The insertion of ion mobility spectrometry (IMS) between LC and MS can improve peptide identification in both proteomics and phosphoproteomics by providing structural information that is complementary to LC and MS, because IMS separates ions on the basis of differences in their shapes and charge states. However, it is necessary to know how phosphate groups affect the peptide collision cross sections (CCS) in order to accurately predict phosphopeptide CCS values and to maximize the usefulness of IMS. In this work, we systematically characterized the CCS values of 4,433 pairs of mono-phosphopeptide and corresponding unphosphorylated peptide ions using trapped ion mobility spectrometry (TIMS). Nearly one-third of the mono-phosphopeptide ions evaluated here showed smaller CCS values than their unphosphorylated counterparts, even though phosphorylation results in a mass increase of 80 Da. Significant changes of CCS upon phosphorylation occurred mainly in structurally extended peptides with large numbers of basic groups, possibly reflecting intramolecular interactions between phosphate and basic groups.

CO₃^−• and O₂^−• are known to be strong oxidizing reagents in biological systems. CO₃^−• in particular can cause serious damage to DNA and proteins by H^• abstraction reactions. However, H^• abstraction of CO₃^−• in the gas phase has not yet been reported. In this work we report on gas-phase ion/molecule reactions of CO₃^−• and O₂^−• with various molecules. CO₃^−• was generated by the corona discharge of an O₂ reagent gas using a cylindrical tube ion source. O₂^−• was generated by the application of a 15 kHz high frequency voltage to a sharp needle in ambient air at the threshold voltage for the appearance of an ion signal. In the reactions of CO₃^−•, a decrease in signal intensities of CO₃^−• accompanied by the simultaneous increase of that of HCO₃⁻ was observed when organic compounds with H–C bond energies lower than ∼100 kcal mol⁻¹ such as n-hexane, cyclohexane, methanol, ethanol, 1-propanol, 2-propanol, and toluene were introduced into the ion source. This clearly indicates the occurrence of H^• abstraction. O₂^−• abstracts H⁺ from acid molecules such as formic, acetic, trifluoroacetic, nitric and amino acids. Gas-phase CO₃^−• may play a role as a strong oxidizing reagent as it does in the condensed phase. The major discharge product CO₃^−• in addition to O₂^−•, O₃, and NO_x^• that are formed in ambient air may cause damage to biological systems.

We measured the Re/Os (¹⁸⁵Re/¹⁸⁸Os) and ¹⁸⁷Os/¹⁸⁸Os ratios from nanoparticles (NPs) using a multiple collector-inductively coupled plasma-mass spectrometer equipped with high-time resolution ion counters (HTR-MC-ICP-MS). Using the HTR-MC-ICP-MS system developed in this study, the simultaneous data acquisition of four isotopes was possible with a time resolution of up to 10 μs. This permits the quantitative analysis of four isotopes to be carried out from transient signals (e.g., <0.6 ms) emanating from the NPs. Iridium–Osmium NPs were produced from a naturally occurring Ir–Os alloy (ruthenosmiridium from Hokkaido, Japan; osmiridium from British Columbia, Canada; iridosmine from the Urals region of Russia) through a laser ablation technique, and the resulting nanoparticles were collected by bubbling water through a suspension. The ¹⁸⁷Os/¹⁸⁸Os ratios for individual NPs varied significantly, mainly due to the counting statistics of the ¹⁸⁷Os and ¹⁸⁸Os signals. Despite the large variation in the measured ratios, the resulting ¹⁸⁷Os/¹⁸⁸Os ratios for three Ir–Os bearing minerals, were 0.121±0.013 for Hokkaido, 0.110±0.012 for British Columbia, and 0.122±0.020 for the Urals, and these values were in agreement with the ratios obtained by the conventional laser ablation-MC-ICP-MS technique. The data obtained here provides a clear demonstration that the HTR-MC-ICP-MS technique can become a powerful tool for monitoring elemental and isotope ratios from NPs of multiple components.