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Leopold J, Prabutzki P, Engel KM, Schiller J. A Five-Year Update on Matrix Compounds for MALDI-MS Analysis of Lipids. Biomolecules 2023; 13:biom13030546. [PMID: 36979481 PMCID: PMC10046246 DOI: 10.3390/biom13030546] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 03/11/2023] [Accepted: 03/12/2023] [Indexed: 03/19/2023] Open
Abstract
Matrix-assisted laser desorption and ionization (MALDI) is a widely used soft-ionization technique of modern mass spectrometry (MS). MALDI enables the analysis of nearly all chemical compounds—including polar and apolar (phospho)lipids—with a minimum extent of fragmentation. MALDI has some particular advantages (such as the possibility to acquire spatially-resolved spectra) and is competitive with the simultaneously developed ESI (electrospray ionization) MS. Although there are still some methodological aspects that need to be elucidated in more detail, it is obvious that the careful selection of an appropriate matrix plays the most important role in (lipid) analysis. Some lipid classes can be detected exclusively if the optimum matrix is used, and the matrix determines the sensitivity by which a particular lipid is detected within a mixture. Since the matrix is, thus, crucial for optimum results, we provide here an update on the progress in the field since our original review in this journal in 2018. Thus, only the development during the last five years is considered, and lipids are sorted according to increasing complexity, starting with free fatty acids and ending with cardiolipins and phosphoinositides.
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Wang HYJ, Hsu FF. Structural characterization of phospholipids and sphingolipids by in-source fragmentation MALDI/TOF mass spectrometry. Anal Bioanal Chem 2022; 414:2089-2102. [PMID: 35013808 PMCID: PMC8882230 DOI: 10.1007/s00216-021-03843-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 11/29/2021] [Accepted: 12/09/2021] [Indexed: 11/30/2022]
Abstract
Phospholipids (PLs) and sphingolipids (SLs) perform critical structural and biological functions in cells. The structure of these lipids, including the stereospecificity and double-bond position of fatty acyl (FA) chains, is critical in decoding lipid biology. In this study, we presented a simple in-source fragmentation (ISF) MALDI/TOF mass spectrometry method that affords complete structural characterization of PL and SL molecules. We analyzed several representative unsaturated lipid species including phosphatidylcholine (PC), plasmalogen PC (pPC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), cardiolipin (CL), sphingomyelin (SM), and ceramide (Cer). Fragment ions reflecting the FA chains at sn-1 and sn-2 position, and those characteristics of the head groups of different PL classes, are readily identified. Specific fragment ions from cleavages of the C-C bond immediately adjacent to the cis C=C double-bond position(s) of FA chains and the trans C=C double bond of the sphingosine constituents allow precise localization of double bonds. The identities of the exemplary product ions from vinylic, allylic, and double-bond cleavages were also verified by LIFT-TOF/TOF. Identification of individual PL species in the lipid mixture was also carried out with ISF-MALDI/TOF. Together, this approach provides a simple yet effective method for structural characterization of PLs and SLs without the additional modification on the instrument hardware, and serves as a simple tool for the identification of lipids.
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Affiliation(s)
- Hay-Yan J Wang
- Department of Biological Sciences, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan.
- Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Washington University School of Medicine, Box 8127, St. Louis, MO, 63110, USA.
| | - Fong-Fu Hsu
- Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Washington University School of Medicine, Box 8127, St. Louis, MO, 63110, USA
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Engel KM, Prabutzki P, Leopold J, Nimptsch A, Lemmnitzer K, Vos DRN, Hopf C, Schiller J. A new update of MALDI-TOF mass spectrometry in lipid research. Prog Lipid Res 2022; 86:101145. [PMID: 34995672 DOI: 10.1016/j.plipres.2021.101145] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/06/2021] [Accepted: 12/29/2021] [Indexed: 01/06/2023]
Abstract
Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is an indispensable tool in modern lipid research since it is fast, sensitive, tolerates sample impurities and provides spectra without major analyte fragmentation. We will discuss some methodological aspects, the related ion-forming processes and the MALDI MS characteristics of the different lipid classes (with the focus on glycerophospholipids) and the progress, which was achieved during the last ten years. Particular attention will be given to quantitative aspects of MALDI MS since this is widely considered as the most serious drawback of the method. Although the detailed role of the matrix is not yet completely understood, it will be explicitly shown that the careful choice of the matrix is crucial (besides the careful evaluation of the positive and negative ion mass spectra) in order to be able to detect all lipid classes of interest. Two developments will be highlighted: spatially resolved Imaging MS is nowadays well established and the distribution of lipids in tissues merits increasing interest because lipids are readily detectable and represent ubiquitous compounds. It will also be shown that a combination of MALDI MS with thin-layer chromatography (TLC) enables a fast spatially resolved screening of an entire TLC plate which makes the method competitive with LC/MS.
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Affiliation(s)
- Kathrin M Engel
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Patricia Prabutzki
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Jenny Leopold
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Ariane Nimptsch
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - Katharina Lemmnitzer
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany
| | - D R Naomi Vos
- Center for Biomedical Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied Sciences, Paul-Wittsack-Strasse 10, D-68163 Mannheim, Germany
| | - Carsten Hopf
- Center for Biomedical Mass Spectrometry and Optical Spectroscopy (CeMOS), Mannheim University of Applied Sciences, Paul-Wittsack-Strasse 10, D-68163 Mannheim, Germany
| | - Jürgen Schiller
- Leipzig University, Faculty of Medicine, Institute for Medical Physics and Biophysics, Härtelstraße 16-18, D-04107, Germany.
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Choi YK, Oh JY, Han SY. Large-Area Graphene Films as Target Surfaces for Highly Reproducible Matrix-Assisted Laser Desorption Ionization Suitable for Quantitative Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:2003-2011. [PMID: 29998363 DOI: 10.1007/s13361-018-2024-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 06/25/2018] [Accepted: 06/26/2018] [Indexed: 06/08/2023]
Abstract
Due to the known sweet-spot issues that intrinsically arise from inhomogeneous formation of matrix-analyte crystals utilized as samples in matrix-assisted laser desorption ionization (MALDI) mass spectrometry, its reproducibility and thus its applications for quantification have been somewhat limited. In this paper, we report a simple strategy to improve the uniformity of matrix-analyte crystal spots, which we realized by adapting large-area graphene films, i.e., non-inert, interacting surfaces, as target surfaces. In this example, the graphitic surfaces of the graphene films interact with excess matrix molecules during the sample drying process, which induces spontaneous formation of optically uniform MALDI sample crystal layers on the film surfaces. Further, mass spectrometric imaging reveals that the visible uniformity is indeed accompanied by reproducible MALDI ionization over an entire sample spot, which greatly suppresses the appearance of sweet spots. The results of this study confirm that the proposed method achieves good linear responses of ion intensity to the analyte concentration (R2 > 0.99) with small relative standard deviations (σ < 10%), which is a range applicable for quantitative measurements using MALDI mass spectrometry. Graphical Abstract ᅟ.
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Affiliation(s)
- Yoon Kyung Choi
- Department of Nanochemistry, Gachon University, 1342 Seongnam-daero, Sujeong-gu, Seongnam-si, 13120, Gyeonggi-do, Republic of Korea
| | - Joo Yeon Oh
- ASTA Corp., 145 Gwanggyo-ro, Yeongtong-gu, Suwon-si, 16229, Gyeonggi-do, Republic of Korea
| | - Sang Yun Han
- Department of Nanochemistry, Gachon University, 1342 Seongnam-daero, Sujeong-gu, Seongnam-si, 13120, Gyeonggi-do, Republic of Korea.
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Rao W, Pan N, Yang Z. High Resolution Tissue Imaging Using the Single-probe Mass Spectrometry under Ambient Conditions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:986-993. [PMID: 25804891 DOI: 10.1007/s13361-015-1091-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/25/2015] [Accepted: 02/03/2015] [Indexed: 06/04/2023]
Abstract
Ambient mass spectrometry imaging (MSI) is an emerging field with great potential for the detailed spatial analysis of biological samples with minimal pretreatment. We have developed a miniaturized sampling and ionization device, the Single-probe, which uses in-situ surface micro-extraction to achieve high detection sensitivity and spatial resolution during MSI experiments. The Single-probe was coupled to a Thermo LTQ Orbitrap XL mass spectrometer and was able to create high spatial and high mass resolution MS images at 8 ± 2 and 8.5 μm on flat polycarbonate microscope slides and mouse kidney sections, respectively, which are among the highest resolutions available for ambient MSI techniques. Our proof-of-principle experiments indicate that the Single-probe MSI technique has the potential to obtain ambient MS images with very high spatial resolutions with minimal sample preparation, which opens the possibility for subcellular ambient tissue MSI to be performed in the future.
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Affiliation(s)
- Wei Rao
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, 73019, USA
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Hutchings LR, Brooks PP, Parker D, Mosely JA, Sevinc S. Monomer Sequence Control via Living Anionic Copolymerization: Synthesis of Alternating, Statistical, and Telechelic Copolymers and Sequence Analysis by MALDI ToF Mass Spectrometry. Macromolecules 2015. [DOI: 10.1021/ma5016038] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lian R. Hutchings
- Durham Centre for Soft Matter,
Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Paul P. Brooks
- Durham Centre for Soft Matter,
Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - David Parker
- Durham Centre for Soft Matter,
Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Jackie A. Mosely
- Durham Centre for Soft Matter,
Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Serkan Sevinc
- Durham Centre for Soft Matter,
Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
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Parameters affecting the accuracy of the MALDI-TOF MS determination of the phosphatidylcholine/lysophosphatidylcholine (PC/LPC) ratio as potential marker of spermatozoa quality. Chem Phys Lipids 2011; 164:696-702. [PMID: 21827741 DOI: 10.1016/j.chemphyslip.2011.07.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 02/04/2023]
Abstract
Matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is increasingly used to characterize (phospho)lipids. However, quantitative MALDI data are often questioned because ion suppression may occur if mixtures are analyzed. Therefore, relative (but no absolute) data are normally derived from the MALDI mass spectra of lipid mixtures. We are particularly interested in the phosphatidylcholine/lysophosphatidylcholine (PC/LPC) ratio because it seems to represent a suitable measure of the inflammatory activity. In this study, different parameters affecting the achievable accuracy of the MALDI-TOF MS determination of the PC/LPC ratio are compared. It will be shown that particularly the applied laser fluence as well as the used solvents influence the accuracies. Using artificial lipid mixtures it will be demonstrated that the PC/LPC ratio can be determined with an accuracy of about ±10% making the MALDI assay comparable to established methods. Finally, it will be shown that the optimized conditions are also useful to determine the PC/LPC ratios in human seminal plasma.
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