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Geue N. Modern Electrospray Ionization Mass Spectrometry Techniques for the Characterization of Supramolecules and Coordination Compounds. Anal Chem 2024; 96:7332-7341. [PMID: 38686955 PMCID: PMC11099892 DOI: 10.1021/acs.analchem.4c01028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 04/15/2024] [Accepted: 04/17/2024] [Indexed: 05/02/2024]
Abstract
Mass spectrometry is routinely used for myriad applications in clinical, industrial, and research laboratories worldwide. Developments in the areas of ionization sources, high-resolution mass analyzers, tandem mass spectrometry, and ion mobility have significantly extended the repertoire of mass spectrometrists; however, for coordination compounds and supramolecules, mass spectrometry remains underexplored and arguably underappreciated. Here, the reader is guided through different tools of modern electrospray ionization mass spectrometry that are suitable for larger inorganic complexes. All steps, from sample preparation and technical details to data analysis and interpretation are discussed. The main target audience of this tutorial is synthetic chemists as well as technicians/mass spectrometrists with little experience in characterizing labile inorganic compounds.
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Affiliation(s)
- Niklas Geue
- Michael Barber Centre for Collaborative
Mass Spectrometry, Manchester Institute of Biotechnology, Department
of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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2
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Kantnerová K, Kuhlbusch N, Juchelka D, Hilkert A, Kopf S, Neubauer C. A guide to precise measurements of isotope abundance by ESI-Orbitrap MS. Nat Protoc 2024:10.1038/s41596-024-00981-5. [PMID: 38654136 DOI: 10.1038/s41596-024-00981-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 02/08/2024] [Indexed: 04/25/2024]
Abstract
Stable isotopes of carbon, hydrogen, nitrogen, oxygen and sulfur are widespread in nature. Nevertheless, their relative abundance is not the same everywhere. This is due to kinetic isotope effects in enzymes and other physical principles such as equilibrium thermodynamics. Variations in isotope ratios offer unique insights into environmental pollution, trophic relationships in ecology, metabolic disorders and Earth history including climate history. Although classical isotope ratio mass spectrometry (IRMS) techniques still struggle to access intramolecular information like site-specific isotope abundance, electrospray ionization-Orbitrap mass spectrometry can be used to achieve precise and accurate intramolecular quantification of isotopically substituted molecules ('isotopocules'). This protocol describes two procedures. In the first one, we provide a step-by-step beginner's guide for performing multi-elemental, intramolecular and site-specific stable isotope analysis in unlabeled polar solutes by direct infusion. Using a widely available calibration solution, isotopocules of trifluoroacetic acid and immonium ions from the model peptide MRFA are quantified. In the second approach, nitrate is used as a simple model for a flow injection routine that enables access to a diverse range of naturally occurring isotopic signatures in inorganic oxyanions. Each procedure takes 2-3 h to complete and requires expertise only in general mass spectrometry. The workflows use optimized Orbitrap IRMS data-extraction and -processing software and are transferable to various analytes amenable to soft ionization, including metabolites, peptides, drugs and environmental pollutants. Optimized mass spectrometry systems will enable intramolecular isotope research in many areas of biology.
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Affiliation(s)
- Kristýna Kantnerová
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, CO, USA
| | - Nils Kuhlbusch
- Thermo Fisher Scientific GmbH, Bremen, Germany
- University of Münster, Münster, Germany
| | | | | | - Sebastian Kopf
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, CO, USA
| | - Cajetan Neubauer
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, CO, USA.
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Agten A, Vilenne F, Prostko P, Valkenborg D. A compositional data model to predict the isotope distribution for average peptides using a compositional spline model. Proteomics 2024; 24:e2300154. [PMID: 38044297 DOI: 10.1002/pmic.202300154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 11/09/2023] [Accepted: 11/15/2023] [Indexed: 12/05/2023]
Abstract
We propose an updated approach for approximating the isotope distribution of average peptides given their monoisotopic mass. Our methodology involves in-silico cleavage of the entire UNIPROT database of human-reviewed proteins using Trypsin, generating a theoretical peptide dataset. The isotope distribution is computed using BRAIN. We apply a compositional data modelling strategy that utilizes an additive log-ratio transformation for the isotope probabilities followed by a penalized spline regression. Furthermore, due to the impact of the number of sulphur atoms on the course of the isotope distribution, we develop separate models for peptides containing zero up to five sulphur atoms. Additionally, we propose three methods to estimate the number of sulphur atoms based on an observed isotope distribution. The performance of the spline models and the sulphur prediction approaches is evaluated using a mean squared error and a modified Pearson's χ2 goodness-of-fit measure on an experimental UPS2 data set. Our analysis reveals that the variability in spectral accuracy, that is, the variability between MS1 scans, contributes more to the errors than the approximation of the theoretical isotope distribution by our proposed average peptide model. Moreover, we find that the accuracy of predicting the number of sulphur atoms based on the observed isotope distribution is limited by measurement accuracy.
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Affiliation(s)
- Annelies Agten
- Data Science Institute, Hasselt University, Diepenbeek, Belgium
| | - Frédérique Vilenne
- Data Science Institute, Hasselt University, Diepenbeek, Belgium
- Health, Flemish Institute for Technological Research (VITO), Mol, Belgium
| | - Piotr Prostko
- Data Science Institute, Hasselt University, Diepenbeek, Belgium
| | - Dirk Valkenborg
- Data Science Institute, Hasselt University, Diepenbeek, Belgium
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Lu W, McBride MJ, Lee WD, Xing X, Xu X, Li X, Oschmann AM, Shen Y, Bartman C, Rabinowitz JD. Selected Ion Monitoring for Orbitrap-Based Metabolomics. Metabolites 2024; 14:184. [PMID: 38668312 PMCID: PMC11051813 DOI: 10.3390/metabo14040184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 03/08/2024] [Accepted: 03/18/2024] [Indexed: 04/28/2024] Open
Abstract
Orbitrap mass spectrometry in full scan mode enables the simultaneous detection of hundreds of metabolites and their isotope-labeled forms. Yet, sensitivity remains limiting for many metabolites, including low-concentration species, poor ionizers, and low-fractional-abundance isotope-labeled forms in isotope-tracing studies. Here, we explore selected ion monitoring (SIM) as a means of sensitivity enhancement. The analytes of interest are enriched in the orbitrap analyzer by using the quadrupole as a mass filter to select particular ions. In tissue extracts, SIM significantly enhances the detection of ions of low intensity, as indicated by improved signal-to-noise (S/N) ratios and measurement precision. In addition, SIM improves the accuracy of isotope-ratio measurements. SIM, however, must be deployed with care, as excessive accumulation in the orbitrap of similar m/z ions can lead, via space-charge effects, to decreased performance (signal loss, mass shift, and ion coalescence). Ion accumulation can be controlled by adjusting settings including injection time and target ion quantity. Overall, we suggest using a full scan to ensure broad metabolic coverage, in tandem with SIM, for the accurate quantitation of targeted low-intensity ions, and provide methods deploying this approach to enhance metabolome coverage.
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Affiliation(s)
- Wenyun Lu
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
- DOE Center for Advanced Bioenergy and Bioproducts Innovation, Princeton University, Princeton, NJ 08544, USA
| | - Matthew J. McBride
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA
| | - Won Dong Lee
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
| | - Xi Xing
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
- DOE Center for Advanced Bioenergy and Bioproducts Innovation, Princeton University, Princeton, NJ 08544, USA
| | - Xincheng Xu
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Xi Li
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
- DOE Center for Advanced Bioenergy and Bioproducts Innovation, Princeton University, Princeton, NJ 08544, USA
| | - Anna M. Oschmann
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Yihui Shen
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- DOE Center for Advanced Bioenergy and Bioproducts Innovation, Princeton University, Princeton, NJ 08544, USA
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Caroline Bartman
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joshua D. Rabinowitz
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; (W.L.)
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
- DOE Center for Advanced Bioenergy and Bioproducts Innovation, Princeton University, Princeton, NJ 08544, USA
- Rutgers Cancer Institute of New Jersey (CINJ), Rutgers University, New Brunswick, NJ 08901, USA
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ 08544, USA
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Neubauer C, Kantnerová K, Lamothe A, Savarino J, Hilkert A, Juchelka D, Hinrichs KU, Elvert M, Heuer V, Elsner M, Bakkour R, Julien M, Öztoprak M, Schouten S, Hattori S, Dittmar T. Discovering Nature's Fingerprints: Isotope Ratio Analysis on Bioanalytical Mass Spectrometers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:525-537. [PMID: 36971362 DOI: 10.1021/jasms.2c00363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
For a generation or more, the mass spectrometry that developed at the frontier of molecular biology was worlds apart from isotope ratio mass spectrometry, a label-free approach done on optimized gas-source magnetic sector instruments. Recent studies show that electrospray-ionization Orbitraps and other mass spectrometers widely used in the life sciences can be fine-tuned for high-precision isotope ratio analysis. Since isotope patterns form everywhere in nature based on well-understood principles, intramolecular isotope measurements allow unique insights into a fascinating range of research topics. This Perspective introduces a wider readership to current topics in stable isotope research with the aim of discussing how soft-ionization mass spectrometry coupled with ultrahigh mass resolution can enable long-envisioned progress. We highlight novel prospects of observing isotopes in intact polar compounds and speculate on future directions of this adventure into the overlapping realms of biology, chemistry, and geology.
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Affiliation(s)
- Cajetan Neubauer
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, Colorado 80303, United States
| | - Kristýna Kantnerová
- University of Colorado Boulder & Institute for Arctic and Alpine Research (INSTAAR), Boulder, Colorado 80303, United States
| | - Alexis Lamothe
- University Grenoble Alpes, CNRS, IRD, INRAE, Grenoble-INP, IGE, Grenoble 38400, France
| | - Joel Savarino
- University Grenoble Alpes, CNRS, IRD, INRAE, Grenoble-INP, IGE, Grenoble 38400, France
| | | | | | - Kai-Uwe Hinrichs
- MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Marcus Elvert
- MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Verena Heuer
- MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Martin Elsner
- Department of Chemistry, Technical University of Munich, D-85748 Garching, Germany
| | - Rani Bakkour
- Department of Chemistry, Technical University of Munich, D-85748 Garching, Germany
| | - Maxime Julien
- GFZ German Research Center for Geosciences, 14473 Potsdam, Germany
| | - Merve Öztoprak
- NIOZ Royal Netherlands Institute for Sea Research, Texel 1797 SZ, Netherlands
| | - Stefan Schouten
- NIOZ Royal Netherlands Institute for Sea Research, Texel 1797 SZ, Netherlands
| | - Shohei Hattori
- International Center for Isotope Effects Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
| | - Thorsten Dittmar
- Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, 26129 Oldenburg, Germany
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