteichoic acid (LTA) through direct binding, and promotes re-epithelialization and angiogenesis at wound sites via EGFR transactivation and VEGF induction.

Research Applications

  • Primary: Antimicrobial host defense — bacterial membrane disruption, biofilm inhibition, LPS neutralization
  • Secondary: Immunomodulation and chemotaxis research, wound healing and re-epithelialization, chronic inflammatory disease models (rosacea, psoriasis)
  • Model Systems: In vitro (MIC assays against multi-drug resistant bacteria, neutrophil chemotaxis assays, keratinocyte scratch assays), in vivo murine infection models (Pseudomonas aeruginosa, MRSA)

Quality Control & Analytical Methods

  • HPLC: ≥99% purity verification at 214/220 nm (C18 reversed-phase column)
  • Mass Spectrometry: ESI-MS for molecular weight confirmation (~4,493 ±1.0 Da)
  • Peptide Content: Amino acid analysis (AAA) for net peptide content determination
  • Endotoxin: <1 EU/mg (LAL assay)
  • TFA Content: <1% (ion chromatography)

Stability & Storage

Condition Stability
-20°C (lyophilized) 24 months
4°C (lyophilized) 6 months
25°C (lyophilized) 1 month
Reconstituted (4°C) 7 days
Reconstituted (-20°C) 30 days

Key Research References

  • Zanetti (2004) — Cathelicidins, multifunctional peptides of the innate immunity. J Leukoc Biol. PMID: 14634170
  • Dürr et al. (2006) — LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochim Biophys Acta. PMID: 17037832
  • Kahlenberg & Kaplan (2013) — The multifunctional LL-37 and its role in autoimmunity. J Immunol. PMID: 24191614

Source & Purchase

For researchers requiring research-grade LL 37 with full analytical documentation including HPLC, LC-MS, and Certificate of Analysis, visit the HK Peptides product page for specifications, bulk pricing, and ordering.

View LL 37 Product →

FAQ

Q: What purity level is standard for LL-37? A: HK Peptides supplies LL-37 at ≥99% purity by HPLC with full COA documentation.

Q: How should LL-37 be stored for research use? A: Lyophilized LL-37 should be stored at -20°C. Reconstituted solutions at 4°C for short-term use (up to 7 days).