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Cruz FT, Rosa DP, Vasconcelos AVB, de Oliveira JS, Bleicher L, Santos AMC. Purification and partial physical-chemical characterization of a new bovine trypsin proteoform (zeta-trypsin). Int J Biol Macromol 2024; 268:131860. [PMID: 38670206 DOI: 10.1016/j.ijbiomac.2024.131860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 04/01/2024] [Accepted: 04/23/2024] [Indexed: 04/28/2024]
Abstract
Recent advancements in enzyme research have unveiled a new proteoform of bovine trypsin, expanding our understanding of this well-characterized enzyme. While generally similar to other trypsins, this novel proteoform comprises three polypeptide chains, marking a significant difference in activity, kinetic properties, and conformational stability. Compared with the already known bovine trypsin proteoforms, the results showed a lower: activity, kcat and kcat.KM-1 and protein 'foldedness' ratio for the new proteoform. Molecular autolysis, a common feature in trypsin and chymotrypsin, has been explored through comparative physical chemistry properties with other proteoforms. This new proteoform of trypsin not only enriches the existing enzyme repertoire but also promises to shed light on the intricate physiological pathway for enzyme inactivation. Our results suggest that the new trypsin proteoform is one of the likely final pathways for enzyme inactivation in a physiological environment. This discovery opens up new avenues for further research into the functional implications of this new trypsin proteoform.
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Affiliation(s)
- Fabiano Torres Cruz
- Pos-Graduate Program of Biotechnology - Federal University of Espírito Santo, Vitória, ES, Brazil
| | - Dayanne Pinho Rosa
- Pos-Graduate Program of Biochemistry - Federal University of Espírito Santo, Vitória, ES, Brazil
| | | | - Jamil Silvano de Oliveira
- Department of Biochemistry and Immunology - Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
| | - Lucas Bleicher
- Department of Biochemistry and Immunology - Federal University of Minas Gerais, Belo Horizonte, MG, Brazil; Pos-Graduate at Biochemistry and Immunology - Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
| | - Alexandre Martins Costa Santos
- Pos-Graduate Program of Biotechnology - Federal University of Espírito Santo, Vitória, ES, Brazil; Pos-Graduate Program of Biochemistry - Federal University of Espírito Santo, Vitória, ES, Brazil.
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2
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Pseudotrypsin: A Little-Known Trypsin Proteoform. Molecules 2018; 23:molecules23102637. [PMID: 30322187 PMCID: PMC6222510 DOI: 10.3390/molecules23102637] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/06/2018] [Accepted: 10/09/2018] [Indexed: 01/06/2023] Open
Abstract
Trypsin is the protease of choice for protein sample digestion in proteomics. The most typical active forms are the single-chain β-trypsin and the two-chain α-trypsin, which is produced by a limited autolysis of β-trypsin. An additional intra-chain split leads to pseudotrypsin (ψ-trypsin) with three chains interconnected by disulfide bonds, which can be isolated from the autolyzate by ion-exchange chromatography. Based on experimental data with artificial substrates, peptides, and protein standards, ψ-trypsin shows altered kinetic properties, thermodynamic stability and cleavage site preference (and partly also cleavage specificity) compared to the above-mentioned proteoforms. In our laboratory, we have analyzed the performance of bovine ψ-trypsin in the digestion of protein samples with a different complexity. It cleaves predominantly at the characteristic trypsin cleavage sites. However, in a comparison with common tryptic digestion, non-specific cleavages occur more frequently (mostly after the aromatic residues of Tyr and Phe) and more missed cleavages are generated. Because of the preferential cleavages after the basic residues and more developed side specificity, which is not expected to occur for the major trypsin forms (but may appear anyway because of their autolysis), ψ-trypsin produces valuable information, which is complementary in part to data based on a strictly specific trypsin digestion and thus can be unnoticed following common proteomics protocols.
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3
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Qiu R, Zhang C, Qin Z, Luo H. A multichannel rotating electrospray ionization mass spectrometry (MRESI): instrumentation and plume interactions. RSC Adv 2016. [DOI: 10.1039/c6ra06471j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A multichannel rotating electrospray ionization (MRESI) mass spectrometry method is described. Plume interactions are also systematically studied.
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Affiliation(s)
- Ran Qiu
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Peking University
- Beijing
- China
| | - Chengsen Zhang
- Department of Chemistry
- Indiana University-Purdue University Indianapolis
- Indianapolis
- USA
| | - Zhen Qin
- Institute of Materials
- China Academy of Engineering Physics
- Mianyang
- China
| | - Hai Luo
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Peking University
- Beijing
- China
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Shi H, Gu L, Clemmer DE, Robinson RAS. Effects of Fe(II)/H2O2 oxidation on ubiquitin conformers measured by ion mobility-mass spectrometry. J Phys Chem B 2013; 117:164-73. [PMID: 23211023 PMCID: PMC3552375 DOI: 10.1021/jp3099544] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxidative modifications can have significant effects on protein structure in solution. Here, the structures and stabilities of oxidized ubiquitin ions electrosprayed from an aqueous solution (pH 2) are studied by ion mobility spectrometry-mass spectrometry (IMS-MS). IMS-MS has proven to be a valuable technique to assess gas phase and in many cases, solution structures. Herein, in vitro oxidation is performed by Fenton chemistry with Fe(II)/hydrogen peroxide. Most molecules in solution remain unmodified, whereas ∼20% of the population belongs to an M+16 Da oxidized species. Ions of low charge states (+7 and +8) show substantial variance in collision cross section distributions between unmodified and oxidized species. Novel and previously reported gaussian conformers are used to model cross section distributions for +7 and +8 oxidized ubiquitin ions, respectively, in order to correlate variances in observed gas-phase distributions to changes in populations of solution states. Based on gaussian modeling, oxidized ions of charge state +7 have an A-state conformation which is more populated for oxidized relative to unmodified ions. Oxidized ubiquitin ions of charge state +8 have a distribution of conformers arising from native-state ubiquitin and higher intensities of A- and U-state conformers relative to unmodified ions. This work provides evidence that incorporation of a single oxygen atom to ubiquitin leads to destabilization of the native state in an acidic solution (pH ∼2) and to unfolding of gas-phase compact structures.
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Affiliation(s)
- Huilin Shi
- Department of Chemistry, Indiana University, 800 Kirkwood Ave. Bloomington, IN 47405
| | - Liqing Gu
- Department of Chemistry, University of Pittsburgh, 200 University Drive, Pittsburgh, PA 15260
| | - David E. Clemmer
- Department of Chemistry, Indiana University, 800 Kirkwood Ave. Bloomington, IN 47405
| | - Renã A. S. Robinson
- Department of Chemistry, University of Pittsburgh, 200 University Drive, Pittsburgh, PA 15260
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5
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Ganisl B, Taucher M, Riml C, Breuker K. Charge as you like! Efficient manipulation of negative ion net charge in electrospray ionization of proteins and nucleic acids. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2011; 17:333-343. [PMID: 22006635 DOI: 10.1255/ejms.1140] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Acidic proteins and nucleic acids such as RNA are most readily ionized in electrospray ionization (ESI) operated in negative-ion mode. The multiply deprotonated protein or RNA ions can be used as precursors in top- down mass spectrometry. Because the performance of the dissociation method used critically depends on precursor ion negative net charge, it is important that the extent of charging in ESI can be manipulated efficiently. We show here that (M - nH)(n-) ion net charge of proteins and RNA can be controlled efficiently by the addition of organic bases to the electrosprayed solution. Our study also highlights the fact that ion formation in ESI in negative mode is only poorly understood.
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Nabuchi Y, Hirose K, Takayama M. Ion Mobility and Collision-Induced Dissociation Analysis of Carbonic Anhydrase 2. Anal Chem 2010; 82:8890-6. [DOI: 10.1021/ac101482b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yoshiaki Nabuchi
- Graduate School of Nanobioscience, Yokohama City University, Yokohama, Kanagawa 236-0027, Japan, and Technology Application Department, Nihon Waters K.K., Osaka, Osaka, 532-0011, Japan
| | - Kenji Hirose
- Graduate School of Nanobioscience, Yokohama City University, Yokohama, Kanagawa 236-0027, Japan, and Technology Application Department, Nihon Waters K.K., Osaka, Osaka, 532-0011, Japan
| | - Mitsuo Takayama
- Graduate School of Nanobioscience, Yokohama City University, Yokohama, Kanagawa 236-0027, Japan, and Technology Application Department, Nihon Waters K.K., Osaka, Osaka, 532-0011, Japan
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7
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Lee S, Ewing MA, Nachtigall FM, Kurulugama RT, Valentine SJ, Clemmer DE. Determination of cross sections by overtone mobility spectrometry: evidence for loss of unstable structures at higher overtones. J Phys Chem B 2010; 114:12406-15. [PMID: 20822127 PMCID: PMC2989665 DOI: 10.1021/jp1060123] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Overtone mobility spectrometry (OMS) is examined as a means of determining the collision cross sections for multiply charged ubiquitin and substance P ions, as well as for singly charged rafinose and melezitose ions. Overall, values of collision cross section measured by OMS for stable ion conformations are found to be in agreement with values determined by conventional ion mobility spectrometry (IMS) measurements to within ∼1% relative uncertainty. The OMS spectra for ubiquitin ions appear to favor different conformations at higher overtones. We propose that the changes in the distributions as a function of the overtone region in which they are measured arise from the elimination of ions that undergo structural transitions in the drift regions. Kinetics simulations suggest that structural transitions occurring on the order of a few ms and resulting in an ∼4% change in ion collision cross sections are detected by OMS measurements. The unique method of distinguishing ion mobilities with OMS reveals these structural transitions which are not readily apparent from traditional IMS measurements.
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Affiliation(s)
- Sunyoung Lee
- Department of Chemistry, Indiana University, Bloomington, IN 47405
| | - Michael A. Ewing
- Department of Chemistry, Indiana University, Bloomington, IN 47405
| | | | | | | | - David E. Clemmer
- Department of Chemistry, Indiana University, Bloomington, IN 47405
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Pierson NA, Valentine SJ, Clemmer DE. Evidence for a quasi-equilibrium distribution of states for bradykinin [M + 3H]3+ ions in the gas phase. J Phys Chem B 2010; 114:7777-83. [PMID: 20469905 PMCID: PMC2922466 DOI: 10.1021/jp102478k] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Multidimensional ion mobility spectrometry coupled with mass spectrometry (IMS-IMS-MS) techniques are used to select and activate six different gas-phase conformations of bradykinin [M + 3H](3+) ions. Drift time distributions as a function of activation voltage show that at low voltages selected structures undergo conformational transitions in what appears to be a pathway dependent fashion. Over a relatively wide range of intermediate activation voltages a distribution of states that is independent of the initial conformation selected for activation (as well as the activation voltage in this intermediate region) is established. This distribution appears to represent an equilibrium distribution of gas-phase structures that is reached prior to the energy required for dissociation. Establishment of a quasi-equilibrium prior to dissociation results in identical dissociation patterns for different selected conformations. A discussion of the transition from solution-like to gas-phase structures is provided.
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Affiliation(s)
| | | | - David E. Clemmer
- Department of Chemistry, Indiana University, Bloomington, IN 47405
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Pukala TL, Urathamakul T, Watt SJ, Beck JL, Jackway RJ, Bowie JH. Binding studies of nNOS-active amphibian peptides and Ca2+ calmodulin, using negative ion electrospray ionisation mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:3501-3509. [PMID: 18853393 DOI: 10.1002/rcm.3757] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Amphibian peptides which inhibit the formation of nitric oxide by neuronal nitric oxide synthase (nNOS) do so by binding to the protein cofactor, Ca2+calmodulin (Ca2+CaM). Complex formation between active peptides and Ca2+CaM has been demonstrated by negative ion electrospray ionisation mass spectrometry using an aqueous ammonium acetate buffer system. In all cases studied, the assemblies are formed with a 1:1:4 calmodulin/peptide/Ca2+ stoichiometry. In contrast, the complex involving the 20-residue binding domain of the plasma Ca2+ pump C20W (LRRGQILWFRGLNRIQTQIK-OH) with CaM has been shown by previous two-dimensional nuclear magnetic resonance (2D NMR) studies to involve complexation of the C-terminal end of CaM. Under identical conditions to those used for the amphibian peptide study, the ESI complex between C20W and CaM shows specific 1:1:2 stoichiometry. Since complex formation with the studied amphibian peptides requires Ca2+CaM to contain its full complement of four Ca2+ ions, this indicates that the amphibian peptides require both ends of the CaM to effect complex formation. Charge-state analysis and an H/D exchange experiment (with caerin 1.8) suggest that complexation involves Ca2+CaM undergoing a conformational change to a more compact structure.
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Affiliation(s)
- Tara L Pukala
- Department of Chemistry, The University of Adelaide, South Australia, 5005, Australia
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Nabuchi Y, Murao N, Asoh Y, Takayama M. Probing the Unfolding and Refolding Processes of Carbonic Anhydrase 2 Using Electrospray Ionization Mass Spectrometry Combined with pH Jump. Anal Chem 2007; 79:8342-9. [PMID: 17900145 DOI: 10.1021/ac071130u] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A novel method for proving the time course of the unfolding and refolding processes of metalloprotein bovine carbonic anhydrase 2 (CA2) is demonstrated using electrospray ionization mass spectrometry (ESI MS) combined with pH jumps between 3.6 and 4.4. The shift in mass accompanied by the release or coordination of a zinc ion and the change in the charge state distribution were measured to evaluate the folding process. The time course of the ESI mass spectra revealed the existence of four types of ions in the experimental system, i.e., lower charged apo-CA2 and holo-CA2 ions and higher charged apo-CA2 and holo-CA2 ions. The deconvolution spectrum of the ion peak ensemble for each type of ion was processed and time course plots of the relative intensities of the four ions were prepared in order to analyze the folding processes. These analyses revealed the coexistence of two folding states of the lower and higher charged apo-CA2 under the condition of pH 3.6. The lower and higher charged apoproteins spontaneously refolded to the lower charged holoprotein by a pH jump from 3.6 to 4.4 without the addition of an extra zinc ion. The higher charged holoprotein observed during both the unfolding and refolding processes was considered to be an intermediate of the change in folding. The present study indicates that ESI MS combined with pH jump would be a powerful method to probe the unfolding and refolding of proteins. This method simultaneously measures mass spectra and analyzes the folding processes as a function of time using deconvolution spectra constructed by selecting a suitable m/z range for the analysis from the peaks of charge state distributions.
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Affiliation(s)
- Yoshiaki Nabuchi
- Fuji Gotemba Research Laboratories, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka 412-8513, Japan.
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11
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Hanson CL, Videler H, Santos C, Ballesta JPG, Robinson CV. Mass Spectrometry of Ribosomes from Saccharomyces cerevisiae. J Biol Chem 2004; 279:42750-7. [PMID: 15294894 DOI: 10.1074/jbc.m405718200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The acidic ribosomal P proteins form a distinct protuberance on the 60 S subunit of eukaryotic ribosomes. In yeast this structure is composed of two heterodimers (P1alpha-P2beta and P1beta-P2alpha) attached to the ribosome via P0. Although for prokaryotic ribosomes the isolation of a pentameric stalk complex comprising the analogous proteins is well established, its observation has not been reported for eukaryotic ribosomes. We used mass spectrometry to examine the composition of the stalk proteins on ribosomes from Saccharomyces cerevisiae. The resulting mass spectra reveal a noncovalent complex of mass 77,291 +/- 7 Da assigned to the pentameric stalk. Tandem mass spectrometry confirms this assignment and is consistent with the location of the P2 proteins on the periphery of the stalk complex, shielding the P1 proteins, which in turn interact with P0. No other oligomers are observed, confirming the specificity of the pentameric complex. At lower m/z values the spectra are dominated by individual proteins, largely from the stalk complex, giving rise to many overlapping peaks. To define the composition of the stalk proteins in detail we compared spectra of ribosomes from strains in which genes encoding either or both of the interacting stalk proteins P1alpha or P2beta are deleted. This enables us to define novel post-translational modifications at very low levels, including a population of P2alpha molecules with both phosphorylation and trimethylation. The deletion mutants also reveal interactions within the heterodimers, specifically that the absence of P1alpha or P2beta destabilizes binding of the partner protein on the ribosome. This implies that assembly of the stalk complex is not governed solely by interactions with P0 but is a cooperative process involving binding to partner proteins for additional stability on the ribosome.
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Affiliation(s)
- Charlotte L Hanson
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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12
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Ilag LL, Westblade LF, Deshayes C, Kolb A, Busby SJW, Robinson CV. Mass spectrometry of Escherichia coli RNA polymerase: interactions of the core enzyme with sigma70 and Rsd protein. Structure 2004; 12:269-75. [PMID: 14962387 DOI: 10.1016/j.str.2004.01.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Revised: 10/08/2003] [Accepted: 10/09/2003] [Indexed: 11/18/2022]
Abstract
The E. coli RNA polymerase core enzyme is a multisubunit complex of 388,981 Da. To initiate transcription at promoters, the core enzyme associates with a sigma subunit to form holo RNA polymerase. Here we have used nanoflow electrospray mass spectrometry, coupled with tandem mass spectrometry, to probe the interaction of the RNA polymerase core enzyme with the most abundant sigma factor, sigma70. The results show remarkably well-resolved spectra for both the core and holo RNA polymerases. The regulator of sigma70, Rsd protein, has previously been identified as a protein that binds to free sigma70. We show that Rsd also interacts with core enzyme. In addition, by adding increasing amounts of Rsd, we show that sigma70 is displaced from holo RNA polymerase, resulting in complexes of Rsd with core and sigma70. The results argue for a model in which Rsd not only sequesters sigma70, but is also an effector of core RNA polymerase.
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Affiliation(s)
- Leopold L Ilag
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
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13
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Rostom AA, Sunde M, Richardson SJ, Schreiber G, Jarvis S, Bateman R, Dobson CM, Robinson CV. Dissection of multi-protein complexes using mass spectrometry: Subunit interactions in transthyretin and retinol-binding protein complexes. Proteins 1998. [DOI: 10.1002/(sici)1097-0134(1998)33:2+<3::aid-prot2>3.0.co;2-h] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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14
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Bruce JE, Hofstadler SA, Winger BE, Smith RD. Characterization of ribonuclease B heterogeneity and the identification and removal of phosphate adducts by high resolution electrospray ionization Fourier transform ion clylotron resonance mass spectrometry. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0168-1176(93)03936-g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Cox KA, Julian RK, Cooks RG, Kaiser RE. Conformer selection of protein ions by ion mobility in a triple quadrupole mass spectrometer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 1994; 5:127-136. [PMID: 24222541 DOI: 10.1016/1044-0305(94)85025-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/1993] [Revised: 10/29/1993] [Accepted: 11/03/1993] [Indexed: 06/02/2023]
Abstract
Electrospray mass spectra of multiply charged protein molecules show two distinct charge state distributions proposed to correspond to a more highly charged, open conformational form and a lower charged, folded form. Elastic collisions carried out in the radiofrequency-only collision cell of a triple quadrupole mass spectrometer have dramatic effects on the appearance of the mass spectra. The different cross sectional areas of the conformers allow preferential selection of one charge state distribution over the other on the basis of ion mobility. Preferential selection is dependent on the nature and pressure of the target gas as well as the nature of the protein. In the case of positively charged horse heart apomyoglobin (MW 16,951 da), a high charge state distribution centered around (M + 20H)(20+) predominates at low target gas pressures and a second distribution centered around (M + 10H)(10+) predominates at high target gas pressures. Bimodal distributions are observed at intermediate pressures and, remarkably, charge states between the two distributions are not effectively populated under most of the conditions examined. Hard sphere collision calculations show large differences in collision frequencies and in the corresponding kinetic energy losses for the two conformational states and they demonstrate that the observed charge state selectivity can be explained through elastic collisions.
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Affiliation(s)
- K A Cox
- Department of Chemistry, Purdue University, 47907, West Lafayette, IN, USA
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16
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The Analysis of Biomolecules by Electrospray Ionization—Mass Spectrometry and Tandem Mass Spectrometry. Mass Spectrom (Tokyo) 1992. [DOI: 10.1007/978-1-4899-1173-5_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] Open
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