(349c) Study of the Orientation of Mabs at the Air/Water Interface

Protein unfolding on hydrophobic surfaces has been reported – particularly for globular ones. Here, we report a different class of proteins that has a confined Y shaped structure, known as monoclonal antibodies (mAbs). mAb adsorption at air/water interfaces is one of the major problems for therapeutic formulations in the pharmaceutical industry. Their molecular structure being different than the globular ones provide a contrast in their adsorption behavior. This has been studied using X-ray reflectivity combined with computational simulations where mAb adsorption as a function of concentration will be discussed. A dynamic orientational change was observed in the adsorbed antibody, where at early times mAbs adsorb in a “flat-on” states, but, with continued adsorption, the mAbs reorient to “side-on” configuration. This change that maintains the configurational structure is a consequence of their rigid “Y” shape due to the presence of the cystine bonds. This is in contrast to the globular proteins that gradually unfolds at the interface and do not maintain their native structure.