Potentiometric and spectral investigations of anhydrotetracycline and its metal-ion complexes.

The interaction of various metal ions with anhydrotetracycline was investigated. A comparison of the UV-visible and fluorescence spectral characteristics of anhydrotetracycline and its metal-ion complexes with a number of modified anhydrotetracyclines in the presence of metal ions suggested that the C-11 oxygen was involved in metal-ion binding. Secondary binding was observed in the A-ring by circular dichroism when the primary site was blocked.