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Benoit F, Wang X, Dai J, Geue N, England RM, Bristow AWT, Barran PE. Exploring the Conformational Landscape of Poly(l-lysine) Dendrimers Using Ion Mobility Mass Spectrometry. Anal Chem 2024; 96:9390-9398. [PMID: 38812282 PMCID: PMC11170554 DOI: 10.1021/acs.analchem.4c00099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 05/22/2024] [Accepted: 05/22/2024] [Indexed: 05/31/2024]
Abstract
Ion mobility mass spectrometry (IM-MS) measures the mass, size, and shape of ions in the same experiment, and structural information is provided via collision cross-section (CCS) values. The majority of commercially available IM-MS instrumentation relies on the use of CCS calibrants, and here, we present data from a family of poly(l-lysine) dendrimers and explore their suitability for this purpose. In order to test these compounds, we employed three different IM-MS platforms (Agilent 6560 IM-QToF, Waters Synapt G2, and a home-built variable temperature drift tube IM-MS) and used them to investigate six different generations of dendrimers in two buffer gases (helium and nitrogen). Each molecule gives a highly discrete CCS distribution suggestive of single conformers for each m/z value. The DTCCSN2 values of this series of molecules (molecular weight: 330-16,214 Da) range from 182 to 2941 Å2, which spans the CCS range that would be found by many synthetic molecules including supramolecular compounds and many biopolymers. The CCS values for each charge state were highly reproducible in day-to-day analysis on each instrument, although we found small variations in the absolute CCS values between instruments. The rigidity of each dendrimer was probed using collisionally activated and high-temperature IM-MS experiments, where no evidence for a significant CCS change ensued. Taken together, this data indicates that these polymers are candidates for CCS calibration and could also help to reconcile differences found in CCS measurements on different instrument geometries.
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Affiliation(s)
- Florian Benoit
- Michael
Barber Centre for Collaborative Mass Spectrometry, Manchester Institute
of Biotechnology, Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Xudong Wang
- Michael
Barber Centre for Collaborative Mass Spectrometry, Manchester Institute
of Biotechnology, Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Junxiao Dai
- Michael
Barber Centre for Collaborative Mass Spectrometry, Manchester Institute
of Biotechnology, Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - 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, U.K.
| | - Richard M. England
- Advanced
Drug Delivery, Pharmaceutical Sciences, R&D, AstraZeneca, Macclesfield SK10 2NA, U.K.
| | - Anthony W. T. Bristow
- Chemical
Development, Pharmaceutical Technology and Development, Operations, AstraZeneca, Macclesfield SK10 2NA, U.K.
| | - Perdita E. Barran
- Michael
Barber Centre for Collaborative Mass Spectrometry, Manchester Institute
of Biotechnology, Department of Chemistry, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
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Redding MJ, Grayson SM, Charles L. Mass spectrometry of dendrimers. MASS SPECTROMETRY REVIEWS 2024. [PMID: 38504498 DOI: 10.1002/mas.21876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 11/14/2023] [Accepted: 03/06/2024] [Indexed: 03/21/2024]
Abstract
Mass spectrometry (MS) has become an essential technique to characterize dendrimers as it proved efficient at tackling analytical challenges raised by their peculiar onion-like structure. Owing to their chemical diversity, this review covers benefits of MS methods as a function of dendrimer classes, discussing advantages and limitations of ionization techniques, tandem mass spectrometry (MS/MS) strategies to determine the structure of defective species, as well as most recently demonstrated capabilities of ion mobility spectrometry (IMS) in the field. Complementarily, the well-defined structure of these macromolecules offers major advantages in the development of MS-based method, as reported in a second section reviewing uses of dendrimers as MS and IMS calibration standards and as multifunctional charge inversion reagents in gas phase ion/ion reactions.
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Affiliation(s)
- McKenna J Redding
- Department of Chemistry, Tulane University, New Orleans, Los Angeles, USA
| | - Scott M Grayson
- Department of Chemistry, Tulane University, New Orleans, Los Angeles, USA
| | - Laurence Charles
- Aix Marseille Université, CNRS, Institut de Chimie Radicalaire, Marseille, France
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Wan J, Nytka M, Qian H, Lemr K, Tureček F. Do d(GCGAAGC) Cations Retain the Hairpin Structure in the Gas Phase? A Cyclic Ion Mobility Mass Spectrometry and Density Functional Theory Computational Study. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:2323-2340. [PMID: 37696624 DOI: 10.1021/jasms.3c00228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
d(GCGAAGC) is the smallest oligonucleotide with a well-defined hairpin structure in solution. We report a study of multiply protonated d(GCGAAGC) and its sequence-scrambled isomers, d(CGAAGCG), d(GCGAACG), and d(CGGAAGC), that were produced by electrospray ionization with the goal of investigating their gas-phase structures and dissociations. Cyclic ion mobility measurements revealed that dications of d(GCGAAGC) as well as the scrambled-sequence ions were mixtures of protomers and/or conformers that had collision cross sections (CCS) within a 439-481 Å2 range. Multiple ion conformers were obtained by electrospray under native conditions as well as from aqueous methanol. Arrival time distribution profiles were characteristic of individual isomeric heptanucleotides. Extensive Born-Oppenheimer molecular dynamics (BOMD) and density functional theory (DFT) calculations of d(GCGAAGC)2+ isomers indicated that hairpin structures were high-energy isomers of more compact distorted conformers. Protonation caused a break up of the C2···G6 pair that was associated with the formation of strong hydrogen bonds in zwitterionic phosphate anion-nucleobase cation motifs that predominated in low energy ions. Multiple components were also obtained for d(GCGAAGC)3+ trications under native and denaturing electrospray conditions. The calculated trication structures showed disruption of the G···C pairs in low energy zwitterions. A hairpin trication was calculated to be a high energy isomer. d(GCGAAGC)4+ tetracations were produced and separated by c-IMS as two major isomers. All low energy d(GCGAAGC)4+ ions obtained by DFT geometry optimizations were zwitterions in which all five purine bases were protonated, and the ion charge was balanced by a phosphate anion. Tetracations of the scrambled sequences were each formed as one dominant isomer. The CCS calculated with the MobCal-MPI method were found to closely match experimental values. Collision-induced dissociation (CID) spectra of multiply charged heptanucleotides showed nucleobase loss and backbone cleavages occurring chiefly at the terminal nucleosides. Electron-transfer-CID tandem mass spectra were used to investigate dissociations of different charge and spin states of charge-reduced heptanucleotide cation radicals.
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Affiliation(s)
- Jiahao Wan
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Marianna Nytka
- Department of Analytical Chemistry, Faculty of Science, Palacký University, 17. listopadu 12, 779 00 Olomouc, Czech Republic
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic
| | - Haocheng Qian
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - Karel Lemr
- Department of Analytical Chemistry, Faculty of Science, Palacký University, 17. listopadu 12, 779 00 Olomouc, Czech Republic
- Institute of Microbiology of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague, Czech Republic
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
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Konermann L, Liu Z, Haidar Y, Willans MJ, Bainbridge NA. On the Chemistry of Aqueous Ammonium Acetate Droplets during Native Electrospray Ionization Mass Spectrometry. Anal Chem 2023; 95:13957-13966. [PMID: 37669319 DOI: 10.1021/acs.analchem.3c02546] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Ammonium acetate (NH4Ac) is a widely used solvent additive in native electrospray ionization (ESI) mass spectrometry. NH4Ac can undergo proton transfer to form ammonia and acetic acid (NH4+ + Ac- → NH3 + HAc). The volatility of these products ensures that electrosprayed ions are free of undesired adducts. NH4Ac dissolution in water yields pH 7, providing "physiological" conditions. However, NH4Ac is not a buffer at pH 7 because NH4+ and Ac- are not a conjugate acid/base pair (Konermann, L. J. Am. Soc. Mass Spectrom. 2017, 28, 1827-1835.). In native ESI, it is desirable that analytes experience physiological conditions not only in bulk solution but also while they reside in ESI droplets. Little is known about the internal milieu of NH4Ac-containing ESI droplets. The current work explored the acid/base chemistry of such droplets, starting from a pH 7 analyte solution. We used a two-pronged approach involving evaporation experiments on bulk solutions under ESI-mimicking conditions, as well as molecular dynamics simulations using a newly developed algorithm that allows for proton transfer. Our results reveal that during droplet formation at the tip of the Taylor cone, electrolytically generated protons get neutralized by Ac-, making NH4+ the net charge carriers in the weakly acidic nascent droplets. During the subsequent evaporation, the droplets lose water as well as NH3 and HAc that were generated by proton transfer. NH3 departs more quickly because of its greater volatility, causing the accumulation of HAc. Together with residual Ac-, these HAc molecules form an acetate buffer that stabilizes the average droplet pH at 5.4 ± 0.1, as governed by the Henderson-Hasselbalch equation. The remarkable success of native ESI investigations in the literature implies that this pH drop by ∼1.6 units relative to the initially neutral analyte solution can be tolerated by most biomolecular analytes on the short time scale of the ESI process.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Zeyuan Liu
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Yousef Haidar
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Mathew J Willans
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Nicholas A Bainbridge
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Konermann L, Haidar Y. Mechanism of Magic Number NaCl Cluster Formation from Electrosprayed Water Nanodroplets. Anal Chem 2022; 94:16491-16501. [DOI: 10.1021/acs.analchem.2c04141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Yousef Haidar
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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