Visual inspection of the trajectories can also reveal characteristics of excipient-protein interaction. Qualitatively, compounds with a high PEG content, such as polysorbates or linear compounds with 20 PEG units, have a tendency to wrap around the protein while shorter ethoxylated compounds form localised, hemicellar clusters around a small number of residues (Figure ). Unsurprisingly, of the simulations that showed little to no contact (such as phospholipids), little information can be gleaned from the nature of their interaction from inspecting the arrangement in space. However, in the trajectories containing free arginine as an excipient, there is little evidence of continued, sustained interaction, supporting the notion that its interaction is transient.