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Zhao X, Ren J, Wang Z, Chen X. Analyzing noncovalent interactions between notoginseng saponins and lysozyme by deposition scanning intensity fading MALDI-TOF mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2024; 59:e5058. [PMID: 38842112 DOI: 10.1002/jms.5058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 05/06/2024] [Accepted: 05/12/2024] [Indexed: 06/07/2024]
Abstract
Analysis of noncovalent interactions between natural products and proteins is important for rapid screening of active ingredients and understanding their pharmacological activities. In this work, the intensity fading MALDI-TOF mass spectrometry (IF-MALDI-MS) method with improved reproducibility was implemented to investigate the binding interactions between saponins from Panax notoginseng and lysozyme. The benchmark IF-MALDI-MS experiment was established using N,N',N″-triacetylchitotriose-lysozyme as a model system. The reproducibility of ion intensities in IF-MALDI-MS was improved by scanning the whole sample deposition with a focused laser beam. The relative standard deviation (RSD) of deposition scanning IF-MALDI-MS is 5.7%. Similar decay trends of the relative intensities of notoginseng saponins against increasing amounts of lysozyme were observed for all six notoginseng saponins. The half-maximal fading concentration (FC50) was calculated to quantitatively characterize the binding affinity of each ligand based on the decay curve. According to the FC50 values obtained, the binding affinities of the six notoginseng saponins were evaluated in the following order: notoginsenoside S > notoginsenoside Fc > ginsenoside Rb1 > ginsenoside Rd > notoginsenoside Ft1 > ginsenoside Rg1. The binding order was in accordance with molecular docking studies, which showed hydrogen bonding might play a key role in stabilizing the binding interaction. Our results demonstrated that deposition scanning IF-MALDI-MS can provide valuable information on the noncovalent interactions between ligands and proteins.
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Affiliation(s)
- Xintong Zhao
- Key Laboratory for Applied Technology of Sophisticated Analytical Instruments, Shandong Analysis and Test Centre, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China
| | - Juan Ren
- Department of Pharmaceutical Science, Zunyi Medical University at Zhuhai Campus, Zhuhai, China
| | - Ze Wang
- Department of Pharmaceutical Science, Zunyi Medical University at Zhuhai Campus, Zhuhai, China
| | - Xiangfeng Chen
- Key Laboratory for Applied Technology of Sophisticated Analytical Instruments, Shandong Analysis and Test Centre, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China
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2
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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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Li G, Wang Y, Sun C, Liu F. Determination of the microscopic acid dissociation constant of piperacillin and identification of dissociated molecular forms. Front Chem 2023; 11:1177128. [PMID: 37179774 PMCID: PMC10169600 DOI: 10.3389/fchem.2023.1177128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 04/12/2023] [Indexed: 05/15/2023] Open
Abstract
For amphoteric ß-lactam antibiotics, the acid dissociation constant (pK a) is a fundamental parameter to characterize physicochemical and biochemical properties of antibiotics and to predict persistence and removal of drugs. pK a of piperacillin (PIP) is determined by potentiometric titration with a glass electrode. Electrospray ionization mass spectrometry (ESI-MS) is creatively applied to verify the reasonable pK a value at every dissociation step. Two microscopic pK a values (3.37 ± 0.06 and 8.96 ± 0.10) are identified and attributed to the direct dissociation of the carboxylic acid functional group and one secondary amide group, respectively. Different from other ß-lactam antibiotics, PIP presents a dissociation pattern where direct dissociation is involved instead of protonation dissociation. Moreover, the degradation tendency of PIP in an alkaline solution may alter the dissociation pattern or dismiss the corresponding pK a of the amphoteric ß-lactam antibiotics. This work offers a reliable determination of the acid dissociation constant of PIP and a clear interpretation of the effect of stability of antibiotics on the dissociation process.
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Affiliation(s)
- Guoao Li
- Beijing Key Laboratory of Water Resources and Environmental Engineering, School of water resource and Environment, China University of Geosciences (Beijing), Beijing, China
| | - Yaling Wang
- Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing, China
- National Engineering Research Center for Urban Environmental Pollution Control, Beijing, China
| | - Chengyi Sun
- Beijing Municipal Research Institute of Eco-Environmental Protection, Beijing, China
- National Engineering Research Center for Urban Environmental Pollution Control, Beijing, China
| | - Fei Liu
- Beijing Key Laboratory of Water Resources and Environmental Engineering, School of water resource and Environment, China University of Geosciences (Beijing), Beijing, China
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Du Y, Zhao F, Xing J, Liu Z, Cui M. Stabilization of Labile Lysozyme-Ligand Interactions in Native Electrospray Ionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:366-373. [PMID: 36735536 DOI: 10.1021/jasms.2c00238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Flavonoids are polyphenolic secondary metabolites with extensive biological activities and pharmacological effects. Exploring the interactions of flavonoids with proteins may be helpful for understanding their biological processes. Electrospray ionization mass spectrometry (ESI-MS) is a powerful tool to characterize the noncovalent protein-ligand (PL) complexes. However, some protein-flavonoid complexes are labile during electrospray ionization. Here, the labile lysozyme-flavonoid (rutin, icariin, and naringin) complexes were determined by direct ESI-MS without derivation. It has been found that low amounts of N-methylpyrrolidinone and dimethylformamide can protect labile lysozyme-flavonoid complexes away from dissociation during electrospray ionization process. The intact lysozyme-flavonoid complexes were specifically observed in mass spectra, and the measured binding affinities by ESI-MS were matched with the fluorescence data. The effects of additives on the analysis of lysozyme-flavonoid complexes were investigated by ESI-MS, combined with the molecular docking and fluorescence. This strategy was helpful to investigate the labile PL interactions by direct ESI-MS.
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Affiliation(s)
- Yang Du
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin130022, China
- University of Science and Technology of China, Hefei, Anhui230029, China
| | - Fengjiao Zhao
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin130022, China
- University of Science and Technology of China, Hefei, Anhui230029, China
| | - Junpeng Xing
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin130022, China
| | - Zhiqiang Liu
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin130022, China
| | - Meng Cui
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin130022, China
- University of Science and Technology of China, Hefei, Anhui230029, China
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Płonka D, Wiśniewska MD, Peris-Díaz MD, Krężel A, Bonna AM, Bal W. An Overlooked Hepcidin-Cadmium Connection. Int J Mol Sci 2022; 23:ijms232415483. [PMID: 36555126 PMCID: PMC9779829 DOI: 10.3390/ijms232415483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/03/2022] [Accepted: 12/05/2022] [Indexed: 12/12/2022] Open
Abstract
Hepcidin (DTHFPICIFCCGCCHRSKCGMCCKT), an iron-regulatory hormone, is a 25-amino-acid peptide with four intramolecular disulfide bonds circulating in blood. Its hormonal activity is indirect and consists of marking ferroportin-1 (an iron exporter) for degradation. Hepcidin biosynthesis involves the N-terminally extended precursors prepro-hepcidin and pro-hepcidin, processed by peptidases to the final 25-peptide form. A sequence-specific formation of disulfide bonds and export of the oxidized peptide to the bloodstream follows. In this study we considered the fact that prior to export, reduced hepcidin may function as an octathiol ligand bearing some resemblance to the N-terminal part of the α-domain of metallothioneins. Consequently, we studied its ability to bind Zn(II) and Cd(II) ions using the original peptide and a model for prohepcidin extended N-terminally with a stretch of five arginine residues (5R-hepcidin). We found that both form equivalent mononuclear complexes with two Zn(II) or Cd(II) ions saturating all eight Cys residues. The average affinity at pH 7.4, determined from pH-metric spectroscopic titrations, is 1010.1 M-1 for Zn(II) ions; Cd(II) ions bind with affinities of 1015.2 M-1 and 1014.1 M-1. Using mass spectrometry and 5R-hepcidin we demonstrated that hepcidin can compete for Cd(II) ions with metallothionein-2, a cellular cadmium target. This study enabled us to conclude that hepcidin binds Zn(II) and Cd(II) sufficiently strongly to participate in zinc physiology and cadmium toxicity under intracellular conditions.
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Affiliation(s)
- Dawid Płonka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Marta D. Wiśniewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Manuel D. Peris-Díaz
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Arkadiusz M. Bonna
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland
- Correspondence:
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6
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Opening opportunities for K d determination and screening of MHC peptide complexes. Commun Biol 2022; 5:488. [PMID: 35606511 PMCID: PMC9127112 DOI: 10.1038/s42003-022-03366-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 04/13/2022] [Indexed: 01/15/2023] Open
Abstract
An essential element of adaptive immunity is selective binding of peptide antigens by major histocompatibility complex (MHC) class I proteins and their presentation to cytotoxic T lymphocytes. Using native mass spectrometry, we analyze the binding of peptides to an empty disulfide-stabilized HLA-A*02:01 molecule and, due to its unique stability, we determine binding affinities of complexes loaded with truncated or charge-reduced peptides. We find that the two anchor positions can be stabilized independently, and we further analyze the contribution of additional amino acid positions to the binding strength. As a complement to computational prediction tools, our method estimates binding strength of even low-affinity peptides to MHC class I complexes quickly and efficiently. It has huge potential to eliminate binding affinity biases and thus accelerate drug discovery in infectious diseases, autoimmunity, vaccine design, and cancer immunotherapy. The authors present a sensitive and rapid method to determine the binding strength of MHC class 1 peptide complexes using native mass spectrometry.
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7
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Norovirus-glycan interactions - how strong are they really? Biochem Soc Trans 2021; 50:347-359. [PMID: 34940787 PMCID: PMC9022987 DOI: 10.1042/bst20210526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/01/2021] [Accepted: 12/06/2021] [Indexed: 12/25/2022]
Abstract
Infection with human noroviruses requires attachment to histo blood group antigens (HBGAs) via the major capsid protein VP1 as a primary step. Several crystal structures of VP1 protruding domain dimers, so called P-dimers, complexed with different HBGAs have been solved to atomic resolution. Corresponding binding affinities have been determined for HBGAs and other glycans exploiting different biophysical techniques, with mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy being most widely used. However, reported binding affinities are inconsistent. At the extreme, for the same system MS detects binding whereas NMR spectroscopy does not, suggesting a fundamental source of error. In this short essay, we will explain the reason for the observed differences and compile reliable and reproducible binding affinities. We will then highlight how a combination of MS techniques and NMR experiments affords unique insights into the process of HBGA binding by norovirus capsid proteins.
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8
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Płonka D, Kotuniak R, Dąbrowska K, Bal W. Electrospray-Induced Mass Spectrometry Is Not Suitable for Determination of Peptidic Cu(II) Complexes. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2766-2776. [PMID: 34738801 PMCID: PMC8640992 DOI: 10.1021/jasms.1c00206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 10/22/2021] [Accepted: 10/25/2021] [Indexed: 06/13/2023]
Abstract
The toolset of mass spectrometry (MS) is still expanding, and the number of metal ion complexes researched this way is growing. The Cu(II) ion forms particularly strong peptide complexes of biological interest which are frequent objects of MS studies, but quantitative aspects of some reported results are at odds with those of experiments performed in solution. Cu(II) complexes are usually characterized by fast ligand exchange rates, despite their high affinity, and we speculated that such kinetic lability could be responsible for the observed discrepancies. In order to resolve this issue, we selected peptides belonging to the ATCUN family characterized with high and thoroughly determined Cu(II) binding constants and re-estimated them using two ESI-MS techniques: standard conditions in combination with serial dilution experiments and very mild conditions for competition experiments. The sample acidification, which accompanies the electrospray formation, was simulated with the pH-jump stopped-flow technique. Our results indicate that ESI-MS should not be used for quantitative studies of Cu(II)-peptide complexes because the electrospray formation process compromises the entropic contribution to the complex stability, yielding underestimations of complex stability constants.
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9
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Protein Secondary Structure Affects Glycan Clustering in Native Mass Spectrometry. Life (Basel) 2021; 11:life11060554. [PMID: 34208397 PMCID: PMC8231113 DOI: 10.3390/life11060554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 01/01/2023] Open
Abstract
Infection by the humannoroviruses (hNoV), for the vast majority of strains, requires attachment of the viral capsid to histo blood group antigens (HBGAs). The HBGA-binding pocket is formed by dimers of the protruding domain (P dimers) of the capsid protein VP1. Several studies have focused on HBGA binding to P dimers, reporting binding affinities and stoichiometries. However, nuclear magnetic resonance spectroscopy (NMR) and native mass spectrometry (MS) analyses yielded incongruent dissociation constants (KD) for the binding of HBGAs to P dimers and, in some cases, disagreed on whether glycans bind at all. We hypothesized that glycan clustering during electrospray ionization in native MS critically depends on the physicochemical properties of the protein studied. It follows that the choice of a reference protein is crucial. We analysed carbohydrate clustering using various P dimers and eight non-glycan binding proteins serving as possible references. Data from native and ion mobility MS indicate that the mass fraction of β-sheets has a strong influence on the degree of glycan clustering. Therefore, the determination of specific glycan binding affinities from native MS must be interpreted cautiously.
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Liu T, Marcinko TM, Vachet RW. Protein-Ligand Affinity Determinations Using Covalent Labeling-Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:1544-1553. [PMID: 32501685 PMCID: PMC7332385 DOI: 10.1021/jasms.0c00131] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Determining the binding affinity is an important aspect of characterizing protein-ligand complexes. Here, we describe an approach based on covalent labeling (CL)-mass spectrometry (MS) that can accurately provide protein-ligand dissociation constants (Kd values) using diethylpyrocarbonate (DEPC) as the labeling reagent. Even though DEPC labeling reactions occur on a time scale that is similar to the dissociation/reassociation rates of many protein-ligand complexes, we demonstrate that relatively accurate binding constants can still be obtained as long as the extent of protein labeling is kept below 30%. Using two well-established model systems and one insufficiently characterized system, we find that Kd values can be determined that are close to values obtained in previous measurements. The CL-MS-based strategy that is described here should serve as an alternative for characterizing protein-ligand complexes that are challenging to measure by other methods. Moreover, this method has the potential to provide, simultaneously, the affinity and binding site information.
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Affiliation(s)
| | | | - Richard W. Vachet
- Corresponding author: Prof. Richard W. Vachet, Department of Chemistry, University of Massachusetts, Amherst, MA 01003, , Phone: (413) 545-2733
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Chen PW, Tseng CY, Shi F, Bi B, Lo YH. Detecting Protein-Ligand Interaction from Integrated Transient Induced Molecular Electronic Signal (i-TIMES). Anal Chem 2020; 92:3852-3859. [PMID: 32045225 DOI: 10.1021/acs.analchem.9b05310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Quantitative information about protein-ligand interactions is central to drug discovery. To obtain the quintessential reaction dissociation constant, ideally measurements of reactions should be performed without perturbations by molecular labeling or immobilization. The technique of transient induced molecular electrical signal (TIMES) has provided a promising technique to meet such requirements, and its performance in a microfluidic environment further offers the potential for high throughput and reduced consumption of reagents. In this work, we further the development by using integrated TIMES signal (i-TIMES) to greatly enhance the accuracy and reproducibility of the measurement. While the transient response may be of interest, the integrated signal directly measures the total amount of surface charge density resulted from molecules near the surface of electrode. The signals enable quantitative characterization of protein-ligand interactions. We have demonstrated the feasibility of i-TIMES technique using different biomolecules including lysozyme, N,N',N″-triacetylchitotriose (TriNAG), aptamer, p-aminobenzamidine (pABA), bovine pancreatic ribonuclease A (RNaseA), and uridine-3'-phosphate (3'UMP). The results show i-TIMES is a simple and accurate technique that can bring tremendous value to drug discovery and research of intermolecular interactions.
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Affiliation(s)
- Ping-Wei Chen
- Chemical Engineering Program, University of California San Diego, La Jolla, California 92093-0448, United States
| | - Chi-Yang Tseng
- Materials Science and Engineering Program, University of California San Diego, La Jolla, California 92093-0418, United States
| | - Fumin Shi
- InnoScounting LLC, Rockville, Maryland 20850-4432, United States
| | - Bo Bi
- InnoScounting LLC, Rockville, Maryland 20850-4432, United States
| | - Yu-Hwa Lo
- Chemical Engineering Program, University of California San Diego, La Jolla, California 92093-0448, United States.,Materials Science and Engineering Program, University of California San Diego, La Jolla, California 92093-0418, United States.,Electrical and Computer Engineering Department, University of California San Diego, La Jolla, California 92093-0407, United States
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Zheng S, Yuan S, Hou Z, Li G, Chen Y, Pan Y, Liu Y, Huang G. Charge-dependent modulation of specific and nonspecific protein-metal ion interactions in nanoelectrospray ionization mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:1502-1511. [PMID: 31151135 DOI: 10.1002/rcm.8493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 05/21/2019] [Accepted: 05/22/2019] [Indexed: 06/09/2023]
Abstract
RATIONALE Previous studies found that charge state could affect both specific and nonspecific binding of protein-metal ion interactions in nanoelectrospray ionization mass spectrometry (nESI-MS). However, the two kinds of interactions have been studied individually in spite of the problem that they often coexist in the same system. Thus, it is necessary to study the effects of charge state on specific and nonspecific protein-metal ion interactions in one system to reveal more accurate binding state. METHODS The HIV-1 nucleocapsid protein (NCp7(31-55)) which can bind specifically and nonspecifically to Zn2+ served as the model to show the charge-dependent protein-metal ion interactions. Hydrogen/deuterium exchange (HDX) and photodissociation (PD) were used to demonstrate that specific binding state was correlated with protein structure. In addition to NCp7(31-55), three other model proteins were used to investigate the reason for the charge-dependent nonspecific binding. RESULTS For specific binding, we proposed that protein ions with different charge states had different conformations. The HDX results showed that labile protons in the NCp7(31-55)-Zn complex were exchanged in a charge-state-dependent way. The PD experiments revealed differential fragment yields for different charge states. For nonspecific binding, higher charge states had more Zn2+ additions, but less SO4 2- additions. The effects of charge states on nonspecific binding levels were entirely the opposite for Zn2+ and SO4 2- . These results could reveal that the nonspecific binding was caused by electrostatic interaction. CONCLUSIONS For specific binding, NCp7(31-55) with lower charge states have folding and undenatured structures. The binding states of lower charge states can better reflect more native binding states. For nonspecific binding, when multiple metal ions adduct to proteins, the proteins have more net positive charges, which tend to generate higher charge ions during electrospray.
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Affiliation(s)
- Shihui Zheng
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Siming Yuan
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Zhuanghao Hou
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Gongyu Li
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Yuting Chen
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Yang Pan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, P. R. China
| | - Yangzhong Liu
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Guangming Huang
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, P. R. China
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Sengupta A, Wu J, Seffernick JT, Sabag-Daigle A, Thomsen N, Chen TH, Capua AD, Bell CE, Ahmer BMM, Lindert S, Wysocki VH, Gopalan V. Integrated Use of Biochemical, Native Mass Spectrometry, Computational, and Genome-Editing Methods to Elucidate the Mechanism of a Salmonella deglycase. J Mol Biol 2019; 431:4497-4513. [PMID: 31493410 DOI: 10.1016/j.jmb.2019.08.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 01/18/2023]
Abstract
Salmonellais a foodborne pathogen that causes annually millions of cases of salmonellosis globally, yet Salmonella-specific antibacterials are not available. During inflammation, Salmonella utilizes the Amadori compound fructose-asparagine (F-Asn) as a nutrient through the successive action of three enzymes, including the terminal FraB deglycase. Salmonella mutants lacking FraB are highly attenuated in mouse models of inflammation due to the toxic build-up of the substrate 6-phosphofructose-aspartate (6-P-F-Asp). This toxicity makes Salmonella FraB an appealing drug target, but there is currently little experimental information about its catalytic mechanism. Therefore, we sought to test our postulated mechanism for the FraB-catalyzed deglycation of 6-P-F-Asp (via an enaminol intermediate) to glucose-6-phosphate and aspartate. A FraB homodimer model generated by RosettaCM was used to build substrate-docked structures that, coupled with sequence alignment of FraB homologs, helped map a putative active site. Five candidate active-site residues-including three expected to participate in substrate binding-were mutated individually and characterized. Native mass spectrometry and ion mobility were used to assess collision cross sections and confirm that the quaternary structure of the mutants mirrored the wild type, and that there are two active sites/homodimer. Our biochemical studies revealed that FraB Glu214Ala, Glu214Asp, and His230Ala were inactive in vitro, consistent with deprotonated-Glu214 and protonated-His230 serving as a general base and a general acid, respectively. Glu214Ala or His230Ala introduced into the Salmonella chromosome by CRISPR/Cas9-mediated genome editing abolished growth on F-Asn. Results from our computational and experimental approaches shed light on the catalytic mechanism of Salmonella FraB and of phosphosugar deglycases in general.
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Affiliation(s)
- Anindita Sengupta
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Jikang Wu
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Justin T Seffernick
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Anice Sabag-Daigle
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Nicholas Thomsen
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Tien-Hao Chen
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Angela Di Capua
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Charles E Bell
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210, USA
| | - Brian M M Ahmer
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH 43210, USA
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Vicki H Wysocki
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Venkat Gopalan
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
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14
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Ozdemir A, Gulfen M, Lin JL, Chen CH. A Comparative Study for Sonic Spray and Electrospray Ionization Methods to Determine Noncovalent Protein–Ligand Interactions. ANAL LETT 2019. [DOI: 10.1080/00032719.2019.1622558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Abdil Ozdemir
- Department of Chemistry, Faculty of Arts and Sciences, Sakarya University, 54187 Esentepe, Sakarya, Turkey
| | - Mustafa Gulfen
- Department of Chemistry, Faculty of Arts and Sciences, Sakarya University, 54187 Esentepe, Sakarya, Turkey
| | - Jung-Lee Lin
- Genomics Research Center, Academia Sinica, Taipei, Taiwan
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15
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Ferey J, Da Silva D, Colas C, Nehmé R, Lafite P, Roy V, Morin P, Daniellou R, Agrofoglio L, Maunit B. Monitoring of successive phosphorylations of thymidine using free and immobilized human nucleoside/nucleotide kinases by Flow Injection Analysis with High-Resolution Mass Spectrometry. Anal Chim Acta 2019; 1049:115-122. [DOI: 10.1016/j.aca.2018.10.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 10/09/2018] [Accepted: 10/13/2018] [Indexed: 11/30/2022]
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16
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Rabuck-Gibbons JN, Lodge JM, Mapp AK, Ruotolo BT. Collision-Induced Unfolding Reveals Unique Fingerprints for Remote Protein Interaction Sites in the KIX Regulation Domain. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:94-102. [PMID: 30136215 PMCID: PMC6320266 DOI: 10.1007/s13361-018-2043-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 07/24/2018] [Accepted: 07/28/2018] [Indexed: 06/08/2023]
Abstract
The kinase-inducible domain (KIX) of the transcriptional coactivator CBP binds multiple transcriptional regulators through two allosterically connected sites. Establishing a method for observing activator-specific KIX conformations would facilitate the discovery of drug-like molecules that capture specific conformations and further elucidate how distinct activator-KIX complexes produce differential transcriptional effects. However, the transient and low to moderate affinity interactions between activators and KIX are difficult to capture using traditional biophysical assays. Here, we describe a collision-induced unfolding-based approach that produces unique fingerprints for peptides bound to each of the two available sites within KIX, as well as a third fingerprint for ternary KIX complexes. Furthermore, we evaluate the analytical utility of unfolding fingerprints for KIX complexes using CIUSuite, and conclude by speculating as to the structural origins of the conformational families created from KIX:peptide complexes following collisional activation. Graphical Abstract ᅟ.
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Affiliation(s)
- Jessica N Rabuck-Gibbons
- Department of Chemistry, University of Michigan, 930 N University, Ann Arbor, MI, 48109, USA
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 N Torrey Pines Rd., La Jolla, CA, 92037, USA
| | - Jean M Lodge
- Department of Chemistry, University of Michigan, 930 N University, Ann Arbor, MI, 48109, USA
- Life Science Institute, University of Michigan, 210 Washtenaw Ave., Ann Arbor, MI, 48109, USA
- University of Wisconsin, Genome Center, 425 Henry Mall, Madison, WI, 53706, USA
| | - Anna K Mapp
- Department of Chemistry, University of Michigan, 930 N University, Ann Arbor, MI, 48109, USA
- Life Science Institute, University of Michigan, 210 Washtenaw Ave., Ann Arbor, MI, 48109, USA
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, 930 N University, Ann Arbor, MI, 48109, USA.
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17
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Deep Structural Analysis of RPAP3 and PIH1D1, Two Components of the HSP90 Co-chaperone R2TP Complex. Structure 2018; 26:1196-1209.e8. [DOI: 10.1016/j.str.2018.06.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 05/04/2018] [Accepted: 06/08/2018] [Indexed: 12/22/2022]
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18
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Archer JJ, Karki S, Shi F, Sistani H, Levis RJ. Quantification of Protein-Ligand Interactions by Laser Electrospray Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:1484-1492. [PMID: 29654537 DOI: 10.1007/s13361-018-1935-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 03/01/2018] [Accepted: 03/02/2018] [Indexed: 06/08/2023]
Abstract
Laser electrospray mass spectrometry (LEMS) measurement of the dissociation constant (Kd) for hen egg white lysozyme (HEWL) and N,N',N″-triacetylchitotriose (NAG3) revealed an apparent Kd value of 313.2 ± 25.9 μM for the ligand titration method. Similar measurements for N,N',N″,N″'-tetraacetylchitotetraose (NAG4) revealed an apparent Kd of 249.3 ± 13.6 μM. An electrospray ionization mass spectrometry (ESI-MS) experiment determined a Kd value of 9.8 ± 0.6 μM. In a second LEMS approach, a calibrated measurement was used to determine a Kd value of 6.8 ± 1.5 μM for NAG3. The capture efficiency of LEMS was measured to be 3.6 ± 1.8% and is defined as the fraction of LEMS sample detected after merging with the ESI plume. When the dilution is factored into the ligand titration measurement, the adjusted Kd value was 11.3 μM for NAG3 and 9.0 μM for NAG4. The calibration method for measuring Kd developed in this study can be applied to solutions containing unknown analyte concentrations. Graphical Abstract.
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Affiliation(s)
- Jieutonne J Archer
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Santosh Karki
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Fengjian Shi
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Habiballah Sistani
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Robert J Levis
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA.
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19
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How can native mass spectrometry contribute to characterization of biomacromolecular higher-order structure and interactions? Methods 2018; 144:3-13. [PMID: 29704661 DOI: 10.1016/j.ymeth.2018.04.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 04/03/2018] [Accepted: 04/21/2018] [Indexed: 01/16/2023] Open
Abstract
Native mass spectrometry (MS) is an emerging approach for characterizing biomacromolecular structure and interactions under physiologically relevant conditions. In native MS measurement, intact macromolecules or macromolecular complexes are directly ionized from a non-denaturing solvent, and key noncovalent interactions that hold the complexes together can be preserved for MS analysis in the gas phase. This technique provides unique multi-level structural information such as conformational changes, stoichiometry, topology and dynamics, complementing conventional biophysical techniques. Despite the maturation of native MS and greatly expanded range of applications in recent decades, further dissemination is needed to make the community aware of such a technique. In this review, we attempt to provide an overview of the current body of knowledge regarding major aspects of native MS and explain how such technique contributes to the characterization of biomacromolecular higher-order structure and interactions.
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20
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Chingin K, Barylyuk K. Charge-State-Dependent Variation of Signal Intensity Ratio between Unbound Protein and Protein-Ligand Complex in Electrospray Ionization Mass Spectrometry: The Role of Solvent-Accessible Surface Area. Anal Chem 2018; 90:5521-5528. [PMID: 29653057 DOI: 10.1021/acs.analchem.7b05349] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Native electrospray ionization mass spectrometry (ESI-MS) is nowadays widely used for the direct and sensitive determination of protein complex stoichiometry and binding affinity constants ( Ka). A common yet poorly understood phenomenon in native ESI-MS is the difference between the charge-state distributions (CSDs) of the bound protein-ligand complex (PL) and unbound protein (P) signals. This phenomenon is typically attributed to experimental artifacts such as nonspecific binding or in-source dissociation and is considered highly undesirable, because the determined Ka values display strong variation with charge state. This situation raises serious concerns regarding the reliability of ESI-MS for the analysis of protein complexes. Here we demonstrate that, contrary to the common belief, the CSD difference between P and PL ions can occur without any loss of complex integrity, simply due to a change in the solvent-accessible surface area (ΔSASA) of the protein upon ligand binding in solution. The experimental CSD shifts for PL and P ions in ESI-MS are explained in relation to the magnitude of ΔSASA for diverse protein-ligand systems using a simple model based on the charged residue mechanism. Our analysis shows that the revealed ΔSASA factor should be considered rather general and be given attention for the correct spectral interpretation of protein complexes.
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Affiliation(s)
- Konstantin Chingin
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation , East China University of Technology , Guanglan Road 418 , Nanchang , Jiangxi , China 330013
| | - Konstantin Barylyuk
- Department of Biochemistry , University of Cambridge , Hopkins Building, Tennis Court Road , Cambridge CB2 1QW , United Kingdom
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21
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Lu Y, Pieterse CL, Robertson WD, Miller RJD. Soft Picosecond Infrared Laser Extraction of Highly Charged Proteins and Peptides from Bulk Liquid Water for Mass Spectrometry. Anal Chem 2018. [PMID: 29522677 DOI: 10.1021/acs.analchem.7b04306] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the soft laser extraction and production of highly charged peptide and protein ions for mass spectrometry directly from bulk liquid water at atmospheric pressure and room temperature, using picosecond infrared laser ablation. Stable ion signal from singly charged small molecules, as well as highly charged biomolecular ions, from aqueous solutions at low laser pulse fluence (∼0.3 J cm-2) is demonstrated. Sampling via single picosecond laser pulses is shown to extract less than 27 pL of volume from the sample, producing highly charged peptide and protein ions for mass spectrometry detection. The ablation and ion generation is demonstrated to be soft in nature, producing natively folded proteins ions under sample conditions described for native mass spectrometry. The method provides laser-based sampling flexibility, precision and control with highly charged ion production directly from water at low and near neutral pH. This approach does not require an additional ionization device or high voltage applied directly to the sample.
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Affiliation(s)
- Yinfei Lu
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149 , Hamburg 22761 , Germany
| | - Cornelius L Pieterse
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149 , Hamburg 22761 , Germany
| | - Wesley D Robertson
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149 , Hamburg 22761 , Germany
| | - R J Dwayne Miller
- Max Planck Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149 , Hamburg 22761 , Germany
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22
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Konermann L. Addressing a Common Misconception: Ammonium Acetate as Neutral pH "Buffer" for Native Electrospray Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1827-1835. [PMID: 28710594 DOI: 10.1007/s13361-017-1739-3] [Citation(s) in RCA: 138] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/14/2017] [Accepted: 06/15/2017] [Indexed: 05/12/2023]
Abstract
Native ESI-MS involves the transfer of intact proteins and biomolecular complexes from solution into the gas phase. One potential pitfall is the occurrence of pH-induced changes that can affect the analyte while it is still surrounded by solvent. Most native ESI-MS studies employ neutral aqueous ammonium acetate solutions. It is a widely perpetuated misconception that ammonium acetate buffers the analyte solution at neutral pH. By definition, a buffer consists of a weak acid and its conjugate weak base. The buffering range covers the weak acid pKa ± 1 pH unit. NH4+ and CH3-COO- are not a conjugate acid/base pair, which means that they do not constitute a buffer at pH 7. Dissolution of ammonium acetate salt in water results in pH 7, but this pH is highly labile. Ammonium acetate does provide buffering around pH 4.75 (the pKa of acetic acid) and around pH 9.25 (the pKa of ammonium). This implies that neutral ammonium acetate solutions electrosprayed in positive ion mode will likely undergo acidification down to pH 4.75 ± 1 in the ESI plume. Ammonium acetate nonetheless remains a useful additive for native ESI-MS. It is a volatile electrolyte that can mimic the solvation properties experienced by proteins under physiological conditions. Also, a drop from pH 7 to around pH 4.75 is less dramatic than the acidification that would take place in pure water. It is hoped that the habit of referring to pH 7 solutions as ammonium acetate "buffer" will disappear from the literature. Ammonium acetate "solution" should be used instead. Graphical Abstract ᅟ.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada.
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23
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Morris DL, Zampino AP, Taraboletti AA, Shriver LP, Leeper TC, Ziegler CJ. Lysozyme-catalyzed formation of a conjugated polyacetylene. Polym Chem 2017. [DOI: 10.1039/c7py01250k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Hen egg white lysozyme catalyzes the polymerization of 2-ethynylpyridine in water as the singular protein catalyst. This marks the first time a protein has been observed generating conjugated polymers from alkynes.
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Affiliation(s)
- D. L. Morris
- The University of Akron 302 E Buchtel Ave
- Akron
- USA
| | | | | | | | - T. C. Leeper
- The University of Akron 302 E Buchtel Ave
- Akron
- USA
- Kennesaw State University
- Kennesaw
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24
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Zhang T, Wei T, Han Y, Ma H, Samieegohar M, Chen PW, Lian I, Lo YH. Protein-Ligand Interaction Detection with a Novel Method of Transient Induced Molecular Electronic Spectroscopy (TIMES): Experimental and Theoretical Studies. ACS CENTRAL SCIENCE 2016; 2:834-842. [PMID: 27924312 PMCID: PMC5126721 DOI: 10.1021/acscentsci.6b00217] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Indexed: 05/08/2023]
Abstract
Protein-ligand interaction detection without disturbances (e.g., surface immobilization, fluorescent labeling, and crystallization) presents a key question in protein chemistry and drug discovery. The emergent technology of transient induced molecular electronic spectroscopy (TIMES), which incorporates a unique design of microfluidic platform and integrated sensing electrodes, is designed to operate in a label-free and immobilization-free manner to provide crucial information for protein-ligand interactions in relevant physiological conditions. Through experiments and theoretical simulations, we demonstrate that the TIMES technique actually detects protein-ligand binding through signals generated by surface electric polarization. The accuracy and sensitivity of experiments were demonstrated by precise measurements of dissociation constant of lysozyme and N-acetyl-d-glucosamine (NAG) ligand and its trimer, NAG3. Computational fluid dynamics (CFD) computation is performed to demonstrate that the surface's electric polarization signal originates from the induced image charges during the transition state of surface mass transport, which is governed by the overall effects of protein concentration, hydraulic forces, and surface fouling due to protein adsorption. Hybrid atomistic molecular dynamics (MD) simulations and free energy computation show that ligand binding affects lysozyme structure and stability, producing different adsorption orientation and surface polarization to give the characteristic TIMES signals. Although the current work is focused on protein-ligand interactions, the TIMES method is a general technique that can be applied to study signals from reactions between many kinds of molecules.
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Affiliation(s)
- Tiantian Zhang
- Materials
Science and Engineering Program, University
of California San Diego, La Jolla, California 92093-0418, United States
| | - Tao Wei
- Dan
F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
| | - Yuanyuan Han
- Electrical
and Computer Engineering Department, University
of California San Diego, La Jolla, California 92093-0407, United States
| | - Heng Ma
- Dan
F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
| | - Mohammadreza Samieegohar
- Dan
F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
| | - Ping-Wei Chen
- Chemical
Engineering Program, University of California
San Diego, La Jolla, California 92093-0448, United States
| | - Ian Lian
- Biology
Department, Lamar University, Beaumont, Texas 77710, United States
| | - Yu-Hwa Lo
- Materials
Science and Engineering Program, University
of California San Diego, La Jolla, California 92093-0418, United States
- Electrical
and Computer Engineering Department, University
of California San Diego, La Jolla, California 92093-0407, United States
- E-mail:
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25
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Chingin K, Barylyuk K, Chen H. On the preservation of non-covalent protein complexes during electrospray ionization. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0377. [PMID: 27644969 PMCID: PMC5031642 DOI: 10.1098/rsta.2015.0377] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/13/2016] [Indexed: 06/06/2023]
Abstract
The application range of electrospray ionization mass spectrometry for the quantitative determination of stoichiometries and binding constants for non-covalent protein complexes is broadly discussed. The underlying fundamental question is whether or not the original molecular equilibrium can be preserved during the ionization process and be revealed by subsequent mass spectrometry analysis. Here, we take a new look at this question by discussing recent studies in droplet chemistry.This article is part of the themed issue 'Quantitative mass spectrometry'.
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Affiliation(s)
- Konstantin Chingin
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Guanglan Road 418, Nanchang, Jiangxi 330013, People's Republic of China
| | - Konstantin Barylyuk
- Department of Biochemistry, University of Cambridge, Hopkins Building, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Huanwen Chen
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Guanglan Road 418, Nanchang, Jiangxi 330013, People's Republic of China
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26
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Sun Y, Vahidi S, Sowole MA, Konermann L. Protein Structural Studies by Traveling Wave Ion Mobility Spectrometry: A Critical Look at Electrospray Sources and Calibration Issues. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:31-40. [PMID: 26369778 DOI: 10.1007/s13361-015-1244-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Revised: 07/27/2015] [Accepted: 07/29/2015] [Indexed: 06/05/2023]
Abstract
The question whether electrosprayed protein ions retain solution-like conformations continues to be a matter of debate. One way to address this issue involves comparisons of collision cross sections (Ω) measured by ion mobility spectrometry (IMS) with Ω values calculated for candidate structures. Many investigations in this area employ traveling wave IMS (TWIMS). It is often implied that nanoESI is more conducive for the retention of solution structure than regular ESI. Focusing on ubiquitin, cytochrome c, myoglobin, and hemoglobin, we demonstrate that Ω values and collisional unfolding profiles are virtually indistinguishable under both conditions. These findings suggest that gas-phase structures and ion internal energies are independent of the type of electrospray source. We also note that TWIMS calibration can be challenging because differences in the extent of collisional activation relative to drift tube reference data may lead to ambiguous peak assignments. It is demonstrated that this problem can be circumvented by employing collisionally heated calibrant ions. Overall, our data are consistent with the view that exposure of native proteins to electrospray conditions can generate kinetically trapped ions that retain solution-like structures on the millisecond time scale of TWIMS experiments. ᅟ
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Affiliation(s)
- Yu Sun
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Siavash Vahidi
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Modupeola A Sowole
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada.
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27
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Santos IC, Waybright VB, Fan H, Ramirez S, Mesquita RBR, Rangel AOSS, Fryčák P, Schug KA. Determination of Noncovalent Binding Using a Continuous Stirred Tank Reactor as a Flow Injection Device Coupled to Electrospray Ionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:1204-1212. [PMID: 25832030 DOI: 10.1007/s13361-015-1113-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2014] [Revised: 02/17/2015] [Accepted: 02/18/2015] [Indexed: 06/04/2023]
Abstract
Described is a new method based on the concept of controlled band dispersion, achieved by hyphenating flow injection analysis with ESI-MS for noncovalent binding determinations. A continuous stirred tank reactor (CSTR) was used as a FIA device for exponential dilution of an equimolar host-guest solution over time. The data obtained was treated for the noncovalent binding determination using an equimolar binding model. Dissociation constants between vancomycin and Ac-Lys(Ac)-Ala-Ala-OH peptide stereoisomers were determined using both the positive and negative ionization modes. The results obtained for Ac-L-Lys(Ac)-D-Ala-D-Ala (a model for a Gram-positive bacterial cell wall) binding were in reasonable agreement with literature values made by other mass spectrometry binding determination techniques. Also, the developed method allowed the determination of dissociation constants for vancomycin with Ac-L-Lys(Ac)-D-Ala-L-Ala, Ac-L-Lys(Ac)-L-Ala-D-Ala, and Ac-L-Lys(Ac)-L-Ala-L-Ala. Although some differences in measured binding affinities were noted using different ionization modes, the results of each determination were generally consistent. Differences are likely attributable to the influence of a pseudo-physiological ammonium acetate buffer solution on the formation of positively- and negatively-charged ionic complexes.
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Affiliation(s)
- Inês C Santos
- CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa/Porto, Rua Arquiteto Lobão Vital, Apartado 2511, 4202-401, Porto, Portugal
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28
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Liu W, Chen Q, Lin X, Lin JM. Online multi-channel microfluidic chip-mass spectrometry and its application for quantifying noncovalent protein-protein interactions. Analyst 2015; 140:1551-4. [PMID: 25597452 DOI: 10.1039/c4an02370f] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
To establish an automatic and online microfluidic chip-mass spectrometry (chip-MS) system, a device was designed and fabricated for microsampling by a hybrid capillary. The movement of the capillary was programmed by a computer to aspirate samples from different microfluidic channels in the form of microdroplets (typically tens of nanoliters in volume), which were separated by air plugs. The droplets were then directly analyzed by MS via paper spray ionization without any pretreatment. The feasibility and performance were demonstrated by a concentration gradient experiment. Furthermore, after eliminating the effect of nonuniform response factors by an internal standard method, determination of the association constant within a noncovalent protein-protein complex was successfully accomplished with the MS-based titration indicating the versatility and the potential of this novel platform for widespread applications.
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Affiliation(s)
- Wu Liu
- Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
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29
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Yao Y, Shams-Ud-Doha K, Daneshfar R, Kitova EN, Klassen JS. Quantifying protein-carbohydrate interactions using liquid sample desorption electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:98-106. [PMID: 25315460 DOI: 10.1007/s13361-014-1008-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 09/03/2014] [Accepted: 09/05/2014] [Indexed: 06/04/2023]
Abstract
The application of liquid sample desorption electrospray ionization mass spectrometry (liquid sample DESI-MS) for quantifying protein-carbohydrate interactions in vitro is described. Association constants for the interactions between lysozyme and β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-D-GlcNAc and β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-D-GlcNAc, and between a single chain antibody and α-D-Galp-(1 → 2)-[α-D-Abep-(1 → 3)]-α-D-Manp-OCH3 and β-D-Glcp-(1 → 2)-[α-D-Abep-(1 → 3)]-α-D-Manp-OCH3 measured using liquid sample DESI-MS were found to be in good agreement with values measured by isothermal titration calorimetry and the direct ESI-MS assay. The reference protein method, which was originally developed to correct ESI mass spectra for the occurrence of nonspecific ligand-protein binding, was shown to reliably correct liquid sample DESI mass spectra for nonspecific binding. The suitability of liquid sample DESI-MS for quantitative binding measurements carried out using solutions containing high concentrations of the nonvolatile biological buffer phosphate buffered saline (PBS) was also explored. Binding of lysozyme to β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-D-GlcNAc in aqueous solutions containing up to 1× PBS was successfully monitored using liquid sample DESI-MS; with ESI-MS the binding measurements were limited to concentrations less than 0.02 X PBS.
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Affiliation(s)
- Yuyu Yao
- Alberta Glycomics Center and Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
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Kitova EN, El-Hawiet A, Klassen JS. Screening carbohydrate libraries for protein interactions using the direct ESI-MS assay. Applications to libraries of unknown concentration. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1908-16. [PMID: 25135608 DOI: 10.1007/s13361-014-0964-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 07/02/2014] [Accepted: 07/04/2014] [Indexed: 05/22/2023]
Abstract
A semiquantitative electrospray ionization mass spectrometry (ESI-MS) binding assay suitable for analyzing mixtures of oligosaccharides, at unknown concentrations, for interactions with target proteins is described. The assay relies on the differences in the ratio of the relative abundances of the ligand-bound and free protein ions measured by ESI-MS at two or more initial protein concentrations to distinguish low affinity (≤10(3) M(-1)) ligands from moderate and high affinity (>10(5) M(-1)) ligands present in the library and to rank their affinities. Control experiments were performed on solutions of a single chain antibody and a mixture of synthetic oligosaccharides, with known affinities, in the absence and presence of a 40-component carbohydrate library to demonstrate the implementation and reliability of the assay. The application of the assay for screening natural libraries of carbohydrates against proteins is also demonstrated using mixtures of human milk oligosaccharides, isolated from breast milk, and fragments of a bacterial toxin and human galectin 3.
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Affiliation(s)
- Elena N Kitova
- Alberta Glycomics Center and Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
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31
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Faggi E, Moure A, Bolte M, Vicent C, Luis SV, Alfonso I. Pseudopeptidic Cages as Receptors for N-Protected Dipeptides. J Org Chem 2014; 79:4590-601. [DOI: 10.1021/jo500629d] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Enrico Faggi
- Departamento
de Química Biológica y Modelización Molecular, Instituto de Química Avanzada de Cataluña (IQAC-CSIC), Jordi Girona
18-26, E-08034 Barcelona, Spain
| | - Alejandra Moure
- Departamento
de Química Biológica y Modelización Molecular, Instituto de Química Avanzada de Cataluña (IQAC-CSIC), Jordi Girona
18-26, E-08034 Barcelona, Spain
| | - Michael Bolte
- Institut
für Anorganische Chemie, J.-W.-Goethe-Universität, Max-von-Laue-Strasse 7, D-60438 Frankfurt/Main, Germany
| | | | | | - Ignacio Alfonso
- Departamento
de Química Biológica y Modelización Molecular, Instituto de Química Avanzada de Cataluña (IQAC-CSIC), Jordi Girona
18-26, E-08034 Barcelona, Spain
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32
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Sekar R, Kailasa SK, Chen YC, Wu HF. Electrospray ionization tandem mass spectrometric studies to probe the interaction of Cu(II) with amoxicillin. CHINESE CHEM LETT 2014. [DOI: 10.1016/j.cclet.2013.10.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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33
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Lin H, Kitova EN, Klassen JS. Measuring positive cooperativity using the direct ESI-MS assay. Cholera toxin B subunit homopentamer binding to GM1 pentasaccharide. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:104-110. [PMID: 24122305 DOI: 10.1007/s13361-013-0751-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 08/12/2013] [Accepted: 08/12/2013] [Indexed: 06/02/2023]
Abstract
Direct electrospray ionization mass spectrometry (ESI-MS) assay was used to investigate the stepwise binding of the GM1 pentasaccharide β-D-Galp-(1→3)-β-D-GalpNAc-(1→4)[α-D-Neu5Ac-(2→3)]-β-D-Galp-(1→4)-β-D-Glcp (GM1os) to the cholera toxin B subunit homopentamer (CTB5) and to establish conclusively whether GM1os binding is cooperative. Apparent association constants were measured for the stepwise addition of one to five GM1os to CTB5 at pH 6.9 and 22 °C. The intrinsic association constant, which was established from the apparent association constant for the addition of a single GM1os to CTB5, was found to be (3.2 ± 0.2) × 106 M(–1). This is in reasonable agreement with the reported value of (6.4 ± 0.3) × 106 M(–1), which was measured at pH 7.4 and 25 °C using isothermal titration calorimetry (ITC). Analysis of the apparent association constants provides direct and unambiguous evidence that GM1os binding exhibits small positive cooperativity. Binding was found to be sensitive to the number of ligand-bound nearest neighbor subunits, with the affinities enhanced by a factor of 1.7 and 2.9 when binding occurs next to one or two ligand-bound subunits, respectively. These findings, which provide quantitative support for the binding model proposed by Homans and coworkers [14], highlight the unique strengths of the direct ESI-MS assay for measuring cooperative ligand binding.
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34
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Cubrilovic D, Barylyuk K, Hofmann D, Walczak MJ, Gräber M, Berg T, Wider G, Zenobi R. Direct monitoring of protein–protein inhibition using nano electrospray ionization mass spectrometry. Chem Sci 2014. [DOI: 10.1039/c3sc53360c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We investigated the inhibition of the protein–protein interactions by nanoESI-MS to monitor the extent of inhibition and the binding mechanism.
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Affiliation(s)
- Dragana Cubrilovic
- Department of Chemistry and Applied Biosciences
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Konstantin Barylyuk
- Department of Chemistry and Applied Biosciences
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Daniela Hofmann
- Department of Molecular Biology and Biophysics
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Michal Jerzy Walczak
- Department of Molecular Biology and Biophysics
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Martin Gräber
- Institute of Organic Chemistry
- University of Leipzig
- 04103 Leipzig, Germany
| | - Thorsten Berg
- Institute of Organic Chemistry
- University of Leipzig
- 04103 Leipzig, Germany
| | - Gerhard Wider
- Department of Molecular Biology and Biophysics
- ETH Zurich
- 8093 Zurich, Switzerland
| | - Renato Zenobi
- Department of Chemistry and Applied Biosciences
- ETH Zurich
- 8093 Zurich, Switzerland
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35
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Liu P, Zhang J, Ferguson CN, Chen H, Loo JA. Measuring protein-ligand interactions using liquid sample desorption electrospray ionization mass spectrometry. Anal Chem 2013; 85:11966-72. [PMID: 24237005 PMCID: PMC3901310 DOI: 10.1021/ac402906d] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We have previously shown that liquid sample desorption electrospray ionization-mass spectrometry (DESI-MS) is able to measure large proteins and noncovalently bound protein complexes (to 150 kDa) (Ferguson et al., Anal. Chem. 2011, 83, 6468-6473). In this study, we further investigate the application of liquid sample DESI-MS to probe protein-ligand interactions. Liquid sample DESI allows the direct formation of intact protein-ligand complex ions by spraying ligands toward separate protein sample solutions. This type of "reactive" DESI methodology can provide rapid information on binding stiochiometry, selectivity, and kinetics, as demonstrated by the binding of ribonuclease A (RNaseA, 13.7 kDa) with cytidine nucleotide ligands and the binding of lysozyme (14.3 kDa) with acetyl chitose ligands. A higher throughput method for ligand screening by liquid sample DESI was demonstrated, in which different ligands were sequentially injected as a segmented flow for DESI ionization. Furthermore, supercharging to enhance analyte charge can be integrated with liquid sample DESI-MS, without interfering with the formation of protein-ligand complexes.
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Affiliation(s)
- Pengyuan Liu
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States
| | - Jiang Zhang
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
| | - Carly N. Ferguson
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
| | - Hao Chen
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States
| | - Joseph A. Loo
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California 90095, United States
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36
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Barylyuk K, Gülbakan B, Xie X, Zenobi R. DNA oligonucleotides: a model system with tunable binding strength to study monomer-dimer equilibria with electrospray ionization-mass spectrometry. Anal Chem 2013; 85:11902-12. [PMID: 24274465 DOI: 10.1021/ac402669e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Electrospray ionization (ESI) is increasingly used to measure binding strengths, but it is not always clear whether the ESI process introduces artifacts. Here we propose a model monomer-dimer equilibrium system based on DNA oligonucleotides to systematically explore biomolecular self-association with the ESI-mass spectrometry (MS) titration method. The oligonucleotides are designed to be self-complementary and have the same chemical composition and mass, allowing for equal ionization probability, ion transmission, and detection efficiency in ESI-MS. The only difference is the binding strength, which is determined by the nucleotide sequence and can be tuned to cover a range of dissociation constant values. This experimental design allows one to focus on the impact of ESI on the chemical equilibrium and to avoid the other typical sources of variation in ESI-MS signal responses, which yields a direct comparison of samples with different binding strengths. For a set of seven model DNA oligonucleotides, the monomer-dimer binding equilibrium was probed with the ESI-MS titration method in both positive and negative ion modes. A mathematical model describing the dependence of the monomer-to-dimer peak intensity ratio on the DNA concentration was proposed and used to extract apparent Kd values and the fraction of DNA duplex that irreversibly dissociates in the gas phase. The Kd values determined via ESI-MS titration were compared to those determined in solution with isothermal titration calorimetry and equilibrium thermal denaturation methods and were found to be significantly lower. The observed discrepancy was attributed to a greater electrospray response of dimers relative to that of monomers.
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Affiliation(s)
- Konstantin Barylyuk
- Department of Chemistry and Applied Biosciences, ETH Zurich , Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland
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37
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Cubrilovic D, Zenobi R. Influence of dimehylsulfoxide on protein-ligand binding affinities. Anal Chem 2013; 85:2724-30. [PMID: 23347283 DOI: 10.1021/ac303197p] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Because of its favorable physicochemical properties, DMSO is the standard solvent for sample storage and handling of compounds in drug discovery. To date, little attention was given to how DMSO influences protein-ligand binding strengths. In this study we investigated the effects of DMSO on different noncovalent protein-ligand complexes, in particular in terms of the binding affinities, which we determined using nanoESI-MS. For the investigation, three different protein-ligand complexes were chosen: trypsin-Pefabloc, lysozyme-tri-N-acetylchitotriose (NAG3), and carbonic anhydrase-chlorothiazide. The DMSO content in the nanoESI buffer was increased systematically from 0.5 to 8%. For all three model systems, it was shown that the binding affinity decreases upon addition of DMSO. Even 0.5-1% DMSO alters the KD values, in particular for the tight binding system carbonic anhydrase-chlorothiazide. The determined dissociation constant (KD) is up to 10 times higher than for a DMSO-free sample in the case of carbonic anhydrase-chlorothiazide binding. For the trypsin-Pefabloc and lysozyme-NAG3 complexes, the dissociation constants are 7 and 3 times larger, respectively, in the presence of DMSO. This work emphasizes the importance of effects of DMSO as a co-solvent for quantification of protein-ligand binding strengths in the early stages of drug discovery.
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Affiliation(s)
- Dragana Cubrilovic
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
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38
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Abstract
Native state mass spectrometry (MS) has been recognised as a rapid, sensitive, and high throughput method to directly investigate protein-ligand interactions for some time, however there are few examples reporting this approach as a screening method to identify relevant protein–fragment interactions in fragment-based drug discovery (FBDD). In this paper an overview of native state MS will be presented, highlighting the attractive properties of this method within the context of fragment screening applications. A summary of published examples using MS for fragment screening will be described and reflection on the outlook for the future adoption and implementation of native state MS as a complementary fragment screening method will be presented.
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39
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Bobbitt JM, Li L, Carlton DD, Yasin M, Bhawal S, Foss FW, Wernisch S, Pell R, Lindner W, Schug KA. Diastereoselective discrimination of lysine–alanine–alanine peptides by zwitterionic cinchona alkaloid-based chiral selectors using electrospray ionization mass spectrometry. J Chromatogr A 2012; 1269:308-15. [DOI: 10.1016/j.chroma.2012.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 07/27/2012] [Accepted: 08/03/2012] [Indexed: 11/15/2022]
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40
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Cubrilovic D, Biela A, Sielaff F, Steinmetzer T, Klebe G, Zenobi R. Quantifying protein-ligand binding constants using electrospray ionization mass spectrometry: a systematic binding affinity study of a series of hydrophobically modified trypsin inhibitors. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1768-77. [PMID: 22869298 DOI: 10.1007/s13361-012-0451-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 07/12/2012] [Accepted: 07/17/2012] [Indexed: 05/22/2023]
Abstract
NanoESI-MS is used for determining binding strengths of trypsin in complex with two different series of five congeneric inhibitors, whose binding affinity in solution depends on the size of the P3 substituent. The ligands of the first series contain a 4-amidinobenzylamide as P1 residue, and form a tight complex with trypsin. The inhibitors of the second series have a 2-aminomethyl-5-chloro-benzylamide as P1 group, and represent a model system for weak binders. The five different inhibitors of each group are based on the same scaffold and differ only in the length of the hydrophobic side chain of their P3 residue, which modulates the interactions in the S3/4 binding pocket of trypsin. The dissociation constants (K(D)) for high affinity ligands investigated by nanoESI-MS ranges from 15 nM to 450 nM and decreases with larger hydrophobic P3 side chains. Collision-induced dissociation (CID) experiments of five trypsin and benzamidine-based complexes show a correlation between trends in K(D) and gas-phase stability. For the second inhibitor series we could show that the effect of imidazole, a small stabilizing additive, can avoid the dissociation of the complex ions and as a result increases the relative abundance of weakly bound complexes. Here the K(D) values ranging from 2.9 to 17.6 μM, some 1-2 orders of magnitude lower than the first series. For both ligand series, the dissociation constants (K(D)) measured via nanoESI-MS were compared with kinetic inhibition constants (K(i)) in solution.
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Affiliation(s)
- Dragana Cubrilovic
- Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland
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41
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El-Hawiet A, Kitova EN, Klassen JS. Quantifying Carbohydrate–Protein Interactions by Electrospray Ionization Mass Spectrometry Analysis. Biochemistry 2012; 51:4244-53. [DOI: 10.1021/bi300436x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Amr El-Hawiet
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G
2G2
| | - Elena N. Kitova
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G
2G2
| | - John S. Klassen
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G
2G2
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42
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Jaquillard L, Saab F, Schoentgen F, Cadene M. Improved accuracy of low affinity protein-ligand equilibrium dissociation constants directly determined by electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:908-922. [PMID: 22430390 DOI: 10.1007/s13361-011-0305-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 11/07/2011] [Accepted: 11/23/2011] [Indexed: 05/31/2023]
Abstract
There is continued interest in the determination by ESI-MS of equilibrium dissociation constants (K(D)) that accurately reflect the affinity of a protein-ligand complex in solution. Issues in the measurement of K(D) are compounded in the case of low affinity complexes. Here we present a K(D) measurement method and corresponding mathematical model dealing with both gas-phase dissociation (GPD) and aggregation. To this end, a rational mathematical correction of GPD (f(sat)) is combined with the development of an experimental protocol to deal with gas-phase aggregation. A guide to apply the method to noncovalent protein-ligand systems according to their kinetic behavior is provided. The approach is validated by comparing the K(D) values determined by this method with in-solution K(D) literature values. The influence of the type of molecular interactions and instrumental setup on f(sat) is examined as a first step towards a fine dissection of factors affecting GPD. The method can be reliably applied to a wide array of low affinity systems without the need for a reference ligand or protein.
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Affiliation(s)
- Lucie Jaquillard
- Centre de Biophysique Moléculaire, CNRS UPR 4301, affiliated with Université d'Orléans, rue Charles-Sadron, 45071 Orléans, Cedex 2, France
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43
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El-Hawiet A, Kitova EN, Arutyunov D, Simpson DJ, Szymanski CM, Klassen JS. Quantifying Ligand Binding to Large Protein Complexes Using Electrospray Ionization Mass Spectrometry. Anal Chem 2012; 84:3867-70. [DOI: 10.1021/ac3005082] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amr El-Hawiet
- Alberta
Glycomics Centre and †Department of Chemistry or §Department of Biological Sciences, University of Alberta, Edmonton, Alberta,
Canada T6G 2G2
| | - Elena N. Kitova
- Alberta
Glycomics Centre and †Department of Chemistry or §Department of Biological Sciences, University of Alberta, Edmonton, Alberta,
Canada T6G 2G2
| | - Denis Arutyunov
- Alberta
Glycomics Centre and †Department of Chemistry or §Department of Biological Sciences, University of Alberta, Edmonton, Alberta,
Canada T6G 2G2
| | - David J. Simpson
- Alberta
Glycomics Centre and †Department of Chemistry or §Department of Biological Sciences, University of Alberta, Edmonton, Alberta,
Canada T6G 2G2
| | - Christine M. Szymanski
- Alberta
Glycomics Centre and †Department of Chemistry or §Department of Biological Sciences, University of Alberta, Edmonton, Alberta,
Canada T6G 2G2
| | - John S. Klassen
- Alberta
Glycomics Centre and †Department of Chemistry or §Department of Biological Sciences, University of Alberta, Edmonton, Alberta,
Canada T6G 2G2
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44
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Liu Y, Su B, Wang X. Study on the noncovalent interactions of saikosaponins and cytochrome c by electrospray ionization mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:719-27. [PMID: 22368050 DOI: 10.1002/rcm.6151] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
RATIONALE The study of interactions between protein and pharmaceutical molecules including natural extracts has become of increasing interest in biological and biomedical research. An investigation of the interaction between saikosaponins and cytochrome c (Cyt c) by electrospray ionization mass spectrometry (ESI-MS) is described in this study. Saikosaponins are found in Bupleurum falcatum (a flowering plant), and they are glycosides that consist of saccharides and the sapogenins of triterpenoids. METHODS Seven model molecules of saccharides and triterpenes, namely maltose (Mal II), maltotriose (Mal III), raffinose (Raf), and stachyose (Sta), glycyrrhetinic acid (Gly), ursolic acid (Urs) and oleanic acid (Ole), were chosen to perform a series of ESI-MS control experiments for the exploration of the interaction groups in saikosaponins with Cyt c. The dissociation constants of detected noncovalent complexes were determined by using a direct ESI-MS assay. RESULTS We have observed in the ESI mass spectra the formation of Cyt c complexes with saikosaponins a and c, and these saccharides, with 1:1 and 1:2 stoichiometry. Our results showed that no complex ions of triterpenes and Cyt c were detected in the ESI-MS and similar Kd values were obtained for the Cyt c complexes of saikosaponins and saccharides. This demonstrates that the glycosyl moiety in the saikosaponins is the effective interaction group with Cyt c. We propose that saikosaponins and saccharides interact with Cyt c by hydrogen bonds. The binding affinity of these six ligands with Cyt c is shown to be in the order Ssa > Ssc > Raf, Mal III > Sta ≥ Mal II. CONCLUSIONS The ESI-MS methodology presented in this study enables us to investigate the interactions of saikosaponins with Cyt c, and allows the direct determination of binding constants. These results could guide further research for providing insights into the structure-binding relationship of ligands with Cyt c.
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Affiliation(s)
- Yingzhi Liu
- Key Laboratory of Analytical Chemistry of the State Ethnic Affairs Commission, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan, Hubei, 430074, PR China
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45
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Ferreira R, Marchand A, Gabelica V. Mass spectrometry and ion mobility spectrometry of G-quadruplexes. A study of solvent effects on dimer formation and structural transitions in the telomeric DNA sequence d(TAGGGTTAGGGT). Methods 2012; 57:56-63. [PMID: 22465284 DOI: 10.1016/j.ymeth.2012.03.021] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/14/2012] [Accepted: 03/17/2012] [Indexed: 11/25/2022] Open
Abstract
We survey here state of the art mass spectrometry methodologies for investigating G-quadruplexes, and will illustrate them with a new study on a simple model system: the dimeric G-quadruplex of the 12-mer telomeric DNA sequence d(TAGGGTTAGGGT), which can adopt either a parallel or an antiparallel structure. We will discuss the solution conditions compatible with electrospray ionisation, the quantification of complexes using ESI-MS, the interpretation of ammonium ion preservation in the complexes in the gas phase, and the use of ion mobility spectrometry to resolve ambiguities regarding the strand stoichiometry, or separate and characterise different structural isomers. We also describe that adding electrospray-compatible organic co-solvents (methanol, ethanol, isopropanol or acetonitrile) to aqueous ammonium acetate increases the stability and rate of formation of dimeric G-quadruplexes, and causes structural transitions to parallel structures. Structural changes were probed by circular dichroism and ion mobility spectrometry, and the excellent correlation between the two techniques validates the use of ion mobility to investigate G-quadruplex folding. We also demonstrate that parallel G-quadruplex structures are easier to preserve in the gas phase than antiparallel structures.
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Affiliation(s)
- Rubén Ferreira
- Department of Chemistry and Molecular Pharmacology, Institute for Research in Biomedicine (IRB Barcelona), IQAC-CSIC, CIBER-BNN, Baldiri i Reixac 10, E-08028 Barcelona, Spain
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46
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Kitova EN, El-Hawiet A, Schnier PD, Klassen JS. Reliable determinations of protein-ligand interactions by direct ESI-MS measurements. Are we there yet? JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:431-41. [PMID: 22270873 DOI: 10.1007/s13361-011-0311-9] [Citation(s) in RCA: 188] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 11/25/2011] [Accepted: 11/29/2011] [Indexed: 05/11/2023]
Abstract
The association-dissociation of noncovalent interactions between protein and ligands, such as other proteins, carbohydrates, lipids, DNA, or small molecules, are critical events in many biological processes. The discovery and characterization of these interactions is essential to a complete understanding of biochemical reactions and pathways and to the design of novel therapeutic agents that may be used to treat a variety of diseases and infections. Over the last 20 y, electrospray ionization mass spectrometry (ESI-MS) has emerged as a versatile tool for the identification and quantification of protein-ligand interactions in vitro. Here, we describe the implementation of the direct ESI-MS assay for the determination of protein-ligand binding stoichiometry and affinity. Additionally, we outline common sources of error encountered with these measurements and various strategies to overcome them. Finally, we comment on some of the outstanding challenges associated with the implementation of the assay and highlight new areas where direct ESI-MS measurements are expected to make significant contributions in the future.
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Affiliation(s)
- Elena N Kitova
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2
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47
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Pacholarz KJ, Garlish RA, Taylor RJ, Barran PE. Mass spectrometry based tools to investigate protein–ligand interactions for drug discovery. Chem Soc Rev 2012; 41:4335-55. [DOI: 10.1039/c2cs35035a] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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48
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El-Hawiet A, Shoemaker GK, Daneshfar R, Kitova EN, Klassen JS. Applications of a catch and release electrospray ionization mass spectrometry assay for carbohydrate library screening. Anal Chem 2011; 84:50-8. [PMID: 22128847 DOI: 10.1021/ac202760e] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Applications of a catch and release electrospray ionization mass spectrometry (CaR-ESI-MS) assay for screening carbohydrate libraries against target proteins are described. Direct ESI-MS measurements were performed on solutions containing a target protein (a single chain antibody, an antigen binding fragment, or a fragment of a bacterial toxin) and a library of carbohydrates containing multiple specific ligands with affinities in the 10(3) to 10(6) M(-1) range. Ligands with moderate affinity (10(4) to 10(6) M(-1)) were successfully detected from mixtures containing >200 carbohydrates (at concentrations as low as 0.25 μM each). Additionally, the absolute affinities were estimated from the abundance of free and ligand-bound protein ions determined from the ESI mass spectrum. Multiple low affinity ligands (~10(3) M(-1)) were successfully detected in mixtures containing >20 carbohydrates (at concentrations of ~10 μM each). However, identification of specific interactions required the use of the reference protein method to correct the mass spectrum for the occurrence of nonspecific carbohydrate-protein binding during the ESI process. The release of the carbohydrate ligands, as ions, was successfully demonstrated using collision-induced dissociation performed on the deprotonated ions of the protein-carbohydrate complexes. The use of ion mobility separation, performed on deprotonated carbohydrate ions following their release from the complex, allowed for the positive identification of isomeric ligands.
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Affiliation(s)
- Amr El-Hawiet
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
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49
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Hopper JTS, Oldham NJ. Alkali metal cation-induced destabilization of gas-phase protein-ligand complexes: consequences and prevention. Anal Chem 2011; 83:7472-9. [PMID: 21863818 DOI: 10.1021/ac201686f] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrospray ionization, now a well established technique for studying noncovalent protein-ligand interactions, is prone to production of alkali metal adducts. Here it is shown that this adduction significantly destabilizes the interactions between two model proteins and their ligands and that destabilization correlates with cation size. For both the [FKBP·FK506] and [lysozyme·NAG(n)] systems, dissociation of the metalated complex occurs at markedly lower collision energies than their purely protonated equivalents. Dependency upon size of the metal(+) demonstrates the importance of electrostatic charge density during the dissociation process. Differences in the gas phase basicities (GBapp) of the multiply charged protein ions and proton and sodium affinities of the ligands explain the observed charge partitioning during dissociation of the complexes. Ion mobility-mass spectrometry measurements demonstrate that metal cation adduction does not induce a significant increase in unfolding of the polypeptides, indicating that this is not the principal mechanism responsible for destabilization. Destabilizing effects can be largely reduced by exposing the electrospray to solvent (e.g., acetonitrile) vapor, a method that acts to reduce the amount of adduct formation as well as decrease the charge states of the resulting ions. This approach leads to more accurate determination of apparent K(D)s in the presence of trace alkali metals.
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Affiliation(s)
- Jonathan T S Hopper
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD
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50
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Wang R, Allmendinger P, Zhu L, Gröhn AJ, Wegner K, Frankevich V, Zenobi R. The role of nebulizer gas flow in electrosonic spray ionization (ESSI). JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:1234-1241. [PMID: 21953106 DOI: 10.1007/s13361-011-0124-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 03/04/2011] [Accepted: 03/04/2011] [Indexed: 05/31/2023]
Abstract
In this work, we investigated the role of the nebulizer gas flow in electrosonic spray ionization (ESSI), by systematically studying the relation between the flow and the ion signals of proteins, such as cytochrome c and holomyoglobin using ESSI-mass spectrometry (MS). When a neutral solution was delivered with a small sample flow rate (≤5 μL/min), no obvious transition from electrospray ionization (ESI) to ESSI was found as the gas velocity varies from subsonic to supersonic speed. Droplets mostly experienced acceleration instead of breakup by the high-speed nebulizer gas. On the contrary, using particular experimental conditions, such as an acidic solution or high sample flow rate (≥200 μL/min), more folded protein ions appear to be kept in droplets of diminishing size due to breakup by the high-speed nebulizer gas in ESSI compared with ESI. Theoretical analyses and numerical simulations were also performed to explain the observed phenomena. These systematic studies clarify the ionization mechanism of ESSI and provide valuable insight for optimizing ESSI and other popular pneumatically assisted electrospray ionization methods for future applications.
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Affiliation(s)
- Rui Wang
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093, Zurich, Switzerland
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