LL-37
Also known as Cathelicidin antimicrobial peptide, CAMP, hCAP18 C-terminal peptide
LL-37 is the only human cathelicidin, a 37-residue host-defense peptide cleaved from hCAP18. A research-use profile: its cathelicidin lineage, amphipathic structure, and handling.
LL-37 sits in a different lineage from most of the peptides in this catalog. It is not a growth-factor fragment or a synthetic recovery construct — it is a host-defense peptide, and specifically the only cathelicidin the human body makes. That single fact organizes almost everything worth knowing about it.
Below is the verifiable profile: where LL-37 comes from in the cathelicidin system, what its amphipathic α-helical structure means, and how researchers handle it. It stays clear of therapeutic framing, which is neither established nor appropriate on a research-use page.
LL-37 is the C-terminal 37-residue peptide released from the human cathelicidin precursor hCAP18. Its name comes from its length (37 residues) and its two N-terminal leucines. It is an α-helical, amphipathic peptide — too long to reduce to a short public residue list here, so the sequence is described rather than enumerated.
The cathelicidin / host-defense lineage
Cathelicidins are a family of host-defense peptides carried as inactive precursors that share a conserved 'cathelin' pro-domain. Humans have exactly one cathelicidin gene, CAMP, whose product is the precursor protein hCAP18. LL-37 is the mature peptide released when hCAP18 is processed and its C-terminal domain is cleaved free.
This makes LL-37 a member of the innate host-defense-peptide world — the same broad category as the defensins — rather than the hormone-fragment world. That lineage is why it is studied in the context of innate barrier and antimicrobial-peptide research, and why it is grouped with barrier-context peptides like KPV in discussion even though they are unrelated in structure.
Where the name comes from
The naming is refreshingly literal. 'LL' marks the two leucine residues at the peptide's N-terminus, and '37' is its length — thirty-seven amino acids. Together they give a compact, unambiguous label for the mature cathelicidin peptide.
At 37 residues it is far longer than the short tripeptides elsewhere in this catalog, which is why this page describes its structure rather than listing every residue: enumerating a long sequence invites transcription errors, and the defining structural facts are captured better in words.
An amphipathic α-helix
Under the right conditions LL-37 folds into an amphipathic α-helix — a helix with hydrophobic residues clustered on one face and cationic (positively charged) residues on the other. That segregation of charge and greasiness is the classic structural signature of membrane-active host-defense peptides and is the feature most often invoked to explain the peptide's interactions in the literature.
Because its behavior is sensitive to its environment — salt, pH, and concentration all matter — LL-37 is a peptide where careful, consistent handling in the lab is especially important for reproducible characterization.
These are research areas the compound is associated with in the literature — not medical claims or intended uses.
Handling & storage
Supplied lyophilized. Stored sealed and cold; reconstituted only when a protocol requires it. As a cationic amphipathic peptide its solubility and behavior are sensitive to buffer, salt, and pH — handle per accepted laboratory practice and follow lot-specific guidance.
Verify a certificate by lot →Common questions
The two Ls stand for the pair of leucine residues at the peptide's N-terminus, and 37 is the number of amino acids in the chain.
It is the C-terminal peptide released from hCAP18, the product of the human cathelicidin gene CAMP. LL-37 is the only cathelicidin peptide humans produce.
At 37 residues LL-37 is long enough that spelling out every amino acid invites transcription errors. Its defining structure — an amphipathic, cationic α-helix — is more usefully described than enumerated.
This monograph is a research-use reference. It describes composition and the contexts in which the compound has been studied — it is not medical advice, a description of effects, or a recommendation for use. Sold strictly for laboratory and research use; not for human or animal consumption.