Structure of the human adult hemoglobin minor fraction A sub(1b) by electrospray and secondary ion mass spectrometry. Pyruvic acid as amino-terminal blocking group

Hemoglobin A sub(1b) is a minor hemoglobin component from human hemolysate (less than 0.5% of total hemoglobin) whose structure has never been established. It was purified and studied by mass spectrometry. Electrospray ionization of its abnormal beta -chain indicated a 70-Da mass increase. Separation of the tryptic digest by reversed-phase liquid chromatography revealed an abnormal beta T1 peptide. The results are consistent with a ketimine-linked pyruvic acid at the amino end of the beta -chain of hemoglobin.