Linear free energy relationship (LFER) plots analyzing the correlation between ΔGbinding with calculated cation-π binding energies (CπBE)20 for a range of Y20 (green) and F44 (blue) variants binding peptidomimetic ligands UNC6212 (Kme2), UNC6349 (Ket2), and UNC6864 (Kei) from left to right. Error bars reflect the standard deviation for replicates or the highest individual error from an individual experiment among the replicates, whichever is greater. The error in the slopes is ±0.01 for both Y20 and F44 with UNC6212 (Kme2), ±0.01 for Y20 and ±0.02 for F44 with UNC6349 (Ket2), and ±0.01 for Y20 and ±0.02 for F44 with UNC6864 (Kei).