# LL-37 (Cathelicidin)

> LL-37, the human cathelicidin — a 37-residue antimicrobial host-defence peptide

All products are sold strictly for laboratory research use only. Not for human or veterinary use.

- Web page: https://peptidemedixeu.com/en/products/ll-37/
- Brand: Peptide Medix EU
- Category: [Anti-Inflammatory Peptides](https://peptidemedixeu.com/en/collections/anti-inflammatory-peptides/)
- Purity: ≥99% by HPLC; lot-matched COA available
- CAS number: 154947-66-7
- from €97 (EUR)

## Sizes and prices (EUR)

| Size | Price | SKU |
| --- | --- | --- |
| 5 mg | €97 | LL-37-5-MG |
| 10 mg | €165 | LL-37-10-MG |

_Catalog prices at build time; the web page and checkout are authoritative._

## Specifications

- **CAS number:** 154947-66-7
- **Molecular weight:** 4493.33 g/mol
- **Amino acid sequence:** LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
- **Chain length:** 37 amino acids
- **Peptide class:** Cathelicidin-family antimicrobial host-defence peptide
- **Form:** Lyophilized powder, sealed glass vial with crimped stopper
- **Purity:** ≥99% by HPLC; lot-matched COA available
- **Available sizes:** 5 mg, 10 mg
- **Storage (lyophilized):** −20 °C, sealed and protected from light and moisture
- **Storage (reconstituted):** 2–8 °C, protected from light, used within the study window
- **Precursor:** hCAP18; released by proteinase 3 cleavage of the C-terminal domain
- **Structure:** Cationic amphipathic alpha helix with a strong net positive charge
- **Research areas:** Antimicrobial and antibiofilm assays, wound repair, immunomodulation, barrier immunity

## Description

LL-37 is the sole antimicrobial peptide of the cathelicidin family made by humans. Proteinase 3 cuts it from the C-terminal end of its precursor, hCAP18, and its name reflects its 37-residue length and the two leucines at its start. Neutrophils, epithelial cells and keratinocytes all produce it, and it operates where innate antimicrobial defence meets the control of inflammation.

Structurally, it forms a strongly positively charged, amphipathic alpha helix 37 residues long. This shape underpins the mechanism most often described: electrostatic attraction to negatively charged bacterial membranes, followed by breakdown of membrane integrity. The same amphipathic nature makes it a difficult peptide to synthesise and purify, which explains why it costs more than shorter sequences.

It comes as lyophilised powder in sealed vials of 5 mg or 10 mg; every lot is purified by reversed-phase HPLC to ≥99%, mass-confirmed and documented with its own certificate of analysis. Labs use it in antimicrobial and biofilm assays, wound models and immunomodulation research. Sold strictly for laboratory research.

## Frequently asked questions

### What is LL-37?

The only cathelicidin antimicrobial peptide humans express — a cationic helix of 37 residues cleaved from the hCAP18 precursor. We supply it as a lyophilised research powder for antimicrobial, biofilm, wound-repair and immunomodulation studies.

### Why does LL-37 cost more than shorter peptides?

Thirty-seven residues is a long chain to synthesise, and its amphipathic, strongly cationic nature makes both coupling and purification harder than for a short, water-loving sequence. Each synthesis run yields less, and that shows in the price per milligram.

### What purity do you guarantee, and is there a COA?

Each lot is purified and analysed by reversed-phase HPLC to ≥99%, with mass spectrometry confirming the expected 4493.33 g/mol. The certificate bearing your vial's lot number can be requested before or after you order.

### Does LL-37 require special handling?

It helps. The peptide clings to plastic and aggregates more easily than short hydrophilic peptides, so labs usually work with low-binding tubes, avoid the vortex mixer and make working dilutions fresh instead of keeping very dilute stocks for a long time.

### In which research areas is it used?

Membrane-targeted antimicrobial assays against bacteria, fungi and enveloped viruses; biofilm disruption at sub-lethal levels; wound-repair models involving keratinocyte migration; and immunomodulation studies of lipopolysaccharide binding and dendritic-cell responses, including its suspected role in psoriasis.

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All products offered on this website are intended solely for in-vitro laboratory research and development by qualified professionals. They are not drugs, foods, cosmetics or dietary supplements, and are not intended to diagnose, treat, cure or prevent any disease. Products must not be introduced into humans or animals in any manner. By purchasing, you confirm that you are a qualified researcher and accept full responsibility for handling and storage in accordance with applicable laws.

Peptide Medix EU · https://peptidemedixeu.com/en/products/ll-37/