Proteins charge variants, detection

In the 1950s, new methods of protein separation were developed that enabled the systematic study of molecular variation in many more human proteins. Starch gel electrophoresis allowed the separation of closely related protein variants by differences in charge and molecular size. Smithies (1955) detected the amazing polymorphism of haptoglobin. In later years the method was extended to the study of allozymes (enzyme polymorphisms). 

Intact hemoglobin variants can also be detected with ESI-MS. The ESI mass spectrum contains a series of multiply charged ions that usually complicate the detection of a protein mixture. The data can, however, be software-transformed to provide a single peak that is unique to a specific protein. This approach has been used to identify hemoglobin from a blood sample from a newborn sickle-cell carrier [46]. 

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