Host Defense Peptide / Cathelicidin Class / Innate Immunity Research Compounds
Antimicrobial Peptides Research — LL-37, Cathelicidins & Defensins
Antimicrobial peptides (AMPs) are short, amphipathic peptides that form a critical component of innate immunity across virtually all multicellular organisms. In humans, the primary cathelicidin is LL-37 — the mature C-terminal domain of the hCAP-18 precursor protein (CAS 154947-66-7; 37 residues; MW ~4493 Da; sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). LL-37 is the most studied human AMP and serves as the archetype for the broader class. Alongside cathelicidins, the defensin family (α-defensins, β-defensins) constitutes the other major class of human AMPs, with roles in epithelial barrier defense, neutrophil granule function, and mucosal immunity. This hub covers LL-37 and the broader antimicrobial peptide research context. Research use only.
Compound identity
- Name
- Antimicrobial Peptides — LL-37 & Defensin Research Hub
- Class
- Host Defense Peptide / Cathelicidin Class / Innate Immunity Research Compounds
- Also known as
- antimicrobial peptide research, LL-37 research, cathelicidin peptide, CAP-18 antimicrobial, host defense peptide research, defensin peptide research, innate immunity peptide, cathelicidin LL-37, antimicrobial host defense peptide, LL37 research compound, AMP research, cathelicidin antimicrobial peptide
Research context
LL-37's mechanism of action in antimicrobial models is primarily membrane disruption: the helical peptide inserts into bacterial membranes, forming pores or causing membrane disintegration through carpet-mechanism or toroidal-pore models. This broad-spectrum activity — effective against gram-positive and gram-negative bacteria, some fungi, and enveloped viruses — is of significant interest to researchers studying alternatives to conventional antibiotics, particularly against biofilm-forming pathogens and antibiotic-resistant organisms. In-vitro studies have examined LL-37's minimum inhibitory concentrations (MICs) against clinical isolates of S. aureus (including MRSA), P. aeruginosa (high biofilm producer), E. coli, and C. albicans. Anti-biofilm models are a particularly active area: LL-37 has been shown in vitro to disrupt P. aeruginosa biofilm formation at sub-MIC concentrations.
Beyond direct antimicrobial activity, LL-37 is studied as an immunomodulator. It is expressed by neutrophils, macrophages, NK cells, and epithelial cells and is upregulated in response to infection, inflammation, and vitamin D signaling — the vitamin D receptor (VDR) directly regulates cathelicidin gene expression, which underlies research interest in the LL-37/vitamin D axis. Immunomodulatory research contexts include: macrophage activation, chemotaxis of immune cells (LL-37 acts as a chemoattractant for monocytes and T cells), mast cell degranulation, and wound healing models. The peptide also interacts with TLR3 and TLR9, modulating innate immune signaling through non-antimicrobial pathways. These diverse effects make LL-37 one of the most multifunctional research peptides available.
For researchers sourcing antimicrobial peptides: LL-37's 37-residue length places it at the upper end of research peptide synthesis complexity; purity by HPLC (≥98%+) and endotoxin testing are particularly important for antimicrobial peptide research because LPS contamination confounds innate immunity readouts. Defensins (α-defensins HNP-1–4 from neutrophils; β-defensins hBD-1–3 from epithelia) are studied in this context and are synthesized with disulfide bonds requiring oxidative folding — technically distinct from LL-37 and not currently in the DMV Research catalog. DMV Research offers LL-37 as a synthetic research peptide with ≥99% purity, HPLC data, and mass-spec COA. Research use only.
Frequently asked questions
What is LL-37 and why is it studied?+
LL-37 (CAS 154947-66-7, 37 residues, MW ~4493 Da) is the mature C-terminal domain of the human cathelicidin precursor protein hCAP-18 — the only cathelicidin expressed in humans. It is studied for broad-spectrum antimicrobial activity (gram-positive, gram-negative, fungi, enveloped viruses), anti-biofilm effects, and immunomodulatory functions including macrophage activation, chemotaxis, and wound healing models. Research use only.
What is the sequence and structure of LL-37?+
LL-37 sequence (N→C): LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES (37 residues). It adopts an amphipathic α-helical conformation in lipid environments, which underlies its membrane-disruption mechanism. CAS: 154947-66-7; MW: ~4493 Da; no disulfide bonds (unlike defensins). Research use only.
How does LL-37 differ from defensins as antimicrobial peptides?+
LL-37 is a cathelicidin — a single-peptide, α-helical AMP with broad-spectrum activity and no disulfide bonds. Defensins (α-defensins from neutrophil granules; β-defensins from epithelial cells) are β-sheet structures stabilized by 3 disulfide bonds, require oxidative folding in synthesis, and have distinct receptor interactions and expression patterns. Both classes are host defense peptides from human innate immunity; LL-37 is the better-studied research compound. Research use only.
What research applications use LL-37?+
Key research applications: (1) antimicrobial MIC assays against gram-positive/negative organisms and MRSA; (2) anti-biofilm models (P. aeruginosa, S. aureus); (3) innate immunity signaling (TLR3/9 modulation, macrophage activation); (4) wound healing and epithelial repair models; (5) vitamin D/cathelicidin axis studies. All are in-vitro or animal-model research; LL-37 has no regulatory approval as a therapeutic agent. Research use only.
Research use only
All products are intended for laboratory and research use only (RUO) and are not for human consumption, ingestion, or any in-vivo use.
The statements on this page have not been evaluated by the FDA. Antimicrobial Peptides — LL-37 & Defensin Research Hub is not intended to diagnose, treat, cure, or prevent any disease. Content is provided for laboratory research reference only.