For therapies that rely on internalization (such as ADCs or in vivo CAR-T delivery via LNPs), verifying that the target is being taken up by the cell is vital. ACRO offers a pH-sensitive anti-G4S linker labeling reagent specifically for endocytosis assays. This technology allows researchers to distinguish between CARs on the cell surface and those that have been successfully internalized, which is a key parameter for therapeutic efficacy.

Developing specific anti-idiotype antibodies for every new CAR-T or scFv construct is time-consuming and expensive. Since the G4S motif is a standard structural component in many of these therapies, an anti-G4S linker antibody allows researchers to detect and quantify the expression of virtually any scFv-based construct. This "universal" approach is essential for early-stage screening where multiple constructs are being compared simultaneously.

Linker length is a critical factor in controlling scFv stability and the noncovalent association between the VH and VL domains. A shorter linker may restrict domain movement or lead to the formation of "diabodies," while a longer linker generally increases flexibility. Researchers must carefully optimize this length to ensure maximum antigen-binding affinity and to prevent aggregation of the therapeutic construct.

The poly-Glycine-Serine (G4S) linker is a flexible, unstructured synthetic peptide sequence (Gly-Gly-Gly-Gly-Ser) often repeated in 15-mer or 20-mer lengths. Its primary role is to connect the variable heavy (VH) and variable light (VL) domains of single-chain variable fragments (scFvs). Because it is composed of small, non-polar glycine and polar serine residues, it provides high flexibility and solubility, allowing the connected protein domains to move and fold independently while maintaining their antigen-binding activity.

Selected human ADAM9 ectodomain proteins have been evaluated for antibody binding by ELISA or SPR and for catalytic activity using a fluorogenic peptide substrate. Selected ADAM9 proteins have also been characterized by SDS-PAGE, SEC-HPLC, or SEC-MALS, depending on the product. These data apply to the specified protein and assay conditions and should not be generalized across the entire ADAM9 portfolio.

The current ACROBiosystems portfolio includes recombinant ADAM9 proteins from human, cynomolgus, mouse, and rat. Unconjugated and biotinylated formats are available for selected species to support comparative antibody-binding studies. Equivalent construct boundaries and tag formats should be used where possible so that observed differences are more likely to reflect species-dependent binding rather than assay configuration.

Biotinylated His/AviTag™ ADAM9 supports streptavidin-based capture, making it suitable for immobilization in ELISA, SPR, or BLI assays. Unconjugated His-tagged ADAM9 is appropriate for direct coating, solution-phase analysis, or alternative capture strategies. ACROBiosystems provides both formats, allowing the protein configuration to be matched to the planned assay design.

The aa 206–697 construct covers a broader portion of the ADAM9 ectodomain, including the metalloprotease domain and additional extracellular regions. The aa 206–413 construct focuses on the metalloprotease region and is more directly aligned with catalytic-domain binding or inhibition studies. Both formats are available within the current ACROBiosystems human ADAM9 protein portfolio.