1
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Kancharla V, Bashir S, Liu JL, Ramirez OM, Derrick PJ, Beran KA. Effect of metal surfaces on matrix-assisted laser desorption/ionization analyte peak intensities. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2017; 23:287-299. [PMID: 29028384 DOI: 10.1177/1469066717712694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Different metal surfaces in the form of transmission electron microscope grids were examined as support surfaces in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with a view towards enhancement of peptide signal intensity. The observed enhancement between 5-fold and 20-fold relative to the normal stainless steel slide was investigated by applying the thermal desorption model for matrix-assisted laser desorption/ionization. A simple model evaluates the impact that the thermal properties of the metals have on the ion yield of the analyte. It was observed that there was not a direct, or strong, correlation between the thermal properties of the metals and the corresponding ion yield of the peptides. The effects of both fixed and variable laser irradiances versus ion yield were also examined for the respective metals studied. In all cases the use of transmission electron microscope grids required much lower laser irradiances in order to generate similar peak intensities as those observed with a stainless steel surface.
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Affiliation(s)
| | - Sajid Bashir
- 1 Department of Chemistry, Texas A&M University-Kingsville, Kingsville, TX, USA
- 2 Institute of Mass Spectrometry, University of Warwick, Coventry, UK
| | - Jingbo L Liu
- 2 Institute of Mass Spectrometry, University of Warwick, Coventry, UK
| | - Oscar M Ramirez
- 5 Department of Physical Sciences, The University of Texas of the Permian Basin, Odessa, TX, USA
| | - Peter J Derrick
- 1 Department of Chemistry, Texas A&M University-Kingsville, Kingsville, TX, USA
- 3 Department of Physics, University of Auckland, Auckland, New Zealand
- 4 Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Kyle A Beran
- 5 Department of Physical Sciences, The University of Texas of the Permian Basin, Odessa, TX, USA
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2
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Knochenmuss R. Comment on "Non-linear photoelectron effect contributes to the formation of negative matrix ions in UV-MALDI". Phys Chem Chem Phys 2017; 19:16276-16279. [PMID: 28604859 DOI: 10.1039/c7cp00454k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alonso and Zenobi (AZ) recently claimed "a comprehensive theoretical description of negative ion formation in UV-MALDI" (Phys. Chem. Chem. Phys., 2016, 18, 19574). Emphasizing photoelectrons, it is found to be unphysical in several respects, including violation of charge and mass conservation, and in the treatment of ablation, expansion and electron capture. It is not internally consistent, and ions created by the photoelectron mechanism are given artificial preference. Although AZ claimed the "first proposal for a comprehensive theoretical description of negative ion formation in UV-MALDI", the Coupled Physical and Chemical Dynamics model has successfully reproduced a number of phenomena relevant to negative ion production over many years.
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Affiliation(s)
- Richard Knochenmuss
- Departement für Chemie und Biochemie, Universität Bern, 3012 Bern, Switzerland.
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3
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Knochenmuss R. The Coupled Chemical and Physical Dynamics Model of MALDI. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2016; 9:365-385. [PMID: 27070182 DOI: 10.1146/annurev-anchem-071015-041750] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The coupled physical and chemical dynamics model of ultraviolet matrix-assisted laser desorption/ionization (MALDI) has reproduced and explained a wide variety of MALDI phenomena. The rationale behind and elements of the model are reviewed, including the photophysics, kinetics, and thermodynamics of primary and secondary reaction steps. Experimental results are compared with model predictions to illustrate the foundations of the model, coupling of ablation and ionization, differences between and commonalities of matrices, secondary charge transfer reactions, ionization in both polarities, fluence and concentration dependencies, and suppression and enhancement effects.
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Affiliation(s)
- Richard Knochenmuss
- Departement für Chemie und Biochemie, Universität Bern, CH-3012 Bern, Switzerland;
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4
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Bae YJ, Kim MS. A Thermal Mechanism of Ion Formation in MALDI. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:41-60. [PMID: 26161971 DOI: 10.1146/annurev-anchem-081413-024102] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
An important recent discovery concerning the fundamentals of matrix-assisted laser desorption/ionization (MALDI) is that the abundance of each ion appearing in a spectrum is fixed, regardless of the experimental condition, when an effective temperature associated with the spectrum is fixed. We describe this phenomenon and the thermal picture for the ion formation in MALDI derived from it. Accepting that matrix-to-analyte proton transfer is in quasi-equilibrium as supported by experimental data, the above thermal determination occurs because the primary (matrix) ion formation processes are thermally governed. We propose that the abundances of the primary ions are limited by the autoprotolysis-recombination process regardless of how they are initially produced. Finally, we note that primary ion formation, secondary (analyte) ion formation, and their dissociations occur sequentially while the effective temperature of the matrix plume falls steadily due to cooling associated with expansion.
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Affiliation(s)
- Yong Jin Bae
- Department of Chemistry, Seoul National University, Seoul 151-742, Korea;
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5
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Gabriel SJ, Schwarzinger C, Schwarzinger B, Panne U, Weidner SM. Matrix segregation as the major cause for sample inhomogeneity in MALDI dried droplet spots. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1356-1363. [PMID: 24781460 DOI: 10.1007/s13361-014-0913-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/08/2014] [Accepted: 04/08/2014] [Indexed: 06/03/2023]
Abstract
The segregation in dried droplet MALDI sample spots was analyzed with regard to the matrix-to-sample ratio using optical microscopy, MALDI imaging mass spectrometry (MALDI MSI) and IR imaging spectroscopy. In this context, different polymer/matrix/solvent systems usually applied in the analysis of synthetic polymers were investigated. The use of typical matrix concentrations (10 mg mL⁻¹) in almost every case resulted in ring patterns, whereas higher concentrated matrix solutions always led to homogeneous sample spot layers. The data revealed that segregation is predominantly caused by matrix transport in the drying droplet, whereas polymer segregation seems to be only secondary.
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Affiliation(s)
- Stefan J Gabriel
- Federal Institute for Materials Research and Testing (BAM), D-12489, Berlin, Germany
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6
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Diologent L, Franck J, Wisztorski M, Treizebre A, Focsa C, Fournier I, Ziskind M. On the Origin of Increased Sensitivity and Mass Resolution Using Silicon Masks in MALDI. Anal Chem 2014; 86:1404-13. [DOI: 10.1021/ac401329r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Laurent Diologent
- Laboratoire de
Spectrométrie de Masse Biologique Fondamentale et Appliquée
- EA 4550, Bât SN3, Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
- Laboratoire
de Physique des Lasers, Atomes et Molécules - CNRS UMR 8523, Bât P5,Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
| | - Julien Franck
- Laboratoire de
Spectrométrie de Masse Biologique Fondamentale et Appliquée
- EA 4550, Bât SN3, Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
| | - Maxence Wisztorski
- Laboratoire de
Spectrométrie de Masse Biologique Fondamentale et Appliquée
- EA 4550, Bât SN3, Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
| | - Anthony Treizebre
- Institute of Electronics,
Microelectronics and Nanotechnology - UMR-CNRS 8520, Université Lille 1, F59655 Villeneuve d’Ascq, France
| | - Cristian Focsa
- Laboratoire
de Physique des Lasers, Atomes et Molécules - CNRS UMR 8523, Bât P5,Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
| | - Isabelle Fournier
- Laboratoire de
Spectrométrie de Masse Biologique Fondamentale et Appliquée
- EA 4550, Bât SN3, Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
| | - Michael Ziskind
- Laboratoire
de Physique des Lasers, Atomes et Molécules - CNRS UMR 8523, Bât P5,Université Lille 1, F-59655 Villeneuve
d’Ascq Cedex, France
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7
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Knochenmuss R. MALDI ionization mechanisms: the coupled photophysical and chemical dynamics model correctly predicts 'temperature'-selected spectra. JOURNAL OF MASS SPECTROMETRY : JMS 2013; 48:998-1004. [PMID: 24078239 DOI: 10.1002/jms.3248] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 05/30/2013] [Accepted: 06/14/2013] [Indexed: 06/02/2023]
Abstract
A number of possible ultraviolet MALDI ionization mechanisms based on different fundamental phenomena have been proposed. Recently, it has been argued, based on 'temperature'-selected spectra, that photoionization models should be rejected in favor of thermal ones. Here, one non-thermal photoionization model, the coupled photophysical and chemical dynamics model, is shown to be fully consistent with the data.
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Affiliation(s)
- Richard Knochenmuss
- Research and Development, Tofwerk AG, Uttigenstrasse 22, 3600 Thun, Switzerland
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8
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Roth MJ, Kim J, Maresh EM, Plymire DA, Corbett JR, Zhang J, Patrie SM. Thin-layer matrix sublimation with vapor-sorption induced co-crystallization for sensitive and reproducible SAMDI-TOF MS analysis of protein biosensors. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1661-1669. [PMID: 22847391 DOI: 10.1007/s13361-012-0442-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 06/19/2012] [Accepted: 06/22/2012] [Indexed: 06/01/2023]
Abstract
Coupling immunoassays on self-assembled monolayers (SAMs) to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) provides improved assay selectivity compared with traditional photometric detection techniques. We show that thin-layer-transfer (TLT) of α-cyano-4-hydroxycinnaminic acid (CHCA) MALDI matrix via vacuum sublimation followed by organic solvent-based vapor-sorption induced co-crystallization (VIC) results in unique matrix/analyte co-crystallization tendencies that optimizes assay reproducibility and sensitivity. Unique matrix crystal morphologies resulted from VIC solvent vapors, indicating nucleation and crystal growth characteristics depend upon VIC parameters. We observed that CHCA microcrystals generated by methanol VIC resulted in >10× better sensitivity, increased analyte charging, and improved precision compared with dried droplet measurements. The uniformity of matrix/analyte co-crystallization across planar immunoassays directed at intact proteins yielded low spectral variation for single shot replicates (18.5 % relative standard deviation, RSD) and signal averaged spectra (<10 % RSD). We envision that TLT and VIC for MALDI-TOF will enable high-throughput, reproducible array-based immunoassays for protein molecular diagnostic assays in diverse biochemical and clinical applications.
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Affiliation(s)
- Michael J Roth
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, 75390, USA
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9
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Huang JT, Hannah-Qiuhua L, Szyszka R, Veselov V, Reed G, Wang X, Price S, Alquier L, Vas G. Molecular imaging of drug-eluting coronary stents: method development, optimization and selected applications. JOURNAL OF MASS SPECTROMETRY : JMS 2012; 47:155-162. [PMID: 22359324 DOI: 10.1002/jms.2046] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A molecular imaging application was developed to characterize the drug distribution on CYPHER® and NEVO™ Drug-eluting Stents using MALDI Qq-ToF analytical methodology. The coating matrix, laser energy, laser frequency, spatial resolution (related to rastering speed) and mass spectrometer parameters were optimized to analyze drug distribution in both durable and biodegradable polymer matrices. The developed method was extended to generate data from stents explanted from porcine coronary arteries. Due to the method's intrinsic specificity, it offers a significant advantage over other techniques in that it allows low-level detection of the target molecule without biological interferences from the blood or tissue. The method is also capable of detecting drug-related degradation products both from the finished stent product and from explanted stents.
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Affiliation(s)
- Jiun-Tang Huang
- Cordis Analytical R&D, Convergent Product Development, Spring House, PA, USA
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10
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Stolee JA, Walker BN, Zorba V, Russo RE, Vertes A. Laser–nanostructure interactions for ion production. Phys Chem Chem Phys 2012; 14:8453-71. [DOI: 10.1039/c2cp00038e] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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11
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Knochenmuss R, Zhigilei LV. What determines MALDI ion yields? A molecular dynamics study of ion loss mechanisms. Anal Bioanal Chem 2011; 402:2511-9. [PMID: 21725831 DOI: 10.1007/s00216-011-5194-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 05/25/2011] [Accepted: 06/19/2011] [Indexed: 11/28/2022]
Abstract
Ion recombination in matrix-assisted laser desorption/ionization (MALDI) is as important as any ion formation process in determining the quantity of ions observed but has received comparatively little attention. Molecular dynamics simulations are used here to investigate some models for recombination, including a Langevin-type model, a soft threshold model and a tunneling model. The latter was found to be superior due to its foundations in a widespread physical phenomenon, and its lack of excessive sensitivity to parameter choice. Tunneling recombination in the Marcus inverted region may be a major reason why MALDI is a viable analytical method, by allowing ion formation to exceed ion loss on the time scale of the plume expansion. Ion velocities, photoacoustic transients and pump-probe measurements might be used to investigate the role of recombination in different MALDI matrices, and to select new matrices.
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12
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Jaskolla TW, Karas M. Compelling evidence for Lucky Survivor and gas phase protonation: the unified MALDI analyte protonation mechanism. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:976-88. [PMID: 21953039 DOI: 10.1007/s13361-011-0093-0] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/03/2011] [Accepted: 01/03/2011] [Indexed: 05/03/2023]
Abstract
This work experimentally verifies and proves the two long since postulated matrix-assisted laser desorption/ionization (MALDI) analyte protonation pathways known as the Lucky Survivor and the gas phase protonation model. Experimental differentiation between the predicted mechanisms becomes possible by the use of deuterated matrix esters as MALDI matrices, which are stable under typical sample preparation conditions and generate deuteronated reagent ions, including the deuterated and deuteronated free matrix acid, only upon laser irradiation in the MALDI process. While the generation of deuteronated analyte ions proves the gas phase protonation model, the detection of protonated analytes by application of deuterated matrix compounds without acidic hydrogens proves the survival of analytes precharged from solution in accordance with the predictions from the Lucky Survivor model. The observed ratio of the two analyte ionization processes depends on the applied experimental parameters as well as the nature of analyte and matrix. Increasing laser fluences and lower matrix proton affinities favor gas phase protonation, whereas more quantitative analyte protonation in solution and intramolecular ion stabilization leads to more Lucky Survivors. The presented results allow for a deeper understanding of the fundamental processes causing analyte ionization in MALDI and may alleviate future efforts for increasing the analyte ion yield.
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Affiliation(s)
- Thorsten W Jaskolla
- Cluster of Excellence Macromolecular Complexes, Institute of Pharmaceutical Chemistry, Goethe University Frankfurt, Frankfurt, Germany.
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13
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Lourantos E, Ramirez OM, Giannakopulos AE, Beran KA, Derrick PJ, Bashir S. The use of a silica-based heat sink to “uncouple” the matrix-assisted laser desorption/ionization (MALDI) mechanism. CAN J CHEM 2011. [DOI: 10.1139/v10-154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The relationships between ion yield(s) as a function of desorption alone and (or) ionization was investigated using two model systems. In the first model system, a carbohydrate (2,3,6-tri-O-methyl-β-cyclodextrin, TMBCD), which could be directly laser desorbed, was analyzed with and without a silicon-based heat sink compound (HSC). The HSC allowed heat to pass through but obstructed the flow of charge. In the second model system, a peptide (substance P), which ccould not be laser desorbed, was analyzed under similar conditions. The ion yield of TMBCD under either system of heat conductivity was similar, whereas the ion yield of the peptide with the heat sink was negligible. Compounds that are predominately cationized either in the gas phase or preformed in solution give an ion yield that is not dependent upon the surface conditions, whereas compounds that are not ordinarily cationized are affected by the emission of electrons from the metal surface.
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Affiliation(s)
- E. Lourantos
- Institute of Mass Spectrometry, University of Warwick, Coventry CV4 7AL, UK
- Department of Physical Sciences, The University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762, USA
| | - O. M. Ramirez
- Institute of Mass Spectrometry, University of Warwick, Coventry CV4 7AL, UK
- Department of Physical Sciences, The University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762, USA
| | - A. E. Giannakopulos
- Institute of Mass Spectrometry, University of Warwick, Coventry CV4 7AL, UK
- Department of Physical Sciences, The University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762, USA
| | - K. A. Beran
- Institute of Mass Spectrometry, University of Warwick, Coventry CV4 7AL, UK
- Department of Physical Sciences, The University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762, USA
| | - Peter J. Derrick
- Institute of Mass Spectrometry, University of Warwick, Coventry CV4 7AL, UK
- Department of Physical Sciences, The University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762, USA
| | - S. Bashir
- Institute of Mass Spectrometry, University of Warwick, Coventry CV4 7AL, UK
- Department of Physical Sciences, The University of Texas of the Permian Basin, 4901 E. University Blvd., Odessa, TX 79762, USA
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14
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Harvey DJ. Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for the period 2005-2006. MASS SPECTROMETRY REVIEWS 2011; 30:1-100. [PMID: 20222147 DOI: 10.1002/mas.20265] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This review is the fourth update of the original review, published in 1999, on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2006. The review covers fundamental studies, fragmentation of carbohydrate ions, method developments, and applications of the technique to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, glycated proteins, glycolipids from bacteria, glycosides, and various other natural products. There is a short section on the use of MALDI-TOF mass spectrometry for the study of enzymes involved in glycan processing, a section on industrial processes, particularly the development of biopharmaceuticals and a section on the use of MALDI-MS to monitor products of chemical synthesis of carbohydrates. Large carbohydrate-protein complexes and glycodendrimers are highlighted in this final section.
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Affiliation(s)
- David J Harvey
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, Oxford OX1 3QU, UK.
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15
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Svoboda M, Kodíček M. Azo-group reduction during the matrix-assisted laser desorption/ionization process in the presence of 2,5-dihydroxybenzoic acid. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:3351-3356. [PMID: 20973011 DOI: 10.1002/rcm.4781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Some time ago, we published an announcement that the azo group that closes model cyclic peptides is often reduced in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) in the presence of 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix. In this work, we demonstrate that these peptides are ionized in all DHB matrix isomers, although threshold ionization laser energies as well as the reduction ratios differ in each matrix. Using a NALDI plate, we confirmed that their reduction depends on the presence of DHB matrix and that the hydrogen atoms participating in the reaction come from the DHB matrix hydroxyl group. We show that the reduction ratio is affected by the overall covalent structure of the peptide, by the presence of a free carboxyl group in DHB matrix, by the mutual position of the hydroxyl and carboxyl groups, as well as the laser beam intensity. Based on these results, it can be concluded that the azo-group reduction in cyclic peptides is a very complex process and we are far from fully understanding its nature. We hope that our experimental results will help to shed some light on the MALDI process that still remains mysterious in some of its aspects.
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Affiliation(s)
- Martin Svoboda
- Institute of Chemical Technology, Technická 5, Prague 16628, Czech Republic.
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16
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Abonnenc M, Qiao L, Liu B, Girault HH. Electrochemical aspects of electrospray and laser desorption/ionization for mass spectrometry. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2010; 3:231-54. [PMID: 20636041 DOI: 10.1146/annurev.anchem.111808.073740] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Soft-ionization methods, namely electrospray ionization and laser desorption/ionization, are widely used to transfer large molecules as intact gas-phase ions either from a solution or from a solid substrate. During both processes, in-source electrochemical and photoelectrochemical reactions occur. These electrode reactions, which take place at interfaces, play important roles in influencing the ionization products, but they have received little attention. We show that having good control over both types of electrochemical reactions can lead to new analytical applications. Examples include online tagging by grafting of mass tags and in-source photooxidation of peptides.
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Affiliation(s)
- Mélanie Abonnenc
- Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
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17
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Holcomb A, Owens KG. Optimization of a modified aerospray deposition device for the preparation of samples for quantitative analysis by MALDI-TOFMS. Anal Chim Acta 2009; 658:49-55. [PMID: 20082773 DOI: 10.1016/j.aca.2009.10.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 10/26/2009] [Accepted: 10/27/2009] [Indexed: 10/20/2022]
Abstract
A modified aerospray apparatus was used to prepare a thin layer sample of matrix and analyte for quantitative analysis by MALDI-TOFMS. The apparatus consists of a set of coaxial tubing; the liquid sample is forced by a syringe pump through the inner capillary and it is nebulized by a flow of gas through the outer capillary. The small droplets of sample exiting the device are deposited onto a rotating plate, which serves as the sample surface for a time-of-flight mass spectrometer. An optimization was carried out after initial experiments with the device resulted in poorer than expected reproducibility of analyte signal. A two-level plus center point factorial experiment was performed investigating several factors, including the inner capillary internal diameter, gas pressure, liquid flow, spray distance, and time. After optimization the within-sample reproducibility of the analyte signal improved 3-fold, while the sample-to-sample reproducibility improved 4.5-fold.
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Affiliation(s)
- April Holcomb
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
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18
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Jaskolla TW, Karas M, Roth U, Steinert K, Menzel C, Reihs K. Comparison between vacuum sublimed matrices and conventional dried droplet preparation in MALDI-TOF mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1104-14. [PMID: 19299165 DOI: 10.1016/j.jasms.2009.02.010] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 01/28/2009] [Accepted: 02/04/2009] [Indexed: 05/20/2023]
Abstract
The properties of several cinnamic acid compounds used as matrices for matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were investigated as standard dried droplet (DD) and vacuum sublimed preparations. The differences between both preparation methods were analyzed with regard to matrix grain size, internal ion energy, initial velocity, analyte intensity, and analyte incorporation depth. Some of the used cinnamic acid derivatives exhibit clearly reduced grain sizes as sublimed preparations compared with standard DD approaches. In these cases higher effective temperatures could be measured accompanied by increased analyte intensities, which can be explained by stronger volatilization processes caused by a hindered heat dissipation resulting in a raised analyte transfer into the gas phase. For all sublimed compounds, a strong increase of the initial ion velocity compared with DD preparations could be measured. Higher initial ion velocities correlate with a decrease in internal ion energy which might be attributed to the very uniform crystal morphology exhibited by sublimed compounds. For sublimed matrices without reduced grain size, at least slightly higher analyte intensities could be detected at raised laser fluences. Analyte accumulation in the uppermost matrix layers or the detected higher ion stability can be explanations for these results.
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Affiliation(s)
- Thorsten W Jaskolla
- Cluster of Excellence Macromolecular Complexes, Institute of Pharmaceutical Chemistry, Goethe University, Frankfurt, Germany
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19
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Knochenmuss R. Laser desorption/ablation plumes from capillary-like restricted volumes. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2009; 15:189-198. [PMID: 19423904 DOI: 10.1255/ejms.960] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Laser desorption/ionization from structured surfaces has been the object of recently renewed interest. Conditions in the plume of material ablated from such surfaces may differ from those of a sample which is ablated in bulk. Since recombination and secondary ion-molecule reactions in the plume play a major role in determining the types and quantities of ions observed at the detector, these differences are analytically relevant. Desorption/ionization substrates with channels of high aspect ratio are modeled as capillary nozzles, from which free jets are emitted. A previously developed matrix-assisted laser desorption/ionization ablation/ionization model is adapted for these jets. More primary ions reach the detector when ablated from a capillary orifice, but fewer analye ions are created in secondary reactions. These differences in ion yield can persist for arrays of capillaries on the surface, depending on the ratio of their diameter to spacing.
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Affiliation(s)
- Richard Knochenmuss
- Novartis Institutes for Biomedical Research, WSJ 503.1104, 4052 Basel, Switzerland.
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Hughes L, Wyatt MF, Stein BK, Brenton AG. Investigation of Solvent-Free MALDI-TOFMS Sample Preparation Methods for the Analysis of Organometallic and Coordination Compounds. Anal Chem 2008; 81:543-50. [DOI: 10.1021/ac801483d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Laura Hughes
- EPSRC National Mass Spectrometry Service Centre (NMSSC), Institute of Mass Spectrometry (IMS), School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, U.K
| | - Mark F. Wyatt
- EPSRC National Mass Spectrometry Service Centre (NMSSC), Institute of Mass Spectrometry (IMS), School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, U.K
| | - Bridget K. Stein
- EPSRC National Mass Spectrometry Service Centre (NMSSC), Institute of Mass Spectrometry (IMS), School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, U.K
| | - A. Gareth Brenton
- EPSRC National Mass Spectrometry Service Centre (NMSSC), Institute of Mass Spectrometry (IMS), School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, U.K
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Volný M, Sadílek M, Jackson KE, Diener M, Elam WT, Turecek F. Matrix-free laser desorption/ionization of ions landed on plasma-treated metal surfaces. JOURNAL OF MASS SPECTROMETRY : JMS 2008; 43:1265-1273. [PMID: 18338315 DOI: 10.1002/jms.1402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report new experiments in which laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) was applied to detection and characterization of gramicidin S and IgG pentapeptide (DSDPR) that were reactively landed on plasma-treated stainless steel surfaces. The distributions of [M+H](+), [M+Na](+) and [M + K](+) ion species in LDI-TOF for gramicidin S and IgG pentapeptide (DSDPR) were found to be markedly different from those in conventional MALDI-TOF spectra of the same samples. LDI-TOF mass spectra showed a strong preference for [M+K](+) adducts even in the presence of a large excess of sodium cations, or following surface treatment with trifluoroacetic acid. Alkali metal cations (K(+) and Cs(+)) can be exchanged in reactively landed peptide samples to provide the corresponding cationized peptide ions by LDI. Multiple charged trypsin cations were reactively landed into a layer of 2-(4-hydroxyphenylazo)benzoic acid and ionized by LDI. The ionization mechanisms for LDI of surface-deposited peptides are briefly discussed.
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Affiliation(s)
- Michael Volný
- Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA
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Demeure K, Quinton L, Gabelica V, De Pauw E. Rational Selection of the Optimum MALDI Matrix for Top-Down Proteomics by In-Source Decay. Anal Chem 2007; 79:8678-85. [DOI: 10.1021/ac070849z] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kevin Demeure
- Laboratoire de Spectrométrie de Masse, CART/GIGA-R, Institut de Chimie, Bat. B6c, Université de Liège, Liège B-4000, Belgium
| | - Loïc Quinton
- Laboratoire de Spectrométrie de Masse, CART/GIGA-R, Institut de Chimie, Bat. B6c, Université de Liège, Liège B-4000, Belgium
| | - Valérie Gabelica
- Laboratoire de Spectrométrie de Masse, CART/GIGA-R, Institut de Chimie, Bat. B6c, Université de Liège, Liège B-4000, Belgium
| | - Edwin De Pauw
- Laboratoire de Spectrométrie de Masse, CART/GIGA-R, Institut de Chimie, Bat. B6c, Université de Liège, Liège B-4000, Belgium
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