Separation and tryptic digest mapping of normal and variant haemoglobins by capillary electrophoresis.

Characterization of haemoglobin (Hb) through whole protein separations and tryptic digest mapping allows the identification of structural Hb variants which result in haemoglobinopathies. Tryptic digest mapping by conventional two-dimensional paper chromatograph-electrophoresis provides high resolution but requires 48 h, while gradient elution reversed-phase high-performance liquid chromatography (HPLC) is faster (1.5 h), there is decreased resolution. CE analysis provides a fast separation with high resolution. We have used CE to optimise the tryptic digestion of globin purified from normal human haemoglobin A and to analyze tryptic digests from normal Hb. The separations were optimised and peak identification performed using UV scanning detection. In the optimised tryptic digest separation up to 28 peaks could be resolved in < 20 min. These peaks were identified as far as possible and a high-resolution map of the digest was constructed. The optimised analytical conditions were used to observe the separation pattern obtained from normal adult haemoglobin (HbA), common variant haemoglobins and some rarer haemoglobin variants.