| 1. |
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| 2. |
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| 3. |
- Bankefors, Johan, et al.
(författare)
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Electrospray ionization ion-trap multiple-stage mass spectrometry of Quillaja saponins
- 2011
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 46, s. 658-665
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Tidskriftsartikel (refereegranskat)abstract
- Fifteen identified C-18 fatty acyl-containing saponin structures from Quillaja saponaria Molina have been investigated by electrospray ionization ion-trap multiple-stage mass spectrometry (ESI-IT-MS(n)) in positive ion mode. Their MS(1)-MS(3) spectra were analyzed and ions corresponding to useful fragments, important for the structural identification of Quillaja saponins, were recognized. A few key fragments could describe the structural variations in the C-3 and the C-28 oligosaccharides of the Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from the MS(1)-MS(3) spectra of these saponins, together with key fragments from these saponins and 13 previously investigated saponins, was constructed for the identification of structural elements in Quillaja saponins. Peak intensity ratios in MS(3) spectra were found to be correlated to structural features of the investigated saponins and is therefore of value for the identification of regioisomers. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 4. |
- Bazoti, Fotini N, et al.
(författare)
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Study of the non-covalent interaction between amyloid-beta-peptide and melatonin using electrospray ionization mass spectrometry
- 2005
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 40:2, s. 182-192:40, s. 182-192
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress and unregulated immune response are believed to play a key role in the processes inherent to Alzheimer's disease (AD). The fact that free radicals can result in neurodegeneration suggests that actions against reactive oxygen species may be beneficial in treating and preventing AD. In the light of the suggested link between oxidative stress and AD, it is proposed that antioxidants and, even more, endogenous antioxidants may offer a therapeutic regime for protection against the risk of this disease. For this reason, the formation of non-covalent complexes between amyloid-beta-peptide (A beta) or its oxidized forms and melatonin was studied by quadrupole and Fourier transform ion cyclotron resonance electrospray ionization mass spectrometry. The stability of the non-covalent complex was examined under several experimental conditions, such as orifice voltage, pH, presence of organic modifier, concentration and time. Two different digestion protocols combined with mass spectrometric analysis of the resulting peptide fragments were employed in order to locate the binding site of melatonin in A beta.
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| 5. |
- Benkestock, Kurt, et al.
(författare)
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Influence of droplet size, capillary-cone distance and selected instrumental parameters for the analysis of noncovalent protein-ligand complexes by nano-electrospray ionization mass spectrometry
- 2004
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 39:9, s. 1059-1067
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested in the literature that nano-electrospray ionization (nano-ESI) mass spectrometry better reflects the equilibrium between complex and free protein in solution than pneumatically assisted electrospray ionization (ESI) in noncovalent interaction studies. However, no systematic studies of the effects of ionization conditions have been performed to support this statement. In the present work, different instrumental and sample-derived parameters affecting the stability of noncovalent complexes during analysis by nano-ESI were investigated. In general, increased values of parameters such as drying gas flow-rate, ion-source temperature, capillary tip voltage and buffer concentration lead to a dissociation of ribonuclease A (RNAse)-cytidine 2'-monophosphate (CMP) and cytidine 5'-triphosphate (CTP) complexes. The size of the electrosprayed droplets was shown to be an important issue. Increasing the capillary to cone distance yielded an increased complex to free protein ratio when a hydrophilic ligand was present and the reverse effect was obtained with a hydrophobic ligand. Important in this regard is the degree of sampling of ions originating from late-generation residue droplets, that is, ions present in the droplet bulk. Sampling of these ions increases with longer capillary-cone distance (flight time). Furthermore, when the sample flow-rate was increased by increasing the capillary internal tip i.d. from 4 to 30 mum, a decreased complex to free protein ratio for the RNAse-CTP system was observed. This behavior was consistent with the change in surface to volume ratio for flow-rates between 2 and 100 nl min(-1). Finally, polarity switching between positive and negative ion modes gave a higher complex to free protein ratio when the ligand and the protein had the same polarity.
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| 6. |
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| 7. |
- Boija, Susanne, et al.
(författare)
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Determination of conditional stability constants for some divalent transition metal ion-EDTA complexes by electrospray ionization mass spectrometry
- 2014
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 49:7, s. 550-556
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Tidskriftsartikel (refereegranskat)abstract
- Conditional stability constants of coordination complexes comprising divalent transition metals, Cu2+, Ni2+, Zn2+, Co2+, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co2+ and Zn2+ competed for EDTA at pH 5. When Cu2+ and Ni2+ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.
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| 8. |
- Breimer, Michael, 1951, et al.
(författare)
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Selected ion monitoring of glycospingolipid mixtures. Identification of several blood group type glycolipids in the small intestine of an individual rabbit.
- 1979
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Ingår i: Biomedical mass spectrometry. - : Wiley. - 0306-042X .- 1096-9888. ; 6:6, s. 231-41
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Tidskriftsartikel (refereegranskat)abstract
- A novel application of selected ion monitoring was used for a mixture of non-acid glycosphingolipids of one rabbit small intestine. Earlier studies of permethylated and permethylated-reduced (LiAIH4) derivatives of model compounds have revealed a specificity and abundance of saccharide ions (terminal monosaccharide(s), disaccharide, trisaccharide, etc., and all sugars plus fatty acid) and of ceramide fragments that permit a conclusive detection of separate glycolipid species in a mixture. The sample (50-200 micrograms) was evaporated slowly (1-5 degrees C min-1 from 150-350 degrees C) from the direct inlet probe of an MS 902 mass spectrometer (electron ionization). Mass spectra with fragments up to about m/z 200 were collected on-line by a computer system. A successive partial separation was obtained for glycolipids with from one up to seven sugars. The structures of eight different compounds were identified. They all had 16:0, 22:0 and 24:0 2-hydroxy fatty acids and 18:0 trihydroxy base (phytosphingosine) as major ceramide components. The dominating complex glycolipid was a hexaglycosylceramide with a blood group B type of sequence. A blood group A type sequence was found in a second hexaglycosylceramide. In support of this, the native mixture showed blood group A and B activity. An intense peak, m/z 182, collected from methylated derivatives were evidence for a dominating type 2 carbohydrate chain of the core tetrasaccharide.
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| 9. |
- Brinkmalm, Gunnar, et al.
(författare)
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An online nano-LC-ESI-FTICR-MS method for comprehensive characterization of endogenous fragments from amyloid β and amyloid precursor protein in human and cat cerebrospinal fluid.
- 2012
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Ingår i: Journal of mass spectrometry : JMS. - : Wiley. - 1096-9888 .- 1076-5174. ; 47:5, s. 591-603
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid precursor protein (APP) is the precursor protein to amyloid β (Aβ), the main constituent of senile plaques in Alzheimer's disease (AD). Endogenous Aβ peptides reflect the APP processing, and greater knowledge of different APP degradation pathways is important to understand the mechanism underlying AD pathology. When one analyzes longer Aβ peptides by low-energy collision-induced dissociation tandem mass spectrometry (MS/MS), mainly long b-fragments are observed, limiting the possibility to determine variations such as amino acid variants or post-translational modifications (PTMs) within the N-terminal half of the peptide. However, by using electron capture dissociation (ECD), we obtained a more comprehensive sequence coverage for several APP/Aβ peptide species, thus enabling a deeper characterization of possible variants and PTMs. Abnormal APP/Aβ processing has also been described in the lysosomal storage disease Niemann-Pick type C and the major large animal used for studying this disease is cat. By ECD MS/MS, a substitution of Asp7 → Glu in cat Aβ was identified. Further, sialylated core 1 like O-glycans at Tyr10, recently discovered in human Aβ (a previously unknown glycosylation type), were identified also in cat cerebrospinal fluid (CSF). It is therefore likely that this unusual type of glycosylation is common for (at least) species belonging to the magnorder Boreoeutheria. We here describe a detailed characterization of endogenous APP/Aβ peptide species in CSF by using an online top-down MS-based method.
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| 10. |
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| 11. |
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| 12. |
- Ek, Patrik, et al.
(författare)
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Electrospray Ionization from an Adjustable Gap between two Silicon Chips
- 2009
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 44:2, s. 171-181
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a silicon chip - based electrospray emitter with a variable orifice size is presented. The device consists of two chips, with a thin beam elevating from the center of each of the chips. The chips are individually mounted to form an open gap of a narrow, uniform width between the top areas of the beams. The electrospray is generated at the endpoint of the gap, where the spray point is formed by the very sharp intersection between the crystal planes of the < 100 > silicon chips. Sample solution is applied to the rear end of the gap from a capillary via a liquid bridge, and capillary forces ensure a spontaneous imbibition of the gap. The sample solution is confined to the gap by means of a hydrophobic treatment of the surfaces surrounding the gap, as well as the geometrical boundaries formed by the edges of the gap walls. The gap width could be adjusted between 1 and 25 μm during electrospray experiments without suffering from any interruption of the electrospray process. Using a peptide sample solution, a shift toward higher charge states and increased signal-to-noise ratios was observed when the gap width was decreased. The limit of detection for the peptide insulin (chain B, oxidized) was approximately 4 nM. We also show a successful interfacing of the electrospray setup with capillary electrophoresis.
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| 13. |
- Ekegren, Titti, et al.
(författare)
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Clinical perspectives of high-resolution mass spectrometry-based proteomics in neuroscience: exemplified in amyotrophic lateral sclerosis biomarker discovery research.
- 2008
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Ingår i: Journal of mass spectrometry : JMS. - : Wiley. - 1076-5174 .- 1096-9888. ; 43:5, s. 559-71
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Forskningsöversikt (refereegranskat)abstract
- Biomarker discovery is a central application in today's proteomic research. There is an urgent need for valid biomarkers to improve diagnostic tools and treatment in many disorders, such as the rapidly progressing neurodegenerative disorder amyotrophic lateral sclerosis (ALS) that has a fatal outcome in about 3 years and yet no curative treatment. Screening for clinically relevant biomarkers puts high demands on high-throughput, rapid and precise proteomic techniques. There is a large variety in the methods of choice involving mainly gel-based approaches as well as chromatographic techniques for multi-dimensional protein and peptide separations followed by mass spectrometry (MS) analysis. This special feature article will discuss some important aspects of MS-based clinical proteomics and biomarker discovery in the field of neurodegenerative diseases and ALS research respectively, with the aim to provide a prospective view on current and future research aspects in the field. Furthermore, examples for application of high-resolution MS-based proteomic strategies for ALS biomarker discovery will be demonstrated with two studies previously reported by our group. These studies include among others, utilization of capillary liquid chromatography-Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR-MS) for advanced protein pattern classification in cerebrospinal fluid (CSF) samples of ALS patients as well as highly sensitive protein identification in minimal amounts of postmortem spinal cord tissue and laser micro-dissected motor neurons using FT-ICR-MS in conjunction with nanoflow LC coupled to matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (LC-MALDI-TOF-TOF-MS).
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| 14. |
- Ekström, Simon, et al.
(författare)
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Polymeric integrated selective enrichment target (ISET) for solid-phase-based sample preparation in MALDI-TOF MS
- 2007
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 42:11, s. 1445-1452
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Tidskriftsartikel (refereegranskat)abstract
- d A polymer microfabricated proteomic sample preparation and MALDI MS sample presentation device, the integrated selective enrichment target (ISET), comprising an array of perforated nanovials is reported. Each perforated nanovial can be filled with selective extraction media (microbeads) for purification and concentration of protein/peptides prior to matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). The main areas covered are the influence of the molding-process-induced surface roughness and how to address the lack of inherent conductivity in the polyetheretherketone (PEEK) material for optimal MALDI MS readout. Application of the disposable polymeric ISET devices for solid-phase extraction and phosphopeptide capture is also demonstrated.
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| 15. |
- Ellis, Hanna, 1985-, et al.
(författare)
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Laser desorption/ionization mass spectrometry of dye-sensitized solar cells : identification of the dye-electrolyte interaction
- 2015
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 50:5, s. 734-739
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells (DSCs) have great potential to provide sustainable electricity from sunlight. The photoanode in DSCs consists of a dye-sensitized metal oxide film deposited on a conductive substrate. This configuration makes the photoanode a perfect sample for laser desorption/ionization mass spectrometry (LDI-MS). We applied LDI-MS for the study of molecular interactions between a dye and electrolyte on the surface of a TiO2 photoanode. We found that a dye containing polyoxyethylene groups forms complexes with alkali metal cations from the electrolyte, while a dye substituted with alkoxy groups does not. Guanidinium ion forms adducts with neither of the two dyes.
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| 16. |
- Fridén, Mikael E., et al.
(författare)
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Strategies for differentiation of isobaric flavonoids using liquid chromatography coupled to electrospray ionization mass spectrometry
- 2014
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 49:7, s. 646-663
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Tidskriftsartikel (refereegranskat)abstract
- Flavonoids are a class of secondary plant metabolites existing in great variety in nature. Due to this variety, identification can be difficult, especially as overlapping compounds in both chromatographic separations and mass spectrometric detection are common. Methods for distinguishing isobaric flavonoids using MS2 and MS3 have been developed. Chromatographic separation of various plant extracts was done with RP-HPLC and detected with positive ESI-MS operated in information-dependent acquisition (IDA) mode. Two methods for the determination of flavonoid identity and substitution pattern, both featuring IDA criteria, were used together with the HPLC equipment. A third method where the collision energy was ramped utilized direct infusion. With the developed strategies, it is possible to differentiate between many isobaric flavonoids. Various classes of flavonoids were found in all of the plant extracts, in the red onion extract 45 components were detected and for 29 of them the aglycone was characterized, while the substituents were tentatively identified for 31 of them. For the strawberry extract, those numbers were 66, 30 and 60, and for the cherry extract 99, 56 and 71. The great variety of flavonoids, several of them isobaric, found in each of the extracts highlights the need for reliable methods for flavonoid characterization. Methods capable of differentiating between most of the isobars analyzed have been developed.
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| 17. |
- Groseclose, M Reid, et al.
(författare)
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Identification of proteins directly from tissue : in situ tryptic digestions coupled with imaging mass spectrometry.
- 2007
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 42:2, s. 254-62
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for on-tissue identification of proteins in spatially discrete regions is described using tryptic digestion followed by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) with MS/MS analysis. IMS is first used to reveal the protein and peptide spatial distribution in a tissue section and then a serial section is robotically spotted with small volumes of trypsin solution to carry out in situ protease digestion. After hydrolysis, 2,5-Dihydroxybenzoic acid (DHB) matrix solution is applied to the digested spots, with subsequent analysis by IMS to reveal the spatial distribution of the various tryptic fragments. Sequence determination of the tryptic fragments is performed using on-tissue MALDI MS/MS analysis directly from the individual digest spots. This protocol enables protein identification directly from tissue while preserving the spatial integrity of the tissue sample. The procedure is demonstrated with the identification of several proteins in the coronal sections of a rat brain.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Jha, Durga, et al.
(författare)
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Spatial neurolipidomics-MALDI mass spectrometry imaging of lipids in brain pathologies.
- 2024
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Ingår i: Journal of mass spectrometry : JMS. - 1096-9888. ; 59:3
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Tidskriftsartikel (refereegranskat)abstract
- Given the complexity of nervous tissues, understanding neurochemical pathophysiology puts high demands on bioanalytical techniques with respect to specificity and sensitivity. Mass spectrometry imaging (MSI) has evolved to become an important, biochemical imaging technology for spatial biology in biological and translational research. The technique facilitates comprehensive, sensitive elucidation of the spatial distribution patterns of drugs, lipids, peptides, and small proteins in situ. Matrix-assisted laser desorption ionization (MALDI)-based MSI is the dominating modality due to its broad applicability and fair compromise of selectivity, sensitivity price, throughput, and ease of use. This is particularly relevant for the analysis of spatial lipid patterns, where no other comparable spatial profiling tools are available. Understanding spatial lipid biology in nervous tissue is therefore a key and emerging application area of MSI research. The aim of this review is to give a concise guide through the MSI workflow for lipid imaging in central nervous system (CNS) tissues and essential parameters to consider while developing and optimizing MSI assays. Further, this review provides a broad overview of key developments and applications of MALDI MSI-based spatial neurolipidomics to map lipid dynamics in neuronal structures, ultimately contributing to a better understanding of neurodegenerative disease pathology.
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| 23. |
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| 24. |
- Kivimäki, Antti, et al.
(författare)
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Negative-ion/positive-ion coincidence spectroscopy as a tool to identify anionic fragments : The case of core-excited CHF3
- 2020
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 55:5
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the dissociation of the trifluoromethane molecule, CHF3, into negative ionic fragments at the C 1s and F 1s edges. The measurements were performed by detecting coincidences between negative and positive ions. We observed five different negative ions: F−, H−, C−, CF−, and F2 −. Their production was confirmed by the analysis of triple coincidence events (negative-ion/positive-ion/positive-ion or NIPIPI coincidences) that were recorded with cleaner signals than those of the negative-ion/positive-ion coincidences. The intensities of the most intense NIPIPI coincidence channels were recorded as a function of photon energy across the C 1s and F 1s excitations and ionization thresholds. We also observed dissociation channels involving the formation of one negative ion and three positive ions. Our results demonstrate that negative-ion/positive-ion coincidence spectroscopy is a very sensitive method to observe anions, which at inner-shell edges are up to three orders of magnitude less probable dissociation products than cations.
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| 25. |
- Klintenberg, Rebecka, et al.
(författare)
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Altered extracellular striatal in vivo biotransformation of the opioid neuropeptide dynorphin A(1-17) in the unilateral 6-OHDA rat model of Parkinson's disease
- 2005
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 40:2, s. 261-270
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Tidskriftsartikel (refereegranskat)abstract
- The in vivo biotransformation of dynorphin A(1-17) (Dyn A) was studied in the striatum of hemiparkinsonian rats by using microdialysis in combination with nanoflow reversed-phase liquid chromatography/electrospray time-of-flight mass spectrometry. The microdialysis probes were implanted into both hemispheres of unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats. Dyn A (10 pmol microl(-1)) was infused through the probes at 0.4 microl min(-1) for 2 h. Samples were collected every 30 min and analyzed by mass spectrometry. The results showed for the first time that there was a difference in the Dyn A biotransformation when comparing the two corresponding sides of the brain. Dyn A metabolites 1-8, 1-16, 5-17, 10-17, 7-10 and 8-10 were detected in the dopamine-depleted striatum but not in the untreated striatum. Dyn A biotransformed fragments found in both hemispheres were N-terminal fragments 1-4, 1-5, 1-6, 1-11, 1-12 and 1-13, C-terminal fragments 2-17, 3-17, 4-17, 7-17 and 8-17 and internal fragments 2-5, 2-10, 2-11, 2-12, and 8-15. The relative levels of these fragments were lower in the dopamine-depleted striatum. The results imply that the extracellular in vivo processing of the dynorphin system is being disturbed in the 6-OHDA-lesion animal model of Parkinson's disease.
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| 26. |
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| 27. |
- Lampinen Salomonsson, Matilda, et al.
(författare)
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In vitro formation of phase I and II metabolites of propranolol and determination of their structures using chemical derivatization and liquid chromatography tandem mass spectrometry
- 2009
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 44:5, s. 742-754
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Tidskriftsartikel (refereegranskat)abstract
- Derivatization with 1,2-dimethylimidazole-4-sulfonyl chloride (DMISC) has been successfully used as a tool to differentiate between aromatic and aliphatic O-glucuronides of hydroxypropranolol. The analyses were performed with liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) with both a triple quadrupole and an ion trap instrument. Hydroxylated forms of propranolol can be glucuronidated in aliphatic as well as aromatic positions. These isoforms are not distinguishable by tandem MS alone, as they both initially lose 176 Da, i.e. monodehydrated glucuronic acid, giving back the aglycone. Two in vitro systems were set up for the production of propranolol metabolites. The obtained isomers of 4'-hydroxypropranolol glucuronide were determined to correspond to one aliphatic and one aromatic form, using chemical derivatization with DMISC and LC-MSn. DMISC was shown to react with the secondary amine in the case where the naphtol was occupied by the glucuronyl moiety, resulting in a different fragmentation pattern compared with that of the aliphatic glucuronide, where the naphtol group was accessible to derivatization.
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| 28. |
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| 29. |
- Löfstedt, Christer, et al.
(författare)
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Analysis of moth pheromone acetates by selected ion monitoring using electron impact and chemical ionization mass spectrometry
- 1984
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Ingår i: Biological Mass Spectrometry. - : Wiley. - 0306-042X .- 1096-9888. ; 11:3, s. 106-113
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Tidskriftsartikel (refereegranskat)abstract
- Mass spectrometric determination of moth pheromone components by means of selected ion monitoring with electron impact and chemical ionization has been evaluated. For the analysis of acetates, chemical ionization with ammonia as reactant gas proved advantageous with respect to sensitivity and selectivity. A quantitative assay for determination of pheromone samples from individual turnip moth females (Agrotis segetum, Noctuidae), using internal standards, deuterated at the acyl group, was developed. The assay showed correct linearity in the investigated region (20–2000 pg). Signal to noise ratios for 100 pg of acetates using chemical ionization (ammonia as reactant gas) were in the range 10–50 depending on the degree of unsaturation. Conservative limits of detection (background signal + three times the standard deviation) and quantification (background signal + 10 times the standard deviation) were approximately 70 and 240 pg, respectively. A significant decrease in gland titre of (Z)‐5‐decenyl acetate and (Z)‐7‐dodecenyl acetate after mating was established.
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| 30. |
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| 31. |
- Moberg, My, et al.
(författare)
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A generic stepwise optimization strategy for liquid chromatography electrospray ionization tandem mass spectrometry methods
- 2006
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 41:10, s. 1334-1345
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility and advantages of using sophisticated chemometric tools in combination with the execution of thoroughly planned experiments to determine experimental conditions for optimal performance of an LC-ESI-MS/MS analysis is demonstrated. A stepwise strategy is proposed, which provides a controlled optimization procedure of the chromatographic quality (in terms of separation among the sample constituents) and maximizes the mass spectrometric signal of the selected product ions. Design of experiments (DOE) and response surface methodology are applied throughout the procedure. The stepwise approach has the advantage of dealing with the different optimization criteria separately, i.e. first ensuring sufficient chromatographic separation, then maximizing the amount of precursor ion entering the mass spectrometer, and finally generating high amounts of selected product ions. The experiments are performed on a linear ion trap mass spectrometer. Retention mapping using the band-tracking model is applied during LC development, which facilitates the optimization of segmented gradients. A set of different siderophores, strong iron chelates, is used as the model substances.
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| 32. |
- Moberg, My, et al.
(författare)
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Multi-parameter investigation of tandem mass spectrometry in a linear ion trap using response surface modelling
- 2005
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Ingår i: Journal Of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 40:3, s. 317-324:40, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of experimental design in combination with subsequent response surface modelling was illustrated for the prediction and interpretation of tandem mass spectrometric (MS/MS) fragmentation data using a linear quadrupole ion trap under various experimental conditions. The instrumental parameters included were (i) the pressure of the collision gas, (ii) the collision energy, (iii) the fill time of the linear ion trap and (iv) the scan rate. The spectral intensity and width of five fragment ions of the doubly charged neuro-active peptide bombesin were used for evaluation, and all experiments were performed so as to resemble the results obtained from a liquid chromatographic peak. The reported results show how fairly simple mathematical tools can be utilized successfully to describe fundamental mechanisms associated with multiple collisional activation and collision-induced dissociation processes without an extensively controlled experimental environment. Most beneficial, using the suggested approach, is the ability to study interaction (synergistic) effects between various parameters. As was realized from the results, many interaction effects are indeed significant. For example, the effect on the signal intensity of different collision gas pressure settings is strongly dependent on the settings of the other parameters. The described approach can easily be adopted for optimization purposes of any MS/MS experiment.
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| 33. |
- Oras, Ester, et al.
(författare)
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MALDI‐FT‐ICR‐MS for archaeological lipid residue analysis
- 2017
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 52:10, s. 689-700
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Tidskriftsartikel (refereegranskat)abstract
- Soft‐ionization methods are currently at the forefront of developing novel methods for analysing degraded archaeological organic residues. Here, we present little‐used soft ionization method of matrix assisted laser desorption/ionization‐Fourier transform‐ion cyclotron resonance‐mass spectrometry (MALDI‐FT‐ICR‐MS) for the identification of archaeological lipid residues. It is a high‐resolution and sensitive method with low limits of detection capable of identifying lipid compounds in small concentrations, thus providing a highly potential new technique for the analysis of degraded lipid components. A thorough methodology development for analysing cooked and degraded food remains from ceramic vessels was carried out, and the most efficient sample preparation protocol is described. The identified components, also controlled by independent parallel analysis by gas chromatography‐mass spectrometry (GC‐MS) and gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS), demonstrate its capability of identifying very different food residues including dairy, adipose fats as well as lipids of aquatic origin. The results obtained from experimentally cooked and original archaeological samples prove the suitability of MALDI‐FT‐ICR‐MS for analysing archaeological organic residues. Sample preparation protocol and identification of compounds provide future reference for analysing various aged and degraded lipid residues in different organic and mineral matrices.
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| 34. |
- Paulson, Linda, 1971, et al.
(författare)
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Proteomics and peptidomics in neuroscience. Experience of capabilities and limitations in a neurochemical laboratory.
- 2005
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Ingår i: Journal of mass spectrometry : JMS. - : Wiley. - 1076-5174 .- 1096-9888. ; 40:2, s. 202-13
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Forskningsöversikt (refereegranskat)abstract
- The increasing use of proteomics has created a basis for new strategies to develop methodologies for rapid identification of protein patterns in living organisms. It has also become evident that proteomics has other potential applications than protein and peptide identification, e.g. protein characterization, with the aim of revealing their structure, function(s) and interactions of proteins. In comparative proteomics studies, the protein expression of a certain biological system is compared with another system or the same system under perturbed conditions. Global identification of proteins in neuroscience is extremely complex, owing to the limited availability of biological material and very low concentrations of the molecules. Moreover, in addition to proteins, there are number of peptides that must also be considered in global studies on the central nervous system. In this overview, we focus on and discuss problems related to the different sources of biological material and sample handling, which are part of all preparatory and analytical steps. Straightforward protocols are desirable to avoid excessive purification steps, since loss of material at each step is inevitable. We would like to merge the two worlds of proteomics/peptidomics and neuroscience, and finally we consider different practical and technical aspects, illustrated with examples from our laboratory.
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| 35. |
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| 36. |
- Roepstorff, P., et al.
(författare)
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Application of Plasma Desorption Mass Spectrometry to Molecular Weight Determination of Structural Protein from Insect Cuticle
- 1986
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 13:12, s. 689-691
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Tidskriftsartikel (refereegranskat)abstract
- During sequence determination of a structural protein from the cuticle of the migratory locust, Locusta migratoria, a discrepancy was found between the molecular weight calculated from the sequence data (15 323) and that estimated by SDS-gel electrophoresis (21 600). The protein contains several repeated sequences, and the discrepancy might indicate that part of the sequence was missing or that the protein contained a large prosthetic group. The molecular weight of the protein was determined by 127I-plasma desorption mass spectrometry to be 15 329±50 which confirms the sequence data and shows the molecular weight determination based on SDS-electrophoresis to be too high.
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| 37. |
- Salihovic, Samira, Associate Senior Lecturer, 1985-, et al.
(författare)
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Assessing the performance of a targeted absolute quantification isotope dilution liquid chromatograhy tandem mass spectrometry assay versus a commercial nontargeted relative quantification assay for detection of three major perfluoroalkyls in human blood
- 2024
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Ingår i: Journal of Mass Spectrometry. - : John Wiley & Sons. - 1076-5174 .- 1096-9888. ; 59:2
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Tidskriftsartikel (refereegranskat)abstract
- Isotope dilution ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) is commonly used for trace analysis of polyfluoroalkyl and perfluoroalkyl substances (PFAS) in difficult matrices. Commercial nontargeted analysis of major PFAS where relative concentrations are obtained cost effectively is rapidly emerging and is claimed to provide comparable results to that of absolute quantification using matrix matched calibration and isotope dilution UHPLC-MS/MS. However, this remains to be demonstrated on a large scale. We aimed to assess the performance of a targeted absolute quantification isotope dilution LC-MS/MS assay versus a commercial nontargeted relative quantification assay for detection of three major PFAS in human blood. We evaluated a population-based cohort of 503 individuals. Correlations were assessed using Spearman's rank correlation coefficients (rho). Precision and bias were assessed using Bland-Altman plots. For perfluorooctane sulfonic acid, the median concentrations were 5.10 ng/mL (interquartile range [IQR] 3.50-7.24 ng/mL), the two assays correlated with rho 0.83. For perfluorooctanoic acid, the median concentrations were 2.14 ng/mL (IQR 1.60-3.0 ng/mL), the two assays correlated with rho 0.92. For perfluorohexanesulfonate, the median concentrations were 5.5 ng/mL (IQR 2.50-11.61 ng/mL), the two assays correlated with rho 0.96. The Bland-Altman statistical test showed agreement of the mean difference for the majority of samples (97-98%) between the two assays. Absolute plasma concentrations of PFAS obtained using matrix matched calibration and isotope dilution UHPLC-MS/MS show agreement with relative plasma concentrations from a nontargeted commercial platform by Metabolon. We observed striking consistency between the two assays when examining the associations of the three PFAS with cholesterol, offering additional confidence in the validity of utilizing the nontargeted approach for correlations with various health phenotypes.
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| 38. |
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| 39. |
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| 40. |
- Subramaniam, Raja, et al.
(författare)
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An isomer-specific high-energy collision-induced dissociation MS/MS database for forensic applications : a proof-of-concept on chemical warfare agent markers
- 2011
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 46:9, s. 917-924
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Tidskriftsartikel (refereegranskat)abstract
- Spectra database search has become the most popular technique for the identification of unknown chemicals, minimizing the need for authentic reference chemicals. In the present study, an isomer-specific high-energy collision-induced dissociation (CID) MS/MS spectra database of 12 isomeric O-hexyl methylphosphonic acids (degradation markers of nerve agents) was created. Phosphonate anions were produced by the electrospray ionization of phosphonic acids or negative-ion chemical ionization of their fluorinated derivatives and were analysed in a hybrid magnetic-sector–time-of-flight tandem massspectrometer. A centre-of-mass energy (Ecom) of 65eV led to an optimal sequential carbon–carbon bond breakage, which was interpreted in terms of charge remote fragmentation. The proposed mechanism is discussed in comparison with the routinely used low-energy CID MS/MS. Even-mass (odd-electron) charge remote fragmentation ion series were diagnostic of the O-alkyl chain structure and can be used to interpret unknown spectra. Together with the odd-mass ion series, they formed highly reproducible, isomer-specific spectra that gave significantly higher database matches and probability factors (by 1.5 times) than did the EI MS spectra of the trimethylsilyl derivatives of the same isomers. In addition, ionization by negative-ion chemical ionization and electrospray ionization resulted in similar spectra, which further highlights the general potential of the high-energy CID MS/MS technique.
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| 41. |
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| 42. |
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| 43. |
- Svan, Alfred, et al.
(författare)
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Identification of transformation products from -blocking agents formed in wetland microcosms using LC-Q-ToF
- 2016
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 51:3, s. 207-218
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Tidskriftsartikel (refereegranskat)abstract
- Identification of degradation products from trace organic compounds, which may retain the biological activity of the parent compound, is an important step in understanding the long-term effects of these compounds on the environment. Constructed wetlands have been successfully utilized to remove contaminants from wastewater effluent, including pharmacologically active compounds. However, relatively little is known about the transformation products formed during wetland treatment. In this study, three different wetland microcosm treatments were used to determine the biotransformation products of the -adrenoreceptor antagonists atenolol, metoprolol and propranolol. LC/ESI-Q-ToF run in the MSE and MS/MS modes was used to identify and characterize the degradation products through the accurate masses of precursor and product ions. The results were compared with those of a reference standard when available. Several compounds not previously described as biotransformation products produced in wetlands were identified, including propranolol-O-sulfate, 1-naphthol and the human metabolite N-deaminated metoprolol. Transformation pathways were significantly affected by microcosm conditions and differed between compounds, despite the compounds' structural similarities. Altogether, a diverse range of transformation products in wetland microcosms were identified and elucidated using high resolving MS. This work shows that transformation products are not always easily predicted, nor formed via the same pathways even for structurally similar compounds.
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| 44. |
- Tevell Åberg, Annica, 1978-, et al.
(författare)
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A mass spectromeric study on meloxicam metabolism in horses and the fungus Cunninghamella elegans, and the relevance of this microbial system as a model of drug metabolism in the horse
- 2009
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 44:7, s. 1026-1037
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a study where the metabolism of the non-steroidal anti-inflammatory drug meloxicam was investigated in six horses and in the filamentous fungus Cunninghamella elegans. The metabolites identified were compared between the species, and then the fungus was used to produce larger amounts of the metabolites for future use as reference material. C. elegans proved to be a good model of phase I meloxicam metabolism in horses since all four metabolites found were the same in both species. Apart from the two main metabolites, 5'-hydroxymethylmeloxicam and 5'-carboxymeloxicam, a second isomer of hydroxymeloxicam and dihydroxylated meloxicam were detected for the first time in horse urine and the microbial incubations. Phase II metabolites were not discovered in the C. elegans samples but hydroxymeloxicam glucuronide was detected intact in horse urine for the first time in this study. Urine from six horses was further analyzed in a semi-quantitative sense and 5'-hydroxymethylmeloxicam gave peaks with much higher intensity compared to the parent drug and the other metabolites, and was detected for at least 14 days after the last given dose in some of the horses. From the results presented in this article, we suggest that analytical methods developed for the detection of meloxicam in horse urine after prohibited use should focus on the 5'-hydroxymethyl metabolite and that C. elegans can be used to produce large amounts of this metabolite for potential future use as a reference compound.
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| 45. |
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| 46. |
- Tsybin, Youri O., et al.
(författare)
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Peptide and Protein Characterization by High Rate Electron Capture Dissociation Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
- 2004
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 39:7, s. 719-729
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Tidskriftsartikel (refereegranskat)abstract
- The analytical utility of the electron capture dissociation (ECD) technique, developed by McLafferty and co-workers, has substantially improved peptide and protein characterization using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The limitations of the first ECD implementations on commercial instruments were eliminated by the employment of low-energy electron-injection systems based on indirectly heated dispenser cathodes. In particular, the ECD rate and reliability were greatly increased, enabling the combination of ECD/FTICR-MS with on-line liquid separation techniques. Further technique development allowed the combination of two rapid fragmentation techniques, high-rate ECD and infrared multiphoton dissociation (IRMPD), in a single experimental configuration. Simultaneous and consecutive irradiations of trapped ions with electrons and photons extended the possibilities for ion activation/dissociation and led to improved peptide and protein characterization. The application of high-rate ECD/FTICR-MS has demonstrated its power and unique capabilities in top-down sequencing of peptides and proteins, including characterization of post-translational modifications, improved sequencing of peptides with multiple disulfide bridges and secondary fragmentation (w-ion formation). Analysis of peptide mixtures has been accomplished using high-rate ECD in bottom-up mass spectrometry based on mixture separation by liquid chromatography and capillary electrophoresis. This paper summarizes the current impact of high-rate ECD/FTICR-MS for top-down and bottom-up mass spectrometry of peptides and proteins.
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| 47. |
- Tulej, Marek, et al.
(författare)
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Isotope abundance ratio measurements using femtosecond laser ablation ionization mass spectrometry
- 2020
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 55:12
-
Tidskriftsartikel (refereegranskat)abstract
- Accurate isotope ratio measurements are of high importance in various scientific fields, ranging from radio isotope geochronology of solids to studies of element isotopes fractionated by living organisms. Instrument limitations, such as unresolved isobaric inferences in the mass spectra, or cosampling of the material of interest together with the matrix material may reduce the quality of isotope measurements. Here, we describe a method for accurate isotope ratio measurements using our laser ablation ionization time‐of‐flight mass spectrometer (LIMS) that is designed for in situ planetary research. The method is based on chemical depth profiling that allows for identifying micrometer scale inclusions embedded in surrounding rocks with different composition inside the bulk of the sample. The data used for precise isotope measurements are improved using a spectrum cleaning procedure that ensures removal of low quality spectra. Furthermore, correlation of isotopes of an element is used to identify and reject the data points that, for example, do not belong to the species of interest. The measurements were conducted using IR femtosecond laser irradiation focused on the sample surface to a spot size of ~12 μm. Material removal was conducted for a predefined number of laser shots, and time‐of‐flight mass spectra were recorded for each of the ablated layers. Measurements were conducted on NIST SRM 986 Ni isotope standard, trevorite mineral, and micrometer‐sized inclusions embedded in aragonite. Our measurements demonstrate that element isotope ratios can be measured with accuracies and precision at the permille level, exemplified by the analysis of B, Mg, and Ni element isotopes. The method applied will be used for in situ investigation of samples on planetary surfaces, for accurate quantification of element fractionation induced by, for example, past or present life or by geochemical processes.
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| 48. |
- Tunlid, Anders, et al.
(författare)
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Diastereoisomeric determination of R‐alanine in bacteria using capillary gas chromatography and positive/negative ion mass spectrometry
- 1984
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Ingår i: Biological Mass Spectrometry. - : Wiley. - 0306-042X .- 1096-9888. ; 11:8, s. 428-434
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Tidskriftsartikel (refereegranskat)abstract
- The possibilities of using combined capillary gas chromatography mass spectrometry for highly sensitive and selective determinations of enantiomeric alanines of bacterial origin have been evaluated. The alanines were separated as their diastereoisomeric N‐heptafluorobutyryl‐2‐butyl ester derivatives on a 25 m fused silica capillary column coated with SE‐54 as stationary phase. The mass spectra of the derivative obtained by chemical ionization using methane or ammonia (positive ions) and methane or Isobutane (negative ions) as reagent gases have been recorded. The highest sensitivity of detection was achieved by selected ion monitoring in the negative ion mode (detection limit about 0.8 pg). The method was tested by measuring the R‐alanine content in (a) Escherichia coli cultures and (b) natural bacterial communities associated with plant roots. In (a) the recorded detection limit implied possibilities to detect R‐alanine corresponding to 103−104 E. coli cells. The precision for quantifying R‐alanine in the cultures was 14% (coefficient of variation). (b) demonstrated an application where the R/(R + S) ratio of alanine is low. It was shown that accurate determinations of this ratio in the picogram range could be effected down to 0.4%.
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| 49. |
- Törnkvist, Anna, et al.
(författare)
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Interference of the electrospray voltage on chromatographic separations using porous graphitic carbon columns
- 2004
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 39:2, s. 216-222
-
Tidskriftsartikel (refereegranskat)abstract
- The electrospray ionization (ESI) voltage is shown to interfere with liquid chromatographic separations performed with packed porous graphitic carbon (PGC) capillary columns. This interference is ascribed to the presence of an electric field over the conductive column in the absence of an earth point between the column and the ESI emitter. The current evolved alters the chromatographic behavior of the catecholamine metabolite 3-O-methyl-DOPA significantly, as both peak splitting and a dramatic decrease in the retention time were observed. Furthermore, the response from the mass spectrometer was decreased by 33% at the same time. A related compound, tyrosine, exhibited decreased retention times but no peak splitting, whereas no shifts in the retention times (or peak splitting) were seen for the less retained dopamine and noradrenaline. When the current through the PGC column was eliminated by the use of an earth point between the column and the ESI emitter, the chromatographic behavior of the column was found to return slowly to normal after hours of equilibration with 60 : 40 (v/v) methanol-ammonium formate buffer of pH 2.9. The behavior of the PGC column with and without the earth point was found to be highly reproducible during a period of 1 month. We propose that the effect of the ESI voltage on the chromatographic behavior of the PGC column is due to associated redox reactions affecting both the PGC particles and the analytes. It is concluded that (for analytical reasons), care should be taken to ensure that no current is flowing through the chromatographic system when interfacing PGC columns, and conducting parts in general, to ESI mass spectrometry.
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| 50. |
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