Antimicrobial peptide research works on a different logic from the receptor pharmacology that governs most of this catalog. Antimicrobial peptides (AMPs) are typically cationic and amphipathic, and their primary reported mechanism is physical — partitioning into and permeabilising anionic bacterial membranes — rather than binding a defined receptor. Our antimicrobial topic page collects the peptide standards, antisera and immunoassay kits used across that literature, from human host-defence peptides to insect and amphibian AMPs. This guide maps the families, the formats and the assay-specific handling that AMP work demands.
What sits under the antimicrobial topic
A family is filed here when its parent peptide has documented antibacterial, antifungal or antiviral activity, or when it functions as part of innate immune defence. That includes the two classical human families — cathelicidins and defensins — plus tissue-specific AMPs, iron-withholding peptides, invertebrate and amphibian peptides used as mechanistic models, and the receptor agonists that link AMPs to inflammatory signalling. Many of these peptides are also immunomodulators, so the topic overlaps with immune research generally. Every item is supplied for in-vitro and approved animal research only; nothing here is an anti-infective product.
Human host-defence families
- LL-37 — the only human cathelicidin, the C-terminal 37 residues of hCAP18. It is the most-ordered AMP in the catalog, studied for membrane activity, LPS neutralisation, chemotaxis via FPR2 and wound-repair signalling. Truncated and scrambled variants are stocked as mechanistic controls.
- Defensins — α-defensins (HNP-1 to HNP-4, HD-5, HD-6) and β-defensins (hBD-1 to hBD-4), distinguished by their disulfide connectivity. The three disulfide bridges are structural requirements, so oxidised and linearised forms are genuinely different reagents.
- Dermcidin — an anionic AMP from eccrine sweat, an instructive exception to the cationic rule and a common comparator in mechanism studies.
- LEAP peptides — liver-expressed antimicrobial peptides, including hepcidin (LEAP-1), which sits at the intersection of antimicrobial defence and iron regulation and is measured in a great many phenotyping studies.
- Lipocalin-2 (NGAL) — a siderophore-sequestering protein that starves bacteria of iron; a nutritional-immunity reagent rather than a membrane-lytic one.
- Intelectin — a lectin binding microbial glycans, ordered for pattern-recognition studies.
- Antisecretory factor — studied in enteric fluid secretion and inflammatory bowel models.
Model and comparator AMP families
- CRAMP — the mouse cathelicidin orthologue of LL-37. Any murine study of cathelicidin biology needs CRAMP, not LL-37: the sequences differ substantially and activity does not transfer.
- Apidaecin — an insect proline-rich AMP that acts intracellularly on the ribosome rather than by lysis, and therefore the standard comparator when distinguishing lytic from non-lytic mechanisms.
- Bombinakinin — amphibian skin peptides from the Bombina genus, a rich source of both AMPs and bradykinin-related peptides.
- AMP-IBP5 — an IGF-binding-protein-5-derived antimicrobial peptide, an example of AMP activity emerging from a fragment of a non-immune protein.
Innate-immune signalling companions
- fMLF (fMLP) and WKYMVm — formyl peptide receptor agonists used as neutrophil chemotaxis controls, and the standard reference ligands when testing whether an AMP acts through FPR1 or FPR2.
- Peptidoglycan-related reagents — bacterial cell-wall components used as pattern-recognition receptor stimuli alongside AMP work.
- Ac2-26 — the annexin A1 peptide, a pro-resolving FPR2 agonist frequently paired with LL-37 studies because both converge on the same receptor.
- Interleukin and CXCL families — several chemokines have direct antimicrobial activity, and cytokine readouts are the usual downstream measurement in AMP immunomodulation studies.
Which formats the antimicrobial topic contains
Synthetic peptide standards are the core of this topic and are ordered at larger scale than elsewhere, because minimum inhibitory concentration assays consume material — milligram fills are the norm rather than the exception. Labeled peptides matter for mechanism: fluorescently tagged AMPs are used for bacterial-membrane localisation microscopy, and biotinylated versions for pull-down of binding partners. Polyclonal antisera support tissue detection of endogenous AMP expression, which is how most host-defence papers demonstrate induction. ELISA kits quantify LL-37, hepcidin, lipocalin-2 and beta-defensins in plasma, sputum and culture supernatant. Peptide libraries support structure–activity screening, which is the main route to designed AMP analogs.
How laboratories choose within a family
Species first, and more strictly than in other topics. LL-37 and CRAMP are not interchangeable, and using the human peptide in a mouse model is a recognised source of uninterpretable results. Oxidation state second: defensins require correct disulfide bridge pairing, and a catalog entry should state whether the peptide is supplied oxidised and folded or as the linear form. Counter-ion third, and this is the AMP-specific trap: residual TFA from synthesis is itself antimicrobial and cytotoxic at the concentrations AMP assays use, so acetate-exchanged material is standard for MIC and cell-viability work. Purity and content fourth: an AMP quoted at 95% purity may be substantially less than 95% peptide by mass once salt and water are counted, which shifts every MIC value you report. The COA guide explains peptide content versus gross weight.
Handling notes for this topic
Cationic peptides adsorb strongly to polystyrene and to plastic tips, and losses at low micromolar concentrations are large enough to move an MIC by a dilution or more — use polypropylene, low-binding tips, or a carrier such as 0.01% acetic acid with BSA where the assay tolerates it. Media composition matters: standard cation-adjusted Mueller-Hinton broth suppresses AMP activity relative to low-salt media, which is why AMP papers specify the medium so carefully. Beyond that, the usual applies — sealed lyophilised vials at −20 °C, single-use aliquots, minimal freeze–thaw, and attention to solubility for hydrophobic sequences (peptide solubility, storage guide, aliquoting guide).
Where to go next
Browse the full antimicrobial topic, the immune system hub or the skin hub, where most human AMP expression is studied. Adjacent guides cover the research peptides type guide for specification reading, and the cancer section, which shares the chemokine families.