LL-37: A Laboratory Research Reference

LL-37 is the only human member of the cathelicidin family of host-defence peptides. It is studied in laboratory research for its antimicrobial activity and its broader roles in immune signalling and wound-related processes in experimental models.

This page is a non-promotional scientific reference for researchers. It summarises the chemical identity, molecular characteristics, mechanism as described in the literature, research areas, and analytical testing of LL-37. It does not provide dosing, therapeutic, or human-use guidance of any kind. LL-37 supplied by Bulk Aussie Peptides is for laboratory research purposes only.

What Is LL-37?

LL-37 is a 37-residue, amphipathic, α-helical peptide that is the sole cathelicidin expressed in humans. It is produced as an inactive precursor and released as the active peptide from neutrophils, macrophages, and a range of epithelial cells. Its broad antimicrobial activity and additional host-defence roles make it a well-studied reference peptide in innate-immunity research.

For background on how synthetic research peptides are produced and verified, see the synthetic peptides research guide.

Molecular Characteristics

Several molecular properties are used to identify LL-37 in analytical documentation:

• Classification: a human cathelicidin antimicrobial peptide, the only member of its family in humans.
• Length: 37 amino acid residues, with an amphipathic α-helical structure and a net positive charge.
• Molecular weight: reported in Daltons (Da) on product documentation; the measured value on a Certificate of Analysis should be compared against the theoretical mass derived from the sequence.
• Physical form: supplied as a lyophilised (freeze-dried) powder, the standard presentation for research peptides.

How LL-37 Works

LL-37 exerts its studied antimicrobial effects largely through electrostatic interaction with negatively charged microbial membranes, leading to membrane disruption. Beyond direct antimicrobial activity, research describes additional host-defence roles: regulation of the inflammatory response, chemoattraction of immune cells, binding of lipopolysaccharide, and promotion of re-epithelialisation and wound closure. A shorter fragment, KR-12, has been used to study structure–activity relationships.

These observations are preclinical and describe peptide activity in model systems; they do not constitute a therapeutic use.

Areas of Scientific Research

The research literature describes several lines of investigation involving LL-37:

• Antimicrobial activity: studies against a broad spectrum of Gram-positive and Gram-negative pathogens.
• Immunomodulation: investigation of inflammatory regulation and immune-cell recruitment.
• Wound healing and cancer research: work on re-epithelialisation and reported anticancer effects in cell models.

These investigations are conducted in vitro or in approved animal research models under institutional oversight. They do not translate to approved human use.

Analytical Testing

As with other research peptides, LL-37 is characterised using:

• HPLC for purity assessment, reported as a percentage of total peak area.
• Mass spectrometry for identity confirmation, by comparing measured molecular mass to the theoretical value.

Guidance on interpreting the resulting documents is available in the article on how to read a peptide Certificate of Analysis.

Storage and Handling

In a laboratory context, lyophilised LL-37 is typically stored in a freezer, protected from light and moisture, and handled according to the product-specific documentation. Once reconstituted, the resulting solution is refrigerated and used within the timeframe stated in the documentation. General guidance is covered in the peptide storage and stability reference.

Frequently Asked Questions

• What is LL-37? LL-37 is the only human member of the cathelicidin family of antimicrobial peptides.
• What is LL-37 studied for? It is investigated in laboratory models for antimicrobial activity and immune signalling.
• What is a cathelicidin? Cathelicidins are a family of host-defence peptides; LL-37 is the single human member.
• How long is LL-37? It is 37 amino acid residues in length.
• How is LL-37 purity tested? Purity is commonly estimated by HPLC, while identity is confirmed by mass spectrometry.

References

• Dürr, U. H. N., Sudheendra, U. S., & Ramamoorthy, A. (2006). LL-37, the only human member of the cathelicidin family of antimicrobial peptides. Biochimica et Biophysica Acta, 1758(9), 1408–1425. PubMed 16716248
• Vandamme, D., Landuyt, B., Luyten, W., et al. (2016). The human cathelicidin antimicrobial peptide LL-37 and mimics are potential anticancer drugs. Frontiers in Oncology (and related reviews). PubMed 26175965

Related Research Resources

• BPC-157: A Laboratory Research Reference — a related tissue-repair research peptide.
• Synthetic Peptides: Research Guide — how research peptides are produced and verified.
• Ara-290: A Laboratory Research Reference — another peptide with immune-modulating activity.