The shielding of APRs from solvent by excipient molecules is a key mechanism in the prevention of aggregation and increase in stability of biotherapeutic protein formulations; this can be quantied in an MD model by the extent that the SASA of APRs reduces. HSA without any excipients was found to have a SASA of 271.7 nm 2 ; within that, its APRs have an average SASA of 50.5 nm 2 Polysorbate compounds have the greatest impact on the SASA of APRs (Figure ), and are all statistically signicant from the HSA-only control, according to Kruskal-Wallis and Dunn tests. PSBN, the strongest performer, is signicantly dierent to Brij L2 (p < 0.05), Brij O2 (p < 0.05), and PS85 (p < 0.01). PS80 is signicantly dierent to Brij O2 (p < 0.05), which is somewhat surprising, given that they contain the same aliphatic chain content (a single oleate). Linear ethoxylated compounds were not signicantly dierent from one another, with the exception of Brij O2, which was dierent to every other linear ethoxylated compound. (p < 0.05). The only ethoxylated compounds to not be signicantly dierent from the control were Brij O2, Brij L2, and Span 85. Span 80 was signicantly dierent to the control, but no dierence was found between it and any polysorbate compound. None of the other compounds under study were found to have an impact on the SASA of the APRs of HSA that was signicantly dierent from the control.