Understand the source comparison
LL-37 Purity Verification Standards: Research vs Clinical Grade
Research Grade >95% ±1.0 Da Not tested $4–8 Acceptable for most in vitro studies; minor impurities unlikely to affect mechanistic assays High-Purity Research >98% ±0.5 Da <10 EU/mg $9–15 Preferred for dose-response studies, antimicrobial efficacy testing, and
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This page preserves a source comparison for education. It does not add a rating, recommendation or clinical judgment.
- Research Grade
- >95%
- ±1.0 Da
- Not tested
- $4–8
- Acceptable for most in vitro studies; minor impurities unlikely to affect mechanistic assays
- High-Purity Research
- >98%
- ±0.5 Da
- <10 EU/mg
- $9–15
- Preferred for dose-response studies, antimicrobial efficacy testing, and any work requiring reproducible concentration
- GMP/Clinical Grade
- >99%
- ±0.2 Da
- <1 EU/mg
- $40–80
- Required for in vivo studies, clinical trials, and any regulatory submission; full batch documentation and sterility testing included
- Research-grade peptides (>95% HPLC purity) are adequate for initial exploratory work, mechanistic studies where the endpoint is qualitative (e.g., immunofluorescence localization), or studies where LL-37 is used as a positive control rather than the experimental variable. Impurities in this range. Typically 2–4%. Consist mostly of closely related peptide sequences (n-1 or n+1 deletions) that retain partial biological activity, meaning their presence introduces dose variability but doesn't fundamentally alter the mechanism being studied.
- High-purity research-grade peptides (>98% HPLC purity, <1% single impurity) are necessary for dose-response curves, antimicrobial MIC determination, cytotoxicity assays, and any study where precise LL-37 concentration drives the experimental outcome. The 2–3% purity improvement over standard research grade translates to 20–30 µg more functional peptide per milligram. Enough to shift EC50 values by 15–25% in sensitive assays. For LL-37 specifically, this matters because its antimicrobial potency against Gram-negative bacteria falls off sharply below 5 µM, making concentration accuracy critical.
- GMP-grade peptides are required for any in vivo application, including murine infection models, wound healing studies, or preclinical pharmacokinetics. The FDA defines GMP as manufacturing under 21 CFR Part 211, which mandates sterility testing, endotoxin quantification below 1 EU/mg, and full traceability of raw materials. Research-grade LL-37 is not sterile and may contain bacterial endotoxin levels that trigger immune responses independent of the peptide's intended effect. Introducing a confounding variable that invalidates in vivo results.