ABSTRACT
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To understand the roles of an element we need to know not only the gross amount present, but also the locale and complexes or compounds into which the element enters. The chemistry of aluminum is relatively simple. Its hydroxide is much more soluble than that of Fel+, and it exhibits only one oxidation state in biological systems, All+. Metallic Al is too reactive to be found free in nature, and the metal is won from its ores only with difficulty.1 Thus there is no oxidation-reduction chemistry to Ail+ in biology. (We employ Al(III) as a generic representation of the 3+ ion when a specific form is not indicated.)1
We have argued that in biological systems AJ3+ will be more competitive with Mg2+ than with Ca2+.1.7 In both mineralogy and biology comparable ionic radii frequently outweigh charge in detennining behavior. More AI3+ is accumulated by central nervous system tissue when the Mg2+ concentration is low. 8 Both AJ3+ and Mg2+ favor oxygen donor ligands, especially phosphate groups. 9 AJ3+ is 107 times more effective than Mg2+ in promoting polymerization of tubulin to microtubules.10 In this study the free AJ3+ concentration was controlled near m-•2 M with nitrilotriacetate (NTA). Wherever there is a process involving Mg2+, there exists an opportunity for interference by AI3+.
