Binding of carboxylate and trimethylammonium salts to octa-acid and TEMOA deep-cavity cavitands

In participation of the fifth statistical assessment of modeling of proteins and ligands (SAMPL5), the strength of association of six guests (3-8) to two hosts (1 and 2) were measured by H-1 NMR and ITC. Each host possessed a unique and well-defined binding pocket, whilst the wide array of amphiphilic guests possessed binding moieties that included: a terminal alkyne, nitro-arene, alkyl halide and cyano-arene groups. Solubilizing head groups for the guests included both positively charged trimethylammonium and negatively charged carboxylate functionality. Measured association constants (K (a) ) covered five orders of magnitude, ranging from 56 M-1 for guest 6 binding with host 2 up to 7.43 x 10(6) M-1 for guest 6 binding to host 1.