Product Name: Phe-Arg-Arg-Gly
Sequence: FRRG
Purity: 95%
Storage : Sealed storage, away from moisture
CAS.NO.: 642080-61-3
SMILES: C1=CC=C(C=C1)C[C@@H](C(=O)N[C@@H](CCCN=C(N)N)C(=O)N[C@@H](CCCN=C(N)N)C(=O)NCC(=O)O)N
CHEMICAl FORMULA: C23H38N10O5
IUPACNAME: 2-[[(2S)-2-[[(2S)-2-[[(2S)-2-amino-3-phenylpropanoyl]amino]-5-(diaminomethylideneamino)pentanoyl]amino]-5-(diaminomethylideneamino)pentanoyl]amino]acetic acid
INCHIKEY: RNZLMFKPAJWWPY-ULQDDVLXSA-N
INCHI: InChI=1S/C23H38N10O5/c24-15(12-14-6-2-1-3-7-14)19(36)32-17(9-5-11-30-23(27)28)21(38)33-16(8-4-10-29-22(25)26)20(37)31-13-18(34)35/h1-3,6-7,15-17H,4-5,8-13,24H2,(H,31,37)(H,32,36)(H,33,38)(H,34,35)(H4,25,26,29)(H4,27,28,30)/t15-,16-,17-/m0/s1
Molarmass: 534.61
Application: Phe-Arg-Arg-Gly is a short synthetic polypeptide designed for agent coupling and peptide-based conjugation research. Its defined amino acid sequence provides functional residues that can support attachment, spacing, and biomolecular modification in chemical biology applications. Phe-Arg-Arg-Gly may be used in the preparation of peptide conjugates, targeted delivery systems, and functionalized research molecules where a compact peptide segment is required. This polypeptide is valuable for peptide synthesis, linker design, bioconjugation studies, drug delivery research, and development of agent-coupled molecular platforms for biomedical and pharmaceutical research applications.
Current Research: Overview Phe-Arg-Arg-Gly, also written as FRRG, is a short polypeptide composed of four amino acid residues: phenylalanine, arginine, arginine, and glycine. It can be used for agent coupling, making it relevant to peptide conjugation, linker design, biomolecular modification, and drug delivery research. In current chemical biology and bioconjugation studies, short peptide sequences such as Phe-Arg-Arg-Gly are valuable because they can provide defined structural, chemical, and biological properties within a compact molecular format. Compared with long protein linkers or large polymeric carriers, short peptides are easier to synthesize, modify, purify, and characterize. They can be incorporated into drug conjugates, imaging probes, peptide-drug conjugates, peptide linkers, and other research systems where a functional agent must be connected to a peptide-based component. Phe-Arg-Arg-Gly is especially notable because it contains two arginine residues, giving the sequence a strongly basic character, along with phenylalanine, an aromatic hydrophobic amino acid, and glycine, a flexible residue commonly used in peptide spacers. This combination may make the peptide useful in coupling strategies where charge, flexibility, and compact spacing are important considerations. Structural Features of Phe-Arg-Arg-Gly The biological and chemical behavior of Phe-Arg-Arg-Gly is influenced by its amino acid composition. Phenylalanine is an aromatic amino acid with a hydrophobic benzyl side chain. In peptide conjugates, phenylalanine can contribute to hydrophobic interactions, influence local conformation, and affect binding or recognition by enzymes and biomolecular surfaces. Aromatic residues are often important in molecular recognition because they can participate in hydrophobic packing and π-related interactions. Arginine is a positively charged basic amino acid. Phe-Arg-Arg-Gly contains two arginine residues, which can increase water compatibility and promote interactions with negatively charged molecules, including nucleic acids, acidic proteins, cell-surface components, or anionic biomaterials. Arginine-rich sequences are frequently studied in peptide chemistry because guanidinium groups can participate in strong electrostatic and hydrogen-bonding interactions. Glycine is the smallest amino acid and provides conformational flexibility. Glycine is widely used in peptide spacers and linkers because it introduces minimal steric hindrance. In Phe-Arg-Arg-Gly, the terminal glycine may help improve flexibility when the sequence is attached to another agent or incorporated into a larger conjugate. Together, these residues give FRRG a compact but chemically diverse profile. The peptide contains aromatic, cationic, and flexible structural elements, allowing it to serve as a useful motif in agent coupling and peptide-based conjugate design. Role in Agent Coupling Phe-Arg-Arg-Gly can be used for agent coupling, meaning it may help connect a peptide motif to another molecule or functional agent. The coupled agent may be a small molecule, fluorophore, drug-like compound, imaging probe, biomaterial component, linker, carrier, or targeting unit. Agent coupling is a central technique in medicinal chemistry, peptide chemistry, and biomaterials research. By attaching a functional agent to a peptide, researchers can change the agent’s solubility, localization, recognition profile, stability, or delivery behavior. Peptide-agent conjugates are commonly studied to improve targeting, enhance uptake, support controlled release, or enable detection in biological systems. Phe-Arg-Arg-Gly may be used as a short peptide segment in these conjugates. Its arginine residues can support electrostatic interactions, while its glycine residue can provide a flexible connection point. Depending on the available functional groups and synthetic strategy, the peptide may be modified at the N-terminus, C-terminus, or side chains. Coupling chemistry may involve amide bond formation, activated ester reactions, maleimide-thiol chemistry if additional cysteine is introduced, click chemistry if modified residues are incorporated, or other bioconjugation methods. Use in Peptide-Drug Conjugate Research Peptide-drug conjugates are an active area of research because peptides can help improve the delivery or biological behavior of drug molecules. A peptide sequence may act as a targeting ligand, cell-interaction motif, solubility enhancer, spacer, or enzyme-responsive element. Phe-Arg-Arg-Gly may be considered in this broader research context as a short polypeptide suitable for agent attachment. The inclusion of arginine residues may be useful when designing conjugates that require increased cationic character. Positively charged peptides can interact with negatively charged cell membranes, extracellular matrix components, or nucleic acids. However, cationic character must be optimized carefully. Too much positive charge may increase nonspecific binding, cytotoxicity, aggregation, or rapid clearance. Therefore, Phe-Arg-Arg-Gly should be evaluated experimentally in each conjugate system. The phenylalanine residue may also affect conjugate behavior. Hydrophobic aromatic residues can influence membrane interaction, enzyme recognition, or peptide conformation. In combination with arginine, phenylalanine may help create a sequence with both hydrophobic and cationic properties. This can be useful in some delivery designs, but it may also affect solubility or nonspecific interaction depending on the attached agent. Relevance to Linker and Spacer Design Short peptides are frequently used as linkers or spacers in conjugate chemistry. A linker must provide appropriate distance, flexibility, stability, and chemical compatibility between two molecular components. Phe-Arg-Arg-Gly offers a short peptide framework that may be incorporated into larger linker systems. Unlike neutral glycine-serine linkers, FRRG contains two basic residues and one aromatic residue. This means it may not behave as an inert flexible spacer. Instead, it may contribute charge-mediated interactions or influence biological recognition. This can be advantageous when these properties are desired, but it also means that conjugates containing Phe-Arg-Arg-Gly should be tested for solubility, aggregation, binding specificity, and stability. The terminal glycine residue may help reduce steric hindrance near the coupling site. Glycine-containing peptides are often useful in linker design because they allow the connected agent greater conformational freedom. This may improve access to binding sites, enzymes, or target surfaces. Applications in Current Research Phe-Arg-Arg-Gly may be useful in several research areas involving peptide conjugation and agent coupling. In peptide-drug conjugate design, it can be used as a short peptide motif for attaching small-molecule agents to peptide-based carriers or targeting elements. In imaging probe development, Phe-Arg-Arg-Gly may be coupled to fluorescent dyes, radiolabeling groups, or other detection agents for biochemical studies. In bioconjugation research, the peptide can serve as a defined sequence for studying coupling efficiency, conjugate stability, and structure-property relationships. In delivery system development, its cationic arginine residues may support interaction with negatively charged biological surfaces or materials. In linker optimization, Phe-Arg-Arg-Gly may be compared with other short peptide motifs to evaluate how aromatic, basic, and flexible residues influence conjugate behavior. In biomaterials research, FRRG-containing conjugates may be studied for surface functionalization, peptide-mediated attachment, or interaction with charged matrices. Research Considerations Researchers using Phe-Arg-Arg-Gly for agent coupling should consider several factors. First, the coupling site should be carefully selected. The N-terminus, C-terminus, or side-chain groups may be used depending on the desired orientation and conjugate design. Uncontrolled coupling may generate heterogeneous products, especially if multiple reactive groups are present. Second, charge effects should be evaluated. The two arginine residues give the peptide a strongly basic character. This may improve aqueous solubility, but it may also increase nonspecific interactions with negatively charged biomolecules. Assays should distinguish specific activity from charge-driven binding. Third, solubility should be tested after coupling. While the peptide itself contains hydrophilic arginine residues, the attached agent may be hydrophobic. The final conjugate may require buffer optimization, salt adjustment, pH control, or solubilizing groups. Fourth, stability must be assessed. Short peptides may be susceptible to enzymatic degradation depending on the biological environment. If the conjugate is intended for cell-based or in vivo studies, protease stability should be evaluated. Fifth, analytical characterization is essential. HPLC, LC-MS, MALDI-TOF MS, NMR, amino acid analysis, and purity testing may be used to confirm successful coupling and product identity. For biological studies, additional assays may include cell uptake, binding, cytotoxicity, serum stability, and functional activity tests. Future Research Directions As peptide-based conjugation technologies continue to expand, short motifs such as Phe-Arg-Arg-Gly may be increasingly useful in modular molecular design. Researchers are exploring peptide sequences not only as passive linkers but also as functional elements that influence targeting, uptake, solubility, and release behavior. Future studies may examine how FRRG-containing conjugates compare with other arginine-rich or glycine-containing peptides. Researchers may also investigate how modifying the termini, adding spacers, replacing residues, or incorporating non-natural amino acids affects coupling efficiency and biological performance. Phe-Arg-Arg-Gly may also be explored in combination with cleavable linkers, polymer carriers, nanoparticles, imaging groups, or drug payloads. Its compact sequence makes it adaptable for many synthetic designs, while its basic and aromatic residues provide functional diversity. Conclusion Phe-Arg-Arg-Gly is a short polypeptide that can be used for agent coupling in peptide conjugation and bioconjugation research. Its sequence combines phenylalanine, two arginine residues, and glycine, giving it aromatic, cationic, and flexible structural features. In current research, Phe-Arg-Arg-Gly may be useful for peptide-drug conjugates, imaging probes, linker design, biomaterial functionalization, and molecular delivery systems. Its arginine-rich character may support interactions with negatively charged biological components, while its glycine residue can provide flexibility at the coupling interface. As peptide-based molecular engineering continues to grow, Phe-Arg-Arg-Gly offers a compact and functional sequence for developing agent-coupled conjugates and studying how short peptide motifs influence conjugate behavior, stability, and biological performance.
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