부산대학교 도서관

Hemoglobin Villeparisis was found during a systematic measurement of glycated hemoglobin. Electrospray mass spectra of the globin indicate an apparently unchanged molecular weight within the error range (0.01%). The tryptic digest of the ßchain shows a chromatographically abnormal ßT-9 peptide. The mass-to-charge ratio value of its [M+H]+ion, as measured by liquid secondary ionization mass spectrometry, is one mass unit lower than that of the normal ßT-9. However, the electrospray mass spectrum of this peptide exhibits mainly a doubly charged ion, whereas the normal ßT-9 gives a triply charged ion. None of the allowed single amino acid substitutions for a 1-u shift down (Glu ? Gln, Asp ? Asn, or Asn ? Ile) can explain the suppression of one protonation site. This can be due only to the replacement of the internal histidine by a nonbasic residue. Thus at least two amino acid exchanges occur within the same peptide: one involves the internal histidine, and the sum of the mass shifts is -1 u. Consideration of the ßT-9 sequence and taking account for the genetic code rules, the only possibility was 11His ? Tyr (+26 mass shift) associated with 14Asn ? Ser (-27 mass shift). This conclusion was consistent with the tandem mass spectrum of the [M+H]+ion and was further confirmed by chemical microsequencing.