Aldehyde Complexes with Protonated Peptides in Gas Phase

Document Type

Article

Publication Title

Journal of Physical Chemistry B

Department

Chemistry

ISSN

1520-6106

Volume

115

Issue

38

DOI

10.1021/jp112037a

First Page

11183

Last Page

11192

Publication Date

8-1-2011

Abstract

This Article presents a study of aldehyde complexes with peptide ions formed by bimolecular collisions in the gas phase. Desolvated ions generated by electrospray ionization are stored within a radio frequency (RF) ion trap and exposed to aldehyde vapor. Mass spectrometry measurements were performed on the resulting aldehyde complexes formed with single amino acids (LysH+, HisH+, and ArgH+) and polypeptides [Pr0m-Lys+2H]2+ and [(Gly-Ser)m-Lys+2H]2+. These data identify several interesting and unexpected aspects of the aldehyde complex kinetics. It is observed that the formation of stable complexes requires the presence of water vapor. The formation kinetics of aldehyde–peptide complexes exhibits multiexponential time dependence that is modeled by interactions in the presence of structural heterogeneity. Aldehyde binding appears to involve a competition between conformers with unhindered access to protonation sites and conformers with intramolecular solvation of these sites. Proton transfer to the aldehyde ligand is responsible for the loss of the complexes. This is supported by proton affinity calculations and identified by reaction products exhibiting loss of protonation by the parent ion accompanied by the appearance of aldehyde cations.

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