Formation constants and molecular modelling studies of metal ion-tetracycline complexes

639-642Formation and proton association constants have been determined using BEST and PKAS programs. Species distributions are plotted using program BEST in order to see the presence of M-tetracycline species in biological fluids. Formation constants and species distribution curves indicate the strong interaction of Ca, Mg, Cu, Ni, Co and Fe with tetracycline and the predominant species at biological pH value is of MHL type. Action of tetracycline is explained on the basis of strong chelation behaviour with Mg. Molecular mechanics calculations show that the chelating sites are 010-011 for Cu-tetracycline complex