a, Analytical size exclusion chromatography and crystal image of the CB1–AM11542 complex. Scale bar, 70 µm. b, Analytical size exclusion chromatography and crystal image of the CB1–AM841 complex. Scale bar, 70 µm. c, The overall structures of CB1–AM11542 and CB1–AM841 complexes and crystal packing of CB1–AM11542; receptor is in orange (AM11542)/green (AM841) colour and the flavodoxin fusion protein is in purple-blue colour. The agonists AM11542 (yellow) and AM841 (pink) are shown in sticks representation. The four single mutations T2103.46A, E2735.37K, T2835.47V and R3406.32E are shown as green spheres in the CB1–AM11542 structure.