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Yang Z, Arakawa H. A double sliding-window method for baseline correction and noise estimation for Raman spectra of microplastics. MARINE POLLUTION BULLETIN 2023; 190:114887. [PMID: 37023548 DOI: 10.1016/j.marpolbul.2023.114887] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/19/2023] [Accepted: 03/24/2023] [Indexed: 06/19/2023]
Abstract
When measuring microplastics of environmental samples, additives and attachment of biological materials may result in strong fluorescence in Raman spectra, which increases difficulty for imaging, identification, and quantification. Although there are several baseline correction methods available, user intervention is usually needed, which is not feasible for automated processes. In current study, a double sliding-window (DSW) method was proposed to estimate the baseline and standard deviation of noise. Simulated spectra and experimental spectra were used to evaluate the performance in comparison with two popular and widely used methods. Validation with simulated spectra and spectra of environmental samples showed that DSW method can accurately estimate the standard deviation of spectral noise. DSW method also showed better performance than compared methods when handling spectra of low signal-to-noise ratio (SNR) and elevated baselines. Therefore, DSW method is a useful approach for preprocessing Raman spectra of environmental samples and automated processes.
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Affiliation(s)
- Zijiang Yang
- Tokyo University of Marine Science and Technology, Konan 4-5-7, Minato-Ku, Tokyo 108-8477, Japan.
| | - Hisayuki Arakawa
- Tokyo University of Marine Science and Technology, Konan 4-5-7, Minato-Ku, Tokyo 108-8477, Japan.
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2
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Phetsanthad A, Vu NQ, Yu Q, Buchberger AR, Chen Z, Keller C, Li L. Recent advances in mass spectrometry analysis of neuropeptides. MASS SPECTROMETRY REVIEWS 2023; 42:706-750. [PMID: 34558119 PMCID: PMC9067165 DOI: 10.1002/mas.21734] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 08/22/2021] [Accepted: 08/28/2021] [Indexed: 05/08/2023]
Abstract
Due to their involvement in numerous biochemical pathways, neuropeptides have been the focus of many recent research studies. Unfortunately, classic analytical methods, such as western blots and enzyme-linked immunosorbent assays, are extremely limited in terms of global investigations, leading researchers to search for more advanced techniques capable of probing the entire neuropeptidome of an organism. With recent technological advances, mass spectrometry (MS) has provided methodology to gain global knowledge of a neuropeptidome on a spatial, temporal, and quantitative level. This review will cover key considerations for the analysis of neuropeptides by MS, including sample preparation strategies, instrumental advances for identification, structural characterization, and imaging; insightful functional studies; and newly developed absolute and relative quantitation strategies. While many discoveries have been made with MS, the methodology is still in its infancy. Many of the current challenges and areas that need development will also be highlighted in this review.
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Affiliation(s)
- Ashley Phetsanthad
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Nhu Q. Vu
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Qing Yu
- School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA
| | - Amanda R. Buchberger
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Zhengwei Chen
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Caitlin Keller
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Lingjun Li
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
- School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA
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3
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Vu NQ, DeLaney K, Li L. Neuropeptidomics: Improvements in Mass Spectrometry Imaging Analysis and Recent Advancements. Curr Protein Pept Sci 2021; 22:158-169. [PMID: 33200705 PMCID: PMC8330971 DOI: 10.2174/1389203721666201116115708] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/29/2020] [Accepted: 07/23/2020] [Indexed: 12/13/2022]
Abstract
Neuropeptides are an important class of endogenous peptides in the nervous system that regulate physiological functions such as feeding, glucose homeostasis, pain, memory, reproduction, and many others. In order to understand the functional role of neuropeptides in diseases or disorders, studies investigating their dysregulation in terms of changes in abundance and localization must be carried out. As multiple neuropeptides are believed to play a functional role in each physiological process, techniques capable of global profiling multiple neuropeptides simultaneously are desired. Mass spectrometry is well-suited for this goal due to its ability to perform untargeted measurements without prior comprehensive knowledge of the analytes of interest. Mass spectrometry imaging (MSI) is particularly useful because it has the capability to image a large variety of peptides in a single experiment without labeling. Like all analytical techniques, careful sample preparation is critical to successful MSI analysis. The first half of this review focuses on recent developments in MSI sample preparation and instrumentation for analyzing neuropeptides and other biomolecules in which the sample preparation technique may be directly applicable for neuropeptide analysis. The benefit offered by incorporating these techniques is shown as improvement in a number of observable neuropeptides, enhanced signal to noise, increased spatial resolution, or a combination of these aspects. The second half of this review focuses on recent biological discoveries about neuropeptides resulting from these improvements in MSI analysis. The recent progress in neuropeptide detection and analysis methods, including the incorporation of various tissue washes, matrices, instruments, ionization sources, and computation approaches combined with the advancements in understanding neuropeptide function in a variety of model organisms, indicates the potential for the utilization of MSI analysis of neuropeptides in clinical settings.
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Affiliation(s)
- Nhu Q. Vu
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Kellen DeLaney
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Lingjun Li
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
- School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA
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4
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Schmitt ND, Rawlins CM, Randall EC, Wang X, Koller A, Auclair JR, Kowalski JM, Kowalski PJ, Luther E, Ivanov AR, Agar NYR, Agar JN. Genetically Encoded Fluorescent Proteins Enable High-Throughput Assignment of Cell Cohorts Directly from MALDI-MS Images. Anal Chem 2019; 91:3810-3817. [PMID: 30839199 DOI: 10.1021/acs.analchem.8b03454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) provides a unique in situ chemical profile that can include drugs, nucleic acids, metabolites, lipids, and proteins. MSI of individual cells (of a known cell type) affords a unique insight into normal and disease-related processes and is a prerequisite for combining the results of MSI and other single-cell modalities (e.g. mass cytometry and next-generation sequencing). Technological barriers have prevented the high-throughput assignment of MSI spectra from solid tissue preparations to their cell type. These barriers include obtaining a suitable cell-identifying image (e.g. immunohistochemistry) and obtaining sufficiently accurate registration of the cell-identifying and MALDI-MS images. This study introduces a technique that overcame these barriers by assigning cell type directly from mass spectra. We hypothesized that, in MSI from mice with a defined fluorescent protein expression pattern, the fluorescent protein's molecular ion could be used to identify cell cohorts. A method was developed for the purification of enhanced yellow fluorescent protein (EYFP) from mice. To determine EYFP's molecular mass for MSI studies, we performed intact mass analysis and characterized the protein's primary structure and post-translational modifications through various techniques. MALDI-MSI methods were developed to enhance the detection of EYFP in situ, and by extraction of EYFP's molecular ion from MALDI-MS images, automated, whole-image assignment of cell cohorts was achieved. This method was validated using a well-characterized mouse line that expresses EYFP in motor and sensory neurons and should be applicable to hundreds of commercially available mice (and other animal) strains comprising a multitude of cell-specific fluorescent labels.
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Affiliation(s)
- Nicholas D Schmitt
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Catherine M Rawlins
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Elizabeth C Randall
- Department of Radiology , Brigham and Women's Hospital, Harvard Medical School , Boston , Massachusetts 02115 , United States
| | - Xianzhe Wang
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Antonius Koller
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Jared R Auclair
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States.,Biopharmaceutical Analysis Training Laboratory (BATL) , Northeastern University Innovation Campus , Burlington , Massachusetts 01803 , United States
| | - Jane-Marie Kowalski
- Bruker Daltonics , 40 Manning Road , Billerica , Massachusetts 01821 , United States
| | - Paul J Kowalski
- Bruker Daltonics , 40 Manning Road , Billerica , Massachusetts 01821 , United States
| | - Ed Luther
- Department of Pharmaceutical Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Alexander R Ivanov
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Nathalie Y R Agar
- Department of Radiology , Brigham and Women's Hospital, Harvard Medical School , Boston , Massachusetts 02115 , United States.,Department of Neurosurgery, Brigham and Women's Hospital, Department of Cancer Biology , Dana-Farber Cancer Institute, Harvard Medical School , Boston , Massachusetts 02115 , United States
| | - Jeffrey N Agar
- Department of Chemistry and Chemical Biology and Barnett Institute of Chemical and Biological Analysis , Northeastern University , Boston , Massachusetts 02115 , United States.,Department of Pharmaceutical Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
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6
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Gill EL, Yost RA, Vedam-Mai V, Garrett TJ. Precast Gelatin-Based Molds for Tissue Embedding Compatible with Mass Spectrometry Imaging. Anal Chem 2016; 89:576-580. [PMID: 27935272 DOI: 10.1021/acs.analchem.6b04185] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Preparation of tissue for matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) generally involves embedding the tissue followed by freezing and cryosectioning, usually between 5 and 25 μm thick, depending on the tissue type and the analyte(s) of interest. The brain is approximately 60% fat; it therefore lacks rigidity and poses structural preservation challenges during sample preparation. Histological sample preparation procedures are generally transferable to MALDI-MSI; however, there are various limitations. Optimal cutting temperature compound (OCT) is commonly used to embed and mount fixed tissue onto the chuck inside the cryostat during cryosectioning. However, OCT contains potential interferences that are detrimental to MALDI-MSI, while fixation is undesirable for the analysis of some analytes either due to extraction or chemical modification (i.e., polar metabolites). Therefore, a method for both fixed and fresh tissue compatible with MALDI-MSI and histology is desirable to increase the breadth of analyte(s), maintain the topographies of the brain, and provide rigidity to the fragile tissue while eliminating background interference. The method we introduce uses precast gelatin-based molds in which a whole mouse brain is embedded, flash frozen, and cryosectioned in preparation for mass spectrometry imaging (MSI).
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Affiliation(s)
- Emily L Gill
- Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States
| | - Richard A Yost
- Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.,Department of Pathology, Immunology and Laboratory Medicine, University of Florida , Gainesville, Florida 32610, United States
| | - Vinata Vedam-Mai
- Department of Neurosurgery, University of Florida , Gainesville, Florida 32610, United States
| | - Timothy J Garrett
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida , Gainesville, Florida 32610, United States
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Ong TH, Kissick DJ, Jansson ET, Comi TJ, Romanova EV, Rubakhin SS, Sweedler JV. Classification of Large Cellular Populations and Discovery of Rare Cells Using Single Cell Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. Anal Chem 2015; 87:7036-42. [PMID: 26076060 PMCID: PMC4511976 DOI: 10.1021/acs.analchem.5b01557] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cell-to-cell variability and functional heterogeneity are integral features of multicellular organisms. Chemical classification of cells into cell type is important for understanding cellular specialization as well as organismal function and organization. Assays to elucidate these chemical variations are best performed with single cell samples because tissue homogenates average the biochemical composition of many different cells and oftentimes include extracellular components. Several single cell microanalysis techniques have been developed but tend to be low throughput or require preselection of molecular probes that limit the information obtained. Mass spectrometry (MS) is an untargeted, multiplexed, and sensitive analytical method that is well-suited for studying chemically complex individual cells that have low analyte content. In this work, populations of cells from the rat pituitary, the rat pancreatic islets of Langerhans, and from the Aplysia californica nervous system, are classified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI) MS by their peptide content. Cells were dispersed onto a microscope slide to generate a sample where hundreds to thousands of cells were separately located. Optical imaging was used to determine the cell coordinates on the slide, and these locations were used to automate the MS measurements to targeted cells. Principal component analysis was used to classify cellular subpopulations. The method was modified to focus on the signals described by the lower principal components to explore rare cells having a unique peptide content. This approach efficiently uncovers and classifies cellular subtypes as well as discovers rare cells from large cellular populations.
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Affiliation(s)
- Ta-Hsuan Ong
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - David J Kissick
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Erik T Jansson
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Troy J Comi
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Elena V Romanova
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Stanislav S Rubakhin
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Jonathan V Sweedler
- Department of Chemistry and the Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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8
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Bhandari DR, Schott M, Römpp A, Vilcinskas A, Spengler B. Metabolite localization by atmospheric pressure high-resolution scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging in whole-body sections and individual organs of the rove beetle Paederus riparius. Anal Bioanal Chem 2014; 407:2189-201. [PMID: 25424178 PMCID: PMC4357651 DOI: 10.1007/s00216-014-8327-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 11/04/2014] [Accepted: 11/06/2014] [Indexed: 11/25/2022]
Abstract
Mass spectrometry imaging provides for non-targeted, label-free chemical imaging. In this study, atmospheric pressure high-resolution scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI) was used for the first time to describe the chemical distribution of the defensive compounds pederin, pseudopederin, and pederon in tissue sections (16 μm thick) of the rove beetle Paederus riparius. The whole-insect tissue section was scanned with a 20-μm step size. Mass resolution of the orbital trapping mass spectrometer was set to 100,000 at m/z 200. Additionally, organ-specific compounds were identified for brain, nerve cord, eggs, gut, ovaries, and malpighian tubules. To confirm the distribution of the specific compounds, individual organs from the insect were dissected, and MSI experiments were performed on the dissected organs. Three ganglia of the nerve cord, with a dimension of 250–500 μm, were measured with 10-μm spatial resolution. High-quality m/z images, based on high spatial resolution and high mass accuracy were generated. These features helped to assign mass spectral peaks with high confidence. Mass accuracy of the imaging experiments was <3 ppm root mean square error, and mapping of different compound classes from a single experiment was possible. This approach improved the understanding of the biochemistry of P. riparius. Concentration differences and distributions of pederin and its analogues could be visualized in the whole-insect section. Without any labeling, we assigned key lipids for specific organs to describe their location in the body and to identify morphological structures with a specificity higher than with staining or immunohistology methods.
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Affiliation(s)
- Dhaka Ram Bhandari
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Schubertstraße 60, Building 16, 35392 Giessen, Germany
| | - Matthias Schott
- Institute of Phytopathology and Applied Zoology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Andreas Römpp
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Schubertstraße 60, Building 16, 35392 Giessen, Germany
| | - Andreas Vilcinskas
- Institute of Phytopathology and Applied Zoology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
| | - Bernhard Spengler
- Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Schubertstraße 60, Building 16, 35392 Giessen, Germany
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Challenges and recent advances in mass spectrometric imaging of neurotransmitters. Bioanalysis 2014; 6:525-40. [PMID: 24568355 DOI: 10.4155/bio.13.341] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mass spectrometric imaging (MSI) is a powerful tool that grants the ability to investigate a broad mass range of molecules, from small molecules to large proteins, by creating detailed distribution maps of selected compounds. To date, MSI has demonstrated its versatility in the study of neurotransmitters and neuropeptides of different classes toward investigation of neurobiological functions and diseases. These studies have provided significant insight in neurobiology over the years and current technical advances are facilitating further improvements in this field. Herein, we briefly review new MSI studies of neurotransmitters, focusing specifically on the challenges and recent advances of MSI of neurotransmitters.
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Romanova EV, Aerts JT, Croushore CA, Sweedler JV. Small-volume analysis of cell-cell signaling molecules in the brain. Neuropsychopharmacology 2014; 39:50-64. [PMID: 23748227 PMCID: PMC3857641 DOI: 10.1038/npp.2013.145] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 04/26/2013] [Accepted: 05/06/2013] [Indexed: 12/19/2022]
Abstract
Modern science is characterized by integration and synergy between research fields. Accordingly, as technological advances allow new and more ambitious quests in scientific inquiry, numerous analytical and engineering techniques have become useful tools in biological research. The focus of this review is on cutting edge technologies that aid direct measurement of bioactive compounds in the nervous system to facilitate fundamental research, diagnostics, and drug discovery. We discuss challenges associated with measurement of cell-to-cell signaling molecules in the nervous system, and advocate for a decrease of sample volumes to the nanoliter volume regimen for improved analysis outcomes. We highlight effective approaches for the collection, separation, and detection of such small-volume samples, present strategies for targeted and discovery-oriented research, and describe the required technology advances that will empower future translational science.
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Affiliation(s)
- Elena V Romanova
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jordan T Aerts
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Callie A Croushore
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Jonathan V Sweedler
- Beckman Institute for Advanced Science and Technology and the Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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11
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Van Wielendaele P, Badisco L, Vanden Broeck J. Neuropeptidergic regulation of reproduction in insects. Gen Comp Endocrinol 2013; 188:23-34. [PMID: 23454669 DOI: 10.1016/j.ygcen.2013.02.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 02/01/2013] [Accepted: 02/10/2013] [Indexed: 12/17/2022]
Abstract
Successful animal reproduction depends on multiple physiological and behavioral processes that take place in a timely and orderly manner in both mating partners. It is not only necessary that all relevant processes are well coordinated, they also need to be adjusted to external factors of abiotic and biotic nature (e.g. population density, mating partner availability). Therefore, it is not surprising that several hormonal factors play a crucial role in the regulation of animal reproductive physiology. In insects (the largest class of animals on planet Earth), lipophilic hormones, such as ecdysteroids and juvenile hormones, as well as several neuropeptides take part in this complex regulation. While some peptides can affect reproduction via an indirect action (e.g. by influencing secretion of juvenile hormone), others exert their regulatory activity by directly targeting the reproductive system. In addition to insect peptides with proven activities, several others were suggested to also play a role in the regulation of reproductive physiology. Because of the long evolutionary history of many insect orders, it is not always clear to what extent functional data obtained in a given species can be extrapolated to other insect taxa. In this paper, we will review the current knowledge concerning the neuropeptidergic regulation of insect reproduction and situate it in a more general physiological context.
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Affiliation(s)
- Pieter Van Wielendaele
- Molecular Developmental Physiology and Signal Transduction, Department of Animal Physiology and Neurobiology, University of Leuven, Naamsestraat 59, P.O. Box 02465, B-3000 Leuven, Belgium
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Sturm RM, Greer T, Chen R, Hensen B, Li L. Comparison of NIMS and MALDI platforms for neuropeptide and lipid mass spectrometric imaging in C. borealis brain tissue. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2013; 5:1623-1628. [PMID: 23544036 PMCID: PMC3609542 DOI: 10.1039/c3ay26067d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Nanostructure-initiator mass spectrometry (NIMS) is a recently developed matrix-free laser desorption/ionization technique that has shown promise for peptide analyses. It is also useful in mass spectrometric imaging (MSI) studies of small molecule drugs, metabolites, and lipids, minimizing analyte diffusion caused by matrix application. In this study, NIMS and matrix-assisted laser desorption/ionization (MALDI) MSI of a crustacean model organism Cancer borealis brain were compared. MALDI was found to perform better than NIMS in these neuropeptide imaging experiments. Twelve neuropeptides were identified in MALDI MSI experiments whereas none were identified in NIMS MSI experiments. In addition, lipid profiles were compared using each ionization method. Both techniques provided similar lipid profiles in the m/z range 700 - 900.
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Affiliation(s)
- Robert M Sturm
- Department of Chemistry, University of Wisconsin-Madison
| | - Tyler Greer
- Department of Chemistry, University of Wisconsin-Madison
| | - Ruibing Chen
- Department of Chemistry, University of Wisconsin-Madison
| | | | - Lingjun Li
- Department of Chemistry, University of Wisconsin-Madison
- School of Pharmacy, University of Wisconsin-Madison
- Address reprint requests to: Dr. Lingjun Li, School of Pharmacy & Department of Chemistry, University of Wisconsin, 777 Highland Ave, Madison, WI 53705. . Phone: (608)265-8491, Fax: (608)262-5345
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13
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Li PH, Huang SY, Chen YC, Urban PL. A hybrid nanoparticle matrix for mass spectrometry. RSC Adv 2013. [DOI: 10.1039/c3ra22977g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Hui L, Xiang F, Zhang Y, Li L. Mass spectrometric elucidation of the neuropeptidome of a crustacean neuroendocrine organ. Peptides 2012; 36:230-9. [PMID: 22627023 PMCID: PMC3402701 DOI: 10.1016/j.peptides.2012.05.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 05/14/2012] [Accepted: 05/14/2012] [Indexed: 01/23/2023]
Abstract
The blue crab Callinectes sapidus has been used as an experimental model organism for the study of regulation of cardiac activity and other physiological processes. Moreover, it is an economically and ecologically important crustacean species. However, there was no previous report on the characterization of its neuropeptidome. To fill in this gap, we employed multiple sample preparation methods including direct tissue profiling, crude tissue extraction and tissue extract fractionation by HPLC to obtain a complete description of the neuropeptidome of C. sapidus. Matrix-assisted laser desorption/ionization (MALDI)-Fourier transform mass spectrometry (FTMS) and MALDI-time-of-flight (TOF)/TOF were utilized initially to obtain a quick snapshot of the neuropeptide profile, and subsequently nanoflow liquid chromatography (nanoLC) coupled with electrospray ionization quadrupole time-of-flight (ESI-Q-TOF) tandem MS analysis of neuropeptide extracts was conducted for de novo sequencing. Simultaneously, the pericardial organ (PO) tissue extract was labeled by a novel N,N-dimethylated leucine (DiLeu) reagent, offering enhanced fragmentation efficiency of peptides. In total, 130 peptide sequences belonging to 11 known neuropeptide families including orcomyotropin, pyrokinin, allatostatin A (AST-A), allatostatin B (AST-B), FMRFamide-like peptides (FLPs), and orcokinin were identified. Among these 130 sequences, 44 are novel peptides and 86 are previously identified. Overall, our results lay the groundwork for future physiological studies of neuropeptides in C. sapidus and other crustaceans.
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Affiliation(s)
- Limei Hui
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
| | - Feng Xiang
- School of Pharmacy, University of Wisconsin-Madison, WI, USA
| | - Yuzhuo Zhang
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
| | - Lingjun Li
- Department of Chemistry, University of Wisconsin-Madison, WI, USA
- School of Pharmacy, University of Wisconsin-Madison, WI, USA
- Address correspondence to: Dr. Lingjun Li, School of Pharmacy, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705-2222. Phone: (608)265-8491; Fax: (608)262-5345;
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15
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Schober Y, Guenther S, Spengler B, Römpp A. Single cell matrix-assisted laser desorption/ionization mass spectrometry imaging. Anal Chem 2012; 84:6293-7. [PMID: 22816738 DOI: 10.1021/ac301337h] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Application of mass spectrometry imaging (MS imaging) analysis to single cells was so far restricted either by spatial resolution in the case of matrix-assisted laser desorption/ionization (MALDI) or by mass resolution/mass range in the case of secondary ion mass spectrometry (SIMS). In this study we demonstrate for the first time the combination of high spatial resolution (7 μm pixel), high mass accuracy (<3 ppm rms), and high mass resolution (R = 100,000 at m/z = 200) in the same MS imaging measurement of single cells. HeLa cells were grown directly on indium tin oxide (ITO) coated glass slides. A dedicated sample preparation protocol was developed including fixation with glutaraldehyde and matrix coating with a pneumatic spraying device. Mass spectrometry imaging measurements with 7 μm pixel size were performed with a high resolution atmospheric-pressure matrix-assisted laser desorption/ionization (AP-MALDI) imaging source attached to an Exactive Orbitrap mass spectrometer. Selected ion images were generated with a bin width of Δm/z = ±0.005. Selected ion images and optical fluorescence images of HeLa cells showed excellent correlation. Examples demonstrate that a lower mass resolution and a lower spatial resolution would result in a significant loss of information. High mass accuracy measurements of better than 3 ppm (root-mean-square) under imaging conditions provide confident identification of imaged compounds. Numerous compounds including small metabolites such as adenine, guanine, and cholesterol as well as different lipid classes such as phosphatidylcholine, sphingomyelin, diglycerides, and triglycerides were detected and identified based on a mass spectrum acquired from an individual spot of 7 μm in diameter. These measurements provide molecularly specific images of larger metabolites (phospholipids) in native single cells. The developed method can be used for a wide range of detailed investigations of metabolic changes in single cells.
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Hu JB, Chen YC, Urban PL. On-target labeling of intracellular metabolites combined with chemical mapping of individual hyphae revealing cytoplasmic relocation of isotopologues. Anal Chem 2012; 84:5110-6. [PMID: 22583035 DOI: 10.1021/ac300903x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A microscale analytical platform integrating microbial cell culture, isotopic labeling, along with visual and mass spectrometric imaging with single-cell resolution has been developed and applied in the monitoring of cellular metabolism in fungal mycelium. The method implements open chips with a two-dimensional surface pattern composed of hydrophobic and hydrophilic zones. Two hydrophilic islands are used as medium reservoirs, while the hydrophobic area constitutes the support for the growing aerial hyphae, which do not have direct contact with the medium. The first island, containing (12)C(6)-glucose medium, was initially inoculated with the mycelium (Neurospora crassa), and following the initial incubation period, the hyphae progressed toward the second medium island, containing an isotopically labeled substrate ((13)C(6)-glucose). The (13)C atoms were gradually incorporated into cellular metabolites, which was revealed by MALDI-MS. The fate of the chitin-biosynthesis precursor, uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), was monitored by recording mass spectra with characteristic isotopic patterns, which indicated the presence of various (12)C/(13)C isotopologues. The method enabled mapping the (13)C-labeled UDP-GlcNAc in fungal mycelium and recording its redistribution in hyphae, directly on the chip.
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Affiliation(s)
- Jie-Bi Hu
- Department of Applied Chemistry, National Chiao Tung University, 1001 University Rd, Hsinchu, 300, Taiwan
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17
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Probing neuropeptide signaling at the organ and cellular domains via imaging mass spectrometry. J Proteomics 2012; 75:5014-5026. [PMID: 22465716 DOI: 10.1016/j.jprot.2012.03.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 02/25/2012] [Accepted: 03/05/2012] [Indexed: 11/24/2022]
Abstract
Imaging mass spectrometry (IMS) has evolved to be a promising technology due to its ability to detect a broad mass range of molecular species and create density maps for selected compounds. It is currently one of the most useful techniques to determine the spatial distribution of neuropeptides in cells and tissues. Although IMS is conceptually simple, sample preparation steps, mass analyzers, and software suites are just a few of the factors that contribute to the successful design of a neuropeptide IMS experiment. This review provides a brief overview of IMS sampling protocols, instrumentation, data analysis tools, technological advancements and applications to neuropeptide localization in neurons and endocrine tissues. Future perspectives in this field are also provided, concluding that neuropeptide IMS would greatly facilitate studies of neuronal network and biomarker discovery.
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18
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Tucker KR, Lanni EJ, Serebryannyy LA, Rubakhin SS, Sweedler JV. Stretched tissue mounting for MALDI mass spectrometry imaging. Anal Chem 2011; 83:9181-5. [PMID: 22017527 PMCID: PMC3229305 DOI: 10.1021/ac201857k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) combines information-rich chemical detection with spatial localization of analytes. For a given instrumental platform and analyte class, the data acquired can represent a compromise between analyte extraction and spatial information. Here, we introduce an improvement to the spatial resolution achievable with MALDI MSI conducted with standard mass spectrometric systems that also reduces analyte migration during matrix application. Tissue is placed directly on a stretchable membrane that, when stretched, fragments the tissue into micrometer-sized pieces. Scanning electron microscopy analysis shows that this process produces fairly homogeneous distributions of small tissue fragments separated and surrounded by areas of hydrophobic membrane surface. MALDI matrix is then applied by either a robotic microspotter or an artist's airbrush. Rat spinal cord samples imaged with an instrumental resolution of 50-250 μm demonstrate lipid distributions with a 5-fold high spatial resolution (a 25-fold increase in pixel density) after stretching compared to tissues that were not stretched.
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Affiliation(s)
- Kevin R. Tucker
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801
| | - Eric J. Lanni
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801
| | - Leonid A. Serebryannyy
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801
| | - Stanislav S. Rubakhin
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801
| | - Jonathan V. Sweedler
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801
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Hanrieder J, Ljungdahl A, Fälth M, Mammo SE, Bergquist J, Andersson M. L-DOPA-induced dyskinesia is associated with regional increase of striatal dynorphin peptides as elucidated by imaging mass spectrometry. Mol Cell Proteomics 2011; 10:M111.009308. [PMID: 21737418 PMCID: PMC3205869 DOI: 10.1074/mcp.m111.009308] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Opioid peptides are involved in various pathophysiological processes, including algesia, epilepsy, and drug dependence. A strong association between L-DOPA-induced dyskinesia (LID) and elevated prodynorphin mRNA levels has been established in both patients and in animal models of Parkinson's disease, but to date the endogenous prodynorphin peptide products have not been determined. Here, matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) was used for characterization, localization, and relative quantification of striatal neuropeptides in a rat model of LID in Parkinson's disease. MALDI IMS has the unique advantage of high sensitivity and high molecular specificity, allowing comprehensive detection of multiple molecular species in a single tissue section. Indeed, several dynorphins and enkephalins could be detected in the present study, including dynorphin A(1-8), dynorphin B, α-neoendorphin, MetEnkRF, MetEnkRGL, PEnk (198-209, 219-229). IMS analysis revealed elevated levels of dynorphin B, α-neoendorphin, substance P, and PEnk (220-229) in the dorsolateral striatum of high-dyskinetic animals compared with low-dyskinetic and lesion-only control rats. Furthermore, the peak-intensities of the prodynorphin derived peptides, dynorphin B and α-neoendorphin, were strongly and positively correlated with LID severity. Interestingly, these LID associated dynorphin peptides are not those with high affinity to κ opioid receptors, but are known to bind and activate also μ- and Δ-opioid receptors. In addition, the peak intensities of a novel endogenous metabolite of α-neoendorphin lacking the N-terminal tyrosine correlated positively with dyskinesia severity. MALDI IMS of striatal sections from Pdyn knockout mice verified the identity of fully processed dynorphin peptides and the presence of endogenous des-tyrosine α-neoendorphin. Des-tyrosine dynorphins display reduced opioid receptor binding and this points to possible novel nonopioid receptor mediated changes in the striatum of dyskinetic rats. Because des-tyrosine dynorphins can only be detected by mass spectrometry, as no antibodies are available, these findings highlight the importance of MALDI IMS analysis for the study of molecular dynamics in neurological diseases.
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Affiliation(s)
- Jörg Hanrieder
- Department of Pharmaceutical Biosciences, Drug Safety and Toxicology, Uppsala University, Uppsala, Sweden
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20
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Svatoš A. Single-cell metabolomics comes of age: new developments in mass spectrometry profiling and imaging. Anal Chem 2011; 83:5037-44. [DOI: 10.1021/ac2003592] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Aleš Svatoš
- Max Planck Institute for Chemical Ecology (Germany)
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21
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Tucker KR, Serebryannyy LA, Zimmerman TA, Rubakhin SS, Sweedler JV. The modified-bead stretched sample method: development and application to MALDI-MS imaging of protein localization in the spinal cord. Chem Sci 2011; 2:785-795. [PMID: 21625333 PMCID: PMC3102565 DOI: 10.1039/c0sc00563k] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been used to create spatial distribution maps from lipids, peptides, and proteins in a variety of biological tissues. MALDI-MSI often involves trade-offs between the extent of analyte extraction and desired spatial resolution, compromises that can adversely affect detectability. For example, increasing the extraction time can lead to unwanted analyte spatial redistribution. With the stretched sample method (SSM), the extraction period can be extended, resulting in reduced analyte redistribution while suppressing detection of cationic salt adducts. The SSM involves thaw-mounting a thin tissue section onto a substrate of small glass beads embedded in Parafilm M and then stretching the membrane to fragment the tissue into thousands of bead-sized pieces. Here, we applied the SSM method to MALDI-MSI using rat spinal cord as a model. We used surface-modified beads coated with trypsin or chymotrypsin in order to facilitate controlled digestion and detection of proteins. The enzymatic reactions were maintained by repeatedly condensing water on the stretched sample surface. As a result, new peptides formed by tryptic or chymotryptic protein digestion were detected and identified using a combination of MALDI-MSI and offline liquid chromatography tandem mass spectrometric analysis. Localization of these peptides indicated the distribution of their proteins of origin, including myelin basic protein, actin beta, and tubulin alpha chain. Additionally, we used uncoated beads to create distribution maps of many endogenous lipids and small peptides. The extension of the SSM using modified beads resulted in the creation of mosaic bead surfaces where adjacent beads were coated with different enzymes or other reactive chemicals, permitting investigation of the distributions of a wider range of analytes in biological samples within a single experiment.
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Affiliation(s)
- Kevin R Tucker
- Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801
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Zimmerman TA, Rubakhin SS, Sweedler JV. MALDI mass spectrometry imaging of neuronal cell cultures. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:828-36. [PMID: 21472517 PMCID: PMC3113696 DOI: 10.1007/s13361-011-0111-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 02/21/2011] [Accepted: 02/23/2011] [Indexed: 05/09/2023]
Abstract
Mass spectrometry imaging (MSI) provides the ability to detect and identify a broad range of analytes and their spatial distributions from a variety of sample types, including tissue sections. Here we describe an approach for probing neuropeptides from sparse cell cultures using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MSI--at single cell spatial resolution-in both MS and tandem MS modes. Cultures of Aplysia californica neurons are grown on an array of glass beads embedded in a stretchable layer of Parafilm M. As the membrane is stretched, the beads/neurons are separated physically and the separated beads/neurons analyzed via MALDI TOF MS. Compared with direct MS imaging of samples, the stretching procedure enhances analyte extraction and incorporation into the MALDI matrix, with negligible analyte spread between separated beads. MALDI tandem MSI using the stretched imaging approach yields localization maps of both parent and fragment ions from Aplysia pedal peptide, thereby confirming peptide identification. This methodology represents a flexible platform for MSI investigation of a variety of cell cultures, including functioning neuronal networks.
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Affiliation(s)
- Tyler A. Zimmerman
- Department of Chemistry, University of Illinois, 600 South Mathews Ave.; 63–5, Urbana, IL 61801, USA
- Beckman Institute, University of Illinois, Urbana, IL 61801, USA
| | - Stanislav S. Rubakhin
- Department of Chemistry, University of Illinois, 600 South Mathews Ave.; 63–5, Urbana, IL 61801, USA
- Beckman Institute, University of Illinois, Urbana, IL 61801, USA
| | - Jonathan V. Sweedler
- Department of Chemistry, University of Illinois, 600 South Mathews Ave.; 63–5, Urbana, IL 61801, USA
- Beckman Institute, University of Illinois, Urbana, IL 61801, USA
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Urban PL, Chang CH, Wu JT, Chen YC. Microscale MALDI Imaging of Outer-Layer Lipids in Intact Egg Chambers from Drosophila melanogaster. Anal Chem 2011; 83:3918-25. [DOI: 10.1021/ac200481j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Pawel L. Urban
- Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan
| | - Chia-Hsien Chang
- Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan
| | - June-Tai Wu
- Department of Medical Research, National Taiwan University Hospital, Taipei, Taiwan
| | - Yu-Chie Chen
- Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan
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Rauser S, Deininger SO, Suckau D, Höfler H, Walch A. Approaching MALDI molecular imaging for clinical proteomic research: current state and fields of application. Expert Rev Proteomics 2011; 7:927-41. [PMID: 21142893 DOI: 10.1586/epr.10.83] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
MALDI imaging mass spectrometry ('MALDI imaging') is an increasingly recognized technique for biomarker research. After years of method development in the scientific community, the technique is now increasingly applied in clinical research. In this article, we discuss the use of MALDI imaging in clinical proteomics and put it in context with classical proteomics techniques. We also highlight a number of upcoming challenges for personalized medicine, development of targeted therapies and diagnostic molecular pathology where MALDI imaging could help.
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Affiliation(s)
- Sandra Rauser
- Institute of Pathology, Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstraße 1, Neuherberg, Germany
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25
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Amantonico A, Urban PL, Fagerer SR, Balabin RM, Zenobi R. Single-cell MALDI-MS as an analytical tool for studying intrapopulation metabolic heterogeneity of unicellular organisms. Anal Chem 2011; 82:7394-400. [PMID: 20707357 DOI: 10.1021/ac1015326] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heterogeneity is a characteristic feature of all populations of living organisms. Here we make an attempt to validate a single-cell mass spectrometric method for detection of changes in metabolite levels occurring in populations of unicellular organisms. Selected metabolites involved in central metabolism (ADP, ATP, GTP, and UDP-Glucose) could readily be detected in single cells of Closterium acerosum by means of negative-mode matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). The analytical capabilities of this approach were characterized using standard compounds. The method was then used to study populations of individual cells with different levels of the chosen metabolites. With principal component analysis and support vector machine algorithms, it was possible to achieve a clear separation of individual C. acerosum cells in different metabolic states. This study demonstrates the suitability of mass spectrometric analysis of metabolites in single cells to measure cell-population heterogeneity.
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Affiliation(s)
- Andrea Amantonico
- Department of Chemistry and Applied Biosciences, ETH Zurich, CH-8093 Zurich, Switzerland
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26
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Abstract
Neuropeptidomics refers to a global characterization approach for the investigation of neuropeptides, often under specific physiological conditions. Neuropeptides comprise a complex set of signaling molecules that are involved in regulatory functions and behavioral control in the nervous system. Neuropeptidomics is inherently challenging because neuropeptides are spatially, temporally, and chemically heterogeneous, making them difficult to predict in silico from genomic information. Mature neuropeptides are produced from intricate enzymatic processing of precursor proteins/prohormones via a range of posttranslational modifications, resulting in multiple final peptide products from each prohormone gene. Although there are several methods for targeted peptide studies, mass spectrometry (MS), with its qualitative and quantitative capabilities, is ideally suited to the task. MS provides fast, sensitive, accurate, and high-throughput peptidomic analysis of neuropeptides without requiring prior knowledge of the peptide sequences. Aided by liquid chromatography (LC) separations and bioinformatics, MS is quickly becoming a leading technique in neuropeptidomics. This chapter describes several LC-MS analytical methods to identify, characterize, and quantify neuropeptides while emphasizing the sample preparation steps so integral to experimental success.
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Lagarrigue M, Becker M, Lavigne R, Deininger SO, Walch A, Aubry F, Suckau D, Pineau C. Revisiting rat spermatogenesis with MALDI imaging at 20-microm resolution. Mol Cell Proteomics 2010; 10:M110.005991. [PMID: 21149303 DOI: 10.1074/mcp.m110.005991] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Matrix-assisted laser desorption/ionization (MALDI) molecular imaging technology attracts increasing attention in the field of biomarker discovery. The unambiguous correlation between histopathology and MALDI images is a key feature for success. MALDI imaging mass spectrometry (MS) at high definition thus calls for technological developments that were established by a number of small steps. These included tissue and matrix preparation steps, dedicated lasers for MALDI imaging, an increase of the robustness against cell debris and matrix sublimation, software for precision matching of molecular and microscopic images, and the analysis of MALDI imaging data using multivariate statistical methods. The goal of these developments is to approach single cell resolution with imaging MS. Currently, a performance level of 20-μm image resolution was achieved with an unmodified and commercially available instrument for proteins detected in the 2-16-kDa range. The rat testis was used as a relevant model for validating and optimizing our technological developments. Indeed, testicular anatomy is among the most complex found in mammalian bodies. In the present study, we were able to visualize, at 20-μm image resolution level, different stages of germ cell development in testicular seminiferous tubules; to provide a molecular correlate for its well established stage-specific classification; and to identify proteins of interest using a top-down approach and superimpose molecular and immunohistochemistry images.
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Affiliation(s)
- Mélanie Lagarrigue
- INSERM U625, Proteomics Core Facility Biogenouest, Campus de Beaulieu, Université de Rennes I, F-35042 Rennes, France
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Abstract
Recent discoveries suggest that cells of a clonal population often display multiple metabolic phenotypes at the same time. Motivated by the success of mass spectrometry (MS) in the investigation of population-level metabolomics, the analytical community has initiated efforts towards MS-based single cell metabolomics to investigate metabolic phenomena that are buried under the population average. Here, we review the current approaches and illustrate their advantages and disadvantages. Because of significant advances in the field, different technologies are now at the verge of generating data that are useful for exploring and investigating metabolic heterogeneity.
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Affiliation(s)
- Matthias Heinemann
- ETH Zurich, Institute of Molecular Systems Biology, Wolfgang-Pauli-Strasse 16, Zurich, Switzerland.
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29
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Analytical techniques for single-cell metabolomics: state of the art and trends. Anal Bioanal Chem 2010; 398:2493-504. [DOI: 10.1007/s00216-010-3850-1] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 05/09/2010] [Accepted: 05/13/2010] [Indexed: 01/09/2023]
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