were the more complex guests in the SAMPL8 host-guest challenge, with the presence of multi-ring heterocycles at their core (Figure ), and had the largest errors for any host-guest complex in this challenge. At the cores of guests G3, G4, and G7 are nitrogen centers which may function as chiral centers if protonated. In addition, there are some uncertainties on the protonation states for these guests when bound to CB8. It has been shown that protonation state of guests upon binding to cucurbiturils are modulated due to pKa shifts. Specifically, previous work found exceptions to the common assumption that cucurbiturils selectively bind protonated/cationic ammonium-based guests , and perhaps some SAMPL8 guests fit this exception. The majority of participants modeled the protonation states of the guests based on the pKa in solution, however, assuming a substantial pKa shift occurs upon binding, CB8 perhaps binds a different protomer of the guests, perhaps even in all cases. For the GDCC dataset, binding free energy calculations had greater errors for guests G2 and G4 in the presence of the TEMOA host (Figure ). The guests differ modestly in their amphiphilic character compared to other GDCC guests, where guests G2 and G4 contain two polar edges with a hydrophobic center (Figure ). Thus, their interactions with the host and hydrating cavity waters and/or bulk solvent would differ. These characteristics for G2 and G4 would have greater modeling and simulation implications in the presence of TEMOA, where the binding mechanism is believed to involve the guest displacing cavity waters.