where n i is the number of contacts between the peptides and the polymers in conformational cluster i in its local environment (core or core-shell interface); n total is the total number of contacts between the peptides and all polymers in the local environment. N i is the number of polymers in conformational cluster i that are found in the local environment and N environment is the total number of polymers in the local environment. The fractional enrichment of polymer conformations quantifies the tendency of EEK to interact with a specific polymer cluster, taking into account the abundance of that polymer in the region of the NP where the EEK molecule is located. EEK peptides at the core-shell interface do not preferentially interact with a specific polymer conformation (Fig. (a)), however Figure (b) shows that there is a specific polymer environment that EEK peptides preferentially interact with in the hydrophobic core (cluster 4). EEK molecules found in both locations reside at an interface with water, interacting with the polymers at the point where the LA/GA and EO blocks join. Figures S9 & S10 show the normalized contact maps for peptides in the core and at the surface of the core of the NP respectively. Peptides in both locations interact more with the EO block. Figure shows that peptides within the core of the NP primarily interact with the final monomers of the GA block and first few monomers of the EO block of cluster 4 polymers. While interacting with EO, EEK is also in close proximity to the hydrophobic PLGA block, reflecting EEK's amphiphilicity. The polymers in cluster 4 are found near the trapped water interface: its extended EO block shields the more hydrophobic polymer blocks from water encapsulated in the NP core. Conversely, EEK at the core-corona interface generally interacts with the EO monomers of cluster 3 polymers and has very few contacts with the hydrophobic monomers, as shown in Figure .