Structural Analysis of Human Hemoglobin Variants by Molecular Secondary Ion Mass Spectrometry

Chemically purified abnormal peptides, α62-76 of Hb Ube-2, βT-3 of Hb G-Coushatta, αT-7 of Hb J-Norfolk and βT-1 of Hb Himeji, were subjected to molecular secondary ion mass spectrometry (SIMS). These peptides were identified by the mass number of their protonated molecular ion (M+H)+ and their amino acid sequence was confirmed by a series of the mass number of fragmented ions released by a stepwise removal from their C-terminus. Amino acid substitution of α68 Asn→Asp in Hb Ube-2, β22 Gln→ Ala in Hb G-Coushatta and α51 Gly→Asp in Hb J-Norfolk was successfully determined and a questionable Hb variant, tentatively called Hb Himeji (β140 Ala→ Asp) was proven to have a significant amount of the additive of the glycated N-terminus of the βT-1 peptide