Question

Hemoglobin A has a pI value of 5.6 whereas the variant hemoglobin M has an aspartate residue in place of the normal valine at position 85 of the alpha chain. What effect will this substitution have on the electrophoretic behavior of the protein at pH 7.0

Answer 1

An isoelectric pH is 5.6 and the buffer pH is 7 which means the protein will have net negative charge because if pH is more than there is low H+ concentration and thus protein will loose the H+ and will develop net negative charge..

But if the protein have one aspartate in place of valine then the side chain will have one carboxyl group which will also emit H+ ions .

And thus net negative charge will be more in case of hemoglobin M.

So , in electrophoretic mobility, the HEMOGLOBIN M will migrate more towards the positive charge because it will have more negative charge