What Is Amino-PEG36-CONH-PEG36-acid?

Amino-PEG36-CONH-PEG36-acid is a heterobifunctional polyethylene glycol (PEG) compound composed of two discrete PEG36 blocks joined by a central amide (–CONH–) linkage. One terminus presents a free primary amine (–NH₂) and the other terminus presents a free carboxylic acid (–COOH). This architecture provides two orthogonal reactive handles that can be selectively addressed under mild aqueous conditions.

The total chain spans 72 ethylene glycol repeat units, conferring exceptional hydrophilicity, conformational flexibility, and steric shielding. The internal amide bridge adds a stable, non-cleavable structural element that distinguishes this reagent from simple homo- or heterobifunctional PEGs lacking mid-chain functionality. The compound is catalogued by BroadPharm as BP-24009 and is available from Aladdin Scientific as SKU A596370.

Chemical Properties and Structural Features

The primary amine terminus of Amino-PEG36-CONH-PEG36-acid reacts readily with activated esters (NHS esters), epoxides, isocyanates, and aldehydes (via reductive amination), enabling covalent attachment to carboxylic acid-bearing molecules or surfaces. The carboxylic acid terminus can be activated using standard carbodiimide chemistry (e.g., EDC/NHS) to form amide bonds with amine-containing targets.

The extended PEG backbone (MW approximately 3,500–4,000 Da based on 72 EO units; exact MW should be confirmed from the product certificate of analysis) provides several biophysical benefits: reduced immunogenicity, increased aqueous solubility of hydrophobic payloads, decreased non-specific protein adsorption, and prolonged in vivo circulation half-life of conjugated biomolecules. The central amide bond is stable under physiological conditions (pH 4–9) and is not susceptible to hydrolysis under standard bioconjugation conditions.

Applications in Bioconjugation and PROTAC Research

Bioconjugation and Antibody-Drug Conjugates (ADCs): The amine–acid bifunctionality allows sequential or one-pot conjugation strategies. For example, the amine end can be coupled to a drug payload bearing an activated ester, while the acid end is coupled to a targeting antibody or protein via EDC/NHS chemistry. The long PEG spacer minimizes steric clash between the drug and the antibody binding site and improves ADC pharmacokinetics.

PROTAC Linker Design: PEG-based linkers are widely used in proteolysis-targeting chimera (PROTAC) molecules to bridge an E3 ligase ligand and a target protein ligand. Amino-PEG36-CONH-PEG36-acid provides an exceptionally long, flexible, and water-solubilizing tether suitable for PROTAC candidates requiring extended reach or improved solubility. The amine and acid termini allow straightforward incorporation into PROTAC synthesis via amide bond formation.

Surface Functionalization: The compound can be used to PEGylate nanoparticles, gold surfaces, or solid supports, installing terminal amine or acid groups for further bioorthogonal or affinity ligand attachment.

Handling, Storage, and Solubility Recommendations

Storage: Store Amino-PEG36-CONH-PEG36-acid at –20 °C under dry, inert atmosphere conditions. Protect from moisture and repeated freeze-thaw cycles to prevent hydrolytic degradation of the reactive termini. Confirm specific storage conditions on the product certificate of analysis supplied with each lot.

Solubility: The compound is expected to be freely soluble in water and common polar aprotic solvents such as DMSO and DMF, consistent with high-MW PEG reagents. Aqueous solutions should be prepared fresh and used promptly, particularly when activated derivatives are employed.

Handling Precautions: Use standard laboratory PPE (gloves, eye protection, lab coat). As with all amine-containing PEG reagents, avoid contact with aldehydes or activated electrophiles during storage. Consult the Safety Data Sheet (SDS) before use.

Ordering Information and Related Products

Amino-PEG36-CONH-PEG36-acid is available from Aladdin Scientific under SKU A596370. This product is cross-referenced to BroadPharm catalog number BP-24009. Researchers requiring different PEG chain lengths, alternative functional groups (e.g., azide, maleimide, NHS ester, biotin), or cleavable linker variants are encouraged to contact Aladdin Scientific technical support for guidance on selecting the most appropriate PEG linker for their application.

For bulk quantities or custom PEG synthesis inquiries, please reach out to the Aladdin Scientific sales team. All products are supplied with a certificate of analysis specifying purity, molecular weight confirmation, and batch-specific data.