Sinapultide | CAS 138531-07-4 | SP-B Mimetic Synthetic Peptide (Research Use Only) | Knowlux
Product Description
Sinapultide, CAS 138531-07-4, is a synthetic 21-amino-acid peptide designed to mimic the function of human surfactant protein-B (SP-B), supplied by Knowlux for laboratory research use. The peptide is composed of a repeating five-residue motif of one lysine (K) and four leucines (L4), yielding the sequence H-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-OH, commonly abbreviated as KL4. The molecular formula is C126H238N26O22 and the molecular weight is 2469.40 g/mol on a free-peptide basis. Each lot is released with a lot-specific COA, MSDS and analytical traceability.
CAS and Salt Form Clarification: CAS 138531-07-4 is the free peptide registry for Sinapultide and is the identifier applied across KEGG DRUG, the FDA New Molecular Entity documentation, MedChemExpress, NovoPro, and ChemicalBook. A trifluoroacetate (TFA) salt form circulates in commercial catalogues under CAS 2828433-25-4 and must not be conflated with the free peptide. The TFA counter-ion is analytically consequential: AbMole lists the TFA salt as C128H239F3N26O24 with MW 2583.42, approximately 114 g/mol above the free-peptide mass, while MedChemExpress and InvivoChem list the free-peptide formula C126H238N26O22 and MW 2469.40. A NovoPro technical note explicitly states that the TFA counterion from HPLC purification contributes to total product mass, with peptide content typically constituting >80% of the total weight and TFA accounting for the remainder; the same note observes that TFA salts generally enhance aqueous solubility relative to the free peptide. Knowlux specifies the salt form, counter-ion identity, and peptide content per lot on the COA. Buyers should confirm whether the quoted material is free peptide or TFA salt before procurement, as the mass difference between the two forms is material for molarity calculations and for interpreting solubility data.
Structural and Mechanistic Note: Sinapultide is the first peptide-based replacement for SP-B in a synthetic pulmonary surfactant approved for clinical use. The KL4 penta-residue repeat confers structural plasticity rather than a fixed secondary structure: the peptide adopts adaptive helical conformations that vary with lipid saturation levels and pH, and it partitions differentially into lipid bilayers in response to these environmental cues. Solid-state NMR and circular dichroism studies cited by NovoPro show that the peptide's helical structure modulates lipid curvature strain and phase behavior, with deeper insertion observed in saturated lipid environments, and that the lysine residues are positioned to interact with anionic lipids such as POPG, enhancing interfacial activity. Unlike the disulfide-constrained or terminally blocked peptides in the Nesiritide and Semax families, Sinapultide is linear, contains no cysteine, no methionine, and no tryptophan, and has free N- and C-termini. It is therefore not subject to disulfide scrambling or methionine sulfoxide formation; the principal structural liabilities are aggregation at high concentration and the counter-ion/solubility considerations described above.
Product Parameters
| Item | Specification |
|---|---|
| Product Name | Sinapultide |
| Synonyms | KL4 peptide; KL4; Lucinactant peptide component; ATI-01; H-KLLLLKLLLLKLLLLKLLLLK-OH |
| CAS No. | 138531-07-4 (free peptide); 2828433-25-4 (TFA salt) |
| Molecular Formula | C126H238N26O22 (free peptide); C128H239F3N26O24 (TFA salt) |
| Molecular Weight | 2469.40 g/mol (free peptide); ~2583.42 g/mol (TFA salt) |
| Sequence (1-letter) | KLLLLKLLLLKLLLLKLLLLK |
| Sequence (3-letter) | H-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-OH |
| Sequence Length | 21 amino acids, linear |
| Key Structural Features | Penta-residue KL4 repeat; adaptive helical conformation; no cysteine, methionine, or tryptophan; free N- and C-termini |
| Appearance | White to off-white solid powder |
| Solubility | DMSO 2 mg/mL (0.81 mM, ultrasonic; TFA salt data); H2O/DMSO supplier-declared for free peptide |
| Purity | >=95.0% to >=98.0% (HPLC); lot-specific (see Quality Control) |
| Identity | Confirmed by LC-MS and HPLC |
| Grade | Research grade |
| Counter-ion | Free peptide or TFA (lot-specific, declared on COA) |
| Peptide Content | >=80.0% (typical for TFA salt) |
| Storage | See Storage and Stability section |
| Packaging | 1 mg / 5 mg / 10 mg / 25 mg / 50 mg / 100 mg vial; bulk on request |
| Application | Laboratory research use only |
| Origin | China |
Product Details
1. Overview
Sinapultide (KL4) is a fully synthetic 21-residue peptide modeled after the C-terminal amphipathic helix of human surfactant protein-B (SP-B). SP-B is the most important surfactant protein for proper respiratory system function, and its deficiency in premature infants leads to respiratory distress syndrome (RDS). Sinapultide compensates for surfactant deficiency and restores surface activity to the lungs in this context. The peptide was developed as a component of Lucinactant (Surfaxin), a synthetic pulmonary surfactant preparation that combines Sinapultide with the phospholipids DPPC and POPG and with palmitic acid. Its research interest lies in the biophysics of pulmonary surfactant: the KL4 peptide is a minimal, sequence-defined model for how a small amphipathic helix can organize phospholipid monolayers at the air-water interface, and it has become a reference tool for studying lipid-peptide interactions in surfactant replacement science. The material supplied under this specification is research-grade and is not intended for human administration.
2. Biophysical Mechanism and Surfactant Function
Sinapultide functions not by a receptor-mediated mechanism but by a lipid-interaction mechanism, and this distinguishes it from every receptor-targeted peptide in this catalogue. The penta-residue KL4 repeat produces an adaptive peptide helicity that varies with partitioning depth into lipid bilayers, and this structural plasticity is proposed to be a mechanism for differential trafficking of lipids within the surfactant monolayer. Biophysical studies show that Sinapultide differentially partitions into lipid bilayers in response to the degree of lipid saturation, adopting helical structures that deviate from canonical alpha-helical geometry, and that it interacts preferentially with DPPC and POPG, influencing lipid dynamics and promoting stable monolayer formation at air-water interfaces. Deeper insertion is observed in saturated lipid environments, consistent with the peptide's role in organizing the rigid dipalmitoylphosphatidylcholine component of pulmonary surfactant. Beyond its surfactant biophysics, published research reports an anti-inflammatory action: KL4-surfactant prevents hyperoxic and LPS-induced lung injury in mice, and the evidence suggests that the anti-inflammatory mechanism of the KL4 peptide proceeds through inhibition of polymorphonuclear leukocyte (PMN) transmigration through the endothelium. In vitro, Sinapultide microbubble preparations (2 to 5 microg/mL, 24 h) combined with ultrasound (0.5 MHz, 40 s) promoted functional recovery of injured alveolar type II (AT II) cells via effects on TNF-alpha and IL-6 levels, and in vivo Sinapultide-loaded microbubbles (0.1 mg, nasal delivery) improved pulmonary edema in LPS-induced acute lung injury mice. These descriptions are derived from published research and are provided for scientific reference only.
3. Research Applications
Published pharmacological characterizations and documented protocols describe the following research applications:
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Pulmonary surfactant biophysics and lipid monolayer organization studies (DPPC/POPG interactions, air-water interface behavior)
-
SP-B deficiency and respiratory distress syndrome (RDS) research models
-
Acute lung injury and hyperoxic lung injury research models (anti-inflammatory and PMN transmigration endpoints)
-
Lipid-peptide interaction studies (solid-state NMR, circular dichroism, monolayer techniques)
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Synthetic surfactant formulation development (Lucinactant-type phospholipid/peptide systems)
-
Microbubble-assisted drug delivery and ultrasound-mediated lung targeting research
-
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
| Test Item | Method | Acceptance Criteria |
|---|---|---|
| Purity | RP-HPLC | >=95.0% (entry grade); >=98.0% (standard grade); lot-specific values ranging from 95.72% to 98.54% have been reported |
| Identity | LC-MS and HPLC | Consistent with structure (2469.40 +/- 1 for free peptide; ~2583.42 for TFA salt) |
| Peptide Content | Nitrogen analysis or mass balance | >=80.0% (typical for TFA salt) |
| Appearance | Visual | White to off-white powder |
Solubility and Handling
Solubility: Sinapultide solubility data in the sourced literature are limited and are reported for the TFA salt rather than the free peptide. MedChemExpress reports DMSO solubility of 2 mg/mL (0.81 mM) with ultrasonic assistance for its Sinapultide lot, and explicitly notes that hygroscopic DMSO has a significant impact on solubility and that freshly opened DMSO should be used. ChemicalBook supplier listings from Nanjing Peptide Biology declare solubility as H2O/DMSO without a numeric limit, and Biomart lists Soluble in DMSO with a purity of >=98%. NovoPro's technical note on TFA salts states that TFA salts generally enhance the solubility of peptides in aqueous solutions relative to the free peptide, which is a relevant consideration where the free peptide is supplied. For practical stock preparation, DMSO at 2 mg/mL is the only numerically supported condition across the sourced data, and it should be treated as a starting point rather than a solubility limit. Given the peptide's highly hydrophobic leucine-rich character (17 of 21 residues are leucine), aqueous solubility of the free peptide is likely to be limited, and the TFA salt or a DMSO stock is the more practical route for assay work. Prepare solutions fresh and aliquot; MedChemExpress general guidance for stock solutions is to store aliquots in tightly sealed vials and use within 1 month, avoiding 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. Because the peptide contains no cysteine, methionine, or tryptophan, reducing agents and oxidation-protection measures are not required. The principal handling consideration is the hygroscopic nature of the lyophilized powder and of DMSO; equilibrate vials to room temperature before opening and use freshly opened anhydrous DMSO for stock preparation.
Storage and Stability
| Format | Temperature | Shelf Life |
|---|---|---|
| Lyophilized Powder | -80C, sealed, desiccated | 2 years (MedChemExpress) |
| Lyophilized Powder | -20C, sealed, desiccated | 1 year (MedChemExpress); 2 years (Biomart, InvivoChem); 3 years (AbMole, InvivoChem) |
| Lyophilized Powder | 4C, sealed, desiccated | 2 years (AbMole, InvivoChem) |
| Reconstituted Solution | -80C, aliquoted, sealed | 6 months (MedChemExpress, AbMole, InvivoChem) |
| Reconstituted Solution | -20C, aliquoted, sealed | 1 month (MedChemExpress, AbMole, InvivoChem) |
Documentation Support
Per lot: COA, MSDS, HPLC chromatogram, and mass spectrometry data. Salt-form identity, counter-ion content, and peptide content 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. Sinapultide is a component of an approved medicinal product (Lucinactant) in certain jurisdictions for neonatal respiratory distress syndrome; however, 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 molecular formula C126H238N26O22 and molecular weight 2469.40 are confirmed by KEGG DRUG, the FDA New Molecular Entity documentation (which lists 2469.46), MedChemExpress, NovoPro, InvivoChem, and Solarbio. The sequence H-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-Leu-Leu-Leu-Leu-Lys-OH is confirmed by KEGG DRUG, the FDA chemical review, NovoPro, and MedChemExpress. One InvivoChem product description states 20-amino acid (AA) peptide, which is inconsistent with the 21-residue sequence confirmed across the other sources and is treated as a typographical error. The TFA salt formula C128H239F3N26O24 and MW 2583.42 are from AbMole COA, and the TFA salt CAS 2828433-25-4 is from InvivoChem related CAS listing. The structural plasticity and lipid-partitioning mechanism are from the ScienceDirect review and the Curr Opin Chem Biol reference cited by NovoPro. The anti-inflammatory PMN transmigration data are from the PubMed abstract for the KL4-surfactant mouse study. The in vitro AT II cell and in vivo ALI microbubble data are from MedChemExpress and InvivoChem, both of which note that the methods are from reference [2] (Liu et al., Drug Des Devel Ther, 2020) and have not been independently validated by the supplier. Solubility values are reported with their source and conditions rather than reconciled into a single figure because the DMSO 2 mg/mL value is for the TFA salt and no numeric aqueous solubility value for the free peptide was identified. Storage shelf-life divergence (-20C versus -80C for powder; 1 to 3 years) is reported as-is; -80C is presented as the conservative archival 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.
