A new procedure for the determination of transferrin C (Tf C) subtypes by isoelectric focusing. Existence of two additional alleles, Tf C4 and Tf C5.

Isoelectric focusing (IEF) is widely used for the determination of serum protein polymorphisms in forensic investigations. Because of non-genetic heterogeneity of some proteins and of protein-ligand dissociation observed after IEF standardization of procedures is necessary. In this article the authors point out the main difficulties encountered in studying the transferrin subtype polymorphism and describe a new and sensitive method. Two new Tf C subtypes were observed: Tf C4 in North American, Bolivian and Brazilian Indians, Tf C5 in Black Americans, both with polymorphic allele frequencies. In a Pyrenean population the allele frequencies for Tf C1, Tf C2 and Tf C3 were quite similar to those observed in a German population sample.