Ion parking in native mass spectrometry.

A forced, damped harmonic oscillator model for gas-phase ion parking using single-frequency resonance excitation is described and applied to high-mass ions of relevance to native mass spectrometry. Experimental data are provided to illustrate key findings revealed by the modelling. These include: (i) ion secular frequency spacings between adjacent charge states of a given protein are essentially constant and decrease with the mass of the protein (ii) the mechanism for ion parking of high mass ions is the separation of the ion clouds of the oppositely-charged ions with much less influence from an increase in the relative ion velocity due to resonance excitation, (iii) the size of the parked ion cloud ultimately limits ion parking at high / ratio, and (iv) the extent of ion parking of off-target ions is highly sensitive to the bath gas pressure in the ion trap.

Two-Dimensional Tandem Mass Spectrometry for Biopolymer Structural Analysis.

Biopolymer analysis, including proteomics and glycomics, relies heavily on the use of mass spectrometry for structural elucidation, including sequence determination. Novel methods to improve sample workup, instrument performance, and data analysis continue to be developed to address shortcomings associated with sample preparation, analysis time, data quality, and data interpretation. Here, we present a new method that couples in-source collision-induced dissociation (IS-CID) with two-dimensional tandem mass spectrometry (2D MS/MS) as a way to simplify proteomics and glycomics workflows while also providing additional insight into analyte structures over traditional MS/MS experiments.

Machine-Learning Classification of Bacteria Using Two-Dimensional Tandem Mass Spectrometry.

Biothreat detection has continued to gain attention. Samples suspected to fall into any of the CDC's biothreat categories require identification by processes that require specialized expertise and facilities. Recent developments in analytical instrumentation and machine learning algorithms offer rapid and accurate classification of Gram-positive and Gram-negative bacterial species.

Quantitative Determination of Water in Organic Liquids by Ambient Mass Spectrometry.

This study uses a rapid tandem mass-spectrometry method to determine water content in complex organic solutions. Emphasis is placed on trace-water analysis by a fast and accurate alternative to the Karl-Fischer method. In this new method, water is captured by a charge-labeled molecular probe.

Adaptation and Operation of a Quadrupole/Time-of-Flight Tandem Mass Spectrometer for High Mass Ion/Ion Reaction Studies.

A commercial quadrupole/time-of-flight tandem mass spectrometer has been modified and evaluated for its performance in conducting ion/ion reaction studies involving high mass (>100 kDa) ions. Modifications include enabling the application of dipolar AC waveforms to opposing rods in three quadrupole arrays in the ion path. This modification allows for resonance excitation of ions to effect ion activation, selective ion isolation, and ion parking.

Metabolomic and Lipidomic Profiling of Using Two-Dimensional Tandem Mass Spectrometry.

Lipidomic and metabolomic profiles of sporulated and vegetative and from irradiated lysates were recorded using a quadrupole ion trap mass spectrometer modified to perform two-dimensional tandem mass spectrometry (2D MS/MS). The 2D MS/MS data domains, acquired using a 1.2 s scan of negative ions generated by nanoelectrospray ionization of microwave irradiated spores, showed the presence of dipicolinic acid (DPA) as well as various lipids.

Dipolar DC induced collisional activation of non-dissociated electron-transfer products.

The application of electron transfer and dipolar direct current induced collisional activation (ET-DDC) for enhanced sequence coverage of peptide/protein cations is described. A DDC potential is applied across one pair of opposing rods in the high-pressure collision cell of a hybrid quadrupole/time-of-flight tandem mass spectrometer (QqTOF) to induce collisional activation, in conjunction with electron transfer reactions. As a broadband technique, DDC can be employed for the simultaneous collisional activation of all the first-generation charge-reduced precursor ions (eg, electron transfer no-dissociation or ETnoD products) from electron transfer reactions over a relatively broad mass-to-charge range.

Maximizing Selective Cleavages at Aspartic Acid and Proline Residues for the Identification of Intact Proteins.

A new approach for the identification of intact proteins has been developed that relies on the generation of relatively few abundant products from specific cleavage sites. This strategy is intended to complement standard approaches that seek to generate many fragments relatively non-selectively. Specifically, this strategy seeks to maximize selective cleavage at aspartic acid and proline residues via collisional activation of precursor ions formed via electrospray ionization (ESI) under denaturing conditions.

Fourier-Transform MS and Closed-Path Multireflection Time-of-Flight MS Using an Electrostatic Linear Ion Trap.

An electrostatic linear ion trap (ELIT) has been configured to allow for the simultaneous acquisition of mass spectra via Fourier transform (FT) techniques (frequency measurement) and via time-of-flight (TOF; time measurement). In the former case, the time-domain image charge derived from a pick-up electrode in the field-free region of the ELIT is converted to frequency-domain data via Fourier transformation (i.e.

Determination of Collision Cross Sections Using a Fourier Transform Electrostatic Linear Ion Trap Mass Spectrometer.

Collision cross sections (CCSs) were determined from the frequency-domain linewidths in a Fourier transform electrostatic linear ion trap. With use of an ultrahigh-vacuum precision leak valve and nitrogen gas, transients were recorded as the background pressure in the mass analyzer chamber was varied between 4× 10 and 7 × 10 Torr. The energetic hard-sphere ion-neutral collision model, described by Xu and coworkers, was used to relate the recorded image charge to the CCS of the molecule.

Utility of Higher Harmonics in Electrospray Ionization Fourier Transform Electrostatic Linear Ion Trap Mass Spectrometry.

Mass resolution (M/ΔM fwhm) is observed to linearly increase with harmonic order in a Fourier transform electrostatic linear ion trap (ELIT) mass spectrometer. This behavior was predicted by Grosshans and Marshall for frequency-multiple detection in a Fourier transform ion cyclotron resonance mass spectrometer only for situations when the prominent mechanism for signal decay is ion ejection from the trap. As the analyzer pressure in our ELIT chamber is relatively high, such that collisional scattering and collision-induced dissociation are expected to underlie much of the ion loss, we sought to explore the relationship between harmonic order and mass resolution.

Alkali Cation Chelation in Cold β-O-4 Tetralignol Complexes.

We employ cold ion spectroscopy (UV action and IR-UV double resonance) in the gas phase to unravel the qualitative structural elements of G-type alkali metal cationized (X = Li(+), Na(+), K(+)) tetralignol complexes connected by β-O-4 linkages. The conformation-specific spectroscopy reveals a variety of conformers, each containing distinct infrared spectra in the OH stretching region, building on recent studies of the neutral and alkali metal cationized β-O-4 dimers. The alkali metal ion is discovered to bind in penta-coordinate pockets to ether and OH groups involving at least two of the three β-O-4 linkages.