The competitive equilibrium between aluminium and ferric ions for the binding sites of transferrin

Abstract
Human transferrin is shown to bind 2 mol of aluminium per mol of protein using spectrophotometric titration. Competitive equilibrium between aluminium and ferric ions for transferrin binding sites is observed, and a value of 2.5 (± 0.4) × 1015 M−1 is found for the apparent binding constant under physiological conditions.