1B-O1-1625 PDF
Charge Effects on the Conformation of Highly Basic Peptides Characterized by Ion Mobility Mass Spectrometry
The relationship between the charge and conformation of highly basic peptides was examined by electrospray ionization ion mobility mass spectrometry (ESI-IM-MS).
It has previously been demonstrated that the charges in Arg-rich peptides were distributed throughout the sequence and remained fixed during high-energy collision using a 4-sector MS/MS instrument. To characterize the peptide gas phase structure in detail, we investigated the behaviour of specifically designed Arg-rich basic peptides different in length, and number and proximity of Arg residues, similar Lys-rich peptides, and histone N- and C-terminal tail peptides rich in Arg and Lys residues. To evaluate the experimentally obtained collision cross-section (CCS) values of peptides, they were compared with CCS values of theoretical structures constructed by molecular modelling.
A close linear correlation was observed between either the maximum charge or most abundant charge state of the peptides and the experimental CCS values. However, the experimental CCS values were consistently larger than the theoretically calculated ones, even for ions with the lowest charge (Figure 1). This suggests that the charge repulsion effect is enhanced in the gas phase, resulting in more elongated structure among these basic peptides.