A method for isolating an allosteric effector of a receptor, by determining the variation of the dissociation kinetics of the complex formed between the receptor and one of its ligands in the presence of the allosteric effector, as compared to the kinetics dissociation, in the absence of the effector, and/or the amplitude of the linkage formed between the receptor and the ligand in the presence of the allosteric effector, as compared to the amplitude in the absence of the effector. The receptor and ligand are being involved in at least one biological response, and the allosteric effector is capable of modulating at least one of the responses. The receptor is marked by at least one fluorescent protein, and the ligand by a molecule capable of absorbing light, or by a fluorescent substance.