The isoelectric point, pI, of the protein chymotrypsinogen A is 9.1 , while that of 3a hydroxysteroid dehydrogenase is 6.1 . What is the net charge of chymotrypsinogen A at pH 5.1 ? positivenegative What is the net charge of 3a hydroxysteroid dehydrogenase at pH 7.3 ? positivenegative The isoelectric point of serine is 5.68 ; glutamine , 5.65 . During paper electrophoresis at pH 7.3 , toward which electrode does serine migrate? positivenegative . During paper electrophoresis at pH 5.1 , toward which electrode does glutamine migrate