Quantification of a transferrin variant after isoelectric focusing in agarose gel using carbamylated myoglobin as a colored marker

A widely applicable procedure for electrophoretic separation and quantification of proteins is described. Different colored markers of myoglobin were prepared by carbamylation and those with suitable isoelectric points (pI's) were isolated. Such markers were added to samples of serum and plasma which were examined by improved isoelectric focusing in agarose gel. This facilitated isolation of a certain transferrin with pI 5.7. This protein was quantified in gel pieces by zone immunoelectrophoresis assay. The overall S.D. was <10%. Immunofixations were performed to check the quality of focusing and the accuracy of gel punching.