Antimicrobial · Disulphide-stabilised β-hairpin antimicrobial peptide
Polyphemusin II
Also known as PM-II
An 18-residue horseshoe crab peptide for comparative studies of β-hairpin structure, microbial recognition and membrane activity.
- Length
- 18 amino acids
- Half-life
- Not well characterised
- Mechanism
- Polyphemusin II associates with negatively charged microbial surfaces and lipid bilayers through its cationic, amphipathic structure. Membrane perturbation contributes to its antimicrobial activity, although the native peptide does not have a single established receptor target.
- Studied in
- Microbial culture assays and lipid-bilayer experiments study its antimicrobial activity, membrane interactions and structure–activity relationships alongside related horseshoe crab peptides.
About Polyphemusin II
Isolated from Limulus polyphemus haemocytes, Polyphemusin II belongs to the same cysteine-rich innate-defence peptide family as Polyphemusin I. Its mature structure comprises 18 amino acids, two intramolecular disulphide bonds and an amidated C-terminus. A closely related sequence preserves the strongly basic, amphipathic β-hairpin architecture characteristic of this family. This makes the pair useful for examining how limited sequence variation affects interactions with microbial envelopes without changing the overall peptide scaffold.
Research on Polyphemusin II encompasses microbial growth assays, membrane-permeability measurements and comparisons with engineered derivatives. Negatively charged membrane components provide interaction sites, but binding should not be equated with a unique receptor-mediated mechanism. Some extensively modified peptides derived from this scaffold have been investigated as CXCR4 ligands; those findings cannot automatically be assigned to native Polyphemusin II. Sequence identity, terminal chemistry and folding therefore require explicit documentation when comparing native material with analogue literature.
Laboratory notes
- For research use only; distinguish the native sequence from substituted or truncated derivatives in inventory and assay records.
- Use low-binding labware where practical and assess peptide recovery if adsorption could affect the experimental concentration.
- Confirm disulphide status and terminal chemistry before comparing batches in structure–activity experiments.
Storage and reconstitution basics: storage guide.
Questions about Polyphemusin II
Is native Polyphemusin II necessarily a selective CXCR4 ligand?
No. CXCR4 findings for engineered derivatives should not be transferred to the native peptide without direct receptor-binding and functional evidence.
Why compare Polyphemusin II with Polyphemusin I?
Their closely related sequences and shared β-hairpin architecture provide a useful framework for investigating how sequence variation affects membrane association and antimicrobial assay results.
Which measurements help separate binding from disruption?
Lipid-binding measurements can be paired with vesicle leakage or microbial permeability assays. Association with a membrane does not by itself demonstrate loss of membrane integrity.
Is Polyphemusin II for human use?
No. It is supplied strictly for in-vitro laboratory research and is not for human or animal consumption.
Related research peptides
All products are sold for laboratory research use only. Not for human consumption, not a medicine, not for diagnosing, treating or preventing any condition.