The analysis of human serum transferrins with the PhastSystem: quantitation of microheterogeneity

The PhastSystem was used for three different analyses of human serum transferrins (Tf) by isoelectric focusing: (i) The distribution of iron over the two iron binding sites by separation of the four forms: apoTf, TfFeC, FeNTf and Fe2Tf by using less than 1 microL serum or plasma. The focused bands were visualized by immunoprecipitation and quantified by densitometry. (ii) The relative proportions of the diferic sialo-transferrin fractions in human sera or plasma were determined in a similar way. (iii) The presumed genetic variants can be determined. The methods are easy and reproducible and require much less sample (0.3 microL), time (1 h per run) and antibody (10 microL/sample) than crossed immunoelectrofocusing.