Lucinactant is a new synthetic peptide-containing surfactant for intratracheal use. It contains sinapultide, a novel, hydrophobic, 21-amino acid peptide (leucine and lysine repeating units, KL4 peptide) designed to mimic human surfactant protein-B (SB-P). More specifically, it mimics the C-terminal amphipathic helical domain of this protein. It also consists of phospholipids (dipalmitoylphosphatidylcholine, DPPC and palmitoyloleoyl phosphatidylglycerol, POPG) and a fatty acid (palmitic acid). It is completely devoid of animal-derived components.
CAT No: 10-101-168
CAS No:138531-07-4
Synonyms/Alias:Sinapultide;138531-07-4;Kl4 peptide;ATI 01;KL4 (peptide);Sinapultida;Sinapultide [USAN:INN];UNII-040X3AX99T;PEPTIDE KL4;PEPTIDE KL-4;RWJ 45652;ATI-01;DTXSID30160707;040X3AX99T;RWJ-45652;SINAPULTIDE (MART.);SINAPULTIDE [MART.];L-Lysine, L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-;L-Lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysyl-L-leucyl-L-leucyl-L-leucyl-L-leucyl-L-lysine;Sinapultidum;SINAPULTIDE [MI];SINAPULTIDE [INN];SINAPULTIDE [USAN];SCHEMBL180504;CHEMBL2103901;DTXCID3083198;AT42478;DB11332;DA-67594;NS00124788;
Sinapultide is a synthetic peptide that structurally and functionally mimics the activity of pulmonary surfactant protein B (SP-B), a critical component of the lung surfactant system. As a peptide-based surfactant analog, Sinapultide is characterized by its amphipathic helical structure, which enables it to interact effectively with phospholipid membranes and facilitate surface tension reduction at the air-liquid interface. Its biochemical design and functional properties have made it a valuable tool in surfactant research, membrane biophysics, and pulmonary biology, where it serves as a model compound for investigating the mechanisms of surfactant action and the role of peptide-lipid interactions in respiratory physiology.
Surfactant research: Sinapultide is widely utilized in studies focused on pulmonary surfactant systems, particularly in elucidating the molecular mechanisms underlying surfactant protein function. Its ability to replicate the surface-active properties of native SP-B makes it an essential reagent for in vitro experiments examining the biophysical behavior of surfactant films, vesicle fusion, and lipid reorganization at the alveolar interface. Researchers employ Sinapultide to dissect the contributions of specific peptide sequences to surfactant efficacy and to model the dynamic processes involved in respiratory gas exchange.
Membrane biophysics: Due to its amphipathic nature, Sinapultide is frequently used in biophysical investigations of peptide-lipid interactions. It serves as a model system for analyzing how synthetic peptides incorporate into and modulate the properties of phospholipid bilayers. Experimental applications include the study of membrane stability, permeability, and fusion events, as well as the impact of peptide structure on lipid phase behavior. Such research advances understanding of fundamental membrane processes and supports the rational design of biomimetic surfactants.
Formulation development: In the context of surfactant formulation, Sinapultide is employed as a functional additive or primary component in the development of synthetic surfactant preparations for laboratory use. Its reproducible activity and defined sequence make it a preferred choice for optimizing surfactant mixtures intended for preclinical evaluation or for benchmarking the performance of novel peptide analogs. By enabling controlled formulation studies, Sinapultide facilitates the assessment of surfactant composition, stability, and spreading characteristics under various experimental conditions.
Analytical assay calibration: Sinapultide is used as a reference standard in analytical assays designed to quantify surfactant protein activity or to standardize surface tension measurements. Its well-characterized behavior in biophysical assays, such as captive bubble surfactometry and Langmuir-Blodgett trough experiments, allows researchers to calibrate instrumentation, validate assay protocols, and ensure reproducibility across different experimental setups. The use of Sinapultide as a calibration standard enhances the reliability of data generated in surfactant research.
Structure-activity relationship studies: The defined primary and secondary structure of Sinapultide makes it an ideal tool for systematic investigations into the relationship between peptide sequence, conformation, and biological activity. Researchers employ site-directed mutagenesis, sequence truncation, or amino acid substitution strategies using Sinapultide as a template to identify critical residues and structural motifs responsible for surfactant function. These studies provide valuable insights into the molecular determinants of surfactant protein activity and inform the design of next-generation peptide-based surfactant analogs for research applications.
KL4, a 21-residue peptide containing repeating KLLLL subunits, represents one of the early synthetic surfactant peptides designed to roughly reflect the overall ratio of cationic to hydrophobic amino acids found in native SP-B (22). Despite an early demonstration of SP-B-like activity and the fact that KL4 is currently under evaluation for FDA approval for clinical use as the peptide component of the synthetic exogenous surfactant Surfaxin (Lucinactant), surprisingly little is known about the specific effects of KL4 on phospholipid interfacial film behavior during compression/expansion and collapse.
KL4 Peptide Induces Reversible Collapse Structures on Multiple Length Scales in Model Lung Surfactant
KL4 ([lysine-(leucine)4]4-lysine) is a synthetic peptide based on SP-B structure and is the major constituent of Surfaxin®, a potential therapeutic agent for respiratory distress syndrome in premature infants. There is, however, no clear understanding about the possible lipid-KL4 interactions behind its function, which is an inevitable knowledge to design improved therapeutic agents. To examine the phase behavior, topography, and lipid specificity of KL4/lipid systems, we aimed to study different surfactant model systems containing KL4, neutral dipalmitoylphosphatidylcholine (DPPC) and/or negatively charged dipalmitoylphosphatidylglycerol (DPPG) in the presence of Ca2+ ions. Surface pressure-area isotherms, fluorescence microscopic images, scanning force microscopy as well as time-of-flight secondary ion mass spectrometry suggest that KL4 is not miscible with DPPC and therefore forms peptide aggregates in DPPC/KL4 mixtures; that KL4 specifically interacts with DPPG via electrostatic interactions and induces percolation of DPPG-rich phases; that existing DPPG-Ca2+ interactions are too strong to be overcome by KL4, the reason why the peptide remains excluded from condensed DPPG domains and passively colocalizes with DPPC in a demixed fluid phase; and that the presence of negatively charged lipid is necessary for the formation of bilayer protrusions. These results indicate that the capability of the peptide to induce the formation of a defined surface-confined reservoir depends on the lipid environment, especially on the presence of anionic lipids.
The Surfactant Peptide KL4 in Lipid Monolayers
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