LL-37 — the only human cathelicidin antimicrobial peptide — research reference for laboratory work.
LL-37 is the C-terminal 37-amino-acid fragment of the human cathelicidin antimicrobial peptide hCAP18. It is one of the most heavily characterised endogenous antimicrobial peptides in published research literature and a routine positive control in microbial-killing assays.
- Sequence: LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
- Average mass approximately 4493.3 Da
- α-helical amphipathic conformation in membranes
Why Ll-37 matters to research labs
Australian research teams evaluating ll-37 face three recurring questions before any in-vitro work begins: is the compound what the label claims, will it remain stable across the planned experimental window, and does the supplier's documentation hold up to the standards a principal investigator will sign off on. The remainder of this article is structured around those three questions.
Iron Labs supplies ll-37 as a lyophilised research material packaged for transit at ambient temperatures and long-term storage at −20 °C. Every batch ships with a lot-specific certificate of analysis covering identity, purity, residual solvents and endotoxin where downstream cell culture work is anticipated.
Typical research applications
Across the published literature, ll-37 appears most often in three workflow categories. Each has its own documentation profile and storage requirements, which is why a single supplier batch is frequently subdivided across multiple aliquots to limit freeze-thaw cycling.
- In-vitro receptor binding and signalling characterisation, where milligram-scale aliquots are reconstituted fresh on the day of assay.
- Pharmacokinetic and stability modelling, where reconstituted material is sampled at defined time-points and analysed by RP-HPLC.
- Comparative reference work, where ll-37 is benchmarked against in-house standards or other published research compounds.
Reconstitution and handling reference
Lyophilised ll-37 is reconstituted with sterile bacteriostatic water using slow, side-of-vial addition to avoid foaming. The vial is allowed to dissolve passively rather than being shaken; mechanical agitation accelerates aggregation in many peptide systems and complicates downstream analytical work. The table below summarises common reconstitution volumes used as documentation references.
| Vial Strength | Diluent Volume | Resulting Concentration |
|---|---|---|
| 5 mg | 1.0 mL bacteriostatic water | 5 mg/mL |
| 10 mg | 1.0 mL bacteriostatic water | 10 mg/mL |
| 10 mg | 2.0 mL bacteriostatic water | 5 mg/mL |
| 30 mg | 3.0 mL bacteriostatic water | 10 mg/mL |
Storage and stability envelope
Lyophilised ll-37 is documented as stable for 24+ months at −20 °C protected from light. Once reconstituted, the published storage reference for most research peptides in this class is up to 30 days at 2–8 °C when handled aseptically; longer-term storage of reconstituted material is best achieved by single-use aliquoting at −80 °C to remove freeze-thaw variables from later analytical reads.
- Avoid storing reconstituted vials in the refrigerator door — temperature swings shorten usable life.
- Label aliquots with batch ID, reconstitution date and concentration so retrospective audit is straightforward.
- Do not refreeze previously thawed aliquots; integrate single-use volumes into the assay design from the outset.
Certificate of analysis — what to verify
Every Iron Labs ll-37 lot is dispatched with a certificate of analysis (COA) tied to the batch identifier printed on the vial. Reviewing the COA before the material enters the workflow is the single highest-leverage quality control step a research lab can perform.
- Batch / lot identifier and synthesis date — both must match the vial.
- RP-HPLC purity, typically ≥98% for research-grade ll-37.
- Mass-spectrometry identity confirmation (LC-MS or MALDI-TOF) within ±0.5 Da of the theoretical mass.
- Counterion identity and percent (acetate or trifluoroacetate are the most common).
- Bacterial endotoxin per the published analytical method, reported in EU/mg.
- Residual solvents and water content where the synthesis route makes them analytically meaningful.
Quality benchmarks Iron Labs publishes
| Parameter | Iron Labs Spec | Method |
|---|---|---|
| HPLC purity | ≥ 98% | RP-HPLC, UV 214 nm |
| Identity | ± 0.5 Da of theoretical mass | LC-MS or MALDI-TOF |
| Endotoxin | Reported per lot | LAL kinetic chromogenic |
| Counterion | Quantified | Ion chromatography |
| Water content | < 8% (typical lyophilised) | Karl Fischer |
Frequently asked research questions
Is the ll-37 supplied by Iron Labs intended for human use?
No. All Iron Labs material is supplied strictly for in vitro and laboratory research use. Nothing on this page constitutes medical, veterinary or therapeutic advice.
How is ll-37 shipped and how long is the transit-stable window?
Material is dispatched as a lyophilised powder, sealed and protected from light. Transit at ambient temperatures over typical Australian courier timelines is well within the published stability envelope for this compound class.
Will a Certificate of Analysis be provided with my ll-37 order?
Yes. Every batch ships with a lot-specific COA covering identity, purity and the analytical parameters listed in the quality benchmarks section above.
Can I request a specific batch or repeat lot of ll-37?
Repeat-lot requests are supported for ongoing research programs; contact the Iron Labs research desk with the previous COA reference and the team will hold inventory from a matching batch where available.
Further reading
Continue with the related Iron Labs research references linked at the foot of this article, or browse the full research catalogue for the compound class profile, lab-results archive and laboratory documentation. For sourcing questions, the research team is available via the Iron Labs contact page.
