Cross-Section for Proton Transfer from a Large Peptide Ion to Ammonia in the Gas Phase

Abstract

Proton transfer between ions of the cyclic peptide valinomycin (relative molecular mass 1110.6) and ammonia molecules has been studied over a range of ion energies from 50 eV to 8 keV. Valinomycin ions were produced by field desorption. Collisions of valinomycin ions with ammonia molecules at controlled energies were carried out using an ion-optical lens system situated in the source region of a large research mass spectrometer. The maximum cross-section for proton transfer occurred when the valinomycin ion possessed 1500 e

Interface for a four-sector mass spectrometer with a dual-purpose collision cell: High transmission at low to intermediate energies

“…Davis et a1. [33] have suggested a mechanism analogous to charge stripping for proton transfer observed from a peptide to NH 3 at collision 1 0 0 . .…”

Do amines react with protonated peptides in the gas phase via transacylation reactions to induce peptide bond cleavage?

“…3)11 as well as fragmentation reactions are observed, although the nature of the fragment ions was not identified 11a. At high collision energies two reactions have been observed: endothermic proton transfer12 and covalent adduction via target capture reactions 13. At lower collision energies (in four‐sector or triple quadrupole instruments), fragmentations of the [M + H] + peptide ions are observed, and these have been termed endothermic reaction induced dissociation.…”

Gas-Phase studies of valinomycin-alkali metal cation complexes: attachment rates and cation affinities

“…molecule-I, at a collision energy of 26.5 eV in the center-of-mass frame, has been measured, along with an estimated cross section for collision-induced dissociation (CID; with ND 3 as the neutral target), of 2.0 x 10-14 em? molecule t ' [22]. The very small cross section for proton transfer probably reflects steric or orientational requirements for the reaction.…”