Ion mobility-mass spectrometry has shown tremendous potential for improving the analysis of various subclasses of steroids. Its speed and ability to separate isobaric and isomeric species makes it id...

Ion mobility separates ion in the gas phase based on rotationally averaged cross section, a parameter often correlated with size, providing a versatile measurement strategy when integrated with mass s...

Accurate characterization of RNAs and their chemical modifications is critical for understanding RNA biology and post-transcriptional regulation. Mass spectrometry using data-dependent acquisition (DDA) is a crucial tool for identifying oligonucleotides (OGN) in epitranscriptomics. In this study, the key DDA parameters on an Orbitrap Fusion Lumos mass spectrometer were optimized, and an iterative mass exclusion MS/MS acquisition method was developed to enhance the OGN identification. Optimal performance was achieved with full MS resolving power of 120,000 and an MS/MS resolving power of 15,000, top 15 MS/MS scans, and 30% normalized HCD collision energy. Applying these settings to analyze RNase T1 digested E. coli rRNA resulted in the identification of an average of 358 unique OGNs and 58% rRNA sequence coverage. Our findings highlight the importance of tailored DDA parameter optimization and establish a robust workflow for confident OGN identification in MS-based epitranscriptomics.

We present a novel approach for achieving ultrahigh-resolution ion mobility (UHRIM) separations using a structures for lossless ion manipulation (SLIM) ion mobility-mass spectrometry (IM-MS) system. B...

A quadrupole/drift tube ion mobility/Orbitrap instrument requires pumping from atmosphere to 10–5 Torr in the quadrupole analyzer region, back to 1 Torr for the drift tube, and a return to 10–5 Torr for the Orbitrap high vacuum region. The Orbitrap high vacuum region contains the transfer multipole, C-trap, and HCD cell. Insufficient pumping between the drift tube and quadrupole leads to helium in the quadrupole analyzer chamber which compromises performance. Additional vacuum regions were added between the drift tube and the analyzer chamber to maintain the analyzer pressure below 5.5 × 10–5 Torr with the drift tube pressurized to 1.5 Torr of He. In this configuration, the isolation of a single charge state of C-reactive protein (m/z 5,000) was demonstrated. Fourier transform ion mobility spectra were acquired with the quadrupole in full scan mode and in the isolation mode. Ion optic voltages were optimized for both helium and nitrogen bath gases in the drift tube so that minimal ion heating was observed entering the drift tube. These instrument modifications enable improved ion transfer efficiency, allowing for better ion isolation by the digital quadrupole ion mobility separation of large protein complexes, as illustrated by the 23+ and 24+ charge states of C-reactive protein.

Ion mobility-mass spectrometry has shown tremendous potential for improving the analysis of various subclasses of steroids. Its speed and ability to separate isobaric and isomeric species makes it…

A novel ionic liquid MALDI matrix, 3-aminoquinoline/2′,4′,6′-trihydroxyacetophenone monohydrate (3-AQ/THAP), was developed for the rapid qualitative and quantitative detection of miRNA from biological...

Journal of the American Society for Mass SpectrometryDOI: 10.1021/jasms.4c00424

Journal of the American Society for Mass SpectrometryDOI: 10.1021/jasms.5c00087

Gas-phase ion complexes of dinucleotides and trinucleotides with a diaryltetrazole-tagged peptide underwent covalent cross-linking upon UV photodissociation (UVPD) at 213 nm. The cross-linking reaction involved nitrile-imine intermediates produced by the loss of N2 from the tetrazole, whereby cross-linking between the complex components competed with internal cross-linking within the peptide. The propensity for UVPD-induced cross-linking of DNA nucleobases was established for complexes of dinucleotides dAA, dCC, dGG, and dTT, that gave cross-link yields of 5%, 15%, 40%, and <1%, respectively. Analysis of UVPD-produced nitrile-imine intermediates by collision-induced dissociation (CID-MS3) gave cross-link yields of 71%, 75%, 94%, and 8% for dAA, dCC, dGG, and dTT, respectively. UVPD-CID-MS3 of isomeric trinucleotide–peptide complexes of dCGA, dAGC, dCAG, dACG, and dGCA showed nearly quantitative cross-linking that favored guanine regardless of its position in the sequence. Binding energies for the gas-phase ion complexes were obtained by Born–Oppenheimer molecular dynamics and density functional theory calculations at the M06–2X/def2qzvpp level. These calculations showed similar binding energies for the dAA, dCC, and dCAG complexes that were in the 195–221 kJ mol–1 range, whereas binding to dGG and dTT was weaker. A mechanism for the novel cross-linking reaction between the nitrile imine and guanine was elucidated with a riboguanosine conjugate that was tagged with a diaryltetrazole group at 5′-O. Product analysis as well as the calculated structures and energies suggested that cross-links resulted from an attack on the aromatic ring of an imine intermediate by the guanine carbonyl oxygen, followed by proton migrations.

Photoionization (PI) technology has been widely used for the analysis of volatile organic compounds (VOCs) due to its nondestructive nature and high sensitivity. However, the application of photoionization sources is constrained by inefficient ion transmission under high-pressure conditions and relatively low photon energy. In this study, an ion-funnel-integrated photoionization (IFPI) source was developed. Following a systematic investigation of the effects of radio frequency (RF) amplitude on the ion transmission efficiency and ionization processes, a dual-mode ionization strategy based on RF amplitude (Vpp) modulation was proposed. In the low-amplitude mode (Vpp = 40 V), the focusing performance of the ion funnel enhanced the sensitivity of single-photon ionization (SPI) by over 10-fold. In the high-amplitude mode (Vpp = 80 V), high-sensitivity detection of compounds with higher ionization energies (IEs) was achieved via the charge transfer reaction of O2+ produced by photoelectron ionization (PEI), overcoming the limitation of photon energy. After comprehensive optimization of ion source pressure, RF amplitude, and direct current (DC) voltage difference of the ion funnel, the limits of detection (LODs) of 11 VOCs using time-of-flight mass spectrometry combined with the IFPI source (IFPI-TOFMS) ranged from 2.3 to 32.5 parts per trillion by volume (pptv). Finally, the practical utility of the IFPI-TOFMS in the field of environmental health and public safety was demonstrated through 90-h continuous monitoring of laboratory air and spatial distribution analysis of trichloromethane near an indoor swimming pool.

Journal of the American Society for Mass SpectrometryDOI: 10.1021/jasms.5c00141

Journal of the American Society for Mass SpectrometryDOI: 10.1021/jasms.5c00210

Journal of the American Society for Mass SpectrometryDOI: 10.1021/jasms.5c00098

Scorpion venoms consist of proteins, peptides, and various low molecular weight (LMW) organic compounds, which act as toxins. Despite their potential significance, these compounds in scorpion venoms have been little investigated and their full range has not been well characterized. In this work, a targeted metabolomic approach was used in combination with an HPLC-QTOF-MS methodology to create a library of 55 LMW standard compounds, for the analysis of venoms from three Tityus species scorpions. This strategy enabled reliable identification of 45 compounds, including 20 amino acids, 4 organic acids, 12 biogenic amines, 6 nitrogenated bases and derivatives, 2 β-carboline-derived alkaloids, and 1 amphetamine. Most of the compounds identified were neurotransmitters and/or neurotoxins, while others can act as homeostasis disruptors or affect the diffusion of venom through the bodies of victims. Therefore, the LMW organic compounds in scorpion venoms play roles in the killing or paralyzing of prey, as well as in defense against large predators.