# LL-37

> Research use only. Not for human or veterinary use. Supplied by Veracue Labs.

- Page: https://veracuelabs.com/product/ll-37
- Category: Healing & Recovery
- Sizes and prices in USD: 5 mg at $54.99
- Certificate of analysis: none posted on the page. Request one for a specific lot at https://veracuelabs.com/contact-us.
- Prices are a snapshot from 2026-10-16. The product page shows the current price.

## Overview

LL-37 is a cationic peptide of 37 residues, LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES, named for its two opening leucines and its length. It is the C-terminal stretch of hCAP-18, the 170-residue human precursor (positions 134 to 170), and its chain holds no cysteine, so there are no disulfide bonds. Reference values are formula C205H340N60O53, average mass about 4493.3 g/mol and CAS 154947-66-7. The precursor protein and the short fragments KR-12 and FK-13 are different molecules.

## Product Details

### LL-37 in Brief

LL-37 is a linear peptide of thirty-seven amino acids. The name records two facts about the chain, the pair of leucines at its start and its length, and the one-letter sequence reads LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES. Those 37 residues are the final stretch of hCAP-18, a 170-residue precursor produced from CAMP, the one cathelicidin gene that humans carry. The vial holds the peptide on its own: not the precursor, and not a blend.

Spellings such as LL37, LL 37 and cathelicidin LL-37 all point to the same chain. Veracue supplies it for research use only.

### LL-37 Reference Data

Product name: LL-37 (also LL37, LL 37, cathelicidin LL-37)
Molecule type: Synthetic linear peptide, 37 residues
Sequence (one-letter): LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
Sequence (three-letter): Leu-Leu-Gly-Asp-Phe-Phe-Arg-Lys-Ser-Lys-Glu-Lys-Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg-Asn-Leu-Val-Pro-Arg-Thr-Glu-Ser
Position in the precursor: Residues 134 to 170 of hCAP-18 (170 residues in total)
Gene: CAMP
Molecular formula (free peptide): C205H340N60O53
Molecular weight (average): About 4493.3 g/mol
CAS Registry Number: 154947-66-7
Cysteine content: None, so no disulfide bonds
Net charge at neutral pH: About +6 (eleven basic residues against five acidic ones)
Size offered: 1 mg vial
Research designation: Research Use Only

Formula, mass and CAS number are reference values for the free peptide and are not results from a Veracue lot. Chemical form, purity, lot details and storage conditions for a specific vial belong on its own documentation, and documentation can be requested through the contact page.

### Easily Mistaken For

- hCAP-18, the 170-residue precursor that LL-37 is cut from. It carries an N-terminal pro-region that the 37-residue peptide lacks.
- KR-12 and FK-13, short engineered fragments of 12 and 13 residues taken from the middle of the LL-37 chain.
- ALL-38, a related 38-residue peptide produced from the same precursor by a different cleavage route.
- The human beta-defensins, a separate family of host-defense peptides built on disulfide bonds.
- Any consumer, dietary or cosmetic product, since the material is for laboratory work and not for human or veterinary use.

## Research Focus & Mechanism Overview

### Reading the LL-37 Chain

### What does the sequence contain?

Counting the 37 residues gives six lysines, five arginines, four leucines, four phenylalanines, three glutamic acids, three isoleucines, two each of glycine, aspartic acid, serine and valine, and one each of glutamine, asparagine, proline and threonine. Lysine and arginine together supply eleven basic side chains, set against only five acidic ones from aspartate and glutamate, so the chain is strongly net positive near neutral pH. Alanine, histidine and tyrosine do not occur at all.

### What is missing from the chain, and why does that help?

LL-37 has no cysteine, no methionine and no tryptophan. Without cysteine there are no disulfide bridges to pair up, and without methionine or tryptophan the usual oxidation sites are absent. That keeps identity checking straightforward: once the order of residues and the mass agree with the reference values, there is no folded, cross-linked or oxidized variant to rule out.

### Why is the structure described as depending on surroundings?

LL-37 is both cationic and amphipathic, with charged and hydrophobic residues spaced along the chain so that they can sit on opposite faces of a helix. Biophysical reports describe a flexible chain in dilute buffer that settles into a helix on membrane-like surfaces or under physiological ionic conditions. A statement about the shape of LL-37 therefore needs the medium it was measured in.

### From hCAP-18 to LL-37

Cathelicidins share a conserved N-terminal pro-region, called the cathelin-like domain, joined to a variable C-terminal peptide that only becomes a free peptide after cleavage. Humans have one such gene, CAMP, and its product is hCAP-18. LL-37 is the last 37 residues of that precursor.

The cutting enzyme decides which peptide results. In neutrophils, proteinase 3 releases LL-37 outside the cell. In skin, the kallikreins KLK5 and KLK7 process hCAP-18 and go on to trim it into shorter peptides that are not LL-37. In the reproductive tract, gastricsin yields ALL-38 instead. Each source therefore describes a slightly different material.

### Why do precursor measurements and peptide measurements not interchange?

Many immunoassays report hCAP-18 and LL-37 together as one signal, and expression data usually track the precursor. Activity data are generated with the mature peptide. Before comparing two papers, check which of the two molecules each one measured.

### LL-37 Beside Its Look-Alikes

Several molecules share part of the name, the sequence or the family of LL-37. The table compares identity only and does not rank them.

Material: What it is: Identity cue

LL-37: Mature 37-residue peptide from the C-terminus of hCAP-18: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES, about 4493.3 g/mol
hCAP-18: Full-length 170-residue precursor encoded by CAMP: More than four times the length, with a pro-region at the N-terminus
KR-12 and FK-13: Short engineered fragments from the middle of LL-37: Twelve and thirteen residues, far lighter than the full peptide
ALL-38: Related 38-residue peptide from the same precursor: One residue longer, so a different mass
Human beta-defensins: Separate host-defense peptide family: Disulfide-stabilized and rich in cysteine, which LL-37 lacks

A paper that reports results for a fragment or an analog has not tested LL-37, and the reverse holds too. If a source states neither the sequence nor the terminal chemistry, treat any comparison with it as limited.

### Assay-Level Context

In the literature LL-37 serves as a reference host-defense peptide in membrane-interaction experiments, in binding studies with bacterial lipopolysaccharide, and in cell-based assays at the formyl peptide receptor-like 1 receptor, also written FPR2, a G protein-coupled receptor. Reported outcomes depend heavily on ionic strength, pH, peptide concentration and whether serum or another biological fluid is present, so those conditions are primary variables when results are compared.

Published work is concentrated in biochemical, cell-culture and animal-model systems, and each report describes one model and one set of conditions. Findings about LL-37 made inside a tissue, where local enzymes, lipids and proteins are present, do not automatically describe a purified peptide supplied for the bench. Veracue offers molecular reference information here and provides no dosing, administration or usage guidance of any kind.

## Quality & Purity Standards

### Confirming LL-37 by Mass

At about 4493.3 g/mol, LL-37 does not usually show up in an ESI mass spectrum as a single peak at its neutral mass. With eleven basic side chains plus the free amino terminus it takes up several protons, so the spectrum shows a series of multiply charged ions. The table lists calculated average-mass values for the free peptide.

Ion: Calculated m/z (average mass)

[M+4H]4+: 1124.3
[M+5H]5+: 899.7
[M+6H]6+: 749.9
[M+7H]7+: 642.9
[M+H]+ (typical MALDI-TOF reading): 4494.3

To compare an observed peak with the reference value, multiply the m/z by the charge and subtract one proton per charge. Every ion in the series should land on the same neutral mass. Instruments that report monoisotopic values read about 3 Da lower, near 4490.6, so confirm which convention a result uses before judging a match.

### What Each Method Can and Cannot Show

Method: What it shows: What it cannot show alone

Reverse-phase HPLC: The share of detected signal in the main peak under stated conditions: Which molecule that peak is
ESI-MS or MALDI-TOF: Observed mass against the expected value for LL-37: Purity, or the order of residues
Tandem MS: Fragment evidence for the residue order: Overall purity or quantity
Amino acid analysis: Net peptide content: The identity of impurities

LL-37 has eleven basic sites, and a salt form such as an acetate or trifluoroacetate carries counterion mass at each of them. For this reason fill weight and net peptide content can differ noticeably, and any mass-based calculation should use the chemical form stated on the lot’s own document.

### Reading a Lot Document

A document describes one lot, never the compound in general. If you receive one for LL-37, first check that its lot number matches the lot reference in your order record, then look for the following.

- The product name and the stated chemical form, whether free peptide or a named salt.
- A chromatographic purity figure together with the method and conditions used, not a bare percentage.
- An identity result that gives observed and expected mass on a named convention, compared against about 4493.3 g/mol for the free peptide.
- Net peptide content reported apart from fill weight.
- The test date and the laboratory that carried out the work.

Documentation can be requested through the contact page, and it is issued for the specific lot you are asking about.

### Checks That Catch the Common Mix-Ups

### What would a purity figure alone leave open?

A single sharp peak shows that most of the detected material behaves alike, not that it is LL-37. A precursor, a fragment or a different peptide can score equally well, so the purity figure needs an identity result from the same lot beside it.

### What order is sensible when a lot document arrives?

Match the lot number first, then the chemical form, then the observed mass against 4493.3 g/mol read on the same convention. Only when all three agree is the purity figure worth interpreting.

### What belongs in a lot record?

Keep the listing as it read when you ordered, the lot document, the stated chemical form, the measured mass, the receipt date and the experiments that used the material. A consistent record lets an unexpected result be traced back to one lot.

### Questions About a Specific Lot?

Ask the Veracue team about the documentation for the lot you are considering, or return to the catalog.

- Contact the Veracue team
- See the full research catalog

## Compliance Notice

### Research Use Only Notice

LL-37 is sold for laboratory research and analytical work only. It is not meant for human or veterinary use, for ingestion, injection or any other form of administration, and it is not a drug, dietary supplement, cosmetic or food. Veracue provides no dosing, administration or usage guidance of any kind. Buyers must be qualified researchers or institutions and are responsible for handling the material lawfully. The Medical Disclaimer and the Terms and Conditions set out the sitewide policies.

## Questions and answers

### Why is the peptide called LL-37?

The name comes from the chain itself: it opens with two leucines (LL) and is 37 residues long. The one-letter sequence is LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES.

### What does the LL-37 chain consist of?

Six lysines, five arginines, four leucines, four phenylalanines, three glutamic acids, three isoleucines, two each of glycine, aspartic acid, serine and valine, and one each of glutamine, asparagine, proline and threonine. It has no cysteine, methionine, tryptophan, tyrosine, alanine or histidine.

### What formula and mass does LL-37 have?

The free peptide is C205H340N60O53, with an average mass of about 4493.3 g/mol and a monoisotopic mass near 4490.6. A salt form weighs more because the counterion adds mass.

### Which CAS Registry Number does Veracue list for LL-37?

Veracue lists 154947-66-7 as the reference number. It is a database value for the sequence, not a result from a particular lot.

### Where does LL-37 sit within hCAP-18?

It is the final 37 residues, positions 134 to 170, of the 170-residue precursor hCAP-18, which is encoded by the CAMP gene.

### Is data on hCAP-18 also data on LL-37?

Not automatically. Many assays read hCAP-18 and LL-37 as one combined signal, and expression studies usually follow the precursor, so check which molecule a source actually measured.

### Are KR-12 and FK-13 the same material as LL-37?

No. They are short engineered fragments of 12 and 13 residues from the middle of the LL-37 chain, and results reported for them belong to those fragments.

### What is ALL-38?

ALL-38 is a related 38-residue peptide produced from hCAP-18 by gastricsin in the reproductive tract. It differs from LL-37 in length, and therefore in mass.

### How do LL-37 and the beta-defensins differ?

Both are host-defense peptides, but the beta-defensins are held together by disulfide bonds, while LL-37 has no cysteine and no such bridges. Their sequences and masses are unrelated.

### Why does LL-37 carry a positive charge?

Eleven of its side chains are basic (six lysines and five arginines) against five acidic ones, giving a net charge of about +6 near neutral pH.

### Which ions should an LL-37 mass spectrum show?

On an average-mass basis the 4+ ion falls near m/z 1124.3, the 5+ near 899.7, the 6+ near 749.9 and the 7+ near 642.9. A MALDI-TOF reading of the singly charged ion sits near 4494.3.

### Why do fill weight and peptide content differ for LL-37?

The chain has eleven basic sites, and a salt form carries counterion mass at each one. Net peptide content is therefore reported apart from the weight of the vial contents.

### How can I ask for documentation on an LL-37 lot?

Documentation can be requested through the contact page, and it is issued for the lot you name.

### What size does Veracue offer LL-37 in?

LL-37 is offered as a 1 mg vial, supplied for laboratory research use only.

### What does Research Use Only mean for LL-37?

The material is sold only for laboratory research and analysis, not for human or veterinary use, ingestion, injection or any other form of administration.

### Does Veracue give instructions for using LL-37?

No. Veracue provides no dosing, administration or usage guidance of any kind, because LL-37 is sold for laboratory research use only.

More from Veracue Labs: https://veracuelabs.com/llms.txt