ORCID Profile
0000-0001-9669-8340
Current Organisation
Fritz-Haber-Institut der Max-Planck-Gesellschaft
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Publisher: American Chemical Society (ACS)
Date: 10-03-2011
DOI: 10.1021/JP201171P
Abstract: Far- and mid-infrared multiple photon dissociation spectroscopy has been employed to study both the structure and surface reactivity of isolated cationic rhodium clusters with surface-adsorbed nitrous oxide, Rh(n)N(2)O(+) (n = 4-8). Comparison of experimental spectra recorded using the argon atom tagging method with those calculated using density functional theory (DFT) reveals that the nitrous oxide is molecularly bound on the rhodium cluster via the terminal N-atom. Binding is thought to occur exclusively on atop sites with the rhodium clusters adopting close-packed structures. In related, but conceptually different experiments, infrared pumping of the vibrational modes corresponding with the normal modes of the adsorbed N(2)O has been observed to result in the decomposition of the N(2)O moiety and the production of oxide clusters. This cluster surface chemistry is observed for all cluster sizes studied except for n = 5. Plausible N(2)O decomposition mechanisms are given based on DFT calculations using exchange-correlation functionals. Similar experiments pumping the Rh-O stretch in Rh(n)ON(2)O(+) complexes, on which the same chemistry is observed, confirm the thermal nature of this reaction.
Publisher: Wiley
Date: 02-03-2020
Publisher: Wiley
Date: 24-03-2022
Abstract: Over the course of the COVID-19 pandemic, mRNA-based vaccines have gained tremendous importance. The development and analysis of modified RNA molecules benefit from advanced mass spectrometry and require sufficient understanding of fragmentation processes. Analogous to the degradation of RNA in solution by autohydrolysis, backbone cleavage of RNA strands was equally observed in the gas phase however, the fragmentation mechanism remained elusive. In this work, autohydrolysis-like intermediates were generated from isolated RNA dinucleotides in the gas phase and investigated using cryogenic infrared spectroscopy in helium nanodroplets. Data from both experiment and density functional theory provide evidence for the formation of a five-membered cyclic phosphate intermediate and rule out linear or six-membered structures. Furthermore, the experiments show that another prominent condensed-phase reaction of RNA nucleotides can be induced in the gas phase: the tautomerization of cytosine. Both observed reactions are therefore highly universal and intrinsic properties of the investigated molecules.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP02482A
Abstract: Kinetic trapping in helium nanodroplets enables measurement of conformer thermochemistry via infrared spectroscopy at 0.4 K.
Publisher: American Physical Society (APS)
Date: 28-02-2014
Publisher: Springer Science and Business Media LLC
Date: 11-02-2022
DOI: 10.1007/S00216-022-03927-6
Abstract: Tandem mass spectrometry is arguably the most important analytical tool for structure elucidation of lipids and other metabolites. By fragmenting intact lipid ions, valuable structural information such as the lipid class and fatty acyl composition are readily obtainable. The information content of a fragment spectrum can often be increased by the addition of metal cations. In particular, the use of silver ions is deeply rooted in the history of lipidomics due to their propensity to coordinate both electron-rich heteroatoms and C = C bonds in aliphatic chains. Not surprisingly, coordination of silver ions was found to enable the distinction of sn -isomers in glycerolipids by inducing reproducible intensity differences in the fragment spectra, which could, however, not be rationalized. Here, we investigate the fragmentation behaviors of silver-adducted sn - and double bond glycerophospholipid isomers by probing fragment structures using cryogenic gas-phase infrared (IR) spectroscopy. Our results confirm that neutral headgroup loss from silver-adducted glycerophospholipids leads to dioxolane-type fragments generated by intramolecular cyclization. By combining high-resolution IR spectroscopy and computational modelling of silver-adducted fragments, we offer qualitative explanations for different fragmentation behaviors of glycerophospholipid isomers. Overall, the results demonstrate that gas-phase IR spectroscopy of fragment ions can significantly contribute to our understanding of lipid dissociation mechanisms and the influence of coordinating cations. Graphical abstract
Publisher: Springer Science and Business Media LLC
Date: 22-02-2021
DOI: 10.1038/S41467-021-21480-1
Abstract: Glycolipids are complex glycoconjugates composed of a glycan headgroup and a lipid moiety. Their modular biosynthesis creates a vast amount of erse and often isomeric structures, which fulfill highly specific biological functions. To date, no gold-standard analytical technique can provide a comprehensive structural elucidation of complex glycolipids, and insufficient tools for isomer distinction can lead to wrong assignments. Herein we use cryogenic gas-phase infrared spectroscopy to systematically investigate different kinds of isomerism in immunologically relevant glycolipids. We show that all structural features, including isomeric glycan headgroups, anomeric configurations and different lipid moieties, can be unambiguously resolved by diagnostic spectroscopic fingerprints in a narrow spectral range. The results allow for the characterization of isomeric glycolipid mixtures and biological applications.
Publisher: Wiley
Date: 30-07-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP03776B
Abstract: In past decades, hydrogen bonds involving organic fluorine have been a highly disputed topic. Obtaining clear evidence for the presence of fluorine-specific interactions is generally difficult because of their weak...
Publisher: Wiley
Date: 18-05-2020
Publisher: Wiley
Date: 24-04-2022
Publisher: Wiley
Date: 05-05-2023
Abstract: Fucose ist ein signalgebendes Kohlenhydrat, das am Ende der Glykosylierung angehängt wird. Es ist an einer Reihe von Prozessen beteiligt, z. B. an der Selectin‐abhängigen Leukozytenadhäsion oder an Pathogen‐Rezeptor‐Interaktionen. Massenspektrometrische Verfahren, die üblicherweise zur Bestimmung der Struktur von Glykanen eingesetzt werden, zeigen häufig Fucose‐haltige, chimäre Fragmente, die die Analyse verzerren. Die Umlagerung, die zu diesen Fragmenten führt – oft als Fucose‐Migration bezeichnet – ist seit mehr als 25 Jahren bekannt, aber die chemische Identität des Umlagerungsproduktes bleibt unklar. In dieser Arbeit kombinieren wir Ionenmobilitätsspektrometrie, Massenspektrometrie mit radikalinduzierter Dissoziation, kryogene IR‐Spektroskopie und Computersimulationen mittels Dichtefunktionaltheorie, um das Produkt der Umlagerung der prototypischen Trisaccharide Lewis x und Blutgruppe H2 zu bestimmen. Die Struktursuche ergibt, dass die Fucose, die mit einer α (1→6)‐glykosidischen Bindung an die Galaktose gebunden ist, das wahrscheinlichste Produkt ist.
Publisher: AIP Publishing
Date: 06-01-2010
DOI: 10.1063/1.3285266
Abstract: The geometric structure of the Rh8+ cation is investigated using a combination of far-infrared multiple photon dissociation spectroscopy and density functional theory (DFT) calculations. The energetic ordering of the different structural motifs is found to depend sensitively on the choice of pure or hybrid exchange functionals. Comparison of experimental and calculated spectra suggests the cluster to have a close-packed, bicapped octahedral structure, in contrast to recent predictions of a cubic structure for the neutral cluster. Our findings demonstrate the importance of including some exact exchange contributions in the DFT calculations, via hybrid functionals, when applied to rhodium clusters, and cast doubt on the application of pure functionals for late transition metal clusters in general.
Publisher: Wiley
Date: 24-03-2022
Abstract: Im Laufe der COVID‐19 Pandemie haben mRNA‐basierte Impfstoffe an immenser Bedeutung gewonnen. Massenspektrometrie ist für die Entwicklung und Analyse von modifizierten RNA Molekülen unerlässlich, setzt jedoch ein grundlegendes Verständnis über Fragmentierungsprozesse voraus. Analog zu der Zersetzung von RNA in Lösung durch Autohydrolyse, kann die Spaltung des RNA Rückgrats ebenso in der Gasphase stattfinden. Bislang sind die Fragmentierungsmechanismen jedoch unzureichend untersucht. In dieser Arbeit wurden Intermediate aus isolierten RNA Dinukleotiden in der Gasphase generiert und mittels kryogener Infrarotspektroskopie in Helium‐Nanotröpfchen untersucht. Die experimentellen Daten, unterstützt durch Dichtefunktionaltheorie, liefern Hinweise dafür, dass die Bildung eines fünfgliedrigen zyklischen Phosphat‐Intermediats begünstigt ist, während lineare oder sechsgliedrige Strukturen ausgeschlossen werden können. Weiterhin zeigen die Experimente, dass eine zusätzliche, bekannte Reaktion von RNA Nukleotiden in Lösung auch in der Gasphase induziert werden kann: die Tautomerisierung von Cytosin. Die beiden beobachteten Reaktionen spiegeln daher universelle und intrinsische Eigenschaften der untersuchten Moleküle wider.
Publisher: American Chemical Society (ACS)
Date: 12-05-2021
Publisher: Wiley
Date: 02-03-2020
Publisher: Wiley
Date: 22-06-2020
Publisher: Wiley
Date: 13-04-2022
Abstract: Fluorination is a potent method to modulate chemical properties of glycans. Here, we study how C3‐ and C6‐fluorination of glucosyl building blocks influence the structure of the intermediate of the glycosylation reaction, the glycosyl cation. Using a combination of gas‐phase infrared spectroscopy and first‐principles theory, glycosyl cations generated from fluorinated and non‐fluorinated monosaccharides are structurally characterized. The results indicate that neighboring group participation of the C2‐benzoyl protecting group is the dominant structural motif for all building blocks, correlating with the β‐selectivity observed in glycosylation reactions. The infrared signatures indicate that participation of the benzoyl group in enhanced by resonance effects. Participation of remote acyl groups such as Fmoc or benzyl on the other hand is unfavored. The introduction of the less bulky fluorine leads to a change in the conformation of the ring pucker, whereas the structure of the active dioxolenium site remains unchanged.
Publisher: Wiley
Date: 18-05-2020
Publisher: American Chemical Society (ACS)
Date: 24-04-2023
Publisher: Wiley
Date: 22-06-2020
Publisher: Wiley
Date: 24-04-2022
Publisher: Wiley
Date: 05-05-2023
Abstract: Fucose is a signaling carbohydrate that is attached at the end of glycan processing. It is involved in a range of processes, such as the selectin‐dependent leukocyte adhesion or pathogen‐receptor interactions. Mass‐spectrometric techniques, which are commonly used to determine the structure of glycans, frequently show fucose‐containing chimeric fragments that obfuscate the analysis. The rearrangement leading to these fragments—often referred to as fucose migration—has been known for more than 25 years, but the chemical identity of the rearrangement product remains unclear. In this work, we combine ion‐mobility spectrometry, radical‐directed dissociation mass spectrometry, cryogenic IR spectroscopy of ions, and density‐functional theory calculations to deduce the product of the rearrangement in the model trisaccharides Lewis x and blood group H2. The structural search yields the fucose moiety attached to the galactose with an α (1→6) glycosidic bond as the most likely product.
Publisher: American Chemical Society (ACS)
Date: 27-10-2022
DOI: 10.1021/JACS.2C05859
Publisher: American Chemical Society (ACS)
Date: 13-07-2020
DOI: 10.1021/ACS.ANALCHEM.0C02048
Abstract: Heparan sulfate and heparin are highly acidic polysaccharides with a linear sequence, consisting of alternating glucosamine and hexuronic acid building blocks. The identity of hexuronic acid units shows a variability along their sequence, as d-glucuronic acid and its
Publisher: American Chemical Society (ACS)
Date: 05-11-2020
Publisher: American Chemical Society (ACS)
Date: 02-09-2021
DOI: 10.1021/JACS.1C06944
Publisher: American Chemical Society (ACS)
Date: 15-01-2010
DOI: 10.1021/JA907496C
Abstract: Multiple photon infrared excitation of size-selected Rh(6)N(2)O(+) clusters drives surface chemistry resulting in partially oxidized clusters.
Publisher: AIP Publishing
Date: 07-12-2010
DOI: 10.1063/1.3509778
Abstract: The geometric structures of small cationic rhodium clusters Rh \\documentclass[12pt]{minimal}\\begin{document}$_n^+$\\end{document}n+ (n = 6–12) are investigated by comparison of experimental far-infrared multiple photon dissociation spectra with spectra calculated using density functional theory. The clusters are found to favor structures based on octahedral and tetrahedral motifs for most of the sizes considered, in contrast to previous theoretical predictions that rhodium clusters should favor cubic motifs. Our findings highlight the need for further development of theoretical and computational methods to treat these high-spin transition metal clusters.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2SC06487A
Abstract: 3-Pyridylcarbinol ester derivatization introduces a universal probe for cryogenic gas-phase infrared spectroscopy of fatty acids that enables assignment of the position and configuration of carbon–carbon double bonds even in the presence of isomers.
No related grants have been discovered for Gerard Meijer.