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Zhang Z, Yu X, Peng X, Qi W, Wang M. A facile nanozyme-based colorimetric method to realize the quantitative and specific detection of casein phosphopeptides in food samples. Talanta 2024; 276:126212. [PMID: 38723475 DOI: 10.1016/j.talanta.2024.126212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/29/2024] [Accepted: 05/04/2024] [Indexed: 06/14/2024]
Abstract
As a popular nutritional enhancer, casein phosphopeptides (CPPs) have attracted growing attention in food industry. However, conventional methods for CPPs detection are usually less precise or requires expensive instruments. Herein, a nanozyme-based colorimetric method was developed to achieve the quantitative detection of CPPs in food samples. This method is based on a facilely fabricated peroxidase-like nanozyme (Fe@UiO-66), which combines the specific binding of CPPs, as well as the nanozyme-catalyzed colorimetric sensing that can be easily detected by spectrometer. The method displayed good quantitative ability toward CPPs with the linear range of 2-30 μg/mL, the low limit of detection of 0.267 μg/mL and limit of quantification of 1.335 μg/mL. We highlighted the specificity, anti-interference and practicability of this method, by investigating the performances toward food samples. Besides, a smartphone-based colorimetric sensing platform was also established, which is conducive to the portable detection. The developed nanozyme-based colorimetric sensing method provides a promising strategy for CPPs detection in food samples.
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Affiliation(s)
- Zhiyi Zhang
- School of Life Sciences, Tianjin University, Tianjin, 300072, PR China; School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin, 300350, PR China.
| | - Xiaoxiao Yu
- School of Life Sciences, Tianjin University, Tianjin, 300072, PR China; School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin, 300350, PR China.
| | - Xin Peng
- School of Life Sciences, Tianjin University, Tianjin, 300072, PR China.
| | - Wei Qi
- School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin, 300350, PR China; Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin, 300072, PR China; The Co-Innovation Centre of Chemistry and Chemical Engineering of Tianjin, Tianjin, 300350, PR China.
| | - Mengfan Wang
- School of Life Sciences, Tianjin University, Tianjin, 300072, PR China; School of Chemical Engineering and Technology, State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin, 300350, PR China; Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin, 300072, PR China.
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2
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KITAGAWA F, HAYASHI A, NUKATSUKA I. LVSEP Analysis of Phosphopeptides in Dynamically PVP-Coated Capillaries and Microchannels. CHROMATOGRAPHY 2022. [DOI: 10.15583/jpchrom.2021.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Fumihiko KITAGAWA
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University
| | - Ayaka HAYASHI
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University
| | - Isoshi NUKATSUKA
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University
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3
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Veras MA, Lim YJ, Kuljanin M, Lajoie GA, Urquhart BL, Séguin CA. Protocol for parallel proteomic and metabolomic analysis of mouse intervertebral disc tissues. JOR Spine 2020; 3:e1099. [PMID: 33015574 PMCID: PMC7524214 DOI: 10.1002/jsp2.1099] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 04/25/2020] [Accepted: 05/14/2020] [Indexed: 01/07/2023] Open
Abstract
The comprehensiveness of data collected by "omics" modalities has demonstrated the ability to drastically transform our understanding of the molecular mechanisms of chronic, complex diseases such as musculoskeletal pathologies, how biomarkers are identified, and how therapeutic targets are developed. Standardization of protocols will enable comparisons between findings reported by multiple research groups and move the application of these technologies forward. Herein, we describe a protocol for parallel proteomic and metabolomic analysis of mouse intervertebral disc (IVD) tissues, building from the combined expertise of our collaborative team. This protocol covers dissection of murine IVD tissues, sample isolation, and data analysis for both proteomics and metabolomics applications. The protocol presented below was optimized to maximize the utility of a mouse model for "omics" applications, accounting for the challenges associated with the small starting quantity of sample due to small tissue size as well as the extracellular matrix-rich nature of the tissue.
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Affiliation(s)
- Matthew A Veras
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry The University of Western Ontario London Ontario Canada
- Bone and Joint Institute The University of Western Ontario London Ontario Canada
| | - Yong J Lim
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry The University of Western Ontario London Ontario Canada
| | - Miljan Kuljanin
- Department of Cell Biology Harvard Medical School Boston Massachusetts USA
| | - Gilles A Lajoie
- Department of Biochemistry, Schulich School of Medicine & Dentistry The University of Western Ontario London Ontario Canada
| | - Bradley L Urquhart
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry The University of Western Ontario London Ontario Canada
| | - Cheryle A Séguin
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry The University of Western Ontario London Ontario Canada
- Bone and Joint Institute The University of Western Ontario London Ontario Canada
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4
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KITAGAWA F, MATSUO A, SUEYOSHI K, OTSUKA K. Sensitivity Enhancement by Sweeping via Solid Phase Extraction Using Titania Nanoparticles in Capillary Electrophoretic Analysis of Phosphopeptides. CHROMATOGRAPHY 2017. [DOI: 10.15583/jpchrom.2016.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Fumihiko KITAGAWA
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University
| | - Asako MATSUO
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
| | - Kenji SUEYOSHI
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University
| | - Koji OTSUKA
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
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5
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Hommerson P, Khan AM, de Jong GJ, Somsen GW. Ionization techniques in capillary electrophoresis-mass spectrometry: principles, design, and application. MASS SPECTROMETRY REVIEWS 2011; 30:1096-1120. [PMID: 21462232 DOI: 10.1002/mas.20313] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 06/03/2010] [Indexed: 05/30/2023]
Abstract
A major step forward in the development and application of capillary electrophoresis (CE) was its coupling to ESI-MS, first reported in 1987. More than two decades later, ESI has remained the principal ionization technique in CE-MS, but a number of other ionization techniques have also been implemented. In this review the state-of-the-art in the employment of soft ionization techniques for CE-MS is presented. First the fundamentals and general challenges of hyphenating conventional CE and microchip electrophoresis with MS are outlined. After elaborating on the characteristics and role of ESI, emphasis is put on alternative ionization techniques including sonic spray ionization (SSI), thermospray ionization (TSI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), matrix-assisted laser desorption ionization (MALDI) and continuous-flow fast atom bombardment (CF-FAB). The principle of each ionization technique is outlined and the experimental set-ups of the CE-MS couplings are described. The strengths and limitations of each ionization technique with respect to CE-MS are discussed and the applicability of the various systems is illustrated by a number of typical examples.
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MESH Headings
- Electrophoresis, Capillary/instrumentation
- Electrophoresis, Capillary/methods
- Equipment Design/instrumentation
- Equipment Design/methods
- Pharmaceutical Preparations/analysis
- Pharmaceutical Preparations/chemistry
- Proteins/analysis
- Proteins/chemistry
- Spectrometry, Mass, Electrospray Ionization/instrumentation
- Spectrometry, Mass, Electrospray Ionization/methods
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/instrumentation
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods
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Affiliation(s)
- Paul Hommerson
- Department of Biomedical Analysis, Utrecht University, PO Box 80082, 3508 TB Utrecht, The Netherlands.
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Bachmann S, Bakry R, Huck CW, Polato F, Corradini D, Bonn GK. Peptide mapping using capillary electrophoresis offline coupled to matrix-assisted laser desorption ionization time of flight mass spectrometry. Electrophoresis 2011; 32:2830-9. [PMID: 21953317 DOI: 10.1002/elps.201000653] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 03/14/2011] [Accepted: 03/14/2011] [Indexed: 01/20/2023]
Abstract
This article reports the results of a study carried out to evaluate the offline hyphenation of capillary zone electrophoresis with matrix-assisted lased desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) for the analysis of low-abundant complex samples, represented by the tryptic phosphorylated peptides of phosphoproteins, such as α-casein, β-casein, and fetuin. The proposed method employs a latex-coated capillary and consists in the online preconcentration of the tryptic peptides by a pH-mediated stacking method, their separation by capillary zone electrophoresis, and subsequent deposition of the separated analytes onto a MALDI target for their MS analysis. The online preconcentration method allows loading a large sample volume (∼150 nL), which is introduced into the capillary after the hydrodynamic injection of a short plug of 1.0 M ammonium hydroxide solution and is sandwiched between two plugs of the acidic background electrolyte solution (BGE) filling the capillary. The sample spotting of the separated analytes onto the MALDI target is performed either during or postseparation using an automatic spotting device connected to the exit of the separation capillary. The proposed method allows the separation and identification of multiphosphorylated peptides from other peptides and enables their identification at femtomole level with improved efficiency compared with LC approaches hyphenated to MS.
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Affiliation(s)
- Stefan Bachmann
- Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, Innsbruck, Austria
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7
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Pre- and post-translational regulation of osteopontin in cancer. J Cell Commun Signal 2011; 5:111-22. [PMID: 21516514 DOI: 10.1007/s12079-011-0130-6] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 03/15/2011] [Indexed: 12/15/2022] Open
Abstract
Osteopontin (OPN) is a matricellular protein that binds to a number of cell surface receptors including integrins and CD44. It is expressed in many tissues and secreted into body fluids including blood, milk and urine. OPN plays important physiological roles in bone remodeling, immune response and inflammation. It is also a tumour-associated protein, and elevated OPN levels are associated with tumour formation, progression and metastasis. Research has revealed a promising role for OPN as a cancer biomarker. OPN is subject to alternative splicing, as well as post-translational modifications such as phosphorylation, glycosylation and proteolytic cleavage. Functional differences have been revealed for different isoforms and post-translational modifications. The pattern of isoform expression and post-translational modification is cell-type specific and may influence the potential role of OPN in malignancy and as a cancer biomarker.
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8
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Ly L, Wasinger VC. Protein and peptide fractionation, enrichment and depletion: Tools for the complex proteome. Proteomics 2011; 11:513-34. [DOI: 10.1002/pmic.201000394] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 10/03/2010] [Accepted: 10/18/2010] [Indexed: 12/28/2022]
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9
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Anborgh PH, Mutrie JC, Tuck AB, Chambers AF. Role of the metastasis-promoting protein osteopontin in the tumour microenvironment. J Cell Mol Med 2010; 14:2037-44. [PMID: 20597997 PMCID: PMC3822994 DOI: 10.1111/j.1582-4934.2010.01115.x] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Osteopontin (OPN) is a secreted protein present in bodily fluids and tissues. It is subject to multiple post-translational modifications, including phosphorylation, glycosylation, proteolytic cleavage and crosslinking by transglutamination. Binding of OPN to integrin and CD44 receptors regulates signalling cascades that affect processes such as adhesion, migration, invasion, chemotaxis and cell survival. A variety of cells and tissues express OPN, including bone, vasculature, kidney, inflammatory cells and numerous secretory epithelia. Normal physiological roles include regulation of immune functions, vascular remodelling, wound repair and developmental processes. OPN also is expressed in many cancers, and elevated levels in patients’ tumour tissue and blood are associated with poor prognosis. Tumour growth is regulated by interactions between tumour cells and their tissue microenvironment. Within a tumour mass, OPN can be expressed by both tumour cells and cellular components of the tumour microenvironment, and both tumour and normal cells may have receptors able to bind to OPN. OPN can also be found as a component of the extracellular matrix. The functional roles of OPN in a tumour are thus complex, with OPN secreted by both tumour cells and cells in the tumour microenvironment, both of which can in turn respond to OPN. Much remains to be learned about the cross-talk between normal and tumour cells within a tumour, and the role of multiple forms of OPN in these interactions. Understanding OPN-mediated interactions within a tumour will be important for the development of therapeutic strategies to target OPN.
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Affiliation(s)
- Pieter H Anborgh
- London Regional Cancer Program, London, Ontario, Canada Department of Pathology, University of Western Ontario, London, Ontario, Canada
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10
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Yu HW, Liu QF, Liu GN. Positive regulation of the Egr-1/osteopontin positive feedback loop in rat vascular smooth muscle cells by TGF-beta, ERK, JNK, and p38 MAPK signaling. Biochem Biophys Res Commun 2010; 396:451-6. [PMID: 20417179 DOI: 10.1016/j.bbrc.2010.04.115] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 04/20/2010] [Indexed: 11/29/2022]
Abstract
Previous studies identified a positive feedback loop in rat vascular smooth muscle cells (VSMCs) in which early growth response factor-1 (Egr-1) binds to the osteopontin (OPN) promoter and upregulates OPN expression, and OPN upregulates Egr-1 expression via the extracellular signal-regulated protein kinase (ERK) signaling pathway. The current study examined whether transforming growth factor-beta (TGF-beta) activity contributes to Egr-1 binding to the OPN promoter, and whether other signaling pathways act downstream of OPN to regulate Egr-1 expression. ChIP assays using an anti-Egr-1 antibody showed that amplification of the OPN promoter sequence decreased in TGF-beta DNA enzyme-transfected VSMCs relative to control VSMCs. Treatment of VSMCs with PD98059 (ERK inhibitor), SP600125 (JNK inhibitor), or SB203580 (p38 MAPK inhibitor) significantly inhibited OPN-induced Egr-1 expression, and PD98059 treatment was associated with the most significant decrease in Egr-1 expression. OPN-stimulated VSMC cell migration was inhibited by SP600125 or SB203580, but not by PD98059. Furthermore, MTT assays showed that OPN-mediated cell proliferation was inhibited by PD98059, but not by SP600125 or SB203580. Taken together, the results of the current study show that Egr-1 binding to the OPN promoter is positively regulated by TGF-beta, and that the p38 MAPK, JNK, and ERK pathways are involved in OPN-mediated Egr-1 upregulation.
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Affiliation(s)
- Hong-Wei Yu
- Department of Cardiology, The First Affiliated Hospital of China Medical University, 155th North of Nanjing Street, Heping Block, Shenyang, 110001 Liaoning Province, China
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12
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Abstract
Sample stacking techniques remain an important tool for enhancement of the selectivity and sensitivity of analyses in contemporary CZE. This contribution reviews new knowledge on this topic published since 2006. It is organized according to the operational principles used, which include concentration adjustment, application of a pH step, MEKC and sweeping, and transient ITP. Techniques combining several of these principles and comparative studies are also included.
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Affiliation(s)
- Zdena Malá
- Institute of Analytical Chemistry of the ASCR, Brno, Czech Republic
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13
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Liu QF, Yu HW, Liu GN. Egr-1 upregulates OPN through direct binding to its promoter and OPN upregulates Egr-1 via the ERK pathway. Mol Cell Biochem 2009; 332:77-84. [DOI: 10.1007/s11010-009-0176-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Accepted: 06/09/2009] [Indexed: 11/29/2022]
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14
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Jurcic K, Yeung KKC. Sphingomyelins as semi-permanent capillary coatings for protein separations in CE and off-line analysis with MALDI-MS. Electrophoresis 2009; 30:1817-27. [DOI: 10.1002/elps.200800633] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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15
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Abstract
In the postgenomic era, proteomics has become a dominant field for identifying and quantifying the complex protein machinery of the cell. The expression levels, posttranslational modifications, and specific interactions of proteins control the biology of such processes as development, differentiation, and signal transduction. Studies of the proteins involved in these processes often lead to a better understanding of biology and of human disease. Powerful separation techniques and sensitive detection methods enable researchers to untangle these complicated networks of processes. CE coupled with either MS or LIF are two of the techniques that make this possible. This review will cover proven CE-based methods for proteomics on the cell and tissue level and their application in biological and clinical studies, relevant new developments in enabling technology such as microfluidic CE-MS demonstrated on model systems, and comment on the future of CE in proteomics.
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MESH Headings
- Amino Acid Sequence
- Electrophoresis, Capillary/instrumentation
- Electrophoresis, Capillary/methods
- Humans
- Molecular Sequence Data
- Proteins/analysis
- Proteins/genetics
- Proteome/analysis
- Proteomics/methods
- Sequence Alignment
- Spectrometry, Mass, Electrospray Ionization/instrumentation
- Spectrometry, Mass, Electrospray Ionization/methods
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/instrumentation
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods
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Affiliation(s)
- Bryan R Fonslow
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA 92037, USA
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16
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Nesbitt CA, Yeung KKC. In-capillary enrichment, proteolysis and separation using capillary electrophoresis with discontinuous buffers: application on proteins with moderately acidic and basic isoelectric points. Analyst 2009; 134:65-71. [DOI: 10.1039/b812628c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Recent applications of capillary electrophoresis–mass spectrometry (CE–MS): CE performing functions beyond separation. Anal Chim Acta 2008; 627:3-24. [DOI: 10.1016/j.aca.2008.04.023] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 04/02/2008] [Accepted: 04/08/2008] [Indexed: 11/18/2022]
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18
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Lucy CA, MacDonald AM, Gulcev MD. Non-covalent capillary coatings for protein separations in capillary electrophoresis. J Chromatogr A 2008; 1184:81-105. [DOI: 10.1016/j.chroma.2007.10.114] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2007] [Revised: 10/25/2007] [Accepted: 10/31/2007] [Indexed: 11/27/2022]
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19
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Simpson SL, Quirino JP, Terabe S. On-line sample preconcentration in capillary electrophoresis. J Chromatogr A 2008; 1184:504-41. [DOI: 10.1016/j.chroma.2007.11.001] [Citation(s) in RCA: 269] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 10/30/2007] [Accepted: 11/01/2007] [Indexed: 02/06/2023]
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20
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Nesbitt CA, Jurcic K, Yeung KKC. Nanoliter-volume protein enrichment, tryptic digestion, and partial separation based on isoelectric points by CE for MALDI mass spectral analysis. Electrophoresis 2008; 29:466-74. [DOI: 10.1002/elps.200700339] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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21
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22
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Song EJ, Babar SME, Oh E, Hasan MN, Hong HM, Yoo YS. CE at the omics level: Towards systems biology – An update. Electrophoresis 2008; 29:129-42. [DOI: 10.1002/elps.200700467] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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23
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Dawoud AA, Sarvaiya HA, Lazar IM. Microfluidic platform with mass spectrometry detection for the analysis of phosphoproteins. Electrophoresis 2007; 28:4645-60. [DOI: 10.1002/elps.200700355] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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24
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Ibañez AJ, Muck A, Svatos A. Metal-Chelating Plastic MALDI (pMALDI) Chips for the Enhancement of Phosphorylated-Peptide/Protein Signals. J Proteome Res 2007; 6:3842-8. [PMID: 17655346 DOI: 10.1021/pr070243r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A disposable polymeric pMALDI array with a universal metal cation-chelatable surface for pretreatment/signal enhancement of phosphoproteins and/or phosphopeptides in complex samples was developed. Acrylic acid N-hydroxysuccinimide ester and methyl methacrylate monomers were copolymerized in thin layer molds in a 1:13.3 molar ratio and subsequently treated with Nalpha,Nalpha-bis(carboxymethyl)-l-lysine to obtain a structured planar MALDI array. The prepared NTA pMALDI chip array was activated with metal cations (e.g., Ga(III), Ni(II)), and the selectivities for phosphopeptides (e.g., trypsin-digested alpha-casein (alpha-Cas), and phospho-angiotensin II (p-Ang)) were evaluated using MALDI-TOF/MS. The highest selectivity for proteins was observed for the Ni(II)-NTA chip. The p-Ang was enriched in the presence of BSA tryptic peptides ca. 5 times and represented the major peak after sample adsorption/washing on Ga(III)-NTA chip. The performance of the Ga(III)-chip, tested on alpha-Cas tryptic digest, is fully comparable to commercial systems. Additionally, higher MW peptides and limited methionine oxidation were observed with the chip. A combination of selective absorption of phosphoproteins on Ni(II)-chips and the further enrichment of digested phosphopeptides on the Ga(III)-chip can prove to be very useful for fast identification of unknown proteins using MALDI-TOF/MS.
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Affiliation(s)
- Alfredo J Ibañez
- Mass Spectrometry Research Group, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany
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Ballard JNM, Lajoie GA, Yeung KKC. Selective sampling of multiply phosphorylated peptides by capillary electrophoresis for electrospray ionization mass spectrometry analysis. J Chromatogr A 2006; 1156:101-10. [PMID: 17188697 DOI: 10.1016/j.chroma.2006.12.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 11/30/2006] [Accepted: 12/05/2006] [Indexed: 10/23/2022]
Abstract
The ionization of phosphorylated peptides in positive ion mode mass spectrometry is generally less efficient compared with the ionization of their non-phosphorylated counterparts. This can make phosphopeptides much more difficult to detect. One way to enhance the detection of phosphorylated proteins and peptides is by selectively isolating these species. Current approaches of phosphopeptide isolation are based on the favorable interactions of phosphate groups with immobilized metals. While these methods can be effective in the extraction, they can lead to incomplete sample recovery, particularly for the most strongly bound multiply phosphorylated components. A non-sorptive method of phosphopeptide isolation using capillary electrophoresis (CE) was recently reported [Zhang et al., Anal. Chem. 77 (2005) 6078]. The relatively low isoelectric points of phosphopeptides cause them to remain anionic at acidic sample pH. Hence, they can be selectively injected into the capillary by an applied field after the electroosmotic flow (EOF) is suppressed. The technique was previously coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). In this work, the exploitation of selective sampling in conjugation with electrospray ionization mass spectrometry (ESI-MS) is presented. The transition was not immediately straightforward. A number of major alterations were necessary for ESI interfacing. These adaptations include the choice of a suitable capillary coating for EOF control and the incorporation of organic solvent for efficient ESI. As expected, selective injection of phosphopeptides greatly enhanced the sensitivity of their detection in ESI-MS, particularly for the multiply phosphorylated species that were traditionally most problematic. Furthermore, an electrophoretic separation subsequent to the selective injection of the phosphopeptides was performed prior to analysis by ESI-MS. This allowed us to resolve the multiply phosphorylated peptides present in the samples, predominantly based on the number of phosphorylation sites on the peptides.
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Affiliation(s)
- Jennifer N M Ballard
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
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