(A) Total binding events of 5-HT with 5-HT3A-5mM. (B) Enthalpic contribution to binding energy between 5-HT and the extracellular domain (ECD), where letters correspond to binding orientations on the Right: bpAB (C, ∼ 4.6 μs), bpBC (D, ∼ 4.6 μs), bpCD (E, ∼ 4.6 μs), bpCD (F, ∼ 14.7 μs), and bpDE (G, ∼ 4.6 μs), and monomers colored as follows: A, green; B, purple; C, pink; D, yellow; E, orange.