A sensitive and convenient assay procedure for transferrin and its application to the purification of mouse transferrin

Abstract
A sensitive procedure employing 55Fe binding was developed for the assay of transferrin. This procedure took advantage of the pH dependence and reversibility of Fe binding by transferrin and was applicable to both human and mouse transferrins. Excess Fe after saturation of the transferrin Fe-binding sites with 55Fe, supplied as Fe-citrate, was efficiently removed by its binding to Amberlite CG-400 anino-exchange resin. Mouse transferrin was purified from plasma using a combination of ammonium sulfate fractionation and ion-exchange chromatography. Two peaks of pure transferrin were obtained by DEAE-Sepharose chromatography. Mouse transferrin was a MW of 80,000.