THE AFFINITY OF PHOSVITIN FOR ALUMINUM MEASURED WITH THE DYE, CHROME AZUROL-S

A dye, chrome azurol S, has been used to estimate free Al3+ in aqueous solution at pH 5.0. The apparent dissociation constant, K-D, of the d ye for Al3+ is 1.04 +/- 0.13 X 10(-6) M. Competition with this reactio n has then been used to measure Al3+ binding by the egg yolk protein, phosvitin, at pH 5.0. From a Scatchard plot, the number of atoms of Al 3+ bound per mole of phosvitin was 69 +/-3 and the value of K-D was 0. 08 +/- 0.03 x 10(-6) M. We intend to use this method to measure the bi nding of Al3+ to other phosphorylated proteins. The relevance of this study to diseased conditions will then be analyzed.