CALCIUM IONOPHORE, A23187 AND ITS AMINO-ACID COMPLEXES - SPECTROSCOPIC AND MOLECULAR MODELING STUDIES

The circular dichroism, fluorescence, Nuclear Magnetic Resonance and B LM conductance studies indicate that A23187 forms a stable complex wit h amino acids at low ionophore concentrations (<10(-4)M). However, A23 187 prefers to be in a dimeric structure with no significant binding t o amino acids, at concentrations higher than 10(-4)M. It was also obse rved that at lower concentrations, at which the amino acids bind to th e ionophore, the affinity for calcium ions was several orders of magni tude lower than that at higher ionophore concentrations. We have also conducted molecular modeling studies to examine the structure of the A 23187 dimer and its amino acid complexes. The results of these modelin g studies strongly support our experimental results and validate the f ormation of a hydrogen bonded and energetically stable A23187 dimer an d its amino acid complexes.