Tailored-waveform collisional activation of peptide ion electron transfer survivor ions in cation transmission mode ion/ion reaction experiments.

Broadband resonance excitation via a tailored waveform in a high pressure collision cell (Q2) on a hybrid quadrupole/time-of-flight (QqTOF) tandem mass spectrometer has been implemented for cation transmission mode electron transfer ion/ion reactions of tryptic polypeptides. The frequency components in the broadband waveform were defined to excite the first generation intact electron transfer products for relatively large tryptic peptides. The optimum amplitude of the arbitrary waveform applied has been determined empirically to be 3.

Development of a proton-transfer reaction-linear ion trap mass spectrometer for quantitative determination of volatile organic compounds.

Currently, proton-transfer reaction mass spectrometry (PTR-MS) allows for quantitative determination of volatile organic compounds in real time at concentrations in the low ppt range, but cannot differentiate isomers or isobaric molecules, using the conventional quadrupole mass filter. Here we pursue the application of linear quadrupole ion trap (LIT) mass spectrometry in combination with proton-transfer reaction chemical ionization to provide the advantages of specificity from MS/MS. A commercial PTR-MS platform composed of a quadrupole mass filter with the addition of end cap electrodes enabled the mass filter to operate as a linear ion trap.

Effects of cation charge-site identity and position on electron-transfer dissociation of polypeptide cations.

The effect of cation charge site on gas-phase ion/ion reactions between multiply protonated model peptides and singly charged anions has been examined. Insights are drawn from the quantitative examination of the product partitioning into competing channels, such as proton transfer (PT) versus electron transfer (ET), electron transfer followed by dissociation (ETD) versus electron transfer without dissociation (ET, no D), and fragmentation of backbone bonds versus fragmentation of side chains. Peptide cations containing protonated lysine, arginine, and histidine showed similar degrees of electron transfer, which were much higher than the peptide having fixed-charge sites, that is, trimethyl ammonium groups.

Relative information content and top-down proteomics by mass spectrometry: utility of ion/ion proton-transfer reactions in electrospray-based approaches.

Computer simulations of electrospray ionization (ESI) and collision-induced dissociation (CID) experiments were employed to examine the informing power associated with "top-down" proteomics implemented with some commonly used mass analyzers, i.e., the quadrupole ion trap (QIT), the Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICRMS), and the time-of-flight (TOF) mass spectrometer.

Ion/molecule reactions of cation radicals formed from protonated polypeptides via gas-phase ion/ion electron transfer.

Cation radicals formed via gas-phase electron transfer to multiply protonated polypeptides have been found to react with molecular oxygen. Such cation radicals are of interest within the context of electron transfer dissociation, a phenomenon with high utility for the characterization of peptide and protein primary structures. Most of the cation radicals show the attachment of O(2) under room temperature storage conditions in an electrodynamic ion trap.

Implementation of ion/ion reactions in a quadrupole/time-of-flight tandem mass spectrometer.

A commercial quadrupole/time-of-flight (QqTOF) tandem mass spectrometer has been adapted for ion/ion reaction studies. To enable mutual storage of oppositely charged ions in a linear ion trap, the oscillating quadrupole field of the second quadrupole of the system (Q2) serves to store ions in the radial dimension while auxiliary radio frequency is superposed on the end lenses of Q2 during the reaction period to create barriers in the axial dimension. A pulsed dual electrospray (ESI) source is directly coupled to the instrument interface for the purpose of proton transfer reactions.