Staphylococcus aureus protein A is a 42 kDa cell wall constituent characterized by its binding capacity to the Fc portion of immunoglobulins. Protein A resins is commonly used to purify monoclonal antibodies as a robust capture step during Down-Stream Processing.
Traditional residual protein A test are ELISA which can detect the total amount of residual protein A. Detaching buffer is often necessary because the proposed ELISAs are unable to recognize protein linked to the mAb of interest. However, the mentioned buffer may interfere in a sandwich ELISA assay, and it is not proved that the purified monoclonal antibody is completely detached.
Facing the hurdle, SYnAbs has developed the first rat mAb ables to distinguish free protein A from protein A linked to immunoglobulins with a 0,5 ng/ml sensitivity.