Tetracyclines metal-binding properties

Xanthate-modified cellulose binds metal-TC tetracycline complexes and is evaluated to be an effective controlled release system for TCs complexes, owing to the metal-binding properties of these antibiotics. ... 

The tetracyclines are well known for their ability to form complexes with polyvalent cations. This property changes their solubility characteristics in the mobile solvents and often results in troublesome streaking. To overcome this difficulty, Selzer and Wright used paper dipped in Mcllvaine s buffer (pH 3.5) which contains citrate ions capable of binding the metallic ions. The chromatograms were developed with a mixture of nitromethane, chloroform, and pyridine (20 10 3) on paper still damp from the treatment with the buffer solution. 

Evidence from fluorescence, absorption, and c.d. spectra suggests that the conformations of various tetracycline antibiotics in complexes with Ca + are different from those in the magnesium complexes. The optical properties of the catalytically active cobalt(n) form of liver alcohol dehydrogenase, which normally requires zinc for activity, indicate an unusual binding environment for the metal (c/. the implications of the absorption and c.d. spectra of the cobalt proteases, which have recently been discussed ). 

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