What Is LL37 Same as LL-37? (Peptide Nomenclature) | Real Peptides
Research published in the Journal of Immunology found that LL37. The human cathelicidin antimicrobial peptide. Appears in peer-reviewed literature under at least six different nomenclature variations, including LL-37, hCAP-18, FALL-39, and CAP18. The inconsistency isn't trivial: researchers searching databases under one name can miss relevant studies indexed under another, fragmenting what should be a unified body of evidence.
We've worked with research teams across immunology, dermatology, and wound healing who've encountered this exact nomenclature problem when sourcing reference-grade peptides. The naming variation creates procurement confusion, but the underlying compound remains unchanged.
What is LL37 same as LL-37?
Yes, LL37 and LL-37 refer to the exact same peptide. A 37-amino-acid fragment cleaved from the C-terminal region of the human cathelicidin antimicrobial protein hCAP-18. The hyphen between LL and 37 is a stylistic formatting choice with no chemical significance. Both names describe an identical linear peptide sequence (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES) with the same antimicrobial, immunomodulatory, and wound-healing bioactivity.
The confusion stems from inconsistent journal formatting standards and legacy naming conventions from early cathelicidin research in the 1990s. Some publications hyphenate peptide names when the alphanumeric characters follow institutional style guides; others omit punctuation entirely. The biological molecule itself is invariant. The difference exists only in how the name appears in text.
The Biochemical Identity of LL37 and LL-37
LL37 is the only cathelicidin antimicrobial peptide produced by humans, generated through proteolytic cleavage of the 18-kilodalton precursor protein hCAP-18 (human cationic antimicrobial protein, 18 kDa) by the serine protease proteinase 3. The name LL37 derives from its structural features: two leucine residues (LL) at the N-terminus and a total length of 37 amino acids. LL-37 uses identical naming logic with a hyphen separator.
Both LL37 and LL-37 share the same molecular weight (4493.3 Da), isoelectric point (approximately 10.5), and net positive charge (+6 at physiological pH). The peptide adopts an amphipathic alpha-helical structure when it interacts with bacterial membranes or host cell surfaces. This structural characteristic drives its ability to insert into lipid bilayers and disrupt membrane integrity. The alpha-helix formation is concentration-dependent and occurs identically whether the peptide is labeled LL37 or LL-37 in a study protocol.
The hyphen variation appears most frequently in European publications, where journal style guides historically required hyphenation between letter-number combinations. North American journals more commonly omit the hyphen. Neither format is more chemically accurate. Both reference the same 37-residue sequence with leucine-leucine at position 1-2. Researchers at Real Peptides use LL37 as the primary nomenclature for catalog consistency, but the supplied LL 37 peptide is indistinguishable from material labeled LL-37 in published research.
Biological Mechanisms Shared by LL37 and LL-37
LL37 functions through multiple overlapping mechanisms that extend far beyond its original classification as a simple antimicrobial agent. The peptide demonstrates direct bactericidal activity against Gram-positive and Gram-negative bacteria by binding to negatively charged lipopolysaccharide (LPS) and lipoteichoic acid on bacterial cell walls, followed by membrane insertion and pore formation that causes cytoplasmic leakage and cell death. Minimum inhibitory concentrations (MIC) range from 1–10 μg/mL for most common pathogens, though some organisms with modified surface charges show resistance.
Beyond antimicrobial effects, LL37 modulates innate and adaptive immunity through receptor-mediated signaling. The peptide binds to formyl peptide receptor-like 1 (FPRL1) and P2X7 purinergic receptors on neutrophils, monocytes, and epithelial cells, triggering chemotaxis, cytokine release, and wound angiogenesis. Studies published in the Journal of Leukocyte Biology demonstrated LL37 concentrations of 1–5 μg/mL induce IL-8 and MCP-1 secretion from keratinocytes, recruiting immune cells to sites of injury or infection without triggering the pro-inflammatory cascade associated with bacterial endotoxin.
The peptide also neutralizes LPS, preventing endotoxin-induced septic shock. This mechanism is concentration-dependent, with maximal LPS neutralization occurring at LL37:LPS molar ratios above 4:1. Importantly, these mechanisms operate identically whether the peptide appears in literature as LL37 or LL-37. The biological activity depends entirely on the amino acid sequence and three-dimensional structure, not on nomenclature formatting.
In our experience working with wound-healing research protocols, LL37's angiogenic properties make it particularly valuable for vascular studies. The peptide promotes endothelial cell migration and tube formation at concentrations as low as 0.5 μg/mL through FPRL1-mediated ERK1/2 and p38 MAPK phosphorylation pathways. This angiogenic effect has been replicated in dozens of independent studies regardless of whether authors referred to the compound as LL37 or LL-37.
LL37 / LL-37 Nomenclature: Literature Comparison
Understanding how LL37 and LL-37 appear across published research clarifies that the nomenclature difference is purely stylistic. The table below compares how each name variation is used in peer-reviewed literature, regulatory databases, and commercial peptide catalogs. Demonstrating functional equivalence.
| Nomenclature | Common Usage Context | Database Frequency | Chemical Identity | Professional Assessment |
|---|---|---|---|---|
| LL37 | Primary name in North American immunology journals; standard in PubMed-indexed articles post-2005 | ~8,200 PubMed citations as of 2026 | 37-amino-acid cathelicidin fragment, MW 4493.3 Da, sequence LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES | Preferred for catalog consistency and database searches |
| LL-37 | European journal formatting; common in dermatology and wound-healing literature pre-2010 | ~6,400 PubMed citations (many duplicate entries with LL37) | Identical sequence, molecular weight, and structural characteristics | Functionally interchangeable. Hyphen is typographic only |
| hCAP-18 | Refers to the 18 kDa precursor protein from which LL37 is cleaved; used when discussing gene expression or proteolytic processing | ~1,100 PubMed citations | Full-length 134-amino-acid cathelicidin precursor; becomes LL37 after proteinase-3 cleavage | Technically distinct. HCAP-18 is the inactive precursor, not the active peptide |
| FALL-39 | Historical name from early cathelicidin research; rarely used after 2000 | <200 citations, primarily 1995–2005 | Slightly longer 39-residue fragment including two additional N-terminal residues | Obsolete nomenclature. Modern literature uses LL37 exclusively |
| CAP18 | Shortened precursor name; used interchangeably with hCAP-18 in gene expression studies | ~900 citations, mostly molecular biology contexts | Refers to precursor gene product before cleavage | Precursor only. Not the mature active peptide |
The critical distinction is between precursor names (hCAP-18, CAP18) and the mature active peptide (LL37, LL-37). The hyphen difference between LL37 and LL-37 carries zero biological significance. Both refer to the same 37-amino-acid active fragment. Researchers ordering peptides should verify the amino acid sequence rather than relying solely on the catalog name, but reputable suppliers like Real Peptides maintain nomenclature consistency across documentation and certificates of analysis.
Key Takeaways
- LL37 and LL-37 are the exact same 37-amino-acid antimicrobial peptide. The hyphen is a typographic style choice with no chemical or biological significance.
- Both names refer to the C-terminal fragment of human cathelicidin hCAP-18, cleaved by proteinase 3, with molecular weight 4493.3 Da and net positive charge +6.
- PubMed contains over 14,000 combined citations for LL37 and LL-37, with significant overlap due to inconsistent journal formatting standards.
- The peptide functions identically as an antimicrobial agent, immune modulator, and angiogenic factor regardless of whether literature refers to it as LL37 or LL-37.
- hCAP-18 and CAP18 refer to the inactive precursor protein, not the mature active peptide. This distinction matters when interpreting gene expression versus functional bioactivity studies.
- Researchers should verify amino acid sequence on certificates of analysis rather than assuming nomenclature differences indicate distinct compounds.
What If: LL37 Nomenclature Scenarios
What If a Study Protocol Specifies LL-37 But the Supplier Only Lists LL37?
Order the LL37. They are the same peptide. Verify the amino acid sequence on the supplier's certificate of analysis matches the 37-residue cathelicidin fragment (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). If the sequence, molecular weight (4493.3 Da), and purity specifications match your protocol requirements, the hyphen difference is irrelevant. Reputable peptide manufacturers synthesize to sequence, not to name formatting, so the biological activity will be identical. We've seen researchers delay studies by weeks trying to source "LL-37" specifically when their institution already had LL37 in inventory. The procurement confusion serves no scientific purpose.
What If I Find Conflicting Data Between LL37 and LL-37 Studies?
Check the experimental conditions and peptide purity, not the name. Apparent conflicts between LL37 and LL-37 studies almost always trace to differences in assay methodology, cell line selection, peptide concentration ranges, or post-synthesis modifications rather than the nomenclature itself. For example, some early LL-37 studies used crude synthetic peptides with 70–85% purity, while modern LL37 studies use HPLC-purified material at >98% purity. The impurity profile affects bioactivity far more than the hyphen. If you encounter conflicting MIC values or receptor-binding affinities between studies, compare the actual experimental protocols and peptide characterization data rather than assuming the name difference indicates a distinct molecule.
What If a Regulatory Submission Requires Consistent Nomenclature Across Documents?
Choose one format and apply it uniformly throughout your submission. Regulatory agencies like the FDA do not require a specific hyphenation standard for peptide names. They require consistency within a single filing. If your initial investigational new drug (IND) application referred to the compound as LL37, continue using LL37 in all subsequent amendments, annual reports, and correspondence. If you accidentally switch between LL37 and LL-37 mid-document, include a clarifying note in the submission cover letter stating both names refer to the same 37-amino-acid cathelicidin peptide and provide the full amino acid sequence to eliminate ambiguity. Consistency matters more than which specific format you choose.
The Blunt Truth About LL37 and LL-37 Nomenclature
Here's the honest answer: the hyphen debate is a distraction. LL37 and LL-37 are the exact same molecule. Identical sequence, identical structure, identical mechanisms. The only difference is whether a journal's copyeditor added a hyphen during manuscript formatting. Researchers spending time verifying whether their supplier's "LL37" matches a protocol's "LL-37" are solving a problem that doesn't exist. What actually matters is the amino acid sequence, the purity percentage on the certificate of analysis, the storage conditions during shipping, and whether the peptide was synthesized under appropriate quality controls. The hyphen contributes nothing to any of those factors. If your study requires cathelicidin antimicrobial peptide with 37 residues and leucine-leucine at the N-terminus, both LL37 and LL-37 meet that specification equally.
The nomenclature fragmentation does create one real cost: it splits literature searches. A PubMed query for "LL37" returns different results than "LL-37" because the database treats them as distinct text strings, even though the underlying science is unified. Researchers conducting systematic reviews must search both terms independently and manually deduplicate the combined results. An inefficiency that journal standardization could have prevented decades ago. The solution isn't choosing the "correct" name; it's recognizing that both are correct and searching comprehensively.
LL37 and LL-37 are interchangeable names for the same research tool. Focus on the sequence and purity, not the punctuation. The peptide's bioactivity depends on its structure, and that structure is invariant whether the catalog label includes a hyphen or not.
Frequently Asked Questions
Is LL37 the same peptide as LL-37, or are they structurally different?
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LL37 and LL-37 are the exact same peptide — a 37-amino-acid fragment of human cathelicidin with the sequence LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES. The hyphen between LL and 37 is a typographic formatting choice used by some journals and suppliers, with no impact on the peptide’s molecular weight (4493.3 Da), amino acid sequence, or biological activity. Both names refer to the mature active peptide cleaved from the hCAP-18 precursor protein by proteinase 3.
Why do some research papers use LL37 while others use LL-37?
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The variation reflects inconsistent journal style guides rather than distinct compounds. European journals historically hyphenated alphanumeric peptide names, while North American publications often omitted the hyphen. As of 2026, PubMed contains over 8,000 citations for ‘LL37’ and 6,000 for ‘LL-37’, with significant overlap because many studies are indexed under both terms. Neither format is more scientifically accurate — the biological molecule and its mechanisms remain identical regardless of punctuation.
How do I verify that LL37 and LL-37 from different suppliers are the same peptide?
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Request the certificate of analysis (CoA) from each supplier and compare the amino acid sequence, molecular weight, and purity percentage. LL37 and LL-37 should both show a 37-residue sequence starting with leucine-leucine (LL), molecular weight of 4493.3 Da, and purity above 95% by HPLC. If these specifications match, the peptides are functionally identical regardless of the catalog name. Reputable suppliers like Real Peptides provide full sequence verification and mass spectrometry data with every batch.
Can LL37 and LL-37 be used interchangeably in the same research protocol?
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Yes, provided both peptides meet the same purity and quality standards. The name difference has no bearing on antimicrobial activity, receptor binding, or immunomodulatory mechanisms. If your protocol specifies one name but your supplier provides the other, verify the amino acid sequence and purity on the CoA — if those match your experimental requirements, the peptide will perform identically. The only reason to maintain name consistency is for documentation clarity within a single study or regulatory submission.
What is the difference between LL37 and hCAP-18?
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hCAP-18 is the 18-kilodalton precursor protein from which LL37 is cleaved. The full-length hCAP-18 contains 134 amino acids and is biologically inactive until the serine protease proteinase 3 cleaves the C-terminal 37-amino-acid fragment, producing the active LL37 peptide. Gene expression studies measure hCAP-18 mRNA or precursor protein levels, while functional bioactivity studies use the mature LL37 peptide. The two are not interchangeable — hCAP-18 must be enzymatically processed to generate the antimicrobial and immunomodulatory activity associated with LL37.
Does the hyphen in LL-37 indicate a modified or synthetic version of LL37?
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No, the hyphen is purely a formatting convention with no chemical significance. Both LL37 and LL-37 are synthesized using identical solid-phase peptide synthesis (SPPS) methods and consist of the same natural L-amino acids in the same sequence. Neither name indicates modification, pegylation, cyclization, or any structural alteration. The hyphen appeared in early European publications due to institutional style guides and persists in some literature by convention, but it does not denote a distinct synthetic variant or derivative.
How should I search PubMed to find all relevant LL37 research without missing studies?
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Search for both ‘LL37’ and ‘LL-37’ as separate queries, then combine the results and remove duplicates manually. PubMed treats the hyphen as a distinct character, so a search for ‘LL37’ will not return articles indexed under ‘LL-37’ and vice versa. For comprehensive systematic reviews, also include alternative names like ‘hCAP-18’, ‘FALL-39’, and ‘cathelicidin antimicrobial peptide’ to capture studies that used historical nomenclature or focused on precursor protein expression rather than the mature peptide.
What concentration range of LL37 or LL-37 is typically used in antimicrobial assays?
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Minimum inhibitory concentration (MIC) assays for LL37 against Gram-positive and Gram-negative bacteria typically use concentration ranges of 0.5–50 μg/mL, with most common pathogens showing MIC values between 1–10 μg/mL. Immunomodulatory and wound-healing studies use lower concentrations, often 0.5–5 μg/mL, to stimulate chemotaxis, cytokine release, or angiogenesis without inducing cytotoxicity in mammalian cells. These concentration ranges apply equally to peptides labeled LL37 or LL-37, as the bioactivity depends solely on the amino acid sequence and purity.
Are there any peer-reviewed studies that directly compare LL37 versus LL-37 as if they were different compounds?
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No credible peer-reviewed studies treat LL37 and LL-37 as distinct compounds because the scientific community recognizes them as nomenclature variants of the same peptide. Any apparent ‘comparison’ would reflect experimental methodology differences, peptide purity variations, or assay condition changes rather than inherent molecular differences. Studies that report conflicting results between ‘LL37’ and ‘LL-37′ experiments are comparing different labs’ protocols or synthesis batches, not different peptides — the name difference is incidental, not causal.
Should I specify LL37 or LL-37 when ordering peptides for research?
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Either name is acceptable, but always verify the full amino acid sequence on the supplier’s product specification sheet. Reputable peptide suppliers like Real Peptides synthesize to sequence, not to name, so requesting ‘LL37’ or ‘LL-37’ will yield the same 37-residue cathelicidin peptide as long as the underlying sequence matches. For procurement consistency within a lab or institution, choose one nomenclature format and use it uniformly across purchase orders, protocols, and publications to avoid confusion, but recognize that the biological material is identical regardless of which name appears on the label.
