Hemoglobin, abnormal human amino acid sequence

Peptide mapping has also been used to characterize abnormal variants in human hemoglobin.Table 4.3 lists the amino acid sequences, calculated masses, and masses observed using PDMS for the tryptic peptides from the a-chain of normal human hemoglobin. In this case, peptides were purified by reversed-phase HPLC prior to mass-spectral analysis, and a human a-chain variant (Hb Bobbi) had been identified in which the HPLC peak corresponding to aT6 eluted earlier than expected. A comparison of the PDMS spectra shown in Figure 4.14 for the normal and variant aT6 revealed a mass difference of 22 Da, which corresponds to an Asp - His substitution, or a single substitution (G -> C) in the codon. 

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