Fig. (10).
Pathways of alloswitch-1 (A) binding/unbinding to mGlu5 (R). The receptor displays two states: R (inactive) and R* (active). The ligand adopts two photoisomeric states: AT (trans-azo: bioactive state) and AC (cis-azo: inactive photoisomerized state) with addition of light energy (+hv). The mathematical model includes the possibility of photosimorerization from trans- to cis-azo both in solution and in the receptor allosteric pocket. Selection of trans- and cis-azo alloswitch-1 isomers by the inactive and active receptor states are also included in the mathematical formalism (see [47] for discussion on ligand induction and conformational selection functional mechanisms). Obviously, in dark or green light conditions the proportion of cis-azo isomer is negligible both in solution and in the receptor.