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Compound guide
LL-37: what the research covers
The only antimicrobial peptide of its family in humans, and a molecule with two faces: it kills bacteria at one concentration and signals to immune cells at another.
What LL-37 is
LL-37 is thirty-seven residues long and begins with two leucines, which is where the name comes from. It is the mature product of the human cathelicidin gene CAMP, released by proteolysis from a precursor stored in neutrophil granules and produced by epithelium at barrier surfaces.
Structurally it is amphipathic: when it meets a membrane it folds into a helix with charged residues on one face and hydrophobic residues on the other. That geometry is the mechanism. The cationic face is drawn to the anionic surface of a bacterial membrane, the hydrophobic face inserts, and the membrane loses integrity. Because the target is a physical property of the membrane rather than a protein, resistance develops far less readily than against conventional antibiotics — one of the main reasons the class attracted interest.
Humans have exactly one cathelicidin, where other mammals have several. LL-37 is it.
Two activities, concentration dependent
The direct antimicrobial effect requires relatively high local concentrations. At much lower ones LL-37 behaves as a signalling molecule: chemotactic for neutrophils, monocytes and T cells, modulating dendritic cell maturation, influencing angiogenesis and wound closure, and binding bacterial lipopolysaccharide in a way that dampens the inflammatory response to it.
That dual behaviour is the central methodological issue in the literature. An effect reported at micromolar concentrations and an effect reported at nanomolar ones are not describing the same mechanism, and conclusions do not transfer between them. The same caution applies to the ionic environment: physiological salt concentrations substantially reduce the membrane activity, so an antimicrobial result obtained in low-salt buffer needs careful reading.
Published strands cover antimicrobial and antibiofilm activity, wound healing and re-epithelialisation, and inflammatory disease models in which LL-37 is reported as both protective and pathogenic depending on context.
How Amino Club supplies it
Supplied lyophilised in sealed vials as LL-37, specified at 99% purity or better by HPLC with identity confirmed by mass spectrometry and released against the Certificate of Analysis for its own batch; the lab testing page describes the release sequence.
Highly cationic peptides have their own handling character. They adsorb readily to glass and to ordinary plastic, which at low working concentrations can remove a meaningful fraction of the material from solution, so low-binding labware is the usual precaution. The powder is stored below −18 °C and solutions are prepared fresh in small volumes. Diluent choice matters more than usual here because ionic strength changes the activity: options are under reconstitution supplies.
Related reading
LL-37 sits in the tissue repair research peptides group with BPC-157, TB-500, ARA-290, KPV and VIP. KPV is the closer comparison, since it too combines antimicrobial and anti-inflammatory activity in a much smaller molecule.
Every guide is indexed in the research library. Certificates and storage are covered on the FAQ, quantity pricing through bulk and wholesale.
Research use only
LL-37 supplied by Amino Club is a laboratory reference material. It is not a medicine, not a supplement, and not for human or veterinary use, and no dosing guidance or administration protocol is provided. The full terms are in the research use policy.