Membrane Inlet Mass Spectrometry (MIMS) was used to analyze monochloramine solutions (NH₂Cl) and ammonia solutions in a compact FTICR. Chemical ionization enables identification and quantification of the products present in the permeate. The responses of protonated monochloramine and ammonium increase linearly with the solution concentration. The enrichments were respectively 1.2 and 5.5. Pervaporation is dependent on pH and only the basic form of ammonia NH₃ pervaporates through the membrane. Unexpectedly, the small ammonia molecule permeated very slowly. It could be due to interactions with water molecules inside the membrane that create clusters. Moreover, NH₂Cl solutions, in addition to the NH₃Cl⁺ signal, presented a strong NH₄⁺ signal at m/z 18.034 . Ammonia presence in the low-pressure zone before ionization is probable as NH₄⁺ was detected with all the precursors used, particularly CF₃⁺ and trimethylbenzene that presents a proton affinity higher than monochloramine. Ammonia may be formed inside the membrane due to the fact that NH₂Cl is unstable and may react with the water present in the membrane. Those results highlight the need for caution when dealing with chloramines in MIMS and more generally with unstable molecules.

Gelsolin is an actin-binding protein that is competitively bound by lysophosphatidic acid (LPA), a possible biomarker for the early detection of ovarian cancer. Our group has previously shown the usage of gelsolin 1-3 (a fragment of gelsolin composed of the first three of its six subdomains) along with actin to detect the presence of lysophosphatidic acid. This histidine-tagged gelsolin 1-3 fragment is synthesized in our lab using bl21 Rosetta cells but required further characterization. This study aims to provide sufficient characterization of gelsolin 1-3 synthesized in our lab via both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry using a Fourier-transform ion cyclotron resonance mass spectrometer (FTICR-MS). Both techniques show the presence of protein at the expected mass of approximately 41 kDa. Additionally, the dissociation of a smaller fragment of the complex when introduced into the gas phase which was equivalent to the approximate mass of one subdomain of gelsolin 1-3 further supports this conclusion.

T cell function is determined by transcriptional networks that are regulated by epigenetic programming via posttranslational modifications (PTMs) of histone proteins and DNA. Bottom-up mass spectrometry (MS) can identify histone PTMs, whereas intact protein analysis with high-field Fourier transform ion cyclotron resonance MS (FTICR-MS) can detect species missed by bottom-up approaches. We used high-resolution reversed-phase liquid chromatography (RPLC) FTICR-MS, alternating electron transfer dissociation (ETD) and collision-induced dissociation (CID) on precursor ions to maximize fragmentation of uniquely modified species. First online RPLC separation sorted histone families then weak cation exchange hydrophilic interaction liquid chromatography (WCX-HILIC) separated species heavily clad in PTMs. Tentative PTM identifications were assigned by matching peptide masses to predicted theoretical masses that were verified with tandem MS. We used this innovative approach for Histone-intact protein PTM mapping (HiPTMap) and to quantify PTMs on core histones purified from CD8+ T cells directly isolated ex vivo post-influenza infection. Activation significantly reduced PTMs in vivo following influenza infection, histone maps changed as T cells migrated to infections, and T cells responding to secondary heterologous infections had significantly more PTMs enhancing transcriptional activation. Thus, HiPTMap identifies and quantifies PTMs on CD8+ T cell histones and determines their combinations in T cell states.