Selective cleavage of an antibiotic drug molecule from peptides and proteins in the gas phase by electron capture dissociation fourier transform ion cyclotron resonance mass spectrometry

The selective cleavage of an antibiotic drug molecule was investigated from peptides and proteins in the gas phase by electron capture dissociation (ECD) FTICR mass spectrometry. DFC from plasma extracts was reacted with the cyclic peptide Arg ⁸-vasopressin, which has one disulfide bond, and with bovine insulin, which has three disulfide bonds. A finer isolation was achieved by stored waveform inverse fourier transform (SWIFT), and the selected species were irradiated with electrons for 20 s. The result of the ECD spectrum showed charge reduction to the 3+ and 2+ charge states as well as the loss of a DFC thiyl radical from the 3+ charge state and loss of a DFC molecule from the 2+ charge state.