AEEA-AEEA

This compound carries an amino group and a carboxyl group at both ends, making it an ideal heterobifunctional crosslinker. This design holds irreplaceable value in ADC, PROTAC, and protein labeling.
Advantages of heterobifunctional crosslinking: Compared to homobifunctional crosslinkers (with the same functional groups at both ends), heterobifunctional design allows for stepwise and directed coupling of two different molecules, avoiding the formation of multimers or cyclization products. Specifically for this molecule: First, a carboxyl group (activated via NHS or HATU) can react with a molecule (such as a lysine residue on an antibody) to form an amide bond; then, the amino protection (if pre-protected) is removed, and it reacts with a second molecule (such as a carboxyl group on a drug or fluorescent probe). This sequential coupling allows precise control of 1:1 linkage, with a yield typically higher than 70%.
Typical application scenarios: ① ADC construction: Attach activated carboxyl groups to the surface of antibodies (via lysine or engineered cysteine), and then link amino groups to carboxyl or carbonate groups on drugs (such as MMAE, DM1). AEEA-AEEA serves as a spacer arm, ensuring an appropriate distance between the antibody and the drug. ② PROTAC synthesis: Attach an E3 ubiquitin ligase ligand (such as VHL, CRBN ligands) to the carboxyl end, and attach a target protein ligand to the amino end, forming a PROTAC molecule with a length (approximately 2.5 nm) that precisely promotes the formation of a ternary complex. ③ Surface immobilization: Attach carboxyl groups to the surface of amino-modified magnetic beads or chips, with the amino end used to capture carboxyl-containing biomolecules. ④ Fluorescence labeling: Attach carboxyl groups to antibodies, and link amino groups to the NHS ester of fluorescent dyes (such as FITC, Cy5) to prepare dual-labeled probes.
Comparison with other Linkers: Compared to commercially available heterobifunctional crosslinkers such as Sulfo-SMCC (with NHS ester and maleimide at both ends), the PEG backbone of this molecule provides better water solubility and biocompatibility, avoiding protein aggregation caused by hydrophobic crosslinkers. At the same time, its tunability in length (allowing for the attachment of multiple AEEA units) makes it more advantageous in scenarios where longer spacer arms are required. In summary, the bifunctional design of terminal amino and carboxyl groups achieves high selectivity and high yield sequential coupling, which is the core value of this molecule as a linker.