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Metodiev MD, Steven RT, Loizeau X, Takats Z, Bunch J. Modality Agnostic Model for Spatial Resolution in Mass Spectrometry Imaging: Application to MALDI MSI Data. Anal Chem 2021; 93:15295-15305. [PMID: 34767361 DOI: 10.1021/acs.analchem.1c02470] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Image resolution in mass spectrometry imaging (MSI) is governed by the sampling probe, the motion of the stage relative to the probe, and the noise inherent for the sample and instrumentation employed. A new image formation model accounting for these variables is presented here. The model shows that the size of the probe, stage velocity, and the rate at which the probe consumes material from the surface govern the amount of blur present in the image. However, the main limiting factor for resolution is the signal-to-noise ratio (SNR). To evaluate blurring and noise effects, a new computational method for measuring lateral resolution in MSI is proposed. A spectral decomposition of the observed image signal and noise is used to determine a resolution number. To evaluate this technique, a silver step edge was prepared. This device was imaged at different pixels sizes using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI). A modulation transfer function (MTF) and a noise power spectrum (NPS) were computed for each single-ion image, and resolution was defined as the point of intersection between the MTF and the NPS. Finally, the algorithm was also applied to a MALDI MSI tissue data set.
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Affiliation(s)
- Martin D Metodiev
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory (NPL), Teddington, TW11 0LW, U.K.,Faculty of Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, London SW7 2AZ, U.K
| | - Rory T Steven
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory (NPL), Teddington, TW11 0LW, U.K
| | - Xavier Loizeau
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory (NPL), Teddington, TW11 0LW, U.K
| | - Zoltan Takats
- Faculty of Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, London SW7 2AZ, U.K.,Biological Mass Spectrometry, The Rosalind Franklin Institute, Harwell Campus, Didcot OX11 OFA, U.K
| | - Josephine Bunch
- National Centre of Excellence in Mass Spectrometry Imaging (NiCE-MSI), National Physical Laboratory (NPL), Teddington, TW11 0LW, U.K.,Faculty of Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, London SW7 2AZ, U.K.,Biological Mass Spectrometry, The Rosalind Franklin Institute, Harwell Campus, Didcot OX11 OFA, U.K
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Lin HY, Dyakov YA, Lee YT, Ni CK. Temperature Dependence of Desorbed Ions and Neutrals and Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:95-105. [PMID: 32239933 DOI: 10.1021/jasms.0c00101] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two separate temperature-dependent experiments were performed to investigate the ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) of matrix 2,5-dihydroxybenzoic acid (2,5-DHB). First, the angular resolved intensity and velocity distributions of neutrals desorbed from the 2,5-DHB solid sample through UV laser (355 nm) pulse irradiation were measured using a rotating quadrupole mass spectrometer. Second, the desorbed neutrals, at an angle normal to the surface, and the desorbed ions were simultaneously detected for each laser shot using the quadrupole mass spectrometer and a time-of-flight mass spectrometer, respectively. Both experiments were conducted at two initial temperatures: 100 and 300 K. The measurements from these two experiments were used to calculate the initial temperature dependence of the ion-to-neutral ratio. The results closely agreed with the predictions of the temperature-dependent ion-to-neutral ratio using the thermal model, indicating that thermally induced proton transfer is the dominant reaction that generates initial ions of 2,5-DHB in UV-MALDI.
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Affiliation(s)
- Hou-Yu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Yuri A Dyakov
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Yuan Tseh Lee
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Chi-Kung Ni
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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Lin HY, Song BF, Ni CK. Fluorescence quantum yields of matrices used in ultraviolet matrix-assisted laser desorption/ionization. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34:e8846. [PMID: 32469439 DOI: 10.1002/rcm.8846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 05/27/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
RATIONALE Ultraviolet matrix-assisted laser desorption/ionization (MALDI) is among the most popular soft ionization methods in mass spectrometry. Several theoretical models have been proposed to explain the primary ion generation in MALDI. These models require knowledge of various matrix molecular parameters for simulation. One such parameter is the fluorescence quantum yield. However, the fluorescence quantum yield reported in previous studies remains controversial. METHODS In this study, we used a commercial and a homemade integrating sphere to measure the absorption and fluorescence quantum yields of several commonly used matrices, including 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid (2,4-DHB), 2,5-dihydroxybenzoic acid (2,5-DHB), 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,4,6-trihydroxyacetophenone, and ferulic acid. RESULTS The fluorescence quantum yields of these matrices were determined to be low (<0.08) at low laser fluences and decreased as the laser fluence increased. The fluorescence quantum yields at the typical laser fluence for MALDI are below 0.04 (2,4-DHB and 2,5-DHB) and 0.01 (the other matrices). Shot-to-shot fluctuations of fluorescence intensity and absorption are not directly related to the fluctuation of ions. Possible mechanisms for the decrease in the fluorescence quantum yield as the laser fluence increased were discussed. CONCLUSIONS The fluorescence quantum yields of these commonly used matrices are much lower than those reported in previous studies. Although fluorescence quantum yield is an important parameter and it is crucial to obtain an accurate value for theoretical models in simulations, the use of fluorescence quantum yield alone is not a sufficient parameter to justify these models.
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Affiliation(s)
- Hou-Yu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
- Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan
| | - Botao Farren Song
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, 77005, USA
| | - Chi-Kung Ni
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
- Department of Chemistry, National Tsing Hua University, Hsinchu, 30013, Taiwan
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Lee H, Lai YH, Ou YM, Tsao CW, Jheng YJ, Kuo SY, Chang HT, Wang YS. Enhancing carbohydrate ion yield by controlling crystalline structures in matrix-assisted laser desorption/ionization mass spectrometry. Anal Chim Acta 2017; 994:49-55. [PMID: 29126468 DOI: 10.1016/j.aca.2017.09.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 09/12/2017] [Accepted: 09/13/2017] [Indexed: 10/18/2022]
Abstract
Carbohydrate analysis is challenging due to lack of sensitive detection and efficient separation methods. Although matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is a sensitive tool, the low ionization efficiency of carbohydrates makes mass analyses inefficient. This work systematically examines the correlation between MALDI-MS sensitivity and carbohydrate sample morphology. Depending on the properties of the matrix used, the morphology changes through sample recrystallization after drying or imposition of hydrodynamic flows during droplet drying. Observation shows that amorphous solids and finer crystals offer higher carbohydrate sensitivity and spatial homogeneity than larger crystals. Clear evidences of an inverse correlation between sensitivity and crystal size are obtained when various kinds of carbohydrates are mixed with different matrixes. Similar experiments on proteins and peptides showed a negative or negligible effect. The result serves as a general guideline for improving efficiency in routine carbohydrate analysis.
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Affiliation(s)
- Hsun Lee
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Yin-Hung Lai
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Yu-Meng Ou
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC; Chemistry Department, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Chien-Wei Tsao
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC; Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 106, Taiwan, ROC
| | - Ya-Jin Jheng
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Shu-Yun Kuo
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Huan-Tsung Chang
- Chemistry Department, National Taiwan University, Taipei 106, Taiwan, ROC
| | - Yi-Sheng Wang
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC.
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Lai YH, Wang YS. Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry: Mechanistic Studies and Methods for Improving the Structural Identification of Carbohydrates. Mass Spectrom (Tokyo) 2017; 6:S0072. [PMID: 28959517 PMCID: PMC5610957 DOI: 10.5702/massspectrometry.s0072] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 12/21/2022] Open
Abstract
Although matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is one of the most widely used soft ionization methods for biomolecules, the lack of detailed understanding of ionization mechanisms restricts its application in the analysis of carbohydrates. Structural identification of carbohydrates achieved by MALDI mass spectrometry helps us to gain insights into biological functions and pathogenesis of disease. In this review, we highlight mechanistic details of MALDI, including both ionization and desorption. Strategies to improve the ion yield of carbohydrates are also reviewed. Furthermore, commonly used fragmentation methods to identify the structure are discussed.
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Mirabelli MF, Zenobi R. Observing Proton Transfer Reactions Inside the MALDI Plume: Experimental and Theoretical Insight into MALDI Gas-Phase Reactions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1676-1686. [PMID: 28451953 DOI: 10.1007/s13361-017-1677-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/24/2017] [Accepted: 03/25/2017] [Indexed: 06/07/2023]
Abstract
We evaluated the contribution of gas-phase in-plume proton transfer reactions to the formation of protonated and deprotonated molecules in the MALDI process. A split sample holder was used to separately deposit two different samples, which avoids any mixing during sample preparation. The two samples were brought very close to each other and desorbed/ionized by the same laser pulse. By using a combination of deuterated and non-deuterated matrices, it was possible to observe exclusively in-plume proton transfer processes. The hydrogen/deuterium exchange (HDX) kinetics were evaluated by varying the delayed extraction (DE) time, allowing the desorbed ions and neutrals to interact inside the plume for a variable period of time before being extracted and detected. Quantum mechanical calculations showed that the HDX energy barriers are relatively low for such reactions, corroborating the importance of gas-phase proton transfer in the MALDI plume. The experimental results, supported by theoretical simulations, confirm that the plume is a very reactive environment, where HDX reactions could be observed from 0 ns up to 400 ns after the laser pulse. These results could be used to evaluate the relevance of previously proposed (and partially conflicting) ionization models for MALDI. Graphical Abstract ᅟ.
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Affiliation(s)
- Mario F Mirabelli
- ETH Zurich, Department of Chemistry and Applied Biosciences, CH-8093, Zurich, Switzerland
| | - Renato Zenobi
- ETH Zurich, Department of Chemistry and Applied Biosciences, CH-8093, Zurich, Switzerland.
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7
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Wang CC, Lai YH, Ou YM, Chang HT, Wang YS. Critical factors determining the quantification capability of matrix-assisted laser desorption/ionization- time-of-flight mass spectrometry. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0371. [PMID: 27644968 PMCID: PMC5031637 DOI: 10.1098/rsta.2015.0371] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/17/2016] [Indexed: 05/03/2023]
Abstract
Quantitative analysis with mass spectrometry (MS) is important but challenging. Matrix-assisted laser desorption/ionization (MALDI) coupled with time-of-flight (TOF) MS offers superior sensitivity, resolution and speed, but such techniques have numerous disadvantages that hinder quantitative analyses. This review summarizes essential obstacles to analyte quantification with MALDI-TOF MS, including the complex ionization mechanism of MALDI, sensitive characteristics of the applied electric fields and the mass-dependent detection efficiency of ion detectors. General quantitative ionization and desorption interpretations of ion production are described. Important instrument parameters and available methods of MALDI-TOF MS used for quantitative analysis are also reviewed.This article is part of the themed issue 'Quantitative mass spectrometry'.
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Affiliation(s)
- Chia-Chen Wang
- Department of Biochemistry, National Yang-Ming University, No. 155, Section 2, Linong Street, Taipei 112, Taiwan, Republic of China Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Taipei 115, Taiwan, Republic of China
| | - Yin-Hung Lai
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Taipei 115, Taiwan, Republic of China
| | - Yu-Meng Ou
- Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Taipei 115, Taiwan, Republic of China Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, Republic of China
| | - Huan-Tsung Chang
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, Republic of China
| | - Yi-Sheng Wang
- Department of Biochemistry, National Yang-Ming University, No. 155, Section 2, Linong Street, Taipei 112, Taiwan, Republic of China Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Taipei 115, Taiwan, Republic of China
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8
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Lee C, Lu IC, Hsu HC, Lin HY, Liang SP, Lee YT, Ni CK. Formation of Metal-Related Ions in Matrix-Assisted Laser Desorption Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1491-1498. [PMID: 27306427 DOI: 10.1007/s13361-016-1424-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 05/17/2016] [Accepted: 05/20/2016] [Indexed: 06/06/2023]
Abstract
In a study of the metal-related ion generation mechanism in matrix-assisted laser desorption ionization (MALDI), crystals of matrix used in MALDI were grown from matrix- and salt-containing solutions. The intensities of metal ion and metal adducts of the matrix ion obtained from unwashed crystals were higher than those from crystals washed with deionized water, indicating that metal ions and metal adducts of the matrix ions are mainly generated from the surface of crystals. The contributions of preformed metal ions and metal adducts of the matrix ions inside the matrix crystals were minor. Metal adducts of the matrix and analyte ion intensities generated from a mixture of dried matrix, salt, and analyte powders were similar to or higher than those generated from the powder of dried droplet crystals, indicating that the contributions of the preformed metal adducts of the matrix and analyte ions were insignificant. Correlation between metal-related ion intensity fluctuation and protonated ion intensity fluctuation was observed, indicating that the generation mechanism of the metal-related ions is similar to that of the protonated ions. Because the thermally induced proton transfer model effectively describes the generation of the protonated ions, we suggest that metal-related ions are mainly generated from the salt dissolution in the matrix melted by the laser. Graphical Abstract ᅟ.
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Affiliation(s)
- Chuping Lee
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
- Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan
| | - I-Chung Lu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
| | - Hsu Chen Hsu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
| | - Hou-Yu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
- Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan
| | - Sheng-Ping Liang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
| | - Yuan-Tseh Lee
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
- Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan
| | - Chi-Kung Ni
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
- Department of Chemistry, National Tsing Hua University, Hsinchu, 30013, Taiwan.
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Zeegers GP, Günthardt BF, Zenobi R. Target Plate Material Influence on Fullerene-C60 Laser Desorption/Ionization Efficiency. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:699-708. [PMID: 26894888 DOI: 10.1007/s13361-016-1333-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/03/2015] [Accepted: 12/30/2015] [Indexed: 06/05/2023]
Abstract
Systematic laser desorption/ionization (LDI) experiments of fullerene-C60 on a wide range of target plate materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0-3.53 Jcm(-2)) and the ion extraction delay time (0-950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target plate material increases the fullerene-C60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements. Graphical Abstract ᅟ.
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Affiliation(s)
- Guido P Zeegers
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, CH-8093, Zürich, Switzerland
| | - Barbara F Günthardt
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, CH-8093, Zürich, Switzerland
| | - Renato Zenobi
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 3, CH-8093, Zürich, Switzerland.
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Cai YH, Lai YH, Wang YS. Coupled Space- and Velocity-Focusing in Time-of-Flight Mass Spectrometry-a Comprehensive Theoretical Investigation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:1722-1731. [PMID: 26154940 DOI: 10.1007/s13361-015-1206-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 05/20/2015] [Accepted: 05/22/2015] [Indexed: 06/04/2023]
Abstract
A comprehensive theoretical calculation that couples space- and velocity-focusing is developed for optimizing the design of a time-of-flight (TOF) mass spectrometer. Conventional designs for ion sources of TOF mass spectrometers deviate from the optimal condition because the velocity- and space-focusing conditions are considered separately for two ions with simplified equations. The result of a reexamination taking into account all essential ions reveals that the conventional ion source design, especially the length of the ion extraction region, results in poor resolving power. The comprehensive calculation demonstrates that the resolving power increases when the length of the extraction region is shorter than that of the conventional ion source. A numerical analysis indicates that the resolving power dramatically increases when the effective extraction potential compensates for the initial kinetic energy spread of ions. With typically used extraction potentials, the newly optimized ion source improves the resolving power by more than two orders of magnitude compared with the conventional design. This new theoretical interpretation can also be used to predict the optimal extraction potential and extraction delay in conventional ion sources to substantially improve the resolving power. This comprehensive calculation method is effective not only for designing new high-resolution instruments but also for optimizing commercial products.
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Affiliation(s)
- Yi-Hong Cai
- Genomics Research Center, Academia Sinica, 128, Academia Road, Section 2, Nankang District, Taipei, 115, Taiwan, Republic of China
| | - Yin-Hung Lai
- Genomics Research Center, Academia Sinica, 128, Academia Road, Section 2, Nankang District, Taipei, 115, Taiwan, Republic of China
| | - Yi-Sheng Wang
- Genomics Research Center, Academia Sinica, 128, Academia Road, Section 2, Nankang District, Taipei, 115, Taiwan, Republic of China.
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Harvey DJ. Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for 2009-2010. MASS SPECTROMETRY REVIEWS 2015; 34:268-422. [PMID: 24863367 PMCID: PMC7168572 DOI: 10.1002/mas.21411] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 07/16/2013] [Accepted: 07/16/2013] [Indexed: 05/07/2023]
Abstract
This review is the sixth update of the original article 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 2010. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, arrays and fragmentation are covered in the first part of the review and applications to various structural typed constitutes the remainder. The main groups of compound that are discussed in this section are oligo and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Many of these applications are presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis.
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Affiliation(s)
- David J. Harvey
- Department of BiochemistryOxford Glycobiology InstituteUniversity of OxfordOxfordOX1 3QUUK
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12
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Lu IC, Lee C, Lee YT, Ni CK. Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2015; 8:21-39. [PMID: 26132345 DOI: 10.1146/annurev-anchem-071114-040315] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In past studies, mistakes in determining the ionization mechanism in matrix-assisted laser desorption/ionization (MALDI) were made because an inappropriate ion-to-neutral ratio was used. The ion-to-neutral ratio of the analyte differs substantially from that of the matrix in MALDI. However, these ratios were not carefully distinguished in previous studies. We begin by describing the properties of ion-to-neutral ratios and reviews early experimental measurements. A discussion of the errors committed in previous theoretical studies and a comparison of recent experimental measurements follow. We then describe a thermal proton transfer model and demonstrate how the model appropriately describes ion-to-neutral ratios and the total ion intensity. Arguments raised to challenge thermal ionization are then discussed. We demonstrate how none of the arguments are valid before concluding that thermal proton transfer must play a crucial role in the ionization process of MALDI.
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Affiliation(s)
- I-Chung Lu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan; , , ,
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13
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Lin HY, Hsu HC, Lu IC, Hsu KT, Liao CY, Lee YY, Tseng CM, Lee YT, Ni CK. Fluorescence spectroscopy of UV-MALDI matrices and implications of ionization mechanisms. J Chem Phys 2014; 141:164307. [DOI: 10.1063/1.4898372] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Hou-Yu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Hsu Chen Hsu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - I-Chung Lu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Kuo-Tung Hsu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chih-Yu Liao
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yin-Yu Lee
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chien-Ming Tseng
- Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yuan-Tseh Lee
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Chi-Kung Ni
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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Lai YH, Chen BG, Lee YT, Wang YS, Lin SH. Contribution of thermal energy to initial ion production in matrix-assisted laser desorption/ionization observed with 2,4,6-trihydroxyacetophenone. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:1716-22. [PMID: 24975252 DOI: 10.1002/rcm.6952] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 05/01/2014] [Accepted: 05/21/2014] [Indexed: 05/20/2023]
Abstract
RATIONALE Although several reaction models have been proposed in the literature to explain matrix-assisted laser desorption/ionization (MALDI), further study is still necessary to explore the important ionization pathways that occur under the high-temperature environment of MALDI. 2,4,6-Trihydroxyacetophenone (THAP) is an ideal compound for evaluating the contribution of thermal energy to an initial reaction with minimum side reactions. METHODS Desorbed neutral THAP and ions were measured using a crossed-molecular beam machine and commercial MALDI-TOF instrument, respectively. A quantitative model incorporating an Arrhenius-type desorption rate derived from transition state theory was proposed. Reaction enthalpy was calculated using GAUSSIAN 03 software with dielectric effect. Additional evidence of thermal-induced proton disproportionation was given by the indirect ionization of THAP embedded in excess fullerene molecules excited by a 450 nm laser. RESULTS The quantitative model predicted that proton disproportionation of THAP would be achieved by thermal energy converted from a commonly used single UV laser photon. The dielectric effect reduced the reaction Gibbs free energy considerably even when the dielectric constant was reduced under high-temperature MALDI conditions. With minimum fitting parameters, observations of pure THAP and THAP mixed with fullerene both agreed with predictions. CONCLUSIONS Proton disproportionation of solid THAP was energetically favorable with a single UV laser photon. The quantitative model revealed an important initial ionization pathway induced by the abrupt heating of matrix crystals. In the matrix crystals, the dielectric effect reduced reaction Gibbs free energy under typical MALDI conditions. The result suggested that thermal energy plays an important role in the initial ionization reaction of THAP.
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Affiliation(s)
- Yin-Hung Lai
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
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15
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Lu IC, Lee C, Chen HY, Lin HY, Hung SW, Dyakov YA, Hsu KT, Liao CY, Lee YY, Tseng CM, Lee YT, Ni CK. Ion Intensity and Thermal Proton Transfer in Ultraviolet Matrix-Assisted Laser Desorption/Ionization. J Phys Chem B 2014; 118:4132-9. [DOI: 10.1021/jp5008076] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- I-Chung Lu
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Chuping Lee
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department
of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Hui-Yuan Chen
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Hou-Yu Lin
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department
of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Sheng-Wei Hung
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Yuri A. Dyakov
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Kuo-Tung Hsu
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chih-Yu Liao
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yin-Yu Lee
- National
Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chien-Ming Tseng
- Department
of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yuan-Tseh Lee
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department
of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Chi-Kung Ni
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department
of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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16
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Chu KY, Lee S, Tsai MT, Lu IC, Dyakov YA, Lai YH, Lee YT, Ni CK. Thermal proton transfer reactions in ultraviolet matrix-assisted laser desorption/ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:310-8. [PMID: 24395022 DOI: 10.1007/s13361-013-0792-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Revised: 11/24/2013] [Accepted: 11/25/2013] [Indexed: 05/20/2023]
Abstract
One of the reasons that thermally induced reactions are not considered a crucial mechanism in ultraviolet matrix-assisted laser desorption ionization (UV-MALDI) is the low ion-to-neutral ratios. Large ion-to-neutral ratios (10(-4)) have been used to justify the unimportance of thermally induced reactions in UV-MALDI. Recent experimental measurements have shown that the upper limit of the total ion-to-neutral ratio is approximately 10(-7) at a high laser fluence and less than 10(-7) at a low laser fluence. Therefore, reexamining the possible contributions of thermally induced reactions in MALDI may be worthwhile. In this study, the concept of polar fluid was employed to explain the generation of primary ions in MALDI. A simple model, namely thermal proton transfer, was used to estimate the ion-to-neutral ratios in MALDI. We demonstrated that the theoretical calculations of ion-to-neutral ratios exhibit the same trend and similar orders of magnitude compared with those of experimental measurements. Although thermal proton transfer may not generate all of the ions observed in MALDI, the calculations demonstrated that thermally induced reactions play a crucial role in UV-MALDI.
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Affiliation(s)
- Kuan Yu Chu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
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17
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Lin HY, Song B, Lu IC, Hsu KT, Liao CY, Lee YY, Tseng CM, Lee YT, Ni CK. Is energy pooling necessary in ultraviolet matrix-assisted laser desorption/ionization? RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:77-82. [PMID: 24285392 DOI: 10.1002/rcm.6765] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 10/06/2013] [Accepted: 10/14/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Energy pooling has been suggested as the key process for generating the primary ions during ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). In previous studies, decreases in fluorescence quantum yields as laser fluence increased for 2-aminobenzoic acid, 2,5-dihydroxybenzoic acid (2,5-DHB), and 3-hydroxypicolinic acid were used as evidence of energy pooling. This work extends the research to other matrices and addresses whether energy pooling is a universal property in UV-MALDI. METHODS Energy pooling was investigated in a time-resolved fluorescence experiment by using a short laser pulse (355 nm, 20 ps pulse width) for excitation and a streak camera (1 ps time resolution) for fluorescence detection. RESULTS The excited-state lifetime of 2,5-DHB decreased with increases in laser fluence. This suggests that a reaction occurs between two excited molecules, and that energy pooling may be one of the possible reactions. However, the excited-state lifetime of 2,4,6-trihydroxyacetophenone (THAP) did not change with increases in laser fluence. The upper limit of the energy pooling rate constant for THAP is estimated to be approximately 100-500 times smaller than that of 2,5-DHB. CONCLUSIONS The small energy pooling rate constant for THAP indicates that the potential contribution of the energy pooling mechanism to the generation of THAP matrix primary ions should be reconsidered.
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Affiliation(s)
- Hou-Yu Lin
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan
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18
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Knochenmuss R. MALDI mechanisms: wavelength and matrix dependence of the coupled photophysical and chemical dynamics model. Analyst 2014; 139:147-56. [DOI: 10.1039/c3an01446k] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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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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20
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Knochenmuss R. MALDI and Related Methods: A Solved Problem or Still a Mystery? Mass Spectrom (Tokyo) 2013; 2:S0006. [PMID: 24349925 DOI: 10.5702/massspectrometry.s0006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 01/22/2013] [Indexed: 11/23/2022] Open
Abstract
MALDI ionization mechanisms remain a topic of controversy. Some of the major modern models are compared, with emphasis on those of the author. Primary formation, secondary reaction, and loss mechanisms are considered.
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21
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Wu CL, Wang CC, Lai YH, Lee H, Lin JD, Lee YT, Wang YS. Selective Enhancement of Carbohydrate Ion Abundances by Diamond Nanoparticles for Mass Spectrometric Analysis. Anal Chem 2013; 85:3836-41. [DOI: 10.1021/ac3036469] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chieh-Lin Wu
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Chia-Chen Wang
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
- Institute of Biochemistry and
Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan,
ROC
| | - Yin-Hung Lai
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Hsun Lee
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Jia-Der Lin
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Yuan Tseh Lee
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Yi-Sheng Wang
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan, ROC
- Institute of Biochemistry and
Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan,
ROC
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22
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Lai YH, Wang CC, Chen CW, Liu BH, Lin SH, Lee YT, Wang YS. Analysis of Initial Reactions of MALDI Based on Chemical Properties of Matrixes and Excitation Condition. J Phys Chem B 2012; 116:9635-43. [DOI: 10.1021/jp304709q] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Yin-Hung Lai
- Genomics Research
Center, Academia Sinica, Taipei 115, Taiwan
| | - Chia-Chen Wang
- Genomics Research
Center, Academia Sinica, Taipei 115, Taiwan
- Institute of Biochemistry and
Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan
| | - Chiu Wen Chen
- Genomics Research
Center, Academia Sinica, Taipei 115, Taiwan
| | - Bo-Hong Liu
- Genomics Research
Center, Academia Sinica, Taipei 115, Taiwan
| | - Sheng Hsien Lin
- Department
of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan
| | - Yuan Tseh Lee
- Genomics Research
Center, Academia Sinica, Taipei 115, Taiwan
| | - Yi-Sheng Wang
- Genomics Research
Center, Academia Sinica, Taipei 115, Taiwan
- Institute of Biochemistry and
Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan
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