Pexiganan Acetate | CAS 172820-23-4 | Cationic Antimicrobial Peptide (Research Use Only) | Knowlux
Product Description
Pexiganan Acetate, CAS 172820-23-4, is a synthetic 22-amino-acid cationic antimicrobial peptide corresponding to the acetate salt of Pexiganan (MSI-78), supplied by Knowlux for laboratory research use. The peptide is a synthetic analogue of magainin 2, a host-defense peptide originally isolated from the skin of the African clawed frog Xenopus laevis. The sequence is H-Gly-Ile-Gly-Lys-Phe-Leu-Lys-Lys-Ala-Lys-Lys-Phe-Gly-Lys-Ala-Phe-Val-Lys-Ile-Leu-Lys-Lys-NH2, with a C-terminal lysinamide. The molecular formula is C122H210N32O22 (free peptide) and the molecular weight is 2477.17 g/mol on a free-peptide basis; the acetate salt formula is expressed as C122H210N32O22.xC2H4O2 to reflect variable acetate stoichiometry across suppliers. Each lot is released with a lot-specific COA, MSDS and analytical traceability.
CAS and Salt Form Clarification: The CAS landscape for Pexiganan requires explicit handling because two registries correspond to chemically distinct entities. CAS 147664-63-9 is the free base (Pexiganan, MSI 78 free base), with formula C122H210N32O22 and MW 2477.17. CAS 172820-23-4 is the acetate salt, which is the form most widely supplied in commercial catalogues and the form associated with the product name Pexiganan Acetate. The acetate stoichiometry is not fixed across suppliers: Cayman and MedChemExpress render the formula as C122H210N32O22.xC2H4O2, while BOC Sciences lists C122H210N32O22.C2H4O2 with a molecular weight of 2537.22, and BenchChem lists C124H214N32O24 with a molecular weight of 2537.2. The free-base molecular weight of 2477.17 is the appropriate reference for molarity calculations when the acetate content is declared separately on the COA. Knowlux specifies the salt form, acetate content, and peptide content per lot on the COA. Buyers should confirm whether the quoted material is reported on a free-peptide or acetate-salt basis, and should reconcile the molecular weight on the COA against the declared counter-ion basis rather than relying on the product name alone.
Sequence and Structural Note: One supplier listing renders the sequence with a C-terminal segment that is inconsistent with the consensus 22-residue magainin-analogue sequence and appears to be a transcription artifact. The consensus sequence adopted here is GIGKFLKKAKKFGFKAFVKILKK-NH2, which is confirmed by Sigma-Aldrich, MedChemExpress, Adooq, BenchChem, and Creative Peptides. The peptide is linear, contains no cysteine, and has no intramolecular cross-link, distinguishing its handling profile from the disulfide-constrained peptides in the Linaclotide, Plecanatide, and Ziconotide families. It contains no methionine and no tryptophan, which removes methionine sulfoxide and tryptophan oxidation as principal degradation pathways; the C-terminal lysinamide is amidated against carboxypeptidase attack. The high proportion of basic residues (six lysines) gives the peptide a strongly cationic character at physiological pH, which is the structural basis for its membrane-directed antimicrobial mechanism.
Product Parameters
Product Details
1. Overview
Pexiganan (MSI-78) is a 22-residue synthetic cationic antimicrobial peptide engineered as an analogue of magainin 2, a naturally occurring host-defense peptide from the skin of Xenopus laevis. It is one of the most extensively characterized membrane-active antimicrobial peptides in preclinical and clinical development, and it has been investigated clinically as a topical agent for infected diabetic foot ulcers under the development name Cytolex/Locilex. The peptide exhibits broad-spectrum bactericidal activity against Gram-positive and Gram-negative aerobic bacteria, achieving up to 99% inhibition in susceptibility panels, and it retains activity against methicillin-resistant Staphylococcus aureus (MRSA) and other drug-resistant phenotypes. The material supplied under this specification is research-grade and is not intended for human administration.
2. Antimicrobial Mechanism and Spectrum
Pexiganan acts through a membrane-disruptive mechanism rather than a specific receptor or enzyme target. As a cationic amphipathic peptide, it is electrostatically attracted to the negatively charged phospholipid head groups of bacterial membranes, inserts into the lipid bilayer, and disrupts membrane integrity, leading to increased permeability, loss of ionic gradients, and cell death. This mechanism is concentration-dependent and rapid, and because it does not rely on a single molecular target, the emergence of resistance through point mutations in a target protein is less likely than for conventional antibiotics.
The spectrum of activity is broad and quantitatively documented. Sigma-Aldrich reference data report MIC values of <=16 microg/mL for staphylococci, 8-64 microg/mL for streptococci and MRSA, 16-256 microg/mL for S. pyogenes, 4-32 microg/mL for Gram-negative aerobes, 1-128 microg/mL for Enterobacter cloacae, and 4-64 microg/mL for Alcaligenes faecalis. These values are assay- and strain-dependent and are provided for scientific reference only. The peptide is described in the literature as orally active in addition to its topical activity, which has made it a tool for studying membrane-active antimicrobial pharmacology across administration routes.
3. Research Applications
Published pharmacological characterizations and documented protocols describe the following research applications:
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Antimicrobial susceptibility testing and MIC/MBC determination against Gram-positive and Gram-negative clinical isolates, including MRSA and drug-resistant phenotypes
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Membrane permeabilization and mechanistic studies of cationic antimicrobial peptides
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Diabetic foot ulcer infection and topical antimicrobial research models
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Structure-activity relationship studies of magainin analogues (cationic charge, amphipathicity, and helix propensity)
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Comparative pharmacology of membrane-active antimicrobial peptides versus conventional antibiotics
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Reference standard development for HPLC and LC-MS analytical methods
These descriptions are derived from published research and are provided for scientific reference only.
Quality Control
Solubility and Handling
Solubility: Pexiganan Acetate solubility is strongly solvent-dependent, and the aqueous and organic values diverge to a degree that is experimentally consequential. MedChemExpress reports water solubility of 100 mg/mL (40.37 mM) requiring sonication, and DMSO solubility of only 5 mg/mL (2.02 mM) requiring sonication, warming, and heating to 60C. Cayman reports a qualitatively similar profile: DMF slightly soluble, DMSO slightly soluble, ethanol 12 mg/mL, and PBS (pH 7.2) 5 mg/mL. The high aqueous solubility relative to DMSO is consistent with the peptide's strongly cationic, highly hydrophilic character (six lysine residues) and distinguishes its handling profile from the more lipophilic, DMSO-favoring peptides in this catalogue. For stock preparation, water is the preferred solvent at up to 100 mg/mL with sonication; DMSO is a secondary option at 5 mg/mL where an anhydrous vehicle is required, but the low DMSO solubility and the need for warming should be factored into experimental design. Ethanol at 12 mg/mL and PBS at 5 mg/mL provide alternative working solvents where compatibility with the assay system allows. Prepare solutions fresh and aliquot to avoid repeated freeze-thaw cycles.
Handling Precautions: Use powder-handling containment (glove box or fume hood with particulate control). Avoid inhalation of fine powder. Wear nitrile gloves, lab coat, and eye protection. Sigma-Aldrich classifies the compound as hygroscopic and assigns WGK 3 (severe water hazard) under German water hazard classification; consult the lot-specific MSDS for applicable handling and disposal guidance. The peptide contains no cysteine, methionine, or tryptophan, so reducing agents and methionine/tryptophan oxidation protection measures are not required. The principal handling consideration is moisture exclusion; equilibrate vials to room temperature before opening and store under desiccation.
Storage and Stability
Documentation Support
Per lot: COA, MSDS, HPLC chromatogram, and mass spectrometry data. Acetate content, water content, peptide content, and salt-form stoichiometry available on request. Custom specifications and third-party inspection can be arranged on a project basis.
About Knowlux
Knowlux Biotechnology is a GMP-oriented manufacturer and supplier of peptides, APIs and fine-chemical research compounds, operating from Hubei, China. We serve research groups, CDMOs and distributors in more than 40 countries, and support contract synthesis, custom packaging and technical documentation requests.
Compliance Statement
FOR RESEARCH USE ONLY. NOT FOR HUMAN USE. NOT FOR DIAGNOSTIC OR THERAPEUTIC USE.
This product is supplied for laboratory research use only. It is not for human or animal administration, not for diagnostic or therapeutic use, not for retail sale, and not for personal use. Pexiganan Acetate has been investigated in clinical trials for infected diabetic foot ulcers but is not approved as a medicinal product in the United States or the European Union; the material offered under this specification is research-grade and is not intended for clinical use. The purchaser is responsible for verifying product specifications against their specific research requirements and for compliance with all applicable institutional, local, and national regulations governing research chemical acquisition, storage, and use. Research context statements are for scientific reference only and do not constitute medical advice, promotional claims, or dosing guidance.
Data Verification Notes
The free-base formula C122H210N32O22 and MW 2477.17 are confirmed by MedChemExpress, Adooq, GlpBio, Biorbyt, and WikiPep. The acetate CAS 172820-23-4 is confirmed by Cayman, MedChemExpress, Adooq, Sigma-Aldrich, and BOC Sciences. The free-base CAS 147664-63-9 is confirmed by GlpBio, Biorbyt, Creative Biolabs, and MedChemExpress. The consensus sequence GIGKFLKKAKKFGFKAFVKILKK-NH2 is confirmed by Sigma-Aldrich, MedChemExpress, Adooq, and Creative Peptides; the alternative sequence rendering in one supplier listing is inconsistent with the consensus 22-residue magainin analogue and is treated as a transcription artifact. The acetate stoichiometry variability (xC2H4O2 versus C2H4O2 versus C124H214N32O24) is documented across Cayman, MedChemExpress, BOC Sciences, and BenchChem. The MIC data are from Sigma-Aldrich reference panel and are strain- and assay-dependent. The solubility values (H2O 100 mg/mL, DMSO 5 mg/mL, ethanol 12 mg/mL, PBS 5 mg/mL) are from MedChemExpress and Cayman batch data. The hygroscopic classification and WGK 3 designation are from Sigma-Aldrich. Storage shelf-life divergence (-20C versus -80C for powder; 6 months versus 1 year for -80C solutions) is reported as-is; the -20C powder condition is the most widely supported archival temperature, and -80C is presented as the conservative option.
Formatting Note: All formulas, sequences, and comparison operators use plain ASCII notation to prevent character corruption on the platform. Section headings, table alignment, and spacing follow the approved product detail pattern. No trailing spaces or non-breaking characters are used; tables use consistent pipe alignment.
