Penetratin

Product Name: Penetratin

Sequence One Letter Code: RQIKIWFQNRRMKWKKGG

Sequence Three Letter Code: H-Arg-Gln-Ile-Lys-Ile-Trp-Phe-Gln-Asn-Arg-Arg-Met-Lys-Trp-Lys-Lys-Gly-Gly-OH

Chemical Formula:C108H174N36O22S1

Molecular Weight: 2361

Purity: 95%

Form: Lyophilized

Storage Conditions: - 20 °C

Research Area: Cell Penetrating Peptides

Source / Species: Drosophila

Conjugation: Unconjugated

Code Nacres: NA.26

Application: Penetratin is a widely studied cell-penetrating peptide derived from the first 16 amino acids of the third helix of the Antennapedia homeodomain. As a protein transduction domain, it efficiently traverses cellular and neuronal membranes, facilitating cytosolic delivery of conjugated cargos. Penetratin has been successfully linked to phosphodiester oligonucleotides, peptides, and other biomolecules to enable intracellular gene modulation and functional studies in neuronal systems. Its uptake mechanism involves direct membrane interaction and endocytic pathways, making it a valuable model for investigating translocation processes. This peptide is extensively used in research focused on intracellular delivery strategies, gene regulation, neurobiology, and the development of non-viral platforms for nucleic acid and small-molecule transport.

Current Research: Efficient delivery of biomolecules into living cells remains a central challenge in molecular biology, drug development, and neuroscience research. Large or highly charged molecules—such as peptides, nucleic acids, and proteins—often cannot cross cellular membranes on their own. Over the past several decades, cell-penetrating peptides (CPPs) have emerged as powerful tools to overcome this barrier. Among the earliest and most extensively studied CPPs is Penetratin, a peptide derived from the Antennapedia homeodomain of Drosophila melanogaster. Its robust membrane-translocation ability and compatibility with diverse cargos have made it a widely used platform for intracellular delivery and mechanistic studies of cellular uptake. Origins of Penetratin and Discovery of Cell-Penetrating Peptides Penetratin originates from the first 16 amino acids of the third helix of the Antennapedia homeodomain, a transcription factor involved in developmental patterning in fruit flies. During early investigations into how homeodomain proteins interact with cellular membranes, researchers discovered that this short peptide segment could spontaneously enter living cells and localize within the cytoplasm and nucleus. This unexpected property led to the identification of Penetratin as one of the first protein transduction domains (PTDs)—short peptide sequences capable of transporting themselves and attached molecular cargos across biological membranes. The discovery helped establish the broader class of CPPs, which now includes several widely used delivery peptides such as TAT, transportan, and polyarginine sequences. Structural Features Enabling Membrane Translocation Penetratin is a cationic and amphipathic peptide, meaning it contains positively charged residues along with regions capable of interacting with lipid membranes. These structural features are critical for its ability to associate with negatively charged components of the plasma membrane, such as phospholipid headgroups and glycosaminoglycans. Once bound to the cell surface, Penetratin can cross the membrane through multiple mechanisms. Studies have shown that its uptake may involve direct membrane translocation, where the peptide interacts with lipid bilayers and temporarily destabilizes them to enable entry. In other cases, the peptide is internalized through energy-dependent endocytic pathways, including macropinocytosis and clathrin-mediated endocytosis. The coexistence of these uptake pathways makes Penetratin a useful experimental model for exploring how peptides and macromolecules move across cellular membranes. Delivery of Peptides, Oligonucleotides, and Biomolecules One of the most important applications of Penetratin is its ability to transport conjugated molecules into cells. Researchers have successfully linked Penetratin to a wide variety of cargos, including peptides, proteins, nucleic acids, and small molecules. In particular, Penetratin has been widely used to deliver phosphodiester oligonucleotides, enabling intracellular modulation of gene expression. When conjugated to antisense oligonucleotides or other nucleic acid constructs, the peptide facilitates entry into cells where the nucleic acid cargo can interact with target RNA sequences. Similarly, Penetratin–peptide conjugates allow investigators to introduce functional peptide inhibitors or signaling modulators directly into cells. These tools are especially valuable for studying intracellular pathways that are otherwise difficult to manipulate using traditional extracellular treatments. Applications in Neurobiology Penetratin has gained particular attention in neuroscience research, where efficient intracellular delivery can be challenging due to the specialized structure and sensitivity of neuronal cells. Because the peptide can cross neuronal membranes and access intracellular compartments, it has been used extensively to introduce signaling peptides, inhibitory motifs, and nucleic acids into neurons. In neuronal culture systems and brain slice models, Penetratin-linked cargos have enabled studies of synaptic signaling, receptor trafficking, and gene regulation. Researchers frequently employ Penetratin conjugates to modulate intracellular signaling cascades involved in synaptic plasticity, neuronal survival, and developmental processes. The peptide’s compatibility with delicate neuronal systems makes it a useful tool for investigating the molecular basis of neural communication and plasticity. A Model System for Studying Cellular Uptake Mechanisms Beyond its practical role as a delivery vector, Penetratin is also widely used as a model peptide for studying membrane translocation mechanisms. Understanding how CPPs enter cells remains an active area of research, with implications for drug delivery and therapeutic design. Experimental studies using Penetratin have provided insights into how peptide charge distribution, secondary structure, and lipid interactions influence membrane penetration. Investigations using fluorescence imaging, biophysical assays, and membrane model systems have helped clarify how CPPs interact with lipid bilayers and initiate internalization. These studies contribute to the rational design of improved delivery systems that combine high efficiency with low toxicity. Supporting Development of Non-Viral Delivery Platforms The need for safe and efficient intracellular delivery technologies has become increasingly important in the context of gene editing, RNA therapeutics, and targeted molecular interventions. While viral vectors offer strong delivery capabilities, they also present safety and immunogenicity concerns. Cell-penetrating peptides such as Penetratin provide an alternative strategy. By enabling non-viral transport of nucleic acids and functional biomolecules, CPPs offer a flexible platform for experimental gene regulation and molecular modulation. Ongoing research continues to explore optimized CPP variants, improved conjugation strategies, and hybrid delivery systems that combine CPPs with nanoparticles or liposomes. Insights gained from Penetratin studies have played a foundational role in shaping these approaches. Conclusion Penetratin remains one of the most influential and widely utilized cell-penetrating peptides in modern molecular biology. Derived from the Antennapedia homeodomain, this 16-residue peptide demonstrates remarkable ability to traverse cellular membranes and deliver a wide range of biomolecular cargos into living cells. Its applications span intracellular delivery, gene regulation, neurobiology, and mechanistic studies of membrane translocation. By enabling researchers to introduce otherwise impermeable molecules into cells, Penetratin continues to support advances in understanding cellular signaling, neuronal function, and emerging non-viral delivery technologies.