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Recent advances in top-down mass spectrometry strategies continue to improve the analysis of intact proteins. 193 nm ultraviolet photodissociation (UVPD) is one method well-suited for top-down analysis. UVPD is often performed using relatively low photon flux in order to limit multiple-generation dissociation of fragment ions and maximize sequence coverage. Consequently, a large portion of the precursor ion survives the UVPD process, dominates the spectrum, and may impede identification of fragment ions. Here, we explore the isolation of subpopulations of fragment ions lower and higher than the precursor ion after UVPD as a means to eliminate the impact of the surviving precursor ion on the detection of low abundance fragment ions. This gas-phase fractionation method improved sequence coverage harvested from fragment ions found in the / regions lower and higher than the precursor by an average factor of 1.3 and 2.3, respectively. Combining this gas-phase fractionation method with proton transfer charge reduction (PTCR) further increased the sequence coverage obtained from these / regions by another factor of 1.3 and 1.4, respectively. Implementing a post-UVPD fractionation + PTCR strategy with six fractionation events resulted in a sequence coverage of 75% for enolase, the highest reported for 193 nm UVPD.
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http://dx.doi.org/10.1021/jasms.3c00351 | DOI Listing |
J Phys Chem A
September 2025
Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14850, United States.
Ionic liquids (ILs) have been gaining increasing focus in a variety of applications including emerging electric-propulsion concepts. A quantitative understanding of how IL ions fragment during high-energy collisions with background gases is therefore essential for interpreting mass spectra, predicting ion lifetimes in plasma and vacuum environments, and designing IL-based technologies. This work uses molecular dynamics (MD) simulations with a reactive force field to numerically model the collision-induced dissociation (CID) of isolated ions (both positive and negative) and ion clusters (2:1 and 1:2 clusters) of the prototypical ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF), colliding with a nitrogen (N) molecule, exploring all possible fragmentation channels arising from the breaking of both ionic and covalent bonds at collision energies ranging from 10 electron volts (eV) to 100 electron volts (eV) in the laboratory frame.
View Article and Find Full Text PDFJ Am Soc Mass Spectrom
September 2025
Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
An ongoing goal of top-down mass spectrometry is to increase the performance for larger proteins. Using higher energy activation methods, like 193 nm ultraviolet photodissociation (UVPD), offers the potential to cause more extensive fragmentation of large proteins and thereby yield greater sequence coverage. Obtaining high sequence coverage requires confident identification and assignment of fragment ions, and this process is hampered by spectral congestion and low signal-to-noise ratio (S/N) of the fragment ions.
View Article and Find Full Text PDFAnal Chem
September 2025
Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States.
Tires are complex polymeric materials composed of rubber elastomers (both natural and synthetic), fillers, steel wire, textiles, and a range of antioxidant and curing systems. These constituents are distributed differently among the various tire parts, which are classified based on their function and proximity to the rim. This study presents a rapid and sensitive approach for the characterization of tire components using mild thermal desorption/pyrolysis (TDPy) coupled to direct analysis in real-time mass spectrometry (DART-MS).
View Article and Find Full Text PDFJ Mass Spectrom
October 2025
Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada.
The strong C-F bond found in per- and poly-fluorinated alkyl substances (PFAS) makes them resistant to degradation and thus persistent in the environment. One of the most common methods for quantifying PFAS in environmental matrices is to use tandem mass spectrometry. However, the dissociation of ions made by deprotonating PFAS alcohols and acids has only been qualitatively explored.
View Article and Find Full Text PDFMikrochim Acta
September 2025
Department of Public Health Laboratory Sciences, College of Public Health, Hengyang Medical School, University of South China, 28 Changsheng West Road, Hengyang, 421001, Hunan, China.
We systematically evaluated the DNA adsorption and desorption efficiencies of several nanoparticles. Among them, titanium dioxide (TiO₂) nanoparticles (NPs), aluminum oxide (Al₂O₃) NPs, and zinc oxide (ZnO) NPs exhibited strong DNA-binding capacities under mild conditions. However, phosphate-mediated DNA displacement efficiencies varied considerably, with only TiO₂ NPs showing consistently superior performance.
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