Perhaps the most interesting feature of Fig. , as well as the RDFs for the other systems under study (Figs. ) is the inherent structure to the RDF. Normally, subsequent peaks in an RDF are an indicator of a second or third shell of somewhat weaker interactions that are induced by longer-range structures. However, the secondary peaks in the acetyl group RDFs result from the internal structure of an acetyl group (Fig. ). The primary peak is largely driven by the carbonyl-like oxygen that has both a relatively large partial negative charge and is very accessible to a cation. The second peak in the acetyl RDF comes from the ester carbon, and the third is a combination of the remaining oxygen and methyl carbons (Fig. ). In this way, the acetyl groups can cooperatively coordinate cations, even if the additional carbons and methyl groups contribute to molecular hydrophobicity. : Dwell time analysis of cation interactions with carboxyl groups in 'expanded' and 'constant' systems at each acetylation degree. The interaction dwell time measures how long a specific ion remained bound to a specific between cations and carboxyl groups are depicted, showing the dwell time duration against the proportion of interactions exhibiting this behavior. Quantifications were performed at each acetylation degree within the following systems: (A) expanded system neutralized by Na + ions, (B) constant system neutralized by Na + ions, (C) expanded system neutralized by Fe 3+ ions, and (D) constant system neutralized by Fe 3+ ions.