Electrophoretically silent hemoglobin mutants as revealed by isoelectric focusing in immobilized pH gradients

The applications of isoelectric focusing in immobilized pH gradients to the analysis of (i) human hemoglobin mutants, (ii) animal hemoglobin mutants (from cattle, sheep, dog and mouse), and (iii) tryptic digests of alpha and beta chains, are discussed and evaluated. Immobilized pH gradients appear to be an excellent tool for screening of genetic polymorphism and for detecting "silent mutants", i.e. those substitutions involving amino acids with nonionizable side chains. At present, not even capillary zone electrophoresis, claimed to have a resolving power equivalent to 1 million theoretical plates, has shown a resolution capability comparable to that of immobilized pH gradients, at least in the field of protein separation.