The Regulation of Free Ca2+ Ion Concentration by Metal Chelators
The importance of maintaining adequate control of the calcium ion concentration in biological experiments is clearly emphasized by the number of studies in this volume alone that utilize various calcium chelators. Furthermore, most physiological mechanisms regulated by Ca2+ are fully activated by the contaminating (10−6 M) levels of this ion present in typical test solutions. Thus, one of the uses of divalent metal chelators or ion-exchange resins is to reduce the activity of this ion to levels below that required to affect regulation. If the chelator used to alleviate the problem of contaminating metal has an apparent affinity for Ca2+ about equal to that of the biological system in question, then it will also serve as a divalent metal buffer, enabling an accurate determination of the Ca2+ dependence of that system. This second use of metal chelators is the topic of this chapter. Two metal chelators are compared, and their temperature, pH, and ionic strength dependencies discussed. Finally, methods for calculating the complex equilibria, along with suggestions for solving these calculations by computer, will be presented.
KeywordsIonic Strength Stability Constant Metal Chelator Apparent Affinity Calcium Chelator
Unable to display preview. Download preview PDF.
- Fabiato, A., and Fabiato, F. 1979. Calculator programs for computing the composition of the solutions containing multiple metals and ligands used for experiments in skinned muscle cells. J. Physiol. (Paris), 75: 463–505.Google Scholar
- Martell, A. E., and Smith, R. M. 1974. Critical Stability Constants, Volumes 1–4. Plenum Press, New York.Google Scholar