What's on the label is the measured result — net peptide mass, not gross powder weight, plus RP-HPLC purity, on a lot-numbered COA for every batch.
Net peptide mass and RP-HPLC purity — a lot-numbered COA for every batch.
Net peptide mass + HPLC purity, per lot.
PCAC will review 7 peptides for the 503A bulks list, BPC-157, KPV, TB-500, MOTS-c, Emideltide, Semax, Epitalon. Read our briefing →
PCAC will review 7 peptides for the 503A bulks list. Read →
FDA PCAC reviews 7 peptides in July. Read →
Cathelicidin antimicrobial peptide
PeptideXpo buyer fit
This PeptideXpo page is intentionally positioned for distributors, OEM buyers, and procurement teams comparing LL-37 inside a wider peptide catalog. It is not trying to be the deepest single-molecule monograph; the differentiated intent is assortment planning, export-ready documentation, fill-size comparison, and whether this SKU belongs in a broader buyer program.
Overview
LL-37 is the only human cathelicidin and the C-terminal 37-amino-acid antimicrobial peptide released by proteolytic cleavage of the hCAP-18 precursor protein. The sequence (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES) is highly cationic with an amphipathic α-helical fold in membrane-mimetic environments, properties that drive direct membrane disruption against a broad spectrum of Gram-positive and Gram-negative bacteria, fungi, and enveloped viruses. Beyond direct antimicrobial activity, LL-37 modulates innate immune signaling through formyl-peptide receptor 2 (FPR2) and is studied for its roles in wound-healing chemotaxis, autoimmunity, and inflammatory disease research. PeptideXpo supplies LL-37 as a lyophilized powder at ≥99.0% HPLC purity. The 37-residue cationic sequence presents distinctive analytical and handling challenges: the molecule adsorbs strongly to standard polypropylene and glass surfaces at low working concentrations (the cationic charge density drives surface binding), which can produce 30-70% concentration loss between the nominal weight-out and the effective in-assay concentration if low-bind plasticware is not used. Working dilutions for cell-culture and assay work should be prepared in low-bind tubes with 0.1% acid-free BSA or 0.01% Tween-20 carrier to suppress surface adsorption. Endotoxin (LAL) and microbial limits are essential add-ons for any in vivo or cell-based assay work because LL-37's innate-immune signaling activity overlaps with the pathways activated by bacterial endotoxin.
Who buys this, and why
Buyers in this category are research labs studying immune-modulation, cytokine signaling, and antimicrobial activity. The defining QC requirement is bacterial-endotoxin control: many of the downstream assays (NF-κB reporters, macrophage activation panels, neutrophil-priming readouts) are themselves activated by endotoxin contamination, so a clean LAL on the specific batch is a precondition rather than a nice-to-have. LL-37 and related cationic antimicrobial peptides additionally benefit from low-bind plasticware during dilution.
Primary buyer fit: academic and contract research laboratories.
Specifications
Documentation available on request
Regulatory note
Sold for research use only under the receiving laboratory's local regulations. Not a finished dosage form. For in vivo or cell-based assay workflows, request bacterial-endotoxin testing on the specific batch at quote stage so the COA carries the LAL value.
Frequently asked questions
LL-37 is highly cationic (net charge around +6 at physiological pH) and amphipathic, which produces strong electrostatic and hydrophobic attraction to standard polypropylene microcentrifuge tubes, polystyrene multiwell plates, and glass surfaces. At working concentrations below 10 μg/mL, surface adsorption can deplete 30-70% of the nominal LL-37 within minutes, the practical consequence is that researchers measuring activity at sub-μg/mL concentrations are often measuring a fraction of what they think they're dosing. Use low-bind polypropylene tubes (Eppendorf LoBind or equivalent) for stock preparation, add 0.1% endotoxin-free BSA or 0.01% Tween-20 to dilution buffers as a carrier, and avoid serial dilutions through multiple plastic surfaces.
All three are immune-research peptides, but they target fundamentally different layers of the immune system. LL-37 is a direct-acting antimicrobial peptide that disrupts microbial membranes plus signals through FPR2 for inflammation modulation. KPV is the C-terminal tripeptide of α-MSH that acts through melanocortin-system anti-inflammatory pathways. Thymosin Alpha-1 is a 28-mer thymic peptide that modulates T-cell function through TLR9 and related innate-adaptive interface pathways. Buyers selecting peptides for immune-modulation research should match the peptide's mechanism to the experimental question rather than treat the three as interchangeable.
Because LL-37 itself signals through innate-immune pathways that overlap with bacterial endotoxin signaling, endotoxin contamination in the LL-37 preparation will produce confounded readouts in any cell-based assay measuring inflammation, cytokine release, or innate-immune activation. The recommended specification for cell-based assay use is bacterial endotoxin (LAL per USP <85>) reported in EU/mg on the specific batch, with a typical acceptance criterion of <1 EU/mg for cell-culture research. For in vivo workflows, a tighter spec (<0.1 EU/mg where achievable) is appropriate.
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