Conformations of regulatory peptides interacting with artificial lipid membranes were compared with those of chemically constrained molecules that react selectively with different receptor classes. Striking similarities in the topochemistry of molecules with similar activity were observed. The membrane-induced topomers were almost congruent with the artificial topomers that are selectively recognized by the same receptors. Finally, the ideas developed in the membrane compartments theory which allow a quantitative prediction of receptor preference are compatible with our present knowledge of receptor structure.