Polymeric ovotransferrin and its ability to bind and deliver iron to chick-embryo red blood cells

Polymeric forms of hen ovotransferrin have been obtained by storage at 4 degrees C for 5 years or at 57 degrees C for 14 days and fractionated as dimers and tetramers by gel filtration on Sephadex. The ability of tyrosine to undergo nitration was reduced in the tetrameric protein, so that one could hypothesize that dityrosine formation is somewhat responsible of such polymerization process. Experimental data on the biological functionality showed that: i) dimeric ovotransferrin was able neither to bind nor to deliver iron; ii) tetrameric ovotransferrin was able to bind but not to deliver iron.