Covalent and Non-covalent Dissociations of Gas-phase Complexes of Avoparcin and Bacterial Receptor Mimicking Precursor Peptides Studied by Collisionally Activated Decomposition Mass Spectrometry

Covalent and Non-covalent Dissociations of Gas-phase Complexes of Avoparcin and Bacterial Receptor Mimicking Precursor Peptides Studied by Collisionally Activated Decomposition Mass Spectrometry

Covalent and Non-covalent Dissociations of Gas-phase Complexes of Avoparcin and Bacterial Receptor Mimicking Precursor Peptides Studied by Collisionally Activated Decomposition Mass Spectrometry

Abstract

The gas-phase stability and reactivity of non-covalent complexes of avoparcin and bacterial receptor mimicking precursor peptides were probed by electrospray ionization mass spectrometry combined with collisionally activated decomposition (CAD) studies. The order of the gas-phase stabilities of these non-covalent complexes is different from the order of the stabilities of the same complexes in solution. The specific stereoselectivity observed in non-covalent binding in solution is not retained in the gas phase. The presence of a lysine residue in the bacterial receptor mimicking precursorpeptides appears to promote the gas-phase stabilities of the antibiotic-peptide complexes. Complexes of avoparcin with receptor peptides containing a lysine residue are stabilized in the gas phase to such an extent that CAD of these non-covalent complexes proceeds through a competition between non-covalent and covalent fragmentation pathways. These results indicate clearly that the use of CAD mass spectra for the quantitative characterization of the stability of non-covalent complexes in solution should be applied with extreme caution.

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