Detection of neutral amino acid mutations by immobilized pH gradients: The case of the Tgamma variant in fetal hemoglobin Sardinia

A method for separating fetal hemoglobin Sardinia (AγT, a variant containing threonine in position 75 instead of isoleucine) from normal fetal hemoglobin is described, based on the use of shallow immobilized pH gradients (pH 7.30–7.55). The novelty of the fractionation technique is the direct analysis of intact, native hemoglobin tetramers, while present methods utilize only reverse‐phase, high performance liquid chromatography of denatured, heme‐free globin chains.