Thermodynamic analysis of amines-lasalocid complex formation.

The ionophore lasalocid A selectively transports amines across lipid membranes. Free energy differences of amine-lasalocid complex formation reactions and the activation barriers of the complex transport were calculated by the finite difference thermodynamic integration method. Four catecholamines were treated: serotonin > dopamine > noradrenaline > adrenaline. The concept of transfer selectivity was introduced, combining binding and activation barrier selectivities. The transfer selectivities correlate well with the relative selectivities of the amines under study.