Tetraglycine hydrochloride is an oligopeptide salt composed of four glycine residues. Its compact, highly flexible glycine-rich structure makes it useful as a simple peptide linker, spacer, or model compound in peptide synthesis and biochemical research. The hydrochloride form can support handling and formulation in laboratory workflows. Tetraglycine hydrochloride is commonly applied in studies involving peptide bond formation, short-chain oligopeptide behavior, enzymatic processing, and biomolecule modification. It is also valuable for linker design, chemical biology, protein modification, and bioconjugation research requiring a small, neutral, and flexible glycine-based peptide segment.
Product Name: Tetraglycine hydrochloride
Purity: 99%
Sequence: GGGG
Chemical Formula: C8H15ClN4O5
Molar Mass: 282.68
Form: White to off-white Solid
Storage : Sealed storage, away from moisture and light, under nitrogen
CAS.NO.: 38126-71-5
SMILES: C(C(=O)NCC(=O)NCC(=O)NCC(=O)O)N.Cl
INCHIKEY: ZNCPSPZYWSSTLB-UHFFFAOYSA-N
IUPACNAME: 2-[[2-[[2-[(2-aminoacetyl)amino]acetyl]amino]acetyl]amino]acetic acid;hydrochloride
INCHI: InChI=1S/C8H14N4O5.ClH/c9-1-5(13)10-2-6(14)11-3-7(15)12-4-8(16)17;/h1-4,9H2,(H,10,13)(H,11,14)(H,12,15)(H,16,17);1H
Current Research: Overview Tetraglycine hydrochloride is an oligopeptide composed of four glycine monomers. It may also be written as Gly-Gly-Gly-Gly hydrochloride, Gly4 hydrochloride, or tetraglycine HCl. As a simple glycine-based peptide, tetraglycine hydrochloride is widely relevant to peptide chemistry, linker design, biomolecular conjugation, enzymology, and structure-function research. Glycine is the smallest proteinogenic amino acid, containing only a hydrogen atom as its side chain. Because of this minimal structure, glycine residues provide high conformational flexibility and low steric hindrance. A tetraglycine sequence therefore represents a compact, flexible peptide segment that can be incorporated into larger molecular systems as a spacer, linker, or model oligopeptide. In current research, tetraglycine hydrochloride is best understood as a peptide building block rather than a therapeutic agent. Its value comes from its defined four-residue sequence, high flexibility, simple composition, and compatibility with peptide synthesis and bioconjugation workflows. It can be used in studies that require short glycine-rich motifs, model peptide substrates, or flexible spacing between functional groups. Structural Characteristics of Tetraglycine Hydrochloride Tetraglycine hydrochloride consists of four glycine units joined by peptide bonds. The hydrochloride form indicates that the peptide is supplied as an HCl salt, which may influence handling, solubility, and storage characteristics. The sequence can be represented as: Gly-Gly-Gly-Gly or simply: GGGG This sequence has no bulky side chains, no aromatic groups, no sulfur-containing residues, and no ionizable side chains beyond the N-terminal and C-terminal groups. As a result, tetraglycine is structurally simple and highly flexible compared with peptides containing proline, phenylalanine, lysine, arginine, cysteine, or acidic residues. Because glycine lacks a chiral side-chain carbon, glycine residues also allow backbone conformations that are less accessible to many other amino acids. This makes glycine-rich sequences useful in flexible loop regions of proteins and in synthetic peptide linkers where conformational mobility is desired. Role as a Flexible Peptide Spacer One of the most important research uses of tetraglycine hydrochloride is as a flexible peptide spacer. In many molecular designs, two functional components must be connected without creating steric interference. These components may include peptides, proteins, small molecules, fluorescent probes, affinity tags, surfaces, polymers, or drug-like agents. A tetraglycine spacer can separate these components while maintaining a short and minimally bulky connection. The four glycine residues provide flexibility, allowing the attached molecules to move relative to each other. This can be useful when a functional group must remain accessible for binding, enzymatic cleavage, detection, or interaction with a biological target. Compared with longer glycine-serine linkers or PEG-based spacers, tetraglycine is compact and peptide-based. It introduces a defined length and simple composition without adding hydrophobic aromatic groups or charged side chains. This makes it useful in research systems where researchers want to minimize side-chain effects and focus on spacing, flexibility, or backbone behavior. Use in Peptide Synthesis Research Tetraglycine hydrochloride is also relevant to peptide synthesis. Short oligopeptides are often used as model compounds for studying peptide bond formation, purification, analytical characterization, and sequence-dependent behavior. Because tetraglycine contains only glycine residues, it provides a simple system for evaluating peptide synthesis methods without complications from side-chain protecting groups. Researchers can use glycine oligomers to study coupling efficiency, peptide elongation, solubility, chromatographic behavior, and mass spectrometric analysis. In synthetic workflows, tetraglycine motifs may also be incorporated into larger peptides. Glycine-rich segments are commonly used to increase flexibility or reduce steric hindrance between functional domains. Tetraglycine hydrochloride may therefore serve as a starting material, reference compound, or sequence motif in peptide design. Relevance to Bioconjugation and Linker Design Bioconjugation often requires connecting a biomolecule to another functional entity. The connection may involve a peptide, antibody, enzyme, nucleic acid, polymer, nanoparticle, fluorophore, or small-molecule agent. In these systems, the linker can strongly influence the final conjugate’s properties. Tetraglycine hydrochloride can be relevant in bioconjugation because glycine-rich linkers are frequently used to provide flexibility while minimizing steric bulk. A short Gly4 sequence may help improve accessibility between two conjugated components. For example, a tetraglycine segment may separate a detection tag from a peptide epitope, a fluorophore from a recognition motif, or a ligand from a carrier. The absence of reactive side chains can be advantageous. Since glycine has no side-chain functional group, tetraglycine is less likely to introduce unwanted side reactions during modification. Conjugation can instead be directed through the N-terminus, C-terminus, or intentionally introduced reactive groups in a larger construct. Applications in Protein and Peptide Engineering In protein engineering, glycine-rich sequences are often used to connect domains or provide flexible loop regions. A tetraglycine sequence can act as a short flexible connector in recombinant protein constructs, synthetic peptides, and fusion systems. Although tetraglycine is shorter than many commonly used fusion protein linkers, it may be useful when only a minimal spacer is needed. For example, it can provide limited separation between adjacent domains or functional motifs without dramatically increasing molecular size. This may be helpful in constructs where excessive linker length could reduce stability, alter folding, or disrupt activity. In peptide engineering, Gly4 motifs may be used to evaluate how flexibility affects binding, cleavage, or molecular presentation. Researchers may compare tetraglycine with other short spacers, such as diglycine, triglycine, pentaglycine, glycine-serine motifs, or alanine-containing spacers, to determine how linker length and residue composition influence performance. Model Compound in Enzymology and Analytical Studies Tetraglycine hydrochloride can also serve as a simple model oligopeptide in enzymology and analytical chemistry. Because it contains repeated glycine residues, it provides a straightforward substrate-like molecule for studying peptide behavior, hydrolysis, fragmentation, and detection. In enzymology, short peptides are often used to evaluate protease activity, peptide hydrolysis, or substrate recognition. Although tetraglycine does not contain a highly specific protease recognition motif, it may still be useful in general studies of peptide bond cleavage or as a control peptide. In mass spectrometry, glycine oligomers can provide simple fragmentation patterns and well-defined molecular structures. In chromatography, tetraglycine may be used to examine retention behavior of small hydrophilic peptides. In formulation or solubility studies, it may serve as a model compound for understanding how short peptide chains behave under different pH, salt, or solvent conditions. Potential Research Applications Tetraglycine hydrochloride may be used in several areas of current research. In peptide linker design, it can provide a short flexible Gly4 spacer between functional groups. In bioconjugation research, it may be incorporated into peptide-based conjugates to reduce steric hindrance and improve molecular accessibility. In protein engineering, tetraglycine motifs may be used as compact flexible connectors in fusion proteins or engineered peptide constructs. In peptide synthesis, it can serve as a model oligopeptide or glycine-rich building block for method development and analytical comparison. In enzymology, it may be used as a simple peptide substrate, control compound, or model for studying peptide bond hydrolysis. In analytical chemistry, tetraglycine hydrochloride may support method development for HPLC, LC-MS, peptide mapping, and small peptide characterization. Research Considerations Researchers using tetraglycine hydrochloride should consider several experimental factors. First, the hydrochloride salt form may influence solubility, pH behavior, and compatibility with specific buffers or reaction conditions. Buffer selection should be optimized for the intended assay or synthetic workflow. Second, tetraglycine is highly flexible and lacks functional side chains. This is useful for spacing applications, but it also means that the peptide does not provide strong targeting, binding, or recognition properties by itself. Any biological specificity must come from other parts of the molecule or conjugate. Third, linker length should be matched to the application. A Gly4 spacer may be suitable for compact separation, but larger proteins, bulky payloads, or sterically demanding binding events may require a longer linker. Fourth, terminal chemistry matters. Depending on whether the N-terminus or C-terminus is modified, tetraglycine-containing conjugates may show different orientation, charge, and coupling efficiency. Finally, analytical confirmation is important. HPLC, LC-MS, MALDI-TOF MS, NMR, amino acid analysis, and purity testing may be used to confirm identity and quality. For conjugates containing tetraglycine, researchers should also verify coupling efficiency, stability, and functional performance. Future Research Directions Tetraglycine hydrochloride reflects the continuing importance of simple peptide motifs in molecular design. As peptide-based technologies expand, short glycine-rich sequences remain useful for building flexible and modular systems. Future studies may compare tetraglycine with longer glycine oligomers, glycine-serine linkers, PEG spacers, and more rigid peptide linkers. In bioconjugation, tetraglycine motifs may be used to optimize spacing between targeting ligands and payloads. In protein engineering, Gly4 linkers may be evaluated for their effects on folding, activity, expression, and stability. In analytical chemistry, tetraglycine may remain useful as a simple model compound for peptide method development. Because of its simplicity, tetraglycine hydrochloride is unlikely to be limited to one narrow research field. Instead, it offers a versatile glycine-rich peptide framework for many applications requiring flexibility, minimal steric bulk, and defined oligopeptide composition. Conclusion Tetraglycine hydrochloride is an oligopeptide composed of four glycine monomers. Its Gly-Gly-Gly-Gly sequence provides a short, flexible, and structurally simple peptide motif that can be used in peptide chemistry, linker design, bioconjugation, protein engineering, enzymology, and analytical research. As a compact glycine-rich oligopeptide, tetraglycine hydrochloride is especially useful when researchers need a flexible spacer with minimal side-chain interference. It can support the design of peptide conjugates, model peptide systems, and engineered biomolecular constructs. In current research, its value lies in its simplicity, flexibility, and compatibility with a broad range of peptide-based experimental workflows.
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