LL-37 is the 37-amino-acid C-terminal host defense peptide derived from human cathelicidin hCAP18. It is the best-characterized human cathelicidin-derived peptide and combines direct antimicrobial properties with broader effects on innate immune signaling, membrane interactions, chemotaxis, and epithelial responses.

The native sequence is strongly cationic and can adopt an amphipathic α-helical structure under membrane-associated and appropriate solution conditions. These physicochemical features make LL-37 particularly useful for research in microbial membrane disruption, host–pathogen interactions, peptide biophysics, inflammation, and structure–activity relationships.

Product Information

LL-37 as a Human Host Defense Peptide

LL-37 is generated from the C-terminal region of hCAP18 and is expressed in epithelial and immune-cell environments associated with innate host defense. In experimental systems, it has been investigated against Gram-positive and Gram-negative bacteria as well as fungal and viral models.

Its biological behavior extends beyond direct microbial killing. LL-37 has also been studied in chemotaxis, inflammatory signaling, lipopolysaccharide interactions, epithelial responses, angiogenesis, and wound-repair models.

For this reason, LL-37 is often more accurately described as a host defense peptide rather than solely as an antibiotic-like molecule.

Membrane Interaction and Antimicrobial Research

The cationic character of LL-37 promotes interaction with negatively charged microbial surfaces, while its amphipathic structure supports association with lipid membranes. Membrane perturbation and permeabilization are important components of its experimentally observed antimicrobial behavior.

Activity is highly dependent on experimental conditions. Ionic strength, medium composition, peptide concentration, microbial strain, serum components, and assay format can substantially affect the observed response.

This is particularly important when comparing MIC, membrane-permeabilization, or killing data from different publications. A literature concentration should therefore not automatically be transferred to a new assay without validation.

Researchers studying other membrane-active sequences can also browse our Antimicrobial Peptides collection.

Native LL-37 versus Designed Variants

The native sequence provides a useful reference for determining how charge distribution and amino-acid order influence peptide function.

Alan Scientific also provides LL-37 pentamide (AS2700), a charge-modified analog, and LL-37 reverse sequence (AS2701), which preserves amino-acid composition while reversing sequence direction.

Using these peptides under matched experimental conditions can help separate the effects of native primary sequence, charge engineering, and sequence orientation.

Quality and Experimental Planning

For antimicrobial and cell-based studies, purity is only one component of experimental reproducibility. Salt form, residual TFA, endotoxin requirements, reconstitution conditions, and peptide concentration may also influence downstream results.

Our Peptide Quality Control capabilities include analytical HPLC and mass spectrometry with batch-specific documentation.

For sensitive cellular studies, additional requirements such as reduced TFA, alternative counterions, or endotoxin control can be discussed according to the experimental design.

Storage and Handling

Lyophilized LL-37 should be stored according to the conditions provided for the supplied batch and protected from moisture.

Because LL-37 is a relatively long, highly charged peptide with environment-dependent structural behavior, solution preparation should be kept consistent across comparative experiments. Solvent, ionic strength, peptide concentration, storage duration, and repeated freeze–thaw exposure should be documented where reproducibility is important.

Research Use Only

LL-37, Antimicrobial Peptide, human is supplied for research use only. It is not intended for therapeutic, or human use.