The multi-component coordination for the ions is clarified further by plotting the radial distribution function (RDF, also called a pair-pair distribution function) to evaluate close contacts with the ions (Figs. 4, S5-S7). Focusing on the interactions Na + ions make with their surroundings, the peak of the RDF is nearly equally tall between carboxyl and acetyl groups, complementing the contact view from Fig. highlighting the importance of acetyl-ion interactions with a metric that is less biased by the number of atoms involved. Whereas the peak for the carboxyl group is consistently between 3-5, regardless of the acetylation degree, the peak grows substantially for the acetyl groups as the number of acetylations increases.