Calcium ion-flux across phosphatidylcholine membranes mediated by ionophore A23187.
The antibiotic A23187 carries Ca2+ across Müller-Rudin membranes made from 1,2-dierucoyl-sn-glycero-3-phosphocholine and n-decane. The conductance of the membranes is not increased by the Ca2+-transport. The flux depends linearly on Ca2+ concentration and ionophore concentration (above pH 6). It increases with increasing pH, approximately by a factor of 4-5 between pH 6 and pH 8. Maximal Ca2+-fluxes of about 10(-10) mol-cm-2-s-1 were found. A counter transport of H+ could not be detected. The complex formation between A23187 and Ca2+ in egg phosphotidylcholine vesicles was studied spectroscopically. The results are consistent with the formation of a 2:1 complex. Optical absorption measurements on single phophatidylcholine membranes were used to calculate the concentration of membrane-bound ionophore A23187.
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D013053:Spectrophotometry
D000900:Anti-Bacterial Agents; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D000001:Calcimycin; D002118:Calcium