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Persson LJ, Sahin C, Landreh M, Marklund EG. High-Performance Molecular Dynamics Simulations for Native Mass Spectrometry of Large Protein Complexes with the Fast Multipole Method. Anal Chem 2024; 96:15023-15030. [PMID: 39231152 PMCID: PMC11411496 DOI: 10.1021/acs.analchem.4c03272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2024]
Abstract
Native mass spectrometry (MS) is widely employed to study the structures and assemblies of proteins ranging from small monomers to megadalton complexes. Molecular dynamics (MD) simulation is a useful complement as it provides the spatial detail that native MS cannot offer. However, MD simulations performed in the gas phase have suffered from rapidly increasing computational costs with the system size. The primary bottleneck is the calculation of electrostatic forces, which are effective over long distances and must be explicitly computed for each atom pair, precluding efficient use of methods traditionally used to accelerate condensed-phase simulations. As a result, MD simulations have been unable to match the capacity of MS in probing large multimeric protein complexes. Here, we apply the fast multipole method (FMM) for computing the electrostatic forces, recently implemented by Kohnke et al. (J. Chem. Theory Comput., 2020, 16, 6938-6949), showing that it significantly enhances the performance of gas-phase simulations of large proteins. We assess how to achieve adequate accuracy and optimal performance with FMM, finding that it expands the accessible size range and time scales dramatically. Additionally, we simulate a 460 kDa ferritin complex over microsecond time scales, alongside complementary ion mobility (IM)-MS experiments, uncovering conformational changes that are not apparent from the IM-MS data alone.
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Affiliation(s)
- Louise J Persson
- Department of Chemistry - BMC, Uppsala University, SE-75123 Uppsala, Sweden
| | - Cagla Sahin
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-17165 Solna, Sweden
- Department of Biology, Structural Biology and NMR Laboratory and the Linderstro̷m-Lang Centre for Protein Science, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-17165 Solna, Sweden
- Department of Cell and Molecular Biology, Uppsala University, SE-75124 Uppsala, Sweden
| | - Erik G Marklund
- Department of Chemistry - BMC, Uppsala University, SE-75123 Uppsala, Sweden
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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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Schultz M, Parker SL, Fernando MT, Wellalage MM, Thomas DA. Diserinol Isophthalamide: A Novel Reagent for Complexation with Biomolecular Anions in Electrospray Ionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:745-753. [PMID: 36975839 DOI: 10.1021/jasms.3c00010] [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
Transferring biomolecules from solution to vacuum facilitates a detailed analysis of molecular structure and dynamics by isolating molecules of interest from a complex environment. However, inherent in the ion desolvation process is the loss of solvent hydrogen bonding partners, which are critical for the stability of a condensed-phase structure. Thus, transfer of ions to vacuum can favor structural rearrangement, especially near solvent-accessible charge sites, which tend to adopt intramolecular hydrogen bonding motifs in the absence of solvent. Complexation of monoalkylammonium moieties (e.g., lysine side chains) with crown ethers such as 18-crown-6 can disfavor structural rearrangement of protonated sites, but no equivalent ligand has been investigated for deprotonated groups. Herein we describe diserinol isophthalamide (DIP), a novel reagent for the gas-phase complexation of anionic moieties within biomolecules. Complexation is observed to the C-terminus or side chains of the small model peptides GD, GE, GG, DF-OMe, VYV, YGGFL, and EYMPME in electrospray ionization mass spectrometry (ESI-MS) studies. In addition, complexation is observed with the phosphate and carboxylate moieities of phosphoserine and phosphotyrosine. DIP performs favorably in comparison to an existing anion recognition reagent, 1,1'-(1,2-phenylene)bis(3-phenylurea), that exhibits moderate carboxylate binding in organic solvent. This improved performance in ESI-MS experiments is attributed to reduced steric constraints to complexation with carboxylate groups of larger molecules. Overall, diserinol isophthalamide is an effective complexation reagent that can be applied in future work to study retention of solution-phase structure, investigate intrinsic molecular properties, and examine solvation effects.
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Affiliation(s)
- Madeline Schultz
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Sarah L Parker
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Maleesha T Fernando
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Miyuru M Wellalage
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Daniel A Thomas
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
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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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Hou Z, Luan M, Zhan L, Wang X, Yuan S, Cao K, Sheng Y, Yin H, Liu Y, Huang G. Native Mass Spectrometry for Peptide–Metal Interaction in Picoliter Cell Lysate. Anal Chem 2022; 94:13829-13833. [DOI: 10.1021/acs.analchem.2c02390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhuanghao Hou
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Moujun Luan
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Liujuan Zhan
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Xinchen Wang
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Siming Yuan
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Kaiming Cao
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Yaping Sheng
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Hao Yin
- Mass Spectrometry Lab, Instruments Center for Physical Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Yangzhong Liu
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
| | - Guangming Huang
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230001, China
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230001, China
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230001, China
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Aliyari E, Konermann L. Formation of Gaseous Peptide Ions from Electrospray Droplets: Competition between the Ion Evaporation Mechanism and Charged Residue Mechanism. Anal Chem 2022; 94:7713-7721. [PMID: 35587384 DOI: 10.1021/acs.analchem.2c01355] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The transfer of peptide ions from solution into the gas phase by electrospray ionization (ESI) is an integral component of mass spectrometry (MS)-based proteomics. The mechanisms whereby gaseous peptide ions are released from charged ESI nanodroplets remain unclear. This is in contrast to intact protein ESI, which has been the focus of detailed investigations using molecular dynamics (MD) simulations and other methods. Under acidic liquid chromatography/MS conditions, many peptides carry a solution charge of 3+ or 2+. Because of this pre-existing charge and their relatively small size, prevailing views suggest that peptides follow the ion evaporation mechanism (IEM). The IEM entails analyte ejection from ESI droplets, driven by electrostatic repulsion between the analyte and droplet. Surprisingly, recent peptide MD investigations reported a different behavior, that is, the release of peptide ions via droplet evaporation to dryness which represents the hallmark of the charged residue mechanism (CRM). Here, we resolved this conundrum by performing MD simulations on a common model peptide (bradykinin) in Rayleigh-charged aqueous droplets. The primary focus was on pH 2 conditions (bradykinin solution charge = 3+), but we also verified that our MD strategy captured pH-dependent charge state shifts seen in ESI-MS experiments. In agreement with earlier simulations, we found that droplets with initial radii of 1.5-3 nm predominantly release peptide ions via the CRM. In contrast, somewhat larger radii (4-5 nm) favor IEM behavior. It appears that these are the first MD data to unequivocally demonstrate the viability of peptide IEM events. Electrostatic arguments can account for the observed droplet size dependence. In summary, both CRM and IEM can be operative in peptide ESI-MS. The prevalence of one over the other mechanism depends on the droplet size distribution in the ESI plume.
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Affiliation(s)
- Elnaz Aliyari
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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