DBCO-Insulin B (9-23)

The DBCO-PEG4-Insulin B (9‑23) peptide is a chemically modified version of the well-characterized Insulin B (9‑23) autoantigenic peptide. The N-terminal DBCO-PEG4 modification renders this peptide ready for strain-promoted alkyne-azide cycloaddition (SPAAC) click chemistry, enabling efficient, copper-free conjugation with azide-functionalized molecules. This modification is ideal for researchers aiming to generate fluorescently labeled peptides, bioconjugates, or nanoparticle-functionalized constructs while preserving the core antigenic properties of the Insulin B (9‑23) peptide.

The Insulin B (9-23) peptide is a fragment derived from the B-chain of insulin, encompassing amino acids 9 through 23. This peptide is widely recognized as a major autoantigenic epitope in autoimmune diabetes (Type 1 diabetes, T1D), both in the standard laboratory model the NOD mouse and in human patients. In genetically susceptible individuals (or mice), presentation of this peptide on MHC class II molecules (in mice, MHC II allele I-A^g7) can trigger autoreactive CD4⁺ T cells that mediate immune attack on pancreatic beta cells, leading to insulitis and eventual beta-cell destruction. The peptide contains multiple residues critical for MHC–peptide–TCR interactions; certain “registers” (i.e., peptide alignments in the MHC binding groove) strongly influence immunogenicity.

Functional Roles & Applications

1. Downstream Click Chemistry Conjugation:

• The DBCO group reacts specifically with azide-functionalized probes, such as:

  • Fluorescent dyes (e.g., Alexa Fluor-azide, FAM-azide, Cy5-azide) for imaging T-cell recognition or peptide trafficking.

  • Lipid nanoparticles (LNPs) or polymer carriers functionalized with azide groups for targeted delivery.

  • PEGylated molecules to improve solubility or in vivo stability.

• Copper-free SPAAC avoids cytotoxicity associated with traditional Cu(I)-catalyzed click reactions, making it suitable for live-cell or in vivo applications.

2. Immunological Studies:

• After conjugation, the Insulin B (9‑23) peptide retains its autoantigenic properties, allowing researchers to study T-cell activation, antigen-specific proliferation, or tolerance induction in type 1 diabetes models.

3. Versatile Bioconjugation:

• Enables multifunctional constructs, such as fluorescent peptide-LNP conjugates, for high-throughput screening, imaging, or therapeutic delivery.

Advantages

• Site-specific labeling: N-terminal DBCO allows controlled conjugation without modifying critical residues in the peptide core.

• Enhanced flexibility: PEG4 linker reduces steric interference during click reaction.

• Biocompatible conjugation: Copper-free reaction preserves peptide integrity and biological activity.

• Wide applicability: Suitable for labeling, drug delivery, imaging, and mechanistic studies in autoimmunity research.

Recommended References

• Baskin et al., 2007. Copper-free click chemistry for biomolecular labeling. PNAS, 104(43), 16793–16797.

• Jewett & Bertozzi, 2010. Cu-free click cycloaddition for in vivo bioconjugation. Chem. Soc. Rev., 39, 1272–1279.

• Insulin B (9-23) studies in NOD mice: Anderson & Bluestone, 2005. Nat Rev Immunol, 5, 343–353.