LL-37

LL-37 is a 37-amino-acid cationic, amphipathic α-helical peptide released from the C-terminus of human cathelicidin hCAP18, the only cathelicidin encoded in the human genome. Its name reflects its two N-terminal leucine residues and its 37-residue length. The peptide's cationic charge and amphipathic helix underlie its affinity for anionic microbial membranes. It is produced synthetically for research use and studied as a reference antimicrobial and immunomodulatory peptide.

The research literature characterizes LL-37 through two complementary activities. Its amphipathic helix inserts into and permeabilizes anionic microbial membranes, the basis of its broad-spectrum antimicrobial activity in vitro, and it also neutralizes bacterial lipopolysaccharide (LPS). Beyond direct membrane effects, it is described as an immunomodulatory ligand signaling through formyl peptide receptor 2 (FPR2), driving chemotaxis and cellular activation. In cultured systems this signaling is associated with macrophage and keratinocyte activation and with angiogenic endpoints.

Contexts in which this compound appears in the in-vitro and preclinical research literature:

• Antimicrobial assays: membrane permeabilization against bacterial and fungal targets in vitro.
• Lipopolysaccharide-neutralization and endotoxin-signaling studies.
• FPR2-mediated chemotaxis and immune-cell activation models.
• Keratinocyte and macrophage cultures examining wound-associated and angiogenic responses.
• Preclinical models referenced in the literature examining host-defense and tissue-repair endpoints.

Supplied as a lyophilized powder for reconstitution in the laboratory. Reconstitute with bacteriostatic water (or the sterile solvent your protocol specifies) to the working concentration required by the assay; the cationic peptide can adsorb to surfaces, so low-binding tubes and tips are commonly used. Add diluent slowly down the vial wall and swirl gently; do not vortex, and aliquot to minimize freeze–thaw cycles.

Store the sealed lyophilized vial at −20 °C protected from light, where it is stable long-term. Once reconstituted, keep refrigerated at 2–8 °C and avoid repeated freeze–thaw.

A certificate of analysis for the current lot is in preparation and will be published in the certificate library. Lot documentation is available on request for this compound.