Objectives of this proposal aim to shed light on how adsorption processes such as protein A chromatography, used to purify biologics, affect protein propensity for aggregation. Protein A chromatography has been found to increase the aggregation rate of an IgG-4 subsequently exposed to low pH. Loading a low concentration of IgG onto the resin increased aggregation rates further. Using neutron reflectivity, we wish to study the conformation of IgG-4 when adsorbed to immobilised protein A. We wish to examine whether the conformation or orientation of the adsorbed molecules is affected by either the density of immobilised ligands, or the concentration of protein bound. It is hypothesised that intermolecular forces and rotational freedom affect the structural integrity of the adsorbed proteins, and their orientation in relation to the adsorbent surface, thus influencing aggregation phenomena.