LL-37

Research Benefits

• Broad-Spectrum Antimicrobial — LL-37 is the only human cathelicidin antimicrobial peptide, effective against gram-positive and gram-negative bacteria, fungi, and enveloped viruses in research settings.
• Innate Immunity Research — As a key effector of the innate immune system, LL-37 serves as a reference compound for studying host defense peptide mechanisms.
• Wound Healing Studies — LL-37 promotes re-epithelialization and angiogenesis in wound models, making it valuable for tissue repair research.
• Immune Cell Chemotaxis — LL-37 acts as a chemoattractant for neutrophils, monocytes, and T-cells through formyl peptide receptor-like 1 (FPRL1/FPR2) activation.
• Biofilm Disruption — Research demonstrates LL-37's ability to prevent biofilm formation and disrupt established biofilms at sub-MIC concentrations.

Mechanism of Action

LL-37 (also known as CAMP or hCAP-18 C-terminal fragment) is a 37-amino acid amphipathic α-helical peptide cleaved from the 18-kDa precursor human cathelicidin antimicrobial protein.

Membrane Disruption: LL-37 inserts into microbial membranes via electrostatic attraction to negatively charged phospholipid headgroups. It forms toroidal pores or operates through a carpet-like mechanism, causing membrane depolarization and cell lysis.

Immunomodulation: Beyond direct antimicrobial activity, LL-37 modulates immune responses by activating FPR2 (formyl peptide receptor 2) on immune cells, triggering chemotaxis, degranulation, and cytokine release.

Anti-Endotoxin Activity: LL-37 neutralizes lipopolysaccharide (LPS) by direct binding, preventing TLR4 activation and reducing inflammatory cytokine cascades in sepsis models.

Angiogenesis & Repair: LL-37 stimulates endothelial cell proliferation and migration through VEGF-independent pathways involving FPRL1 signaling, contributing to wound neovascularization.

Research Protocol

Derived from published research literature. For research use only.

Reconstitution

Reconstitute in sterile endotoxin-free water or PBS. Typical stock concentration: 1 mg/mL. LL-37 can adsorb to plastic surfaces; use low-binding tubes or add 0.1% BSA carrier.

Research Dosing (from published studies)

• Antimicrobial MIC assays: 1-64 μg/mL depending on pathogen species and growth conditions.
• Biofilm assays: Sub-MIC concentrations (0.5-4 μg/mL) for prevention; MIC-level for disruption.
• In vivo wound models (murine): 10-50 μg applied topically to wound beds or via hydrogel delivery.
• Chemotaxis assays: 1-10 μM in transwell migration chambers.

Storage

Lyophilized at -20°C. Reconstituted at 2-8°C, use within 7 days. For longer storage, aliquot and freeze at -80°C.

Safety & Handling

Research Use Only. Not for human or veterinary use.

Storage Conditions

• Lyophilized: -20°C, desiccated
• Reconstituted: 2-8°C (7 days) or -80°C (aliquoted, months)
• Use low-binding plasticware to prevent adsorption losses

Known Considerations from Literature

• At high concentrations (>25 μg/mL), LL-37 can be cytotoxic to mammalian cells due to its membrane-active mechanism. Dose-response curves should include cytotoxicity controls.
• LL-37 is sensitive to salt concentration; antimicrobial activity diminishes in physiological salt (150 mM NaCl). Low-salt assay buffers are standard for MIC testing.
• Serum proteases rapidly degrade LL-37; use serum-free conditions or protease inhibitors for in vitro work.

Handling

Standard PPE. Endotoxin-free techniques recommended for immunological assays.

Frequently Asked Questions

What is LL-37?

LL-37 is the sole member of the human cathelicidin family of antimicrobial peptides. It is a 37-amino acid peptide (named for its two N-terminal leucine residues) with broad antimicrobial and immunomodulatory functions.

Why does LL-37 lose activity in salt?

LL-37's antimicrobial mechanism depends on electrostatic interaction with negatively charged microbial membranes. High salt concentrations screen these charges, reducing binding affinity. Researchers typically use low-ionic-strength buffers for antimicrobial assays.

Can LL-37 be used with serum-containing media?

Serum proteases degrade LL-37 rapidly. For cell culture experiments, use serum-free media or add protease inhibitors. For chemotaxis assays, the gradient should be established in serum-free conditions.

What purity is this product?

BeaCapra LL-37 is ≥99% pure by HPLC, with endotoxin levels below 0.1 EU/mg. Full COA provided.