Charge state specific facile gas-phase cleavage of Asp 75-Met 76 peptide bond in the alpha-chain of human apohemoglobin probed by electrospray ionization mass spectrometry.
Herein, we present the first example of charge state specific facile gas-phase cleavage of an aspartic acid-methionine peptide linkage. This cleavage (Asp 75-Met 76) was observed in the alpha-chain of human adult hemoglobin (Hb) and was probed by electrospray ionization mass spectrometry. This specific conformational and/or charge density dependent dissociation was observed primarily in the [M + 11H]11+ and [M + 12H]12+ species. A mechanism involving an intramolecular proton transfer from the protonated carboxyl side chain of Asp 75 to the neighboring Met 76 residue yielding an anhydride moiety at the C-terminal of the Asp 75 is proposed. Dramatic differences in dissociation of [M + 13H]13+ and [M + 14H]14+ species were observed.
Bakhtiar
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R
Chemical Sciences Department, Pacific Northwest Laboratory, Richland, Washington 99352.
Wu
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Q
Hofstadler
S A
SA
Smith
R D
RD
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000032:analysis*; D001224:Aspartic Acid / Q000032:analysis; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D013058:Mass Spectrometry; D008715:Methionine / Q000032:analysis; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis
D001059:Apoproteins; D006454:Hemoglobins; D010455:Peptides; C023478:apohemoglobin; D001224:Aspartic Acid; D008715:Methionine