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Li G, Cao Q, Liu Y, DeLaney K, Tian Z, Moskovets E, Li L. Characterizing and alleviating ion suppression effects in atmospheric pressure matrix-assisted laser desorption/ionization. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:327-335. [PMID: 30430670 PMCID: PMC6353668 DOI: 10.1002/rcm.8358] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 09/14/2018] [Accepted: 11/11/2018] [Indexed: 05/05/2023]
Abstract
RATIONALE As a powerful ambient ion source, atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) enables direct analysis at atmospheric pressure/temperature and minimal sample preparation. With the increasing usage of AP-MALDI sources with Orbitrap instruments, systematic characterization of the extent of ion suppression effect (ISE) in AP-MALDI-Orbitrap mass spectrometry imaging (MSI) is desirable. Recently, a new low-pressure MALDI platform has been introduced that reportedly provided better sensitivity. While extensive research efforts have been devoted to improving spatial resolution, fewer studies focused on the characterization and sensitivity improvement of these MALDI platforms that, coupled with high-resolution Orbitraps, provide powerful strategy for MSI. METHODS We compared the analytical performance of AP and low-pressure (subatmospheric) MALDI sources to study the effect of pressure control in the ion source. Using a model peptide/protein mixture, we systematically evaluated the factors influencing ISE. Furthermore, the effect of laser spot size was evaluated through tissue imaging analysis of lipids and neuropeptides. The effects of ion suppression and laser spot size have also been examined by comparing the number of identified molecular species during MSI analysis. RESULTS Several key operating parameters including source pressure, laser energy, laser repetition rate, and microscopic slide coating materials were optimized to minimize the ISE. Under the optimal conditions, the subatmospheric AP-MALDI-Orbitrap platform with high spatial and mass spectral resolution enabled significantly improved coverage of several lipid and neuropeptide families in the MS analysis of mouse brain tissue sections. CONCLUSIONS The new SubAP-MALDI source coupled with an Orbitrap mass spectrometer was established as a viable platform for in situ endogenous biomolecular analysis with increased sensitivity compared with conventional AP-MALDI sources as evidenced by the confident identification of neuropeptides from mouse brain imaging analyses. The alleviated ISE was key to substantial performance improvement due to optimized intermediate pressure conditions and better ion collection by the ion funnel.
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Affiliation(s)
- Gongyu Li
- School of Pharmacy, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Qinjingwen Cao
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Yang Liu
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Kellen DeLaney
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Zichuan Tian
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | | | - Lingjun Li
- School of Pharmacy, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Contact Information for Corresponding Author: Prof. Dr. Lingjun Li, School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, Wisconsin 53705-2222, USA;, Phone: +1-608-265-8491;, Fax: +1-608-262-5345;,
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Hong SM, Tanaka M, Yoshii S, Mine Y, Matsui T. Enhanced visualization of small peptides absorbed in rat small intestine by phytic-acid-aided matrix-assisted laser desorption/ionization-imaging mass spectrometry. Anal Chem 2013; 85:10033-9. [PMID: 24063774 DOI: 10.1021/ac402252j] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Enhanced visualization of small peptides absorbed through a rat intestinal membrane was achieved by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-IMS) with the aid of phytic acid as a matrix additive. Penetrants through intestinal peptide transporter 1, i.e., glycyl-sarcosine (Gly-Sar, 147.1 m/z) and antihypertensive dipeptide, Val-Tyr (281.2 m/z), were chosen for MALDI-IMS. The signal-to-noise (S/N) ratios of dipeptides Gly-Sar and Val-Tyr were seen to increase by 2.4- and 8.0-fold, respectively, when using a 2',4',6'-trihydroxyacetophenone (THAP) matrix containing 5.0 mM phytic acid, instead of the THAP matrix alone. Owing to the phytic-acid-aided MALDI-IMS method, Gly-Sar and Val-Tyr absorbed in the rat intestinal membrane were successfully visualized. The proposed imaging method also provided useful information on intestinal peptide absorption; to some extent, Val-Tyr was rapidly hydrolyzed to Tyr by peptidases located at the intestinal microvillus during the absorption process. In conclusion, the strongly acidic additive, phytic acid, is beneficial for enhancing the visualization of small peptides using MALDI-IMS, owing to the suppression of ionization-interfering salts in the tissue.
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Affiliation(s)
- Seong-Min Hong
- Division of Bioresources and Bioenvironmental Sciences, Faculty of Agriculture, Graduate School, Kyushu University , 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
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Lou X, Fransen M, Stals PJM, Mes T, Bovee R, van Dongen JJL, Meijer EW. Unusual analyte-matrix adduct ions and mechanism of their formation in MALDI TOF MS of benzene-1,3,5-tricarboxamide and urea compounds. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:1405-1412. [PMID: 23812871 DOI: 10.1007/s13361-013-0672-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 04/11/2013] [Accepted: 05/05/2013] [Indexed: 06/02/2023]
Abstract
Analyte-matrix adducts are normally absent under typical matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) conditions. Interestingly, though, in the analysis of several types of organic compounds synthesized in our laboratory, analyte-matrix adduct ion peaks were always recorded when common MALDI matrices such as 4-hydroxy-α-cyanocinnamic acid (CHCA) were used. These compounds are mainly those with a benzene-1,3,5-tricarboxamide (BTA) or urea moiety, which are important building blocks to make new functional supramolecular materials. The possible mechanism of the adduct formation was investigated. A shared feature of the compounds studied is that they can form intermolecular hydrogen bonding with matrices like CHCA. The intermolecular hydrogen bonding will make the association between analyte ions and matrix molecules stronger. As a result, the analyte ions and matrix molecules in MALDI clusters will become more difficult to be separated from each other. Furthermore, it was found that analyte ions were mainly adducted with matrix salts, which is probably due to the much lower volatility of the salts compared with that of their corresponding matrix acids. It seems that the analyte-matrix adduct formation for our compounds are caused by the incomplete evaporation of matrix molecules from the MALDI clusters because of the combined effects of enhanced intermolecular interaction between analyte-matrix and of the low volatility of matrix salts. Based on these findings, strategies to suppress the analyte-matrix adduction are briefly discussed. In return, the positive results of using these strategies support the proposed mechanism of the analyte-matrix adduct formation.
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Affiliation(s)
- Xianwen Lou
- Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands.
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Park S, Kim T, Lee J, Seo M, Kim J. Effect of phosphoric acid as a matrix additive in matrix-assisted laser desorption/ionization analysis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:842-846. [PMID: 23495031 DOI: 10.1002/rcm.6508] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 01/10/2013] [Accepted: 01/13/2013] [Indexed: 06/01/2023]
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5
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Jun C, Tianxi H, Xuemei F. A novel matrix additive, MCM-41-type mesoporous silica nanoparticles, used for analysis of peptides by MALDI-FT/ICRMS. Talanta 2012; 100:419-24. [DOI: 10.1016/j.talanta.2012.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 08/07/2012] [Accepted: 08/09/2012] [Indexed: 11/30/2022]
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Jardin J, Mollé D, Piot M, Lortal S, Gagnaire V. Quantitative proteomic analysis of bacterial enzymes released in cheese during ripening. Int J Food Microbiol 2012; 155:19-28. [PMID: 22305888 DOI: 10.1016/j.ijfoodmicro.2012.01.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 12/23/2011] [Accepted: 01/07/2012] [Indexed: 11/28/2022]
Abstract
Due to increasingly available bacterial genomes in databases, proteomic tools have recently been used to screen proteins expressed by micro-organisms in food in order to better understand their metabolism in situ. While the main objective is the systematic identification of proteins, the next step will be to bridge the gap between identification and quantification of these proteins. For that purpose, a new mass spectrometry-based approach was applied, using isobaric tagging reagent for quantitative proteomic analysis (iTRAQ), which are amine specific and yield labelled peptides identical in mass. Experimental Swiss-type cheeses were manufactured from microfiltered milk using Streptococcus thermophilus ITG ST20 and Lactobacillus helveticus ITG LH1 as lactic acid starters. At three ripening times (7, 20 and 69 days), cheese aqueous phases were extracted and enriched in bacterial proteins by fractionation. Each sample, standardised in protein amount prior to proteomic analyses, was: i) analysed by 2D-electrophoresis for qualitative analysis and ii) submitted to trypsinolysis, and labelled with specific iTRAQ tag, one per ripening time. The three labelled samples were mixed together and analysed by nano-LC coupled on-line with ESI-QTOF mass spectrometer. Thirty proteins, both from bacterial or bovine origin, were identified and efficiently quantified. The free bacterial proteins detected were enzymes from the central carbon metabolism as well as stress proteins. Depending on the protein considered, the quantity of these proteins in the cheese aqueous extract increased from 2.5 to 20 fold in concentration from day 7 to day 69 of ripening.
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Affiliation(s)
- Julien Jardin
- INRA, UMR1253, Science et Technologie du lait et de l'Œuf, Rennes, France
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Kim JS, Song JS, Kim Y, Park SB, Kim HJ. De novo analysis of protein N-terminal sequence utilizing MALDI signal enhancing derivatization with Br signature. Anal Bioanal Chem 2011; 402:1911-9. [PMID: 22200925 DOI: 10.1007/s00216-011-5642-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/29/2011] [Accepted: 12/06/2011] [Indexed: 11/24/2022]
Abstract
De novo analysis of protein N-terminal sequence is important for identification of N-terminal proteolytic processing such as N-terminal methionine or signal peptide removal, or for the genome annotation of uncharacterized proteins. We introduce a de novo sequencing method of protein N terminus utilizing matrix-assisted laser desorption/ionization (MALDI) signal enhancing picolinamidination with bromine isotopic tag incorporated to the N terminus. The doublet signature of bromine in the tandem mass (MS/MS) spectrum distinguished N-terminal ion series from C-terminal ion series, facilitating de novo N-terminal sequencing of protein. The dual advantage of MALDI signal enhancement by the basic picolinamidine and b-ion selection aided by Br signature is demonstrated using a variety of peptides. The N-terminal sequences of myoglobin and hemoglobin as model proteins were determined by incorporating the Br tag to the N terminus of the proteins and obtaining a series of b-ions with Br signature by MS/MS analysis after chymotryptic digestion of the tagged proteins. The N-terminal peptide was selected for MS/MS analysis from the chymotryptic digest based on the Br signature in the mass spectrum. Identification of phosphorylation site as well as N-terminal sequencing of a phosphopeptide was straightforward.
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Affiliation(s)
- Jong-Seo Kim
- Department of Chemistry, Seoul National University, Seoul 151-742, Republic of Korea.
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Kim JS, Shin M, Song JS, An S, Kim HJ. C-terminal de novo sequencing of peptides using oxazolone-based derivatization with bromine signature. Anal Biochem 2011; 419:211-6. [DOI: 10.1016/j.ab.2011.08.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 07/14/2011] [Accepted: 08/06/2011] [Indexed: 10/17/2022]
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Kim JS, Song SU, Kim HJ. Simultaneous identification of tyrosine phosphorylation and sulfation sites utilizing tyrosine-specific bromination. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:1916-1925. [PMID: 21952757 DOI: 10.1007/s13361-011-0214-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2011] [Revised: 07/06/2011] [Accepted: 07/06/2011] [Indexed: 05/31/2023]
Abstract
Tyrosine phosphorylation and sulfation play many key roles in the cell. Isobaric phosphotyrosine and sulfotyrosine residues in peptides were determined by mass spectrometry using phosphatase or sulfatase to remove the phosphate or the sulfate group. Unique Br signature was introduced to the resulting tyrosine residues by incubation with 32% HBr at -20 °C for 20 min. MS/MS analysis of the brominated peptide enabled unambiguous determination of the phosphotyrosine and the sulfotyrosine sites. When phosphotyrosine and sulfotyrosine as well as free tyrosine were present in the same peptide, they could be determined simultaneously using either phosphatase or sulfatase following acetylation of the free tyrosine.
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Affiliation(s)
- Jong-Seo Kim
- Department of Chemistry, Seoul National University, Seoul 151-742, Republic of Korea.
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Tandem mass spectrometric method for definitive localization of phosphorylation sites using bromine signature. Anal Biochem 2011; 414:294-6. [DOI: 10.1016/j.ab.2011.03.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 03/15/2011] [Accepted: 03/24/2011] [Indexed: 11/23/2022]
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Shin MS, Kim HJ. Peptide C-terminal Sequence Analysis by MALDI-TOF MS Utilizing EDC Coupling with Br Signature. B KOREAN CHEM SOC 2011. [DOI: 10.5012/bkcs.2011.32.4.1183] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Affiliation(s)
- Kamila Chughtai
- FOM-Institute for Atomic and Molecular Physics, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Ron M.A. Heeren
- FOM-Institute for Atomic and Molecular Physics, Science Park 104, 1098 XG Amsterdam, The Netherlands
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Kim JS, Cui E, Kim HJ. Picolinamidination of phosphopeptides for MALDI-TOF-TOF mass spectrometric sequencing with enhanced sensitivity. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1751-1758. [PMID: 19586781 DOI: 10.1016/j.jasms.2009.05.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 05/25/2009] [Accepted: 05/26/2009] [Indexed: 05/28/2023]
Abstract
Two orders of magnitude matrix-assisted laser desorption/ionization (MALDI) signal enhancement of phosphopeptides has been achieved by picolinamidination of N-terminal amine group and epsilon-amine group of lysine residues. Due to the presence of picolinamidination tag at the N-terminal amine of peptides, MS/MS spectra with a strong b-ion series was obtained, which greatly facilitated sequencing and identification of the phosphorylation site. Phosphorylation site of a phosphopeptide could be identified from MALDI TOF/TOF spectrum obtained from a tryptic or a chymotryptic phosphopeptide, which was not even detected in the positive ion mode, without signal enhancement by picolinamidination, due to the negative charge of the phosphate group in the presence of other peptides.
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Affiliation(s)
- Jong-Seo Kim
- Department of Chemistry, Seoul National University, Seoul, Korea
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Interferences and contaminants encountered in modern mass spectrometry. Anal Chim Acta 2008; 627:71-81. [PMID: 18790129 DOI: 10.1016/j.aca.2008.04.043] [Citation(s) in RCA: 419] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 04/14/2008] [Accepted: 04/16/2008] [Indexed: 12/26/2022]
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Kim JS, Kim JH, Kim HJ. Matrix-assisted laser desorption/ionization signal enhancement of peptides by picolinamidination of amino groups. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:495-502. [PMID: 18205249 DOI: 10.1002/rcm.3392] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Picolinamidination of amino groups in peptides was carried out using ethyl picolinimidate tetrafluoroborate synthesized from picolinamide and triethyloxonium tetrafluoroborate. The N-terminal amino group as well as the epsilon-amino group of lysine were derivatized. The matrix-assisted laser desorption/ionization (MALDI) signal of a peptide was enhanced 20-35-fold upon picolinamidination depending on the number of amino groups derivatized. The signal enhancement effect is much higher than that of acetamidination or guanidination previously reported. Improved protein identification by mass mapping of the derivatized peptides was demonstrated.
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Affiliation(s)
- Jong-Seo Kim
- Department of Chemistry, Seoul National University, Seoul, Korea 151-747
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Guo Z, He L. A binary matrix for background suppression in MALDI-MS of small molecules. Anal Bioanal Chem 2007; 387:1939-44. [PMID: 17260136 DOI: 10.1007/s00216-006-1100-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 12/12/2006] [Accepted: 12/14/2006] [Indexed: 10/23/2022]
Abstract
Application of matrix-assisted laser-desorption ionization mass spectrometry (MALDI-MS) to small-molecule detection is often limited, because of high matrix background signals in the low-mass region. We report here an approach in which a mixture of two conventional MALDI matrices with different proton affinity was used to suppress the formation of matrix clusters and fragments. Specifically, when acidic alpha-cyano-4-hydroxycinnamic acid (CHCA) and basic 9-aminoacridine (9-AA) were used as the binary matrix, fewer background matrix peaks were observed in both positive and negative-mode detection of small molecules. In addition, the presence of CHCA substantially reduced the laser fluence needed for analyte desorption and ionization; thus better signal-to-background ratios were observed for negatively charged inositol phosphates in complex plant extracts.
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Affiliation(s)
- Zhong Guo
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
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Grasso G, Fragai M, Rizzarelli E, Spoto G, Yeo KJ. In situ AP/MALDI-MS characterization of anchored matrix metalloproteinases. JOURNAL OF MASS SPECTROMETRY : JMS 2006; 41:1561-9. [PMID: 17094173 DOI: 10.1002/jms.1126] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Several different procedures are available for the immobilization of proteins on solid supports, as many advantages derive from this approach, such as the possibility to develop new protein solid-state assays. Enzymes that are anchored on gold surfaces can interact with several different molecules in a tag-free environment, opening the way to surface plasmon resonance (SPR) investigations. Nevertheless, it is often important to know the identity of the affinity-retained analyte, and mass spectrometric analysis, via its unique molecular mass identification, represents a very valuable complementary method. There are many pieces of evidence to suggest that matrix metalloproteinases (MMPs) are involved in normal and pathological processes, including embryogenesis, wound healing, inflammation, arthritis and cancer, but presumably also exhibiting other functions. The search for new inhibitors of MMPs has prompted research towards the development of new solid-state assays for the rapid evaluation of MMP activity. We have already reported the possibility of measuring the activity of MMP-1 anchored on solid support by coupling SPR with ESI-MS analysis. In this work, we show the in situ atmospheric pressure (AP) MALDI-MS characterization of MMPs anchored on a gold chip with known surface coverage. The study extends the MS analysis to different proteins, and sequence coverage is reported for different digestion and MS procedures.
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Affiliation(s)
- Giuseppe Grasso
- Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici, Via C. Ulpiani 27, Bari, Italy
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