How is that possible?

Question

Haemoglobin from 2 persons are compared by eletrophoresis reveals no diff. in migration, but fingerprinting shows one amino-acid diff.
How is that possible?

Answer 1

Electrophoresis separates items (whether proteins or nucleic acid strands) on the basis of size (ie length). You're basically forcing these strands through a meshwork, where the smaller ones get through the mesh more easily and travel through the gel faster. The difference in size from a one AA difference may not be sufficient to resolve on a gel. This would seem to be a candidate for 2-dimensional electrophoresis, where you first separate based on pH and then run the separated proteins out on a regular gel. The pI of the proteins will be different enough to separate "horizontally", and it may then be possible to see the very tiny size difference when you separate them "vertically"