LL-37

LL-37 is a 37-residue cationic peptide with the sequence LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES, and is the only cathelicidin-family peptide encoded in the human genome. Its name records its first two residues, both of them leucine, and its overall length. It carries the molecular formula C205H340N60O53 and an average molecular weight near 4493 g/mol, and appears in PubChem as CID 16198951 under CAS number 154947-66-7. Under suitable buffer conditions it folds into an amphipathic alpha-helix, with cationic and hydrophobic residues segregated onto opposite faces, the geometry that underlies most biophysical work on the molecule.

LL-37 corresponds to the C-terminal domain of hCAP-18, the human cationic antimicrobial protein of 18 kDa, from which it is released by proteolytic processing. Research-grade LL-37 is made by solid-phase synthesis and supplied as a lyophilized (freeze-dried) solid. At 37 residues it is a long and synthetically demanding peptide, which is reflected in the fill sizes and the small number of brands listing it. This entry covers the synthetic research-grade peptide only, and identity figures above should be reconciled against the Certificate of Analysis supplied with the lot in hand. LL-37 is sold for research use only and is not for human or veterinary use.

LL-37 was described in 1995 by Agerberth and colleagues as FALL-39, a cysteine-free human peptide sequence found in bone marrow (PubMed 7529412). Gudmundsson and colleagues then characterised granulocyte processing of the cathelin precursor and fixed the 37-residue form and its name (PubMed 8681941).

Turner and colleagues measured growth inhibition of cultured bacterial isolates in broth assays, reporting marked sensitivity to salt and serum (PubMed 9736536). Johansson and colleagues linked in vitro activity to helix formation in the assay buffer (PubMed 9452503).

The in vitro and biophysical literature is large and well replicated; work in other systems is far less settled.

Mechanistic descriptions centre on interaction with anionic lipid surfaces. On contact with negatively charged model membranes LL-37 folds into an amphipathic helix and, above a threshold peptide-to-lipid ratio, disorders the bilayer in a carpet-type mode rather than forming a defined pore (PubMed 16716248).

Cathelicidin names the precursor family and its cathelin domain; LL-37 is the processed C-terminal peptide. Shorter fragments such as KR-12 and FK-13 are separate entities, not substitutes for the 37-mer.

In vitro readings depend heavily on ionic strength, divalent cations, serum protein and lipid composition, so values from different conditions are not comparable (PubMed 9736536).

Sealed lyophilized LL-37 is held frozen at -20°C, shielded from light, in its original container. Lyophilized peptides are hygroscopic, so a container reaches ambient temperature before opening. Repeated freeze-thaw cycles are avoided.

Stability for a lot is documented on its Certificate of Analysis rather than assumed here.

Reconstitution means returning a lyophilized compound to solution. This entry gives no preparation procedure: solvent, concentration and handling steps belong to a protocol, not to the compound. LL-37 carries a high net positive charge from its lysine and arginine content and is handled as aqueous-soluble material.

Highly cationic peptides adsorb to container and pipette surfaces, shifting effective concentration in dilute samples. Solubility and water-content figures for a lot appear on its Certificate of Analysis.

Identity and purity of research-grade LL-37 are established analytically, typically by reverse-phase HPLC and mass spectrometry. Verified purity is documented per lot on the Certificate of Analysis. Length is the central quality variable: deletion and truncation sequences accumulate across a 37-residue synthesis and most readily alter assay behaviour.

LL-37 is commonly supplied as a trifluoroacetate or acetate salt, and counter-ion content shifts effective peptide mass. Confirm the salt form on each lot’s COA.

LL-37 is catalogued alongside these encyclopedia compounds.

• KPV.
  Short melanocortin-derived peptide also examined in vitro against cultured microbial isolates.
• Thymosin Alpha-1.
  28-residue peptide studied in immune-signalling models.
• GHK-Cu.
  Copper-binding tripeptide studied in matrix-remodelling models.
• BPC-157.
  Pentadecapeptide investigated in animal tissue-repair models.

Agerberth B, Gunne H, et al. (1995). FALL-39, a putative human peptide antibiotic, is cysteine-free and expressed in bone marrow and testis. Proc Natl Acad Sci U S A.
PubMed 7529412

Gudmundsson GH, Agerberth B, et al. (1996). The human gene FALL39 and processing of the cathelin precursor to the antibacterial peptide LL-37 in granulocytes. Eur J Biochem.
PubMed 8681941

Johansson J, Gudmundsson GH, et al. (1998). Conformation-dependent antibacterial activity of the naturally occurring human peptide LL-37. J Biol Chem.
PubMed 9452503

Turner J, Cho Y, et al. (1998). Activities of LL-37, a cathelin-associated antimicrobial peptide of human neutrophils. Antimicrob Agents Chemother.
PubMed 9736536

Dürr UH, Sudheendra US, Ramamoorthy A (2006). LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochim Biophys Acta.
PubMed 16716248

LL-37 is stocked here in one format: sealed single-compound lyophilized vials from two supplier brands, each listing a 5mg fill. Vials are the only listed format for this compound in this catalog. Per-vial strengths are product specifications only. Each lot is batch tested with a published Certificate of Analysis documenting verified purity and identity for that specific lot.

• • Browse all LL-37 research products
  • Verified Peptides LL-37, 5mg lyophilized vial
  • Real Peptides LL-37, 5mg lyophilized vial
  • Collections: Research Vials. Documentation: COA and Lab Testing.

These products are sold for Research Use Only and are not intended for human consumption.