Biological coupling with engineered unnatural amino acids

In addition to thiomonoclonal antibody technology, the addition of non-standard amino acids (NCAA) provides another possibility for site-specific coupling. The technology uses amino acids with unique chemical structure, which can introduce linker payload complexes in a chemically selective manner. This technique requires the recombination of antibody sequences, using tRNA and aminoacyl tRNA synthetase (AARS) orthogonal to all endogenous tRNAs and synthetases in the host cell to bring NCAA into the protein in response to unassigned codons. Generally, NCAA is added to the medium during fermentation. The selection of unnatural amino acids is important because they may stimulate immunogenicity. The commonly used NCAA is an analog of natural amino acids with unique groups, such as ketones, azides, cyclopropenes or dienes.