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2. Structure and Conformation Determine Gas‐Phase Infrared Spectra of Detergents.

Author

Kirschbaum, Carla, Greis, Kim, Gewinner, Sandy, Schöllkopf, Wieland, Meijer, Gerard, von Helden, Gert, Pagel, Kevin, and Urner, Leonhard H.

Subjects
*COMPUTATIONAL chemistry, *ATOMIC mass, *DETERGENTS, *DENSITY functional theory, *INFRARED spectroscopy, *COLLISION induced dissociation
Abstract

Native mass spectrometry of membrane proteins relies on non‐ionic detergents which protect the protein during transfer from solution into the gas phase. Once in the gas phase, the detergent micelle must be efficiently removed, which is usually achieved by collision‐induced dissociation (CID). Recently, infrared multiple photon dissociation (IRMPD) has emerged as an alternative activation method for the analysis of membrane proteins, which has led to a growing interest in detergents that efficiently absorb infrared light. Here we investigate whether the absorption properties of synthetic detergents can be tailored by merging structural motifs of existing detergents into new hybrid detergents. We combine gas‐phase infrared ion spectroscopy with density functional theory to investigate and rationalize the absorption properties of three established detergents and two hybrid detergents with fused headgroups. We show that, although the basic intramolecular interactions in the parent and hybrid detergents are similar, the three‐dimensional structures differ significantly and so do the infrared spectra. Our results outline a roadmap for guiding the synthesis of tailored detergents with computational chemistry for future mass spectrometry applications. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Reinvestigation of the internal glycan rearrangement of Lewis a and blood group type H1 epitopes.

Author

Kontodimas, Vasilis, Yaman, Murat, Greis, Kim, Lettow, Maike, Pagel, Kevin, and Marianski, Mateusz

Abstract

Protonated ions of fucose-containing oligosaccharides are prone to undergo internal glycan rearrangement which results in chimeric fragments that obfuscate mass-spectrometric analysis. Lack of accessible tools that would facilitate systematic analysis of glycans in the gas phase limits our understanding of this phenomenon. In this work, we use density functional theory modeling to interpret cryogenic IR spectra of Lewis a and blood group type H1 trisaccharides and to establish whether these trisaccharides undergo the rearrangement during gas-phase analysis. Structurally unconstrained search reveals that none of the parent ions constitute a thermodynamic global minimum. In contrast, predicted collision cross sections and anharmonic IR spectra provide a good match to available experimental data which allowed us to conclude that fucose migration does not occur in these antigens. By comparing the predicted structures with those obtained for Lewis x and blood group type H2 epitopes, we demonstrate that the availability of the mobile proton and a large difference in the relative stability of the parent ions and rearrangement products constitute the prerequisites for the rearrangement reaction. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Microhydration of the metastable N-protomer of 4-aminobenzoic acid by condensation at 80 K: H/D exchange without conversion to the more stable O-protomer.

Author

Khuu, Thien, Stropoli, Santino J., Greis, Kim, Yang, Nan, and Johnson, Mark A.

Subjects
CONDENSATION, AMINO group, ION traps, LIQUID nitrogen, ISOTOPOLOGUES, DEUTERIUM, APROTIC solvents
Abstract

4-aminobenzoic acid (4ABA) is a model scaffold for studying solvent-mediated proton transfer. Although protonation at the carboxylic group (O-protomer) is energetically favored in the gas phase, the N-protomer, where the proton remains on the amino group, can be kinetically trapped by electrospray ionization of 4ABA in an aprotic solvent such as acetonitrile. Here, we report the formation of the hydrated deuterium isotopologues of the N-protomers, RND3+·(H2O)n=1–3, (R = C6H4COOD), which are generated by condensing water molecules onto the bare N-protomers in a liquid nitrogen cooled, radiofrequency octopole ion trap at 80 K. The product clusters are then transferred to a 20 K cryogenic ion trap where they are tagged with weakly bound D2 molecules. The structures of these clusters are determined by analysis of their vibrational patterns, obtained by resonant IR photodissociation. The resulting patterns confirm that the metastable N-protomer configuration remains intact even when warmed by the sequential condensation of water molecules. The attachment of H2O molecules onto the RND3+ head group also affords the opportunity to explore the possibility of H/D exchange between the acid scaffold and the proximal water network. The spectroscopic results establish that although the RND3+·(H2O)n=1,2 clusters are formed without H/D exchange, the n = 3 cluster exhibits about 10% H/D exchange as evidenced by the appearance of the telltale HOD bands. The site of exchange on the acid is determined to be the acidic OH group by the emergence of the OH stretching fundamental in the –COOH motif. [ABSTRACT FROM AUTHOR]

Published
2022
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11. Infrared Multiphoton Dissociation Enables Top‐Down Characterization of Membrane Protein Complexes and G Protein‐Coupled Receptors

Author

Lutomski, Corinne A., primary, El‐Baba, Tarick J., additional, Hinkle, Joshua D., additional, Liko, Idlir, additional, Bennett, Jack L., additional, Kalmankar, Neha V., additional, Dolan, Andrew, additional, Kirschbaum, Carla, additional, Greis, Kim, additional, Urner, Leonhard H., additional, Kapoor, Parth, additional, Yen, Hsin‐Yung, additional, Pagel, Kevin, additional, Mullen, Christopher, additional, Syka, John E. P., additional, and Robinson, Carol V., additional

Published
2023
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12. Entschlüsselung des Fucose‐Migrationsproduktes bei der Massenspektrometrischen Analyse von Blutgruppenepitopen

Author

Lettow, Maike, primary, Greis, Kim, additional, Mucha, Eike, additional, Lambeth, Tyler R., additional, Yaman, Murat, additional, Kontodimas, Vasilis, additional, Manz, Christian, additional, Hoffmann, Waldemar, additional, Meijer, Gerard, additional, Julian, Ryan R., additional, von Helden, Gert, additional, Marianski, Mateusz, additional, and Pagel, Kevin, additional

Published
2023
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15. Decoding the Fucose Migration Product during Mass‐Spectrometric Analysis of Blood Group Epitopes

Author

Lettow, Maike, primary, Greis, Kim, additional, Mucha, Eike, additional, Lambeth, Tyler R., additional, Yaman, Murat, additional, Kontodimas, Vasilis, additional, Manz, Christian, additional, Hoffmann, Waldemar, additional, Meijer, Gerard, additional, Julian, Ryan R., additional, von Helden, Gert, additional, Marianski, Mateusz R., additional, and Pagel, Kevin, additional

Published
2023
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16. Cryogenic infrared spectroscopy reveals remarkably short NH+⋯F hydrogen bonds in fluorinated phenylalanines.

Author

Safferthal, Marc, Greis, Kim, Chang, Rayoon, Kirschbaum, Carla, Hoffmann, Waldemar, Meijer, Gerard, von Helden, Gert, and Pagel, Kevin

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 nature. Today, the existence of hydrogen bonds with organic fluorine is widely accepted and supported by numerous studies. However, strong bonds with short H⋯F distances remain scarce and are primarily found in designed model compounds. Using a combination of cryogenic gas-phase infrared spectroscopy and density functional theory, we here analyze a series of conformationally unrestrained fluorinated phenylalanine compounds as protonated species. The results suggest proximal NH+⋯F hydrogen bonds with an exceptionally close H⋯F distance (1.79 Å) in protonated ortho-fluorophenylalanine. [ABSTRACT FROM AUTHOR]

Published
2023
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18. Establishing carbon–carbon double bond position and configuration in unsaturated fatty acids by gas-phase infrared spectroscopy

Author

Kirschbaum, Carla, primary, Young, Reuben S. E., additional, Greis, Kim, additional, Menzel, Jan Philipp, additional, Gewinner, Sandy, additional, Schöllkopf, Wieland, additional, Meijer, Gerard, additional, von Helden, Gert, additional, Causon, Tim, additional, Narreddula, Venkateswara R., additional, Poad, Berwyck L. J., additional, Blanksby, Stephen J., additional, and Pagel, Kevin, additional

Published
2023
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19. Structural Analysis of Glycosyl Cations and Other Intermediates Using Cryogenic Infrared Spectroscopy

Author

Greis, Kim

Subjects
500 Naturwissenschaften und Mathematik::540 Chemie::547 Organische Chemie, 500 Naturwissenschaften und Mathematik::540 Chemie::543 Analytische Chemie, Carbohydrates, 500 Naturwissenschaften und Mathematik::540 Chemie::541 Physikalische Chemie, Infrared Spectroscopy, Mass Spectrometry, Density Functional Theory
Abstract

Knowing the structure of reactive intermediates can yield unprecedented insight into organic reaction mechanisms. In particular for glycosyl cations – the reactive intermediates in glycosylations – the stereoselectivity of the reaction could be predicted by knowing the structure of the intermediate. The structure reveals whether an acyl protecting group of the monosaccharide unit interacts with the positively charged anomeric carbon so that it would shield one side from nucleophilic attack and thus steer the stereoselectivity of the reaction. These postulated approaches have been termed neighboring-group and remote participation. However, the short lifetime of reactive intermediates impedes their structural characterization in solution. Hence, for glycosyl cations, the structure remained elusive until very recently. These intermediates are not intrinsically unstable, but well-defined minima on the potential energy surface. Therefore, the ionic intermediates can be generated inside the vacuum of a mass spectrometer, free from nucleophiles or solvent molecules. In this environment, the isolated intermediates are stable and can subsequently be characterized using spectrometric or spectroscopic techniques. Recent advances in instrumentation allow coupling mass spectrometers with infrared lasers for infrared ion spectroscopy. Thus, highly-resolved infrared spectra of the analyte ions can be obtained by using cryogenic infrared spectroscopy in helium nanodroplets. To assign the obtained spectrum to a structure, it can be compared to harmonic frequencies of promising candidate structures calculated using density functional theory. This workflow was successfully used to determine the structure of several glycosyl cations, based on which, a new selective building block for 1,2-cis galactosylations was developed and its stereoselectivity was rationalized. Furthermore, it was determined that c-fragments of RNA dinucleotides are identical to the intermediate of RNA autohydrolysis. Finally, potentially antiaromatic carbocations were investigated.

Published
2023
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34. Chondroitin Sulfate Disaccharides in the Gas Phase:Differentiation and Conformational Constraints

Author

Lettow, Maike, Greis, Kim, Grabarics, Márkó, Horlebein, Jan, Miller, Rebecca L., Meijer, Gerard, Von Helden, Gert, Pagel, Kevin, Lettow, Maike, Greis, Kim, Grabarics, Márkó, Horlebein, Jan, Miller, Rebecca L., Meijer, Gerard, Von Helden, Gert, and Pagel, Kevin

Abstract

Glycosaminoglycans (GAGs) are a family of complex carbohydrates vital to all mammalian organisms and involved in numerous biological processes. Chondroitin and dermatan sulfate, an important class of GAGs, are linear macromolecules consisting of disaccharide building blocks of N-acetylgalactosamine and two different uronic acids. The varying degree and the site of sulfation render their characterization challenging. Here, we combine mass spectrometry with cryogenic infrared spectroscopy in the wavenumber range from 1000 to 1800 cm-1. Fingerprint spectra were recorded for a comprehensive set of disaccharides bearing all known motifs of sulfation. In addition, state-of-the-art quantum chemical calculations were performed to aid the understanding of the differences in the experimental fingerprint spectra. The results show that the degree and position of charged sulfate groups define the size of the conformational landscape in the gas phase. The detailed understanding of cryogenic infrared spectroscopy for acidic and often highly sulfated glycans may pave the way to utilize the technique in fragment-based sequencing approaches.

Published
2021

35. On Stereocontrol in Organocatalytic α-Chlorinations of Aldehydes

Author

Ponath, Sebastian, primary, Joshi, Chetan, primary, Merrill, Amy T., primary, Schmidts, Volker, primary, Greis, Kim, primary, Lettow, Maike, primary, Weber, Manuela, primary, Steinhauer, Simon, primary, Pagel, Kevin, primary, Thiele, Christina M., primary, Tantillo, Dean, primary, Vetticatt, Mathew, primary, and Christmann, Mathias, primary

Published
2021
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36. Probing the conformational landscape and thermochemistry of DNA dinucleotide anionsviahelium nanodroplet infrared action spectroscopy

Author

Thomas, Daniel A., Chang, Rayoon, Mucha, Eike, Lettow, Maike, Greis, Kim, Gewinner, Sandy, Schöllkopf, Wieland, Meijer, Gerard, and Von Helden, Gert

Subjects
basis-sets, ion mobility, energy landscape, cationized arginine, Physics::Atomic and Molecular Clusters, mobility-mass spectrometry, unsolvated peptides, gas-phase conformations, Physics::Chemical Physics, 500 Naturwissenschaften und Mathematik::540 Chemie::540 Chemie und zugeordnete Wissenschaften, photon dissociation spectroscopy
Abstract

Isolation of biomolecules in vacuum facilitates characterization of the intramolecular interactions that determine three-dimensional structure, but experimental quantification of conformer thermochemistry remains challenging. Infrared spectroscopy of molecules trapped in helium nanodroplets is a promising methodology for the measurement of thermochemical parameters. When molecules are captured in a helium nanodroplet, the rate of cooling to an equilibrium temperature ofca.0.4 K is generally faster than the rate of isomerization, resulting in "shock-freezing" that kinetically traps molecules in local conformational minima. This unique property enables the study of temperature-dependent conformational equilibriaviainfrared spectroscopy at 0.4 K, thereby avoiding the deleterious effects of spectral broadening at higher temperatures. Herein, we demonstrate the first application of this approach to ionic species by coupling electrospray ionization mass spectrometry (ESI-MS) with helium nanodroplet infrared action spectroscopy to probe the structure and thermochemistry of deprotonated DNA dinucleotides. Dinucleotide anions were generated by ESI, confined in an ion trap at temperatures between 90 and 350 K, and entrained in traversing helium nanodroplets. The infrared action spectra of the entrained ions show a strong dependence on pre-pickup ion temperature, consistent with the preservation of conformer population upon cooling to 0.4 K. Non-negative matrix factorization was utilized to identify component conformer infrared spectra and determine temperature-dependent conformer populations. Relative enthalpies and entropies of conformers were subsequently obtained from a van't Hoff analysis. IR spectra and conformer thermochemistry are compared to results from ion mobility spectrometry (IMS) and electronic structure methods. The implementation of ESI-MS as a source of dopant molecules expands the diversity of molecules accessible for thermochemical measurements, enabling the study of larger, non-volatile species.

Published
2020

37. Resolving Sphingolipid Isomers Using Cryogenic Infrared Spectroscopy

Author

Kirschbaum, Carla, Saied, Essa M., Greis, Kim, Mucha, Eike, Gewinner, Sandy, Schöllkopf, Wieland, Meijer, Gerard, von Helden, Gert, Poad, Berwyck L.J., Blanksby, Stephen J., Arenz, Christoph, Pagel, Kevin, Kirschbaum, Carla, Saied, Essa M., Greis, Kim, Mucha, Eike, Gewinner, Sandy, Schöllkopf, Wieland, Meijer, Gerard, von Helden, Gert, Poad, Berwyck L.J., Blanksby, Stephen J., Arenz, Christoph, and Pagel, Kevin

Abstract

1-Deoxysphingolipids are a recently described class of sphingolipids that have been shown to be associated with several disease states including diabetic and hereditary neuropathy. The identification and characterization of 1-deoxysphingolipids and their metabolites is therefore highly important. However, exact structure determination requires a combination of sophisticated analytical techniques due to the presence of various isomers, such as ketone/alkenol isomers, carbon–carbon double-bond (C=C) isomers and hydroxylation regioisomers. Here we demonstrate that cryogenic gas-phase infrared (IR) spectroscopy of ionized 1-deoxysphingolipids enables the identification and differentiation of isomers by their unique spectroscopic fingerprints. In particular, C=C bond positions and stereochemical configurations can be distinguished by specific interactions between the charged amine and the double bond. The results demonstrate the power of gas-phase IR spectroscopy to overcome the challenge of isomer resolution in conventional mass spectrometry and pave the way for deeper analysis of the lipidome.

Published
2020

38. Cryogenic Infrared Spectroscopy Reveals Structural Modularity in the Vibrational Fingerprints of Heparan Sulfate Diastereomers

Author

Chemical Biology and Drug Discovery, Afd Chemical Biology and Drug Discovery, Sub Chemical Biology and Drug Discovery, Lettow, Maike, Grabarics, Marko, Greis, Kim, Mucha, Eike, Thomas, Daniel A, Chopra, Pradeep, Boons, Geert-Jan, Karlsson, Richard, Turnbull, Jeremy E, Meijer, Gerard, Miller, Rebecca L, von Helden, Gert, Pagel, Kevin, Chemical Biology and Drug Discovery, Afd Chemical Biology and Drug Discovery, Sub Chemical Biology and Drug Discovery, Lettow, Maike, Grabarics, Marko, Greis, Kim, Mucha, Eike, Thomas, Daniel A, Chopra, Pradeep, Boons, Geert-Jan, Karlsson, Richard, Turnbull, Jeremy E, Meijer, Gerard, Miller, Rebecca L, von Helden, Gert, and Pagel, Kevin

Published
2020

39. Cryogenic Infrared Spectroscopy Reveals Structural Modularity in the Vibrational Fingerprints of Heparan Sulfate Diastereomers

Author

Lettow, Maike, Grabarics, Márkó, Greis, Kim, Mucha, Eike, Thomas, Daniel A., Chopra, Pradeep, Boons, Geert Jan, Karlsson, Richard, Turnbull, Jeremy E., Meijer, Gerard, Miller, Rebecca L., Von Helden, Gert, Pagel, Kevin, Lettow, Maike, Grabarics, Márkó, Greis, Kim, Mucha, Eike, Thomas, Daniel A., Chopra, Pradeep, Boons, Geert Jan, Karlsson, Richard, Turnbull, Jeremy E., Meijer, Gerard, Miller, Rebecca L., Von Helden, Gert, and Pagel, Kevin

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 C5 epimer, l-iduronic acid, can both occur. The resulting backbone diversity represents a major challenge for an unambiguous structural assignment by mass spectrometry-based techniques. Here, we employ cryogenic infrared spectroscopy on mass-selected ions to overcome this challenge and distinguish isomeric heparan sulfate tetrasaccharides that differ only in the configuration of their hexuronic acid building blocks. High-resolution infrared spectra of a systematic set of synthetic heparan sulfate stereoisomers were recorded in the fingerprint region from 1000 to 1800 cm-1. The experiments reveal a characteristic combination of spectral features for each of the four diastereomers studied and imply structural modularity in the vibrational fingerprints. Strong spectrum-structure correlations were found and rationalized by state-of-the-art quantum chemical calculations. The findings demonstrate the potential of cryogenic infrared spectroscopy to extend the mass spectrometry-based toolkit for the sequencing of heparan sulfate and structurally related biomolecules.

Published
2020

43. Cryogenic Infrared Spectroscopy Reveals Structural Modularity in the Vibrational Fingerprints of Heparan Sulfate Diastereomers

Author

Lettow, Maike, primary, Grabarics, Márkó, additional, Greis, Kim, additional, Mucha, Eike, additional, Thomas, Daniel A., additional, Chopra, Pradeep, additional, Boons, Geert-Jan, additional, Karlsson, Richard, additional, Turnbull, Jeremy E., additional, Meijer, Gerard, additional, Miller, Rebecca L., additional, von Helden, Gert, additional, and Pagel, Kevin, additional

Published
2020
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44. Innentitelbild: Unterscheidung von isomeren Sphingolipiden mittels kryogener Infrarotspektroskopie (Angew. Chem. 32/2020)

Author

Kirschbaum, Carla, primary, Saied, Essa M., additional, Greis, Kim, additional, Mucha, Eike, additional, Gewinner, Sandy, additional, Schöllkopf, Wieland, additional, Meijer, Gerard, additional, Helden, Gert, additional, Poad, Berwyck L. J., additional, Blanksby, Stephen J., additional, Arenz, Christoph, additional, and Pagel, Kevin, additional

Published
2020
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45. Inside Cover: Resolving Sphingolipid Isomers Using Cryogenic Infrared Spectroscopy (Angew. Chem. Int. Ed. 32/2020)

Author

Kirschbaum, Carla, primary, Saied, Essa M., additional, Greis, Kim, additional, Mucha, Eike, additional, Gewinner, Sandy, additional, Schöllkopf, Wieland, additional, Meijer, Gerard, additional, Helden, Gert, additional, Poad, Berwyck L. J., additional, Blanksby, Stephen J., additional, Arenz, Christoph, additional, and Pagel, Kevin, additional

Published
2020
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46. Resolving Sphingolipid Isomers Using Cryogenic Infrared Spectroscopy

Author

Kirschbaum, Carla, primary, Saied, Essa M., additional, Greis, Kim, additional, Mucha, Eike, additional, Gewinner, Sandy, additional, Schöllkopf, Wieland, additional, Meijer, Gerard, additional, Helden, Gert, additional, Poad, Berwyck L. J., additional, Blanksby, Stephen J., additional, Arenz, Christoph, additional, and Pagel, Kevin, additional

Published
2020
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48. Remote Participation during Glycosylation Reactions of Galactose Building Blocks: Direct Evidence from Cryogenic Vibrational Spectroscopy

Author

Marianski, Mateusz, primary, Mucha, Eike, additional, Greis, Kim, additional, Moon, Sooyeon, additional, Pardo, Alonso, additional, Kirschbaum, Carla, additional, Thomas, Daniel A., additional, Meijer, Gerard, additional, Helden, Gert, additional, Gilmore, Kerry, additional, Seeberger, Peter H., additional, and Pagel, Kevin, additional

Published
2020
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49. Fernpartizipation in Glykosylierungen von Galaktose‐Bausteinen: Direktnachweis durch kryogene Schwingungsspektroskopie

Author

Marianski, Mateusz, primary, Mucha, Eike, additional, Greis, Kim, additional, Moon, Sooyeon, additional, Pardo, Alonso, additional, Kirschbaum, Carla, additional, Thomas, Daniel A., additional, Meijer, Gerard, additional, Helden, Gert, additional, Gilmore, Kerry, additional, Seeberger, Peter H., additional, and Pagel, Kevin, additional

Published
2020
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