Product Name: 2× ST-tag II
Sequence: Trp-Ser-His-Pro-Gln-Phe-Glu-Lys-Trp-Ser-His-Pro-Gln-Phe-Glu-Lys
Purity: 95%
Storage : Sealed storage, away from moisture
CAS.NO.: 2771233-98-6
Chemical Formula: C100H132N26O25
Molar Mass: 2098.28
Application: 2× ST-tag II is an oligopeptide tag designed to link proteins and double-stranded DNA molecules in an efficient, rapid, and specific manner. As a peptide ligand of ST Tactin (STN), 2× ST-tag II specifically binds to ST Tactin, enabling stable and selective biomolecular assembly. This peptide is useful for constructing DNA–protein hybrids, supporting applications that require precise protein capture, immobilization, and molecular conjugation. 2× ST-tag II is widely used in chemical biology, protein engineering, synthetic biology, bioconjugation research, and DNA–protein hybrid system development for analytical, diagnostic, and molecular assembly studies.
Current Research: Overview 2× ST-tag II is an oligopeptide tag that can link proteins and double-stranded DNA (dsDNA) molecules in an efficient, rapid, and specific manner. It functions as a peptide ligand of ST-Tactin, also known as STN, and specifically binds to ST-Tactin. Because of this selective interaction, 2× ST-tag II can be used to construct DNA–protein hybrids, a class of biomolecular assemblies that combine the programmability of DNA with the functional diversity of proteins. DNA–protein hybrids are increasingly important in chemical biology, synthetic biology, molecular diagnostics, biosensing, nanotechnology, and targeted biomolecular engineering. DNA offers predictable base pairing, programmable sequence design, and structural organization. Proteins provide catalytic activity, molecular recognition, signaling, binding specificity, and biological function. By connecting proteins with dsDNA in a controlled way, researchers can create hybrid systems that are difficult to achieve using either biomolecule alone. 2× ST-tag II is especially useful because it supports affinity-based assembly rather than random chemical crosslinking. In many protein–DNA conjugation strategies, nonspecific modification can damage protein activity, alter folding, or generate heterogeneous products. The specific binding between 2× ST-tag II and ST-Tactin offers a more controlled strategy for linking proteins and dsDNA molecules. Structural and Functional Features of 2× ST-tag II The designation 2× ST-tag II indicates that the peptide contains two ST-tag II recognition motifs. This duplicated structure can improve binding performance through avidity effects. In affinity systems, multivalent or repeated binding motifs may enhance complex stability, reduce dissociation, and improve retention during washing, separation, imaging, or analytical workflows. As a peptide ligand, 2× ST-tag II is designed to bind specifically to ST-Tactin. ST-Tactin is an engineered protein partner that recognizes ST-tag-type peptide sequences. This peptide–protein interaction provides the basis for selective assembly. When 2× ST-tag II is attached to or incorporated into a biomolecular component, it can bind ST-Tactin-modified partners and help form defined molecular complexes. The small size of peptide tags is an important advantage. Large fusion partners can interfere with protein folding, solubility, activity, or expression. Short peptide tags are generally easier to incorporate into recombinant proteins or synthetic conjugates. 2× ST-tag II provides a compact recognition element that can be used in molecular assembly while minimizing unnecessary structural burden. Specific Binding to ST-Tactin The defining feature of 2× ST-tag II is its specific binding to ST-Tactin/STN. This interaction enables selective linkage between tagged proteins, DNA-linked ST-Tactin components, or other engineered biomolecular modules. Specificity is critical in DNA–protein hybrid construction. If a protein is randomly attached to dsDNA, the resulting conjugate may contain variable numbers of proteins, inconsistent orientation, and unpredictable activity. In contrast, a tag-based recognition system can support more uniform assembly. The 2× ST-tag II/ST-Tactin pair allows researchers to design systems in which the protein and DNA components interact through a defined affinity interface. This approach can also help preserve protein function. Random crosslinking often targets accessible lysine, cysteine, carboxyl, or other reactive groups, which may be located near active sites or binding domains. By using a specific peptide tag, researchers can reduce unwanted modification of functional protein surfaces and improve reproducibility. Construction of DNA–Protein Hybrids 2× ST-tag II can be used to construct DNA–protein hybrids, which are engineered assemblies containing both nucleic acid and protein components. These hybrids are useful because DNA and proteins offer complementary capabilities. DNA can be programmed to form duplexes, hairpins, aptamer structures, DNA origami, or larger nanostructures. Proteins can add biological functions such as enzymatic catalysis, receptor binding, antigen recognition, fluorescence, molecular transport, or signal amplification. When these components are linked efficiently and specifically, researchers can build functional hybrid materials for advanced biological research. In a typical conceptual design, one part of the system may contain or present 2× ST-tag II, while another part contains ST-Tactin associated with dsDNA or a DNA-based structure. The interaction between the tag and ST-Tactin links the protein and DNA modules. This strategy can be applied to both simple DNA–protein conjugates and more complex DNA nanostructures decorated with proteins. Advantages in DNA–Protein Linkage 2× ST-tag II offers several advantages for protein–dsDNA linkage. First, it supports efficient assembly. Affinity-based peptide recognition can occur under mild aqueous conditions and may be faster than multi-step covalent conjugation workflows. Second, it enables specific binding. The interaction with ST-Tactin provides selectivity, reducing nonspecific association and improving control over hybrid formation. Third, it supports modular design. Once the 2× ST-tag II/ST-Tactin system is established, different proteins or DNA constructs can be exchanged while using the same recognition pair. Fourth, it can improve orientation control. If the peptide tag is placed at a defined protein terminus or engineered site, the protein can be displayed in a more predictable orientation relative to the DNA component. Fifth, it may help preserve protein activity. Because assembly can occur through the peptide tag instead of random surface modification, active sites and binding regions may be less likely to be disrupted. Relevance to Protein Engineering 2× ST-tag II is relevant to protein engineering because peptide tags are widely used to control protein purification, immobilization, detection, and assembly. A short affinity tag can be genetically encoded into a recombinant protein or chemically incorporated into a peptide or conjugate. When paired with its binding partner, the tag enables selective capture or organization of the protein. For DNA–protein hybrid research, tag placement is an important design consideration. A 2× ST-tag II sequence may be placed at the N-terminus, C-terminus, or another accessible region of a protein. The best position depends on the protein structure, folding requirements, and intended hybrid architecture. If the tag is buried or sterically blocked, ST-Tactin binding may be reduced. If the tag is placed near a functional domain, it may influence activity. Therefore, tag location should be experimentally optimized. 2× ST-tag II may also be useful for assembling multicomponent systems. For example, researchers may use DNA scaffolds to organize multiple proteins in defined spatial arrangements. This can support studies of enzyme cascades, signaling complexes, synthetic pathways, or nanoscale biomolecular organization. Applications in Current Research 2× ST-tag II can be used in several research areas related to biomolecular assembly and bioconjugation. In DNA–protein hybrid construction, it can link proteins and dsDNA molecules through a specific ST-Tactin-binding interaction. In DNA nanotechnology, it may support the placement of proteins on DNA origami, DNA tiles, DNA scaffolds, or programmable nucleic acid structures. In biosensor development, DNA–protein hybrids can combine DNA-based recognition or amplification with protein-based signal generation, such as enzymes, antibodies, or fluorescent proteins. In synthetic biology, 2× ST-tag II can help build modular systems that combine genetic, enzymatic, and regulatory components. In protein immobilization, the tag can support attachment of proteins to ST-Tactin-presenting surfaces, beads, particles, or DNA-linked platforms. In bioconjugation research, 2× ST-tag II provides an affinity-based alternative to nonspecific covalent crosslinking, allowing more controlled construction of hybrid biomolecules. Research Considerations Researchers using 2× ST-tag II should consider several experimental factors. The first is tag accessibility. Efficient ST-Tactin binding requires that the 2× ST-tag II motif be exposed and not hidden by protein folding, DNA structure, surface immobilization, or steric crowding. The second is ST-Tactin presentation. ST-Tactin must be available in a configuration that allows productive interaction with the peptide tag. If ST-Tactin is attached to dsDNA, a surface, or a nanoparticle, its orientation and spacing can influence binding efficiency. The third is binding stability. Although 2× ST-tag II is designed for specific binding, the stability of the final DNA–protein hybrid should be tested under the intended experimental conditions, including buffer composition, salt concentration, temperature, washing steps, dilution, nuclease exposure, and assay duration. The fourth is stoichiometry. DNA–protein hybrid performance can depend on the ratio of protein to dsDNA. Controlled assembly may require optimization of reaction concentrations, incubation time, and purification strategy. The fifth is functional validation. Formation of a DNA–protein hybrid does not automatically guarantee that the protein remains active or that the DNA remains structurally intact. Researchers should confirm both hybrid formation and biological function. Analytical methods may include native gel electrophoresis, EMSA, fluorescence assays, pull-down assays, surface plasmon resonance, biolayer interferometry, size-exclusion chromatography, atomic force microscopy, electron microscopy, or mass spectrometry. Future Research Directions The ability to connect proteins and dsDNA molecules efficiently and specifically is increasingly important as molecular engineering becomes more programmable. DNA nanotechnology provides precise spatial control, while proteins contribute biochemical and biological functionality. 2× ST-tag II helps bridge these two molecular systems through a compact peptide–protein recognition pair. Future research may explore improved DNA–protein hybrid platforms for diagnostics, nanoscale enzyme organization, programmable therapeutics, biomaterials, and synthetic cell-like systems. Researchers may also compare 2× ST-tag II/ST-Tactin assembly with other conjugation technologies, including biotin–streptavidin, SpyTag/SpyCatcher, HaloTag, SNAP-tag, click chemistry, and maleimide-thiol coupling. As DNA–protein hybrid systems become more sophisticated, small peptide tags such as 2× ST-tag II may help simplify assembly, improve reproducibility, and reduce the need for harsh chemical modification. Its specificity for ST-Tactin makes it a useful tool for designing modular biomolecular architectures. Conclusion 2× ST-tag II is an oligopeptide that can link proteins and dsDNA molecules in an efficient, rapid, and specific manner. It acts as a peptide ligand of ST-Tactin/STN and specifically binds to ST-Tactin. This binding interaction enables the construction of DNA–protein hybrids, which are valuable tools in chemical biology, DNA nanotechnology, biosensing, synthetic biology, and biomolecular engineering. By providing a compact and specific affinity tag, 2× ST-tag II supports controlled protein–DNA assembly while reducing the limitations of nonspecific crosslinking. Its role in DNA–protein hybrid construction makes it a useful reagent for researchers developing programmable biomolecular systems that combine the structural precision of dsDNA with the functional diversity of proteins.
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