Johann Far

Four imidazolium-dithiocarboxylate zwitterions derived from N-heterocyclic olefins serve as chelating ligands in homo- and heteroleptic Ru( ii ) complexes, which are robust catalysts for the transfer hydrogenation of acetophenone with isopropanol.

Per- and polyfluoroalkyl substances (PFAS) are contaminants of increasing concern, with over seven million compounds currently inventoried in the PubChem PFAS Tree. Recently, ion mobility spectrometry has been combined with liquid chromatography and high-resolution mass spectrometry (LC-IMS-HRMS) to assess PFAS. Interestingly, using negative electrospray ionization, perfluoroalkyl carboxylic acids (PFCAs) form homodimers ([2M-H]^-), a phenomenon observed with trapped, traveling wave, and drift-tube IMS. In addition to the limited research on their effect on analytical performance, there is little information on the conformations these dimers can adopt. This study aimed to propose most probable conformations for PFCA dimers. Based on qualitative analysis of how collision cross section (CCS) values change with the mass-to-charge ratio (m/z) of PFCA ions, the PFCA dimers were hypothesized to likely adopt a V-shaped structure. To support this assumption, in silico geometry optimizations were performed to generate a set of conformers for each possible dimer. A CCS value was then calculated for each conformer using the trajectory method with Lennard-Jones and ion-quadrupole potentials. Among these conformers, at least one of the ten lowest-energy conformers identified for each dimer exhibited theoretical CCS values within a ±2% error margin compared to the experimental data, qualifying them as plausible structures for the dimers. Our findings revealed that the fluorinated alkyl chains in the dimers are close to each other due to a combination of C-F···O=C and C-F···F-C stabilizing interactions. These findings, together with supplementary investigations involving environmentally relevant cations, may offer valuable insights into the interactions and environmental behavior of PFAS.

Thirteen imidazolium iodides bearing benzyl, mesityl, or 2,6‐diisopropylphenyl substituents on their nitrogen atoms, and C₁–C₄ alkyl chains on their C2 carbon atom were readily deuterated with D₂O as a cheap and non‐toxic deuterium source in the presence of Cs₂CO₃, a weak, innocuous, inorganic base. The isotopic exchange proceeded quickly and efficiently under mild, aerobic conditions to afford a range of aNHC and NHO precursors regioselectively labeled on their C2α exocyclic position and/or C4=C5 heterocyclic backbone. A “carbene‐free” mechanism was postulated, in which the carbonate anion acts as a catalyst to activate an exocyclic, acidic C−H bond and ease a deuterium transfer from D₂O to the imidazolium salt in a concerted fashion.

Per- and polyfluoroalkyl substances (PFAS) are contaminants of increasing concern, with over seven million compounds currently inventoried in the PubChem PFAS Tree. Recently, ion mobility spectrometry has been combined with liquid chromatography and high-resolution mass spectrometry (LC-IMS-HRMS) to assess PFAS. Interestingly, using negative electrospray ionization, per-fluoroalkyl carboxylic acids (PFCAs) form homodimers ([2M-H]-), a phenomenon observed with trapped, traveling wave, and drift-tube IMS. In addition to the limited research on their effect on analytical performance, there is little information on the conformations these dimers can adopt. This study aimed to propose most probable conformations for PFCA dimers. Based on qualitative analysis of how collision cross section (CCS) values change with the mass-to-charge ratio (m/z) of PFCA ions, the PFCA dimers were hypothesized to likely adopt a V-shaped structure. To support this assumption, in silico geometry optimizations were performed to generate a set of conformers for each possible dimer. A CCS value was then calculated for each conformer using the trajectory method with Lennard-Jones and ion-quadrupole potentials. Among these conformers, at least one of the ten lowest-energy conformers identified for each dimer exhibited theoretical CCS values within a ±2% error margin compared to the experimental data, qualifying them as plausible structures for the dimers. Our findings revealed that the fluorinated alkyl chains in the dimers are close to each other due to a combination of C-F⸱⸱⸱O=C and C-F⸱⸱⸱F-C stabilizing interactions. These findings, together with supplementary investigations involving environmentally relevant cations, may offer valuable insights into the interactions and environmental behavior of PFAS.

Y. Naito proposed the rationalization of ion trajectories using SIMION for the future development of projection mode in mass spectrometry imaging, an emerging technique and one of the very last instrumental developments of MALDI TOF instruments. Thi...

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is a label-free technique, producing images where pixels contain mass spectra. The technique allows the visualization of the spatial distribution of (bio)molecules from metabolites to proteins, on surfaces such as tissues sections or bacteria culture media. One particularly exciting example of MALDI-MSI use rests on its potential to localize ionized compounds produced during microbial interactions and chemical communication, offering a molecular snapshot of metabolomes at a given time. The huge size and the complexity of generated MSI data make the processing of the data challenging, which requires the use of computational methods. Despite recent advances, currently available commercial software relies mainly on statistical tools to identify patterns, similarities, and differences within data sets. However, grouping m/z values unique to a given data set according to microbiological contexts, such as coculture experiments, still requires tedious manual analysis. Here we propose a nontargeted method exploiting the differential signals between negative controls and tested experimental conditions, i.e., differential signal filtering (DSF), and a scoring of the ion images using image structure filtering (ISF) coupled with a fold change score between the controls and the conditions of interest. These methods were first applied to coculture experiments involving Escherichia coli and Streptomyces coelicolor, revealing specific MS signals during bacterial interaction. Two case studies were also investigated: (i) cellobiose-mediated induction for the pathogenicity of Streptomyces scabiei, the causative agent of common scab on root and tuber crops, and (ii) iron-repressed production of siderophores of S. scabiei. This report proposes guidelines for MALDI-MSI data treatment applied in the case of microbiology contexts, with enhanced ion peak annotation in specific culture conditions. The strengths and weaknesses of the methods are discussed.

A recently developed proteolytic reactor, designed for protein structural investigation, was coupled to ion mobility mass spectrometry to monitor collisional cross section (CCS) evolution of model proteins undergoing trypsin-mediated mono enzymatic digestion. As peptides are released during digestion, the CCS of the remaining protein structure may deviate from the classical 2/3 power of the CCS-mass relationship for spherical structures. The classical relationship between CCS and mass (CCS = A x M-2/3) for spherical structures, assuming a globular shape in the gas phase, may deviate as stabilizing elements are lost during digestion. In addition, collision-induced unfolding (CIU) experiments on partially digested proteins provided insights into the CCS resilience in the gas phase to ion activation, potentially due to the presence of stabilizing elements. The study initially investigated a model peptide ModBea (3 kDa), assessing the impact of disulfide bridges on CCS resilience in both reduced and oxidized forms. Subsequently, beta-lactoglobulin (2 disulfide bridges), calmodulin (Ca2+ coordination cation), and cytochrome c (heme) were selected to investigate the influence of common structuring elements on CCS resilience. CIU experiments probed the unfolding process, evaluating the effect of losing specific peptides on the energy landscapes of partially digested proteins. Comparisons of the (CCSN2 -> He)-C-TW to trend curves describing the CCS/mass relationship revealed that proteins with structure-stabilizing elements consistently exhibit (CCSN2 -> He)-C-TW and greater resilience toward CIU compared to proteins lacking these elements. The integration of online digestion, ion mobility, and CIU provides a valuable tool for identifying structuring elements in biopolymers in the gas phase.

Over the past decade, the separation efficiency achieved by linear IMS instruments has increased substantially, with state-of-the-art IM technologies, such as the trapped ion mobility (TIMS), the cyclic traveling wave ion mobility (cTWIMS), and the structure for lossless ion manipulation (SLIM) platforms commonly demonstrating resolving powers in excess of 200. However, for complex sample analysis that require front end separation, the achievement of such high resolving power in TIMS is significantly hampered, since the ion mobility range must be broad enough to analyze all the classes of compounds of interest, whereas the IM analysis time must be short enough to cope with the time scale of the preseparation technique employed. In this paper, we introduce the concept of sliding windows in ion mobility (SWIM) for chromatography hyphenated TIMS applications that bypasses the need to use a wide and fixed IM range by using instead narrow and mobile ion mobility windows that adapt to the analytes' ion mobility during chromatographic separation. GC-TIMS-MS analysis of a mixture of 174 standards from several halogenated persistent organic pollutant (POP) classes, including chlorinated and brominated dioxins, biphenyls, and PBDEs, demonstrated that the average IM resolving power could be increased up to 40% when the SWIM mode was used, thereby greatly increasing the method selectivity for the analysis of complex samples.

Summary: Production of recombinant pharmaceutical glycoproteins has been carried out in multiple expression systems. However, N‐glycosylation, which increases heterogeneity and raises safety concerns due to the presence of non‐human residues, is usually not controlled. The presence and composition of N‐glycans are also susceptible to affect protein stability, function and immunogenicity. To tackle these issues, we are developing glycoengineered Nicotiana tabacum Bright Yellow‐2 (BY‐2) cell lines through knock out and ectopic expression of genes involved in the N‐glycosylation pathway. Here, we report on the generation of BY‐2 cell lines producing deglycosylated proteins. To this end, endoglycosidase T was co‐expressed with an immunoglobulin G or glycoprotein B of human cytomegalovirus in BY‐2 cell lines producing only high mannose N‐glycans. Endoglycosidase T cleaves high mannose N‐glycans to generate single, asparagine‐linked, N‐acetylglucosamine residues. The N‐glycosylation profile of the secreted antibody was determined by mass spectrometry analysis. More than 90% of the N‐glycans at the conserved Asn297 site were deglycosylated. Likewise, extensive deglycosylation of glycoprotein B, which possesses 18 N‐glycosylation sites, was observed. N‐glycan composition of gB glycovariants was assessed by in vitro enzymatic mobility shift assay and proven to be consistent with the expected glycoforms. Comparison of IgG glycovariants by differential scanning fluorimetry revealed a significant impact of the N‐glycosylation pattern on the thermal stability. Production of deglycosylated pharmaceutical proteins in BY‐2 cells expands the set of glycoengineered BY‐2 cell lines.

Lipidomics has developed rapidly over the past decade. Nontargeted lipidomics from biological samples remains a challenge due to the high structural diversity, the concentration range of lipids, and the complexity of biological samples. We introduce here the use of differential Kendrick's plots as a rapid visualization tool for a qualitative nontargeted analysis of lipids categories and classes from data generated by either liquid chromatography-mass spectrometry (LC-MS) or direct infusion (nESI-MS). Each lipid class is easily identified by comparison with the theoretical Kendrick plot pattern constructed from exact mass measurements and by using MSKendrickFilter, an in-house Python software. The lipids are identified with the LIPID MAPS database. In addition, in LC-MS, the software based on the Kendrick plots returns the retention time from all the lipids belonging to the same series. Lipid extracts from a yeast (Saccharomyces cerevisiae) are used as a model. An on/off case comparing Kendrick plots from two cell lines (prostate cancer cell lines treated or not with a DGAT2 inhibition) clearly shows the effect of the inhibition. Our study demonstrates the good performance of direct infusion as a fast qualitative screening method as well as for the analysis of chromatograms. A fast screening semiquantitative approach is also possible, while the targeted mode remains the golden standard for precise quantitative analysis.