LL-37 — wholesale 10-vial kits

Research context

LL-37 is the only cathelicidin-family host-defense peptide encoded in the human genome. The gene, CAMP, produces an 18 kDa precursor, hCAP-18 (UniProt P49913), that is stored in the secondary granules of neutrophils and in epithelial and myeloid cells; extracellular cleavage by proteinase 3 releases the mature 37-residue C-terminal peptide. The name records the first two leucines and the length. The peptide was first described from a cDNA prediction as FALL-39, a 39-residue sequence, before the isolated granulocyte product was shown to be the 37-residue form that is used as the reference peptide today.

Molecular design is the whole story here. The sequence carries six arginines and five lysines against few acidic residues, giving a strongly cationic peptide, and it is cysteine-free, so there is no disulfide to maintain. In water it is largely disordered; in anionic lipid or micellar environments it folds into an amphipathic α-helix with a hydrophobic face and a charged face. NMR work in lipid micelles located that helical core and identified KR-12, the shortest fragment retaining antibacterial activity in vitro, which is why truncation series built on LL-37 are a standard approach in peptide-engineering studies. Transcriptionally, CAMP is a direct vitamin D receptor target gene, which is why 1,25-dihydroxyvitamin D3 appears as a positive control in cathelicidin-expression experiments.

In laboratory models LL-37 is studied on two fronts. As an antimicrobial it permeabilizes bacterial membranes in a charge- and lipid-composition-dependent way and binds lipopolysaccharide; spectroscopic work published in 2020 also showed it sequesters bacterial stealth siderophores, a mechanism that acts on iron acquisition rather than the membrane. As an immune signaling molecule it modulates Toll-like receptor responses, chemotaxis and cytokine release in cell assays, and the direction of those effects is context-dependent: the same peptide reads as pro- or anti-inflammatory depending on cell type, concentration and the co-stimulus used, which is a design consideration rather than a footnote.

Typical bench use spans minimum-inhibitory-concentration and time-kill panels; membrane-permeabilization assays with calcein- or dye-loaded liposomes; circular dichroism and solution NMR for helix formation in SDS or dodecylphosphocholine micelles; surface-plasmon or fluorescence binding studies against LPS and lipid bilayers; and cell-based reporter work on TLR and chemokine-receptor signaling. The peptide also serves as the parent sequence for shortened and stabilized analogs and as an analytical reference standard when quantifying endogenous LL-37 by LC-MS or immunoassay.

Regulatory position, stated factually: there is no FDA-approved LL-37 product, and the peptide is not the active ingredient of any approved U.S. drug. FDA lists cathelicidin LL-37 among bulk drug substances whose compounding nominations were withdrawn by the nominators, and it was not among the peptide substances covered by the October 2026 HHS interim enforcement-discretion notice. WholesalePeptide.us supplies LL-37 as a research reference standard for in-vitro, analytical and preclinical laboratory research.

Practical note for assay design: LL-37 is aggregation-prone and adsorbs to some plastics. Low-binding tubes and freshly prepared aliquots give more reproducible results. Identity is confirmed by LC-MS against the sequence above on every lot's COA.

Research areas

• antimicrobial peptide membrane mechanisms
• innate immunity and Toll-like receptor signaling
• siderophore binding and bacterial iron acquisition
• peptide–lipid biophysics
• design of truncated cathelicidin analogs
• hCAP-18 processing and proteinase 3 cleavage
• vitamin D receptor regulation of the CAMP gene

U.S. regulatory status of the compound (as an active ingredient): Not approved by the FDA. The material sold here is a research reference chemical, not a drug product.

Handling and storage

• Store lyophilized vials at −20 °C, sealed, protected from light and moisture.
• Let the vial equilibrate to room temperature before opening to limit condensation.
• Reconstitute in an appropriate sterile buffer or solvent according to your laboratory SOP.
• Use low-binding tubes; LL-37 adsorbs to some plastics and can aggregate in solution. Aliquot and avoid repeated freeze–thaw.