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Ivanov DG, Cheung K, Kaltashov IA. Probing the Architecture of Multisubunit Protein Complexes with In-line Disulfide Reduction and Native MS Analysis. Anal Chem 2024; 96:8243-8248. [PMID: 38733603 DOI: 10.1021/acs.analchem.4c00879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2024]
Abstract
Native mass spectrometry (MS) continues to enjoy growing popularity as a means of providing a wealth of information on noncovalent biopolymer assemblies ranging from composition and binding stoichiometry to characterization of the topology of these assemblies. The latter frequently relies on supplementing MS measurements with limited fragmentation of the noncovalent complexes in the gas phase to identify the pairs of neighboring subunits. While this approach has met with much success in the past two decades, its implementation remains difficult (and the success record relatively modest) within one class of noncovalent assemblies: protein complexes in which at least one binding partner has multiple subunits cross-linked by disulfide bonds. We approach this problem by inducing chemical reduction of disulfide bonds under nondenaturing conditions in solution followed by native MS analysis with online buffer exchange to remove unconsumed reagents that are incompatible with the electrospray ionization process. While this approach works well with systems comprised of thiol-linked subunits that remain stable upon reduction of the disulfide bridges (such as immunoglobulins), chemical reduction frequently gives rise to species that are unstable (prone to aggregation). This problem is circumvented by taking advantage of the recently introduced cross-path reactive chromatography platform (XPRC), which allows the disulfide reduction to be carried out in-line, thereby minimizing the loss of metastable protein subunits and their noncovalent complexes with the binding partners prior to MS analysis. The feasibility of this approach is demonstrated using hemoglobin complexes with haptoglobin 1-1, a glycoprotein consisting of four polypeptide chains cross-linked by disulfide bonds.
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Affiliation(s)
- Daniil G Ivanov
- Department of Chemistry, University of Massachusetts─Amherst, Amherst, Massachusetts 01002, United States
| | - Kevin Cheung
- Department of Chemistry, University of Massachusetts─Amherst, Amherst, Massachusetts 01002, United States
| | - Igor A Kaltashov
- Department of Chemistry, University of Massachusetts─Amherst, Amherst, Massachusetts 01002, United States
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Kaltashov IA, Ivanov DG, Yang Y. Mass spectrometry-based methods to characterize highly heterogeneous biopharmaceuticals, vaccines, and nonbiological complex drugs at the intact-mass level. MASS SPECTROMETRY REVIEWS 2024; 43:139-165. [PMID: 36582075 PMCID: PMC10307928 DOI: 10.1002/mas.21829] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
The intact-mass MS measurements are becoming increasingly popular in characterization of a range of biopolymers, especially those of interest to biopharmaceutical industry. However, as the complexity of protein therapeutics and other macromolecular medicines increases, the new challenges arise, one of which is the high levels of structural heterogeneity that are frequently exhibited by such products. The very notion of the molecular mass measurement loses its clear and intuitive meaning when applied to an extremely heterogenous system that cannot be characterized by a unique mass, but instead requires that a mass distribution be considered. Furthermore, convoluted mass distributions frequently give rise to unresolved ionic signal in mass spectra, from which little-to-none meaningful information can be extracted using standard approaches that work well for homogeneous systems. However, a range of technological advances made in the last decade, such as the hyphenation of intact-mass MS measurements with front-end separations, better integration of ion mobility in MS workflows, development of an impressive arsenal of gas-phase ion chemistry tools to supplement MS methods, as well as the revival of the charge detection MS and its triumphant entry into the field of bioanalysis already made impressive contributions towards addressing the structural heterogeneity challenge. An overview of these techniques is accompanied by critical analysis of the strengths and weaknesses of different approaches, and a brief overview of their applications to specific classes of biopharmaceutical products, vaccines, and nonbiological complex drugs.
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Affiliation(s)
- Igor A. Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst MA 01003
| | - Daniil G. Ivanov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst MA 01003
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Ivanov DG, Yang Y, Pawlowski JW, Carrick IJ, Kaltashov IA. Rapid Evaluation of the Extent of Haptoglobin Glycosylation Using Orthogonal Intact-Mass MS Approaches and Multivariate Analysis. Anal Chem 2022; 94:5140-5148. [PMID: 35285615 DOI: 10.1021/acs.analchem.1c05585] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Intact-mass measurements are becoming increasingly popular in mass spectrometry (MS) based protein characterization, as they allow the entire complement of proteoforms to be evaluated within a relatively short time. However, applications of this approach are currently limited to systems exhibiting relatively modest degrees of structural diversity, as the high extent of heterogeneity frequently prevents straightforward MS measurements. Incorporation of limited charge reduction into electrospray ionization (ESI) MS is an elegant way to obtain meaningful information on most heterogeneous systems, yielding not only the average mass of the protein but also the mass range populated by the entire complement of proteoforms. Application of this approach to characterization of two different phenotypes of haptoglobin (1-1 and 2-1) provides evidence of a significant difference in their extent of glycosylation (with the glycan load of phenotype 2-1 being notably lighter) despite a significant overlap of their ionic signals. More detailed characterization of their glycosylation patterns is enabled by the recently introduced technique of cross-path reactive chromatography (XP-RC) with online MS detection, which combines chromatographic separation with in-line reduction of disulfide bonds to generate metastable haptoglobin subunits. Application of XP-RC to both haptoglobin phenotypes confirms that no modifications are present within their light chains and provides a wealth of information on glycosylation patterns of the heavy chains. N-Glycosylation patterns of both haptoglobin phenotypes were found to be consistent with bi- and triantennary structures of complex type that exhibit significant level of fucosylation and sialylation. However, multivariate analysis of haptoglobin 1-1 reveals higher number of the triantennary structures, in comparison to haptoglobin 2-1, as well as a higher extent of fucosylation. The glycosylation patterns deduced from the XP-RC/MS measurements are in agreement with the conclusions of the intact-mass analysis supplemented by limited charge reduction, suggesting that the latter technique can be employed in situations when fast assessment of protein heterogeneity is needed (e.g., process analytical technology applications).
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Affiliation(s)
- Daniil G Ivanov
- Department of Chemistry, University of Massachusetts─Amherst, 240 Thatcher Road, Amherst, Massachusetts 01003, United States
| | - Yang Yang
- Department of Chemistry, University of Massachusetts─Amherst, 240 Thatcher Road, Amherst, Massachusetts 01003, United States
| | - Jake W Pawlowski
- Department of Chemistry, University of Massachusetts─Amherst, 240 Thatcher Road, Amherst, Massachusetts 01003, United States
| | - Ian J Carrick
- Department of Chemistry, University of Massachusetts─Amherst, 240 Thatcher Road, Amherst, Massachusetts 01003, United States
| | - Igor A Kaltashov
- Department of Chemistry, University of Massachusetts─Amherst, 240 Thatcher Road, Amherst, Massachusetts 01003, United States
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Yang Y, Niu C, Bobst CE, Kaltashov IA. Charge Manipulation Using Solution and Gas-Phase Chemistry to Facilitate Analysis of Highly Heterogeneous Protein Complexes in Native Mass Spectrometry. Anal Chem 2021; 93:3337-3342. [PMID: 33566581 PMCID: PMC8514162 DOI: 10.1021/acs.analchem.0c05249] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Structural heterogeneity is a significant challenge complicating (and in some cases making impossible) electrospray ionization mass spectrometry (ESI MS) analysis of noncovalent complexes comprising structurally heterogeneous biopolymers. The broad mass distribution exhibited by such species inevitably gives rise to overlapping ionic signals representing different charge states, resulting in a continuum spectrum with no discernible features that can be used to assign ionic charges and calculate their masses. This problem can be circumvented by using limited charge reduction, which utilizes gas-phase chemistry to induce charge-transfer reactions within ionic populations selected within narrow m/z windows, thereby producing well-defined and readily interpretable charge ladders. However, the ionic signal in native MS typically populates high m/z regions of mass spectra, which frequently extend beyond the precursor ion isolation limits of most commercial mass spectrometers. While the ionic signal of single-chain proteins can be shifted to lower m/z regions simply by switching to a denaturing solvent, this approach cannot be applied to noncovalent assemblies due to their inherent instability under denaturing conditions. An alternative approach explored in this work relies on adding supercharging reagents to protein solutions as a means of increasing the extent of multiple charging of noncovalent complexes in ESI MS without compromising their integrity. This shifts the ionic signal down the m/z scale to the region where ion selection and isolation can be readily accomplished with a front-end quadrupole, followed by limited charge reduction of the isolated ionic population. The feasibility of the new approach is demonstrated using noncovalent complexes formed by hemoglobin with structurally heterogeneous haptoglobin.
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Affiliation(s)
- Yang Yang
- Department of Chemistry, University of Massachusetts-Amherst, 240 Thatcher Road, Amherst, MA 01003
| | | | - Cedric E. Bobst
- Department of Chemistry, University of Massachusetts-Amherst, 240 Thatcher Road, Amherst, MA 01003
| | - Igor A. Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, 240 Thatcher Road, Amherst, MA 01003
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Kaltashov IA, Bobst CE, Pawlowski J, Wang G. Mass spectrometry-based methods in characterization of the higher order structure of protein therapeutics. J Pharm Biomed Anal 2020; 184:113169. [PMID: 32092629 DOI: 10.1016/j.jpba.2020.113169] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/06/2020] [Accepted: 02/11/2020] [Indexed: 12/31/2022]
Abstract
Higher order structure of protein therapeutics is an important quality attribute, which dictates both potency and safety. While modern experimental biophysics offers an impressive arsenal of state-of-the-art tools that can be used for the characterization of higher order structure, many of them are poorly suited for the characterization of biopharmaceutical products. As a result, these analyses were traditionally carried out using classical techniques that provide relatively low information content. Over the past decade, mass spectrometry made a dramatic debut in this field, enabling the characterization of higher order structure of biopharmaceuticals as complex as monoclonal antibodies at a level of detail that was previously unattainable. At present, mass spectrometry is an integral part of the analytical toolbox across the industry, which is critical not only for quality control efforts, but also for discovery and development.
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Affiliation(s)
- Igor A Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, USA.
| | - Cedric E Bobst
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, USA
| | - Jake Pawlowski
- Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, USA
| | - Guanbo Wang
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing, Jiangsu Province, PR China
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MS methods to study macromolecule-ligand interaction: Applications in drug discovery. Methods 2018; 144:152-174. [PMID: 29890284 DOI: 10.1016/j.ymeth.2018.06.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 06/01/2018] [Accepted: 06/03/2018] [Indexed: 12/12/2022] Open
Abstract
The interaction of small compounds (i.e. ligands) with macromolecules or macromolecule assemblies (i.e. targets) is the mechanism of action of most of the drugs available today. Mass spectrometry is a popular technique for the interrogation of macromolecule-ligand interactions and therefore is also widely used in drug discovery and development. Thanks to its versatility, mass spectrometry is used for multiple purposes such as biomarker screening, identification of the mechanism of action, ligand structure optimization or toxicity assessment. The evolution and automation of the instruments now allows the development of high throughput methods with high sensitivity and a minimized false discovery rate. Herein, all these approaches are described with a focus on the methods for studying macromolecule-ligand interaction aimed at defining the structure-activity relationships of drug candidates, along with their mechanism of action, metabolism and toxicity.
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Kaltashov IA, Pawlowski JW, Yang W, Muneeruddin K, Yao H, Bobst CE, Lipatnikov AN. LC/MS at the whole protein level: Studies of biomolecular structure and interactions using native LC/MS and cross-path reactive chromatography (XP-RC) MS. Methods 2018; 144:14-26. [PMID: 29702225 DOI: 10.1016/j.ymeth.2018.04.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 04/11/2018] [Accepted: 04/18/2018] [Indexed: 11/25/2022] Open
Abstract
Interfacing liquid chromatography (LC) with electrospray ionization (ESI) to enable on-line MS detection had been initially implemented using reversed phase LC, which in the past three decades remained the default type of chromatography used for LC/MS and LC/MS/MS studies of protein structure. In contrast, the advantages of other types of LC as front-ends for ESI MS, particularly those that allow biopolymer higher order structure to be preserved throughout the separation process, enjoyed relatively little appreciation until recently. However, the past few years witnessed a dramatic surge of interest in the so-called "native" (with "non-denaturing" being perhaps a more appropriate adjective) LC/MS and LC/MS/MS analyses within the bioanalytical and biophysical communities. This review focuses on recent advances in this field, with an emphasis on size exclusion and ion exchange chromatography as front-end platforms for protein characterization by LC/MS. Also discussed are the benefits provided by the integration of chemical reactions in the native LC/MS analyses, including both ion chemistry in the gas phase (e.g., limited charge reduction for characterization of highly heterogeneous biopolymers) and solution-phase reactions (using the recently introduced technique cross-path reactive chromatography).
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Affiliation(s)
- Igor A Kaltashov
- Institute for Applied Life Sciences and Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, United States.
| | - Jake W Pawlowski
- Institute for Applied Life Sciences and Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Wenhua Yang
- Institute for Applied Life Sciences and Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Khaja Muneeruddin
- Institute for Applied Life Sciences and Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Honglin Yao
- Institute for Applied Life Sciences and Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Cedric E Bobst
- Institute for Applied Life Sciences and Department of Chemistry, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Andrei N Lipatnikov
- Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Göteborg, Sweden
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