LL-37: form, reconstitution and laboratory storage

Physical form

LL-37 ships as a lyophilized (freeze-dried) white powder or loose pellet in a glass vial, RUO — for research use only. The standard fill is 5 mg per vial at ≥98% purity (HPLC). The material is not intended for human or veterinary use.

Reconstitution chemistry

LL-37 is a cationic peptide (net charge ≈ +6) that is readily water-soluble. For laboratory work the lyophilizate is typically reconstituted with sterile or bacteriostatic water (water with 0.9% benzyl alcohol). Recommended approach:

• Allow the vial to equilibrate to room temperature before opening to avoid condensation on the powder.
• Add solvent slowly, directing the stream against the vial wall rather than straight onto the powder.
• Do not shake — swirl the vial gently until fully dissolved; foaming and vigorous mixing promote peptide denaturation and adsorption.

The peptide is sensitive to buffer composition: high ionic strength and divalent cations (Ca²⁺, Mg²⁺) affect structure and aggregation, so the solvent is matched to the specific experiment. For solubility, slightly acidified water or water with a small fraction of organic co-solvent is sometimes used, with dissolution confirmed visually.

Storage

Lyophilized LL-37 is the most stable form: store the dry powder at −20 °C (−80 °C for long-term), in a sealed container protected from moisture and light. The peptide is hygroscopic, so avoid repeated cold-warm cycles that cause condensation.

A reconstituted solution is considerably less stable: keep it at +2 to +8 °C for short-term use, or freeze it as aliquots at −20/−80 °C. Split into single-use aliquots to avoid repeated freeze-thaw cycles, which degrade the peptide.

Stability and handling

The main degradation routes are oxidation, hydrolysis and adsorption onto labware surfaces. To minimize losses, use low-binding tubes and tips, prepare the solution shortly before use, and add a carrier protein per protocol if needed. Track the LOT and check the COA (certificate of analysis) for purity and identity.

Research applications

LL-37 is used in studies of antimicrobial-peptide structure and function, peptide-membrane interactions, innate-immunity models and as a reference peptide in screening assays. All uses are strictly research, in vitro / ex vivo.