Newman E C, Frank C W
J Pharm Sci. 1976 Dec;65(12):1728-32. doi: 10.1002/jps.2600651209.
The study of Ca+2 and Mg+2 complexes of tetracycline in buffered solution was undertaken to determine their stoichiometry and the chelation sites. Circular dichroism was used to follow complex formation. Modified tetracyclines, in which potential complexation sites were blocked, were used to determine the participation of particular sites in complexation. Calcium formed a 2:1 metal-ion to ligand complex, while the magnesium complex formed at a 1:1 ratio. Formation of the calcium complex involved addition of one metal ion to the C-10, C-11 site with subsequent addition of a second metal ion at the C-12, C-1 site. The magnesium chelate occurred at the C-11, C-12 beta-diketone site.
为了确定四环素与Ca+2和Mg+2在缓冲溶液中形成配合物的化学计量比和螯合位点，开展了相关研究。采用圆二色性来跟踪配合物的形成。使用特定潜在络合位点被阻断的改性四环素，以确定特定位点在络合过程中的参与情况。钙形成了金属离子与配体比例为2:1的配合物，而镁配合物以1:1的比例形成。钙配合物的形成过程是先有一个金属离子添加到C-10、C-11位点，随后第二个金属离子添加到C-12、C-1位点。镁螯合物在C-11、C-12β-二酮位点形成。
