Methods for Studying the Bindingof Aluminum by Serum Protein

We describe methods for studying the binding of Al by protein in serum: ultrafiltration, gel filtration, and immuno-affinity chromatography. For ultrafiltration we used an Amicon YM1 0 cellophane membrane with a nominal cutoff of 10 000 Da to separate ultrafiltrableand non-ultrafiltrableAl. For gel filtra-tionwe used Sephacryl S-300, and for immuno-affinitychro-matographywe used anti-transferrincoupled to CNBr-acti-vated Sepharose to identify the Al-binding protein. For 30 normal subjects 54 % of the total Al in serum was non-ultrafiltrable; for 30 patients with chronic renal failure being treated by hemodialysis 67 % was non-ultrafiltrable. In both groups transfernn was identified as the major Al-binding protein in the serum. Results of gel-filtration studies should be interpretedwithcaution:somegel mediaadsorb“free”Al, whichcan be subsequentlytaken up by transfemnor desfer