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Updated: Jul 14, 2026
Determining the Thermodynamic and Kinetic Association of a DNA Aptamer and Tetracycline Using Isothermal Titration Calorimetry
Published on: August 23, 2022
Ca2+ and Mg2+ bind tetracycline with distinct stoichiometries and linked deprotonation
Lihua Jin1, Xylenia Amaya-Mazo, Matthew E Apel
1Department of Chemistry, DePaul University, Chicago, IL 60614, USA. ljin1@depaul.edu
Abstract:
Tetracycline depends on divalent metal ions for its biological function, but its multiple ionization states, conformations, and tautomers at varying solution conditions complicate its ion-binding equilibria, and the stoichiometry of the biologically relevant Ca2+ or Mg2+ complexes has not been clear. Isothermal titration calorimetry was used in the present work to study Ca2+ and Mg2+ binding to tetracycline. The two metal ions bind with distinct stoichiometries, one Ca2+ per tetracycline and one Mg2+ per two tetracyclines, and with differing dependence on solution conditions, indicating that these two ions bind TC differently. An endothermic process accompanies ion binding that is proposed to reflect conformational changes in tetracycline. The results identify conditions that limit the distribution of species and may facilitate structural study.
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