Journal of the American Society for Mass Spectrometry最新文献

{"title":"Ion Mobility-Collision Induced Unfolding Detects Stability Shifts within Hidden Protein Conformer Families","authors":"Addison E. Bergman,&nbsp;Devin M. Makey,&nbsp;Rosendo C. Villafuerte-Vega,&nbsp;Thomas R. Slaney,&nbsp;Naresh Chennamsetty,&nbsp;Guodong Chen,&nbsp;Li Tao,&nbsp;Brandon T. Ruotolo","doi":"10.1021/jasms.6c00275","DOIUrl":"https://doi.org/10.1021/jasms.6c00275","url":null,"abstract":"<p>Proteinscommonly exist in complex mixtures, adoptinga diverseensemble of structural conformations. While some of these conformationsare functionally important, others (e.g., preaggregative states),can adversely affect protein function. In monoclonal antibody (mAb)-basedbiotherapeutics such structural polydispersity is essential for nativefunction but requires advanced biophysical and analytical techniquesto assess and properly engineer optimal therapeutics. Methods suchas native mass spectrometry (MS) and ion mobility-mass spectrometry(IM-MS) have become increasingly valuable for studying protein structure.Collision induced unfolding (CIU), an IM-MS assay, is frequently usedto examine global higher-order structures of proteins. However, standardCIU assays are fundamentally limited by the IM resolution achievedfor the precursor ion population, which may contain multiple conformerswith similar collision cross sections. In this report, we use cyclicIM-MS (cIM-MS) to develop and conduct IM-selected CIU assays, whichshow dramatically enhanced capabilities for analyzing structurallypolydisperse samples. To develop the IM-CIU approach, we investigatethe model protein bovine serum albumin under both low and neutralpH conditions, demonstrating that IM-CIU can accurately identify domainIII as the most perturbed region of the protein under these conditions.Additionally, we apply IM-CIU to analyze interleukin dimers, previouslylinked in therapeutic fusion protein constructs, and demonstrate thatthey exist in two distinct solution-based conformations. We concludeby outlining the fundamental principles of the IM-CIU method, highlightingits ability to resolve proteins with near-identical collision crosssections, and discussing its potential impact on the development offuture pharmaceutical applications.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2525–2533"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149093624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid Antibody Structural Characterization and Quantification via Microdroplet Trypsin Digestion","authors":"Mengyuan Xiao,&nbsp;Yongqing Yang,&nbsp;Andrew Schladebeck,&nbsp;Jim Lau,&nbsp;Michael Knierman,&nbsp;Hui Zhao,&nbsp;Xi Qiu,&nbsp;Karen Luo,&nbsp;Harsha P. Gunawardena,&nbsp;Hao Chen","doi":"10.1021/jasms.5c00457","DOIUrl":"10.1021/jasms.5c00457","url":null,"abstract":"<p>Microdropletdigestion of proteins, including monoclonal antibodies(mAbs), has gained increasing attention for its potential in rapidprotein structural characterization. In this study, we developed afast antibody characterization and quantitation method using onlinemicrodroplet trypsin digestion. This automated approach involves ultrafastdigestion in &lt;1 ms (&gt;90% digestion efficiency) and subsequentMSand MS/MS for peptide mapping and pinpointing peptide modifications.For instance, by MS/MS analysis, the N³⁸⁷ residue ratherthan N³⁹² and N³⁹³ of the “PENNYK”peptide, GFYPSDIAVEWESN³⁸⁷GQPEN³⁹²N³⁹³YK generated from NIST mAb microdroplet digestion, was found to undergomajor deamidation due to its proximity to the G³⁸⁸ residue(upon incubation with a pH 8 Tris buffer for 5 days, ca. 32% of theN³⁸⁷ residue was deamidated). To further demonstrate ourmethod’s applications, methionine oxidation, another importanttype of post-translational modification (PTM) of mAbs, was successfullyquantified by spiking the mAb sample with standard peptides for microdropletdigestion. Such an absolute quantitation approach showed a betteraccuracy for measuring the methionine oxidation level, in comparisonto traditional relative quantitation methods, which simply compareion intensities of oxidized and intact peptides to calculate the oxidationlevel (the relative quantitation is problematic as the oxidized andintact peptides have different ionization efficiencies). Similarly,by spiking the antibody with a heavy isotope-labeled antibody, ourmicrodroplet digestion method allowed quick absolute antibody quantification,demonstrating good linearity (<em>R</em>² = 0.99),sensitivity (LOD: 1.2 ng), and accuracy (0.6–10% quantificationerror in comparison to the theoretical amount of injected antibody).</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2281–2291"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146197274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas-Phase Radical Ion Formation from Protonated 1-Methyl-4-nitrosopiperazine: An ESI-MS/MS, Broken-Symmetry DFT, and Multireference Study","authors":"Jianqin Qian,&nbsp;Ji Li,&nbsp;Zhouqi Xia,&nbsp;Shaoqing Ni","doi":"10.1021/jasms.6c00293","DOIUrl":"https://doi.org/10.1021/jasms.6c00293","url":null,"abstract":"<p>The formation ofodd-electron radical ions (open-shell) from even-electronprecursor ions (closed-shell) in electrospray ionization (ESI) tandemmass spectrometry (MS) represents a violation of the “even-electronrule” and has been observed in several classes of compounds.Such processes often involve homolytic bond cleavage and may exhibitmultireference character, which is not always reliably described byconventional single-reference methods, such as density functionaltheory (DFT). In this paper, protonated 1-methyl-4-nitrosopiperazine(MeNP) was employed as a model system to investigate the formationmechanism of an odd-electron fragment ion under ESI-MS/MS conditions.The study integrated high-resolution ESI-MS/MS experiments with conventionalDFT, broken-symmetry DFT (BS-DFT), and multireference methods suchas second-order perturbation theory (CASPT2) based on the completeactive space self-consistent field (CASSCF) approach. Experimentally,the radical ion at <em>m</em>/<em>z</em> 100 was identifiedas the base peak at low collision energies, with an intensity muchhigher than that of the even-electron ion at <em>m</em>/<em>z</em> 99. Conventional closed-shell singlet and open-shell tripletDFT calculations predicted the formation of the radical ion with prohibitivelyhigh energies, inconsistent with the experimental observations. Incontrast, the multireference character of the homolytic N–Nbond cleavage was indicated by <em>T</em>₁ diagnosticand diradical character <em>y</em> values. BS-DFT and CASPT2//CASSCFcalculations support a plausible fragmentation pathway leading tothe radical ion at <em>m</em>/<em>z</em> 100, whichwas kinetically favorable and consistent with experimental results.These findings highlight the importance of multireference treatmentsfor rationalizing radical ion formation in protonated MeNP under ESI-MS/MSconditions.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2565–2576"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149124777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bridging Speed and Confidence in Metabolomics: A Retention Time and MS2-Guided HILIC-Orbitrap Workflow","authors":"Jonas Rösler,&nbsp;Constantin P. Krempe,&nbsp;Feyza Cansiz,&nbsp;Jaqueline Leddin,&nbsp;Friederike Jahr,&nbsp;Jost Guinand,&nbsp;Sven W. Meckelmann,&nbsp;Alpaslan Tasdogan,&nbsp;Oliver J. Schmitz","doi":"10.1021/jasms.6c00203","DOIUrl":"https://doi.org/10.1021/jasms.6c00203","url":null,"abstract":"<p>Personalizedtreatment strategies are rising within modern medicineapproaches to dynamic and heterogeneous diseases such as cancer. Humanmetabolism is important for the understanding of these diseases andtheir mechanisms, but metabolomics remains often unused in multiomicsapproaches due to practical challenges in sample analysis and, moreimportantly, data analysis. Automated feature analysis with many false-positiveannotations and a rather long analysis time is effectively hinderingrapid metabolite screening, as it would be needed in medical research.Here, we report a novel and efficient workflow for rapid metabolitescreening with the capability of yielding high-quality metabolomicsdata, including data analysis. Therefore, a HILIC (superficially poroussulfobetaine) method has been optimized to separate polar metabolitesin complex samples in less than 9 min, and an open-source compatibleretention time database has been implemented for this rapid screeningmethod, including about 400 metabolites in central metabolic pathways.The method operates on a Q-Exactive Plus Orbitrap in DDA full-scanacquisition based on an inclusion list and has been shown to be highlyrepeatable and sensitive. Moreover, false-positive annotations couldbe severely reduced, enabling a simplified and slim data analysisapproach. Using the supplied database and the code for data filtering,a rapid metabolite screening can be conducted, suitable for the applicationas a rapid metabolic profiling strategy in biological and medicalresearch.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2442–2452"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149124856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Differentiation of Bacterial Isolates Using Mass Spectrometry and Machine Learning Analysis of Volatile Organic Compounds","authors":"Sarah Kingsley,&nbsp;Michael Ibrahim,&nbsp;Ana Duran-Viseras,&nbsp;Nagi Gebraeel,&nbsp;Konstantinos T. Konstantinidis,&nbsp;Thomas M. Orlando","doi":"10.1021/jasms.6c00049","DOIUrl":"https://doi.org/10.1021/jasms.6c00049","url":null,"abstract":"<p>Identification of bacteria is a critical task in addressingbacterialcontamination of the indoor environment. Standard culture-independent(e.g., PCR and DNA sequencing) or culture-dependent techniques capableof species-level identification are often costly, time-consuming,and require specialized equipment and personnel. This work presentsa proof-of-concept study demonstrating the feasibility of detectingand identifying bacteria through analysis of the volatile organiccompounds (VOCs) emitted from their cultures using ambient pressuremass spectrometry and machine learning. An <em>E. coli</em> and three <em>Pseudomonas</em> spp. isolateswere grown in pure cultures, and VOCs were collected from cultureheadspaces using sorbent tubes. The VOCs thermally desorbed from thesorbent tubes were detected using a mass spectrometer typically usedfor residual gas analysis. The resulting data was used to train anovel machine learning (ML) model able to identify the four organismsthrough the VOCs emitted by independently replicated cultures. TheML model correctly correlated spectra of the collected VOCs with theirspecies with 84% accuracy, contrasting with ∼56% accuracy basedon the commonly used Bray–Curtis similarity of the resultingmass spectra or principal component analysis (PCA). Additional cultureswere sampled using solid-phase microextraction (SPME), and capturedVOCs were analyzed with gas chromatography–mass spectrometry(GC–MS) for compound identification. The GC–MS datarevealed a unique VOC profile for each species, confirming that theseorganisms can be differentiated solely by VOC analysis. Specific VOCsdistinguishing the isolates and contributing to the success of theML model, such as butanoic acid and 1-propanol detected from onlythe <em>E. coli</em> cultures and 2-ethyl-1-hexanoldetected from only the <em>P. aeruginosa</em> cultures, were also identified. By combining ambient mass spectrometrywith machine learning, the approach discussed in this work achievesbacterial differentiation comparable to that of a standard benchtopapproach. This work provides initial data showing that bacterial identificationthrough VOC analysis may be possible, with potential applicationsin both laboratory and field settings.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2292–2300"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149124828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Protocol for Multivariate Data Visualization and Pseudotime Modeling for Analysis of Disease Trajectories Detected by Mass Spectrometry Imaging","authors":"Bryn Gerding,&nbsp;Taylor Hulahan,&nbsp;Laura Spruill,&nbsp;Harrison B. Taylor,&nbsp;Anand S. Mehta,&nbsp;Richard R. Drake,&nbsp;Peggi M. Angel,&nbsp;Souvik Seal","doi":"10.1021/jasms.6c00183","DOIUrl":"10.1021/jasms.6c00183","url":null,"abstract":"<p>Mass spectrometry imaging (MSI) has emerged as a powerfulmodalityfor spatially resolved molecular profiling of tumor and stromal compartments;however, computational frameworks for MSI data analysis lag significantlybehind those developed for spatial transcriptomics, limiting its translationalpotential. Here, we introduce the Spatial Omics Toolkit (SPOT), anend-to-end, open-source analytical pipeline that operationalizes establishedstatistical methods from single-cell and spatial transcriptomics intoaccessible workflows for MSI data. SPOT is implemented in both R andPython, uses vendor-neutral community data formats, and integratesclassification modeling, dimensionality reduction, and trajectoryinference to enable spatially resolved comparative analysis acrossdisease states with minimal computational overhead. We demonstratethe utility of SPOT on stromal proteomic profiles derived from ductalcarcinoma in situ (DCIS) lesion archetypes, identifying differentiallyexpressed peptides across disease states by orthogonal statisticalapproaches, and reconstructing a pseudotime trajectory from DCIS toinvasive breast cancer from the same patient genetics. Collectively,SPOT provides researchers with a framework for interrogating molecularpathology across diverse MSI data sets. SPOT can be found at https://github.com/angel-omics-lab.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2628–2637"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148872424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid Single-Cell N-glycosylation Profiling of Circulating Human Immune Cells by Mass Spectrometry Imaging","authors":"Lyndsay E. A. Young,&nbsp;Lauren E. Hill,&nbsp;James. W. Dressman,&nbsp;Caroline G. Kittrell,&nbsp;Kaitlyn Bejar,&nbsp;Blake Sells,&nbsp;Anand S. Mehta,&nbsp;Robin J. Leach,&nbsp;David G. DeNardo,&nbsp;Richard R. Drake","doi":"10.1021/jasms.6c00321","DOIUrl":"https://doi.org/10.1021/jasms.6c00321","url":null,"abstract":"<p>The metabolic fitness of immune cells, reflected in partthroughglycosylation of surface proteins, is a key determinant of their activation,persistence, and effector responses. A recently developed high-throughputantibody capture cell array platform was further optimized to profileN-glycosylation across bulk cell and single-cell populations of peripheralblood mononuclear cells (PBMCs). Using antibodies against lymphocyte,monocyte, and dendritic cell markers (CD4⁺, CD8⁺, CD11c⁺, CD14,⁺ CD16⁺, CD3⁺, CD19⁺, CD56⁺, CD68⁺), N-glycosylationpatterns of these immune cell subtypes were mapped across human PBMCcultures from healthy donors and those with pancreatic cancer. Inthis platform, PDMS stamps coated with targeted antibodies createpatterned capture coordinates. Captured single cells are confirmedby brightfield imaging and selected via SoloCell software. FollowingPNGase F digestion and matrix application for MALDI-MSI analysis,N-glycans are acquired from a single laser burst per cell at a rateof 7.5 cells per second (18,000 cells in approximately 40 min). Sialicacid isomer stabilization by chemical amidation provided resolutionof α2,6- versus α2,3-linked sialic acids and enabled detectionof larger mono-, di-, tri- and tetra-sialylated glycans at the single-celllevel. Bulk- and single-cell analyses showed concordant glycomic organizationacross immune cell subtypes. Bulk-level N-glycan profiles clearlydistinguished lymphoid from myeloid lineages, and at single-cell resolution,healthy donor PBMCs similarly segregated into distinct subtype-specificglycomic clusters. In contrast, immune cell subtypes in pancreaticcancer PBMC converged into a common glycomic landscape, with marker-definedpopulations becoming highly intermixed. This convergence was accompaniedby linkage-specific sialylation shifts, including a predominance ofα2,6 sialylation and pronounced enrichment in CD3⁺ and CD8⁺ T cells. Together, these findings demonstratethat single-cell N-glycomic profiling extends bulk analysis to resolvesubtype-specific differences in disease-associated immune N-glycomeremodeling.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2585–2597"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149093659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of Free and Released Sulfur Mustard Diols in Human Blood and Urine Using Multi-ionization GC–QQQ and GC–Q-TOF","authors":"J. Brett Kimbrell,&nbsp;Brian S. Crow,&nbsp;Thomas B. Tinkle,&nbsp;Thomas A. Blake","doi":"10.1021/jasms.6c00197","DOIUrl":"https://doi.org/10.1021/jasms.6c00197","url":null,"abstract":"<p>Exposures to blister agents such as sulfur mustard (HD)have beendocumented in both military and civilian settings, underscoring theneed for reliable clinical assays and biomarkers for confirming humanexposure. Accordingly, the Organisation for the Prohibition of ChemicalWeapons (OPCW) designates sulfur mustard hydrolysis products (diols)as biomarkers for exposure verification. Because confirmatory analysesin public health and forensic contexts often rely on qualitative identificationrather than quantitation alone, we evaluated sensitive qualitativeapproaches for detecting the diol hydrolysis products of eight ofthe nine sulfur mustard analogs listed in Schedule 1.A.04 of the ChemicalWeapons Convention (CWC) Annex on Chemicals. Human serum spiked withsulfur mustard analogs and plasma and urine spiked with correspondingdiols underwent strong base treatment, solid-phase extraction (SPE),derivatization with N-heptafluorobutyrylimidazole (HFBI), and liquid–liquidextraction (LLE). The resulting diol bis-HFB derivatives were analyzedby gas chromatography–triple quadrupole mass spectrometry (GC–QQQ)using electron ionization (EI) and positive chemical ionization (PCI)with methane or ammonia reagent gases. Derivatized diols were detectedat concentrations as low as 1.00 ng/mL across all matrices, with PCI-methaneyielding signal-to-noise ratios (S/N) &gt; 15. Gas chromatography–quadrupoletime-of-flight (GC–Q-TOF) analysis provided high-resolutionMS and MS/MS spectra to support molecular formula confirmation ofprecursor and product ions. By combining EI and PCI with high-resolutionmass spectrometry for structural and molecular formula confirmation,this approach enables sensitive, matrix-independent detection, withPCI(CH₄) providing the most effective balance between structuralinformation and analytical performance for GC–MS/MS implementation.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2410–2421"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149093625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionic Solid Matrices Applied via Low-Temperature Evaporation Enable High-Resolution and Sensitive MALDI Imaging of Metabolites","authors":"Toufik Mahamdi,&nbsp;Nadia Moltó,&nbsp;Mireia Arasa,&nbsp;Roger Giné,&nbsp;Jordi Rofes,&nbsp;María García-Altares,&nbsp;Maria Vinaixa,&nbsp;Oscar Yanes","doi":"10.1021/jasms.6c00219","DOIUrl":"https://doi.org/10.1021/jasms.6c00219","url":null,"abstract":"<p>Matrix-Assisted Laser Desorption/Ionization Mass SpectrometryImaging(MALDI-MSI) enables spatially resolved molecular analysis of biologicaltissues. However, imaging low-molecular-weight metabolites remainschallenging because conventional organic matrices generate intensebackground signals in the low <em>m</em>/<em>z</em> region. Ionic matrices can reduce matrix-related interferences,improve spectral reproducibility, and enhance sensitivity. However,their application in MALDI-MSI has remained limited, largely due tothe need for additional matrix preparation and the challenging wetdeposition of viscous ionic liquid matrices, and has mainly focusedon lipid imaging above <em>m</em>/<em>z</em> 500.Here, we present a novel approach combining ionic solid matrices (ISMs)with low-temperature thermal evaporation (LTE) to enhance MALDI-MSIperformance for small metabolites. ISMs based on α-cyano-4-hydroxycinnamicacid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) provided superiorsensitivity and reduced matrix background. In particular, CHCA + <em>N</em>,<em>N</em>-diethylaniline enabled the detectionand annotation of 69 metabolites with <em>m</em>/<em>z</em> &lt; 500 in mouse brain tissue at 20 μm spatial resolution.When applied to mouse pancreas, this ISM allowed the first specificlocalization of melatonin and 3-iodotyrosine within the islets ofLangerhans, opening new avenues for spatial metabolomics in endocrineresearch.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2463–2471"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149093640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics of Collision-Induced Back-Isomerization of Photoisomer Ions","authors":"Thomas Robert,&nbsp;Gwendal Henrard,&nbsp;Benjamin Tassignon,&nbsp;Quentin Duez,&nbsp;Julien De Winter,&nbsp;Philippe Dugourd,&nbsp;Fabien Chirot,&nbsp;Pascal Gerbaux","doi":"10.1021/jasms.6c00196","DOIUrl":"https://doi.org/10.1021/jasms.6c00196","url":null,"abstract":"<p>Understanding andquantifying activation parameters associatedwith the gas-phase isomerization kinetics of stereoisomeric ions,such as Z- and E-azobenzene ions, remains a key challenge in modernmass spectrometry. Here, we explore collisional activation as a fastand efficient method to probe isomerization kinetics on QToF instrumentsequipped with traveling wave-ion mobility spectrometry (TWIMS), suchas the Waters Synapt platform. Using sequence-defined peptoids bearingan azobenzene chromophore, we investigate the collision-induced isomerization(CII) of Z-isomer ions into stable E-isomer ions within the Trap Cell–IMSconfiguration. The extent of Z → E conversion is monitoredas a function of the activation voltage (Trap CV), allowing the extractionof kinetic constants based on the known residence time of ions inthe Trap Cell. By integrating previously determined gas-phase activationparameters (Δ<em>H</em>^‡ and Δ<em>S</em>^‡) into a modified Eyring framework,we derived effective temperatures (<em>T</em>_eff) that characterize the internal energy distribution of activatedions. The dependence of <em>T</em>_eff on Trap CVyields two critical parameters: α, describing the kinetic-to-internalenergy conversion efficiency, and <em>T</em>₀,the pre-activation ion population temperature. The measured αvalues are of the same order as those previously derived for proteinions. However, <em>T</em>₀ values are found tobe system-dependent, which is detrimental for establishing a universaltemperature calibration. Ongoing work focuses on expanding the switchablemolecule library to map α and <em>T</em>₀ across diverse molecular architectures and decipher at the molecularlevel the origin of these two parameters.</p>","PeriodicalId":672,"journal":{"name":"Journal of the American Society for Mass Spectrometry","volume":"37 10","pages":"2432–2441"},"PeriodicalIF":2.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149093599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}