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  • 151.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Detection of endogenous BMAA in dinoflagellate (Heterocapsa triquetra) hints at evolutionary conservation and environmental concern2014In: PubRaw Science, ISSN 2313-1128, Vol. 1, no 2, p. 1-8Article in journal (Refereed)
  • 152.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åberg, K. Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS2013In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 405, no 4, p. 1283-1292Article in journal (Refereed)
    Abstract [en]

    The cyanobacterial neurotoxin β-N-methylamino--alanine (BMAA) is an amino acid that is putatively associated with the pathology of amyotrophic lateral sclerosis/Parkinsonism –dementia complex (ALS-PDC) disease. It raises serious health risk concerns since cyanobacteria are ubiquitous thus making human exposure almost inevitable. The identification and quantification of BMAA in cyanobacteria is challenging because it is present only in trace amounts and occurs alongside structurally similar compounds such as BMAA isomers. This work describes an enhanced liquid chromatography/tandem mass spectrometry platform that can distinguish BMAA from its isomers β-amino-N-methyl-alanine, N-(2-oethyl) glycine (AEG), and 2,4-diaminobutyric acid, thus ensuring confident identification of BMAA. The method's sensitivity was improved fourfold by a post-column addition of acetonitrile. The instrument and method limits of detection were shown to be 4.2 fmol/injection (or 0.5 g/one column) and 0.1 μg/g dry weight of cyanobacteria, respectively. The quantification method uses synthesized deuterated BMAA as an internal standard and exhibits good linearity, accuracy, and precision. Matrix effects were also investigated, revealing an ion enhancement of around 18 %. A lab-cultured cyanobacterial sample (Leptolyngbya PCC73110) was analyzed and shown to contain about 0.73 μg/g dry weight BMAA. The isomer AEG, whose chromatographic properties closely resemble those of BMAA, was also detected. These results highlight the importance of distinguishing BMAA from its isomers for reliable identification as well as providing a sensitive and accurate quantification method for measuring trace levels of BMAA in cyanobacterial samples.

  • 153.
    Jiang, Liying
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Kiselova, Nadezda
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Rosén, Johan
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Quantification of neurotoxin BMAA (beta-N-methylamino-L-alanine) in seafood from Swedish markets2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, article id 6931Article in journal (Refereed)
    Abstract [en]

    The neurotoxin beta-N-methylamino-L-alanine (BMAA) produced naturally by cyanobacteria, diatoms and dinoflagellates can be transferred and accumulated up the food chain, and may be a risk factor for neurodegenerative diseases. This study provides the first systematic screening of BMAA exposure of a large population through the consumption of seafood sold in metropolitan markets. BMAA was distinguished from known isomers by liquid chromatography tandem mass spectrometry after acidic hydrolysis and derivatization. Using deuterium-labeled internal standard, BMAA was quantified as 0.01-0.90 mu g/g wet weight of tissues in blue mussel, oyster, shrimp, plaice, char and herring, but was undetectable (<0.01 mu g/g) in other samples (salmon, cod, perch and crayfish). Provided that the content of BMAA detected is relevant for intake calculations, the data presented may be used for a first estimation of BMAA exposure through seafood from Swedish markets, and to refine the design of future toxicological experiments and assessments.

  • 154. Johansson, LarsErik
    et al.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jonsson, Gunnar
    Hamp, Sven
    Roeraade, Johan
    Determination of conductivity of bacteria by using cross-flow filtration2006In: Biotechnology Letters, Vol. 28, p. 601–603-Article in journal (Refereed)
  • 155. Johansson, Staffan
    et al.
    Redeby, Theres
    Altamore, Timothy M.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Börje, Anna
    Mechanistic Proposal for the Formation of Specific Immunogenic Complexes via a Radical Pathway: A Key Step in Allergic Contact Dermatitis to Olefinic Hydroperoxides2009In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 22, no 11, p. 1774-1781Article in journal (Refereed)
    Abstract [en]

    The widespread use of scented products causes an increase of allergic contact dermatitis to fragrance compounds in Western countries today. Many fragrance compounds are prone to autoxidation, forming hydroperoxides as their primary oxidation products. Hydroperoxides are known to be strong allergens and to form specific immunogenic complexes. However, the mechanisms for the formation of the immunogenic complexes are largely unknown. We have investigated this mechanism for (5R)-5-isopropenyl-2-methyl-2-cyclohexene-1-hydroperoxide (Lim-2-OOH) by studying the formation of adducts in the reaction between this hydroperoxide and 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)TPPCl) in the presence of protected cysteine (NAc-Cys-OMe) or glutathione (GSH). Isolated adducts originate from the addition of the thiol group of NAc-Cys-OMe over the carbon−carbon double bonds of carvone. Furthermore, adducts between NAc-Cys-OMe and carveol as well as between GSH and carvone have been identified. The formation of these adducts most likely proceeds via the radical thiol−ene mechanism. The addition of a terpene moiety to cysteine offers an explanation of the specificity of the immune response to structurally different hydroperoxides. These results also explain the lack of cross-reactivity between carvone and Lim-2-OOH. In conclusion, we propose that immunogenic complexes of olefinic hydroperoxides can be formed via the radical thiol−ene mechanism. These complexes will be specific for the individual olefinic hydroperoxides due to the inclusion of a terpene moiety derived from the hydroperoxide.

  • 156.
    Jonasson, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Eriksson, Johan
    Stockholm University, Faculty of Science, Department of Botany.
    Berntzon, Lotta
    Stockholm University, Faculty of Science, Department of Botany.
    Spacil, Zdenek
    Stockholm University, Faculty of Science, Department of Analytical Chemistry. Charles University Prague, Czech Republic .
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ronnevi, Lars-Olof
    Rasmussen, Ulla
    Stockholm University, Faculty of Science, Department of Botany.
    Bergman, Birgitta
    Stockholm University, Faculty of Science, Department of Botany.
    Transfer of a cyanobacterial neurotoxin within a temperate aquatic ecosystem suggests pathways for human exposure2010In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 107, no 20, p. 9252-9257Article in journal (Refereed)
    Abstract [en]

    beta-methylamino-L-alanine (BMAA), a neurotoxic nonprotein amino acid produced by most cyanobacteria, has been proposed to be the causative agent of devastating neurodegenerative diseases on the island of Guam in the Pacific Ocean. Because cyanobacteria are widespread globally, we hypothesized that BMAA might occur and bioaccumulate in other ecosystems. Here we demonstrate, based on a recently developed extraction and HPLC-MS/MS method and long-term monitoring of BMAA in cyanobacterial populations of a temperate aquatic ecosystem (Baltic Sea, 2007-2008), that BMAA is biosynthesized by cyanobacterial genera dominating the massive surface blooms of this water body. BMAA also was found at higher concentrations in organisms of higher trophic levels that directly or indirectly feed on cyanobacteria, such as zooplankton and various vertebrates (fish) and invertebrates (mussels, oysters). Pelagic and benthic fish species used for human consumption were included. The highest BMAA levels were detected in the muscle and brain of bottom-dwelling fishes. The discovery of regular biosynthesis of the neurotoxin BMAA in a large temperate aquatic ecosystem combined with its possible transfer and bioaccumulation within major food webs, some ending in human consumption, is alarming and requires attention.

  • 157.
    Karlberg, B
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Publication of chemical research: do we need ethical standards?2007In: Accreditation and Quality Assurance, Vol. 12, p. 49-50Article in journal (Refereed)
  • 158.
    Karlberg, B
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersen, J E T
    Emons, H
    DAC tries a new format, TrAC2008In: Trends in Analytical Chemistry, Vol. 27, p. 97-100Article in journal (Refereed)
  • 159.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Emons, H.
    Andersen, J. E. T.
    European analytical column no. 36 (January 2008)2009In: Journal of Analytical Chemistry, ISSN 1061-9348, E-ISSN 1608-3199, Vol. 64, no 3, p. 319-321Article in journal (Refereed)
  • 160.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Emons, Hendrik
    Andersen, Jens E. T.
    European analytical column No. 36 (January 2008)2008In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 391, no 4, p. 1109-1112Article in journal (Refereed)
  • 161.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Grasserbauer, Manfred
    Andersen, Jens E. T.
    European Analytical Column: Analytical chemistry faces challenges2009In: TrAC. Trends in analytical chemistry, ISSN 0165-9936, E-ISSN 1879-3142, Vol. 28, no 5, p. 515-518Article in journal (Refereed)
  • 162.
    Karlberg, Bo
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Korte, Ernst-Heiner
    European Analytical Column No. 35 (January 2007)2007In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 388, no 3, p. 513-515Article in journal (Refereed)
  • 163. Karlsson, Daniel
    et al.
    Dahlin, Jakob
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Marand, Åsa
    Skarping, Gunnar
    Dalene, Marianne
    Determination of airborne isocyanates as di-n-butylamine derivatives using liquid chromatography and tandem mass spectrometry2005In: Analytica Chimica Acta, ISSN 0003-2670, Vol. 534, no 2, p. 263-269Article in journal (Refereed)
  • 164. Karlsson, Daniel
    et al.
    Dahlin, Jakob
    Marand, Åsa
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Dalene, Marianne
    Determination of airborne isocyanates as di-n-butylamine derivatives using liquid chromatography and tandem mass spectrometryManuscript (Other academic)
  • 165. Karlsson, Daniel
    et al.
    Dahlin, Jakob
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Dalene, Marianne
    Determination of isocyanates, aminoisocyanates and amines in air formed during the thermal degradation of polyurethane2002In: Journal of Environmental Monitoring, ISSN 1464-0325, Vol. 4, no 2, p. 216-222Article in journal (Refereed)
  • 166.
    Karlsson, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Work Environment Chemistry, Lund University.
    Marand, Åsa
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of isocyanic acid in air2004In: Journal of Environmental Monitoring, ISSN 1464-0325, Vol. 3, no 4, p. 432-436Article in journal (Refereed)
    Abstract [en]

    A method is presented for the determination of isocyanic acid (ICA), HNCO, in air samples as a di-n-butylamine (DBA) derivative. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l–1 DBA in toluene. Quantification was made using liquid chromatography (LC) and electrospray mass spectrometry (MS) monitoring positive ions. The instrumental detection limit for the LC-MS was 10 fmol of ICA-DBA. ICA was generated by thermal decomposition of urea. A standard solution containing the DBA derivatives of ICA was prepared by collecting the emitted ICA in an impinger flask containing DBA. ICA in the reference solution was characterised by LC and time-of-flight (TOF) MS and quantified by LC chemiluminescent nitrogen detection (LC-CLND). The instrumental detection limit for the LC-CLND was 1 ng of nitrogen. ICA was emitted during thermal degradation of PFU resins and polyurethane (PUR) lacquers, from car metal sheets. ICA was the most dominant isocyanate and in PUR coating up to 8% of the total weight was emitted as ICA and for PFU resins up to 14% was emitted as ICA. When air samples were collected in an iron foundry during casting in sand moulds with furan resins, concentrations of ICA in the range 50–700 µg m–3 were found in the working atmosphere

  • 167.
    Karlsson, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Skarping, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dalene, Marianne
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of Cotinine in Urine and Saliva Using Hydrophilic Interaction Liquid Chromatography and Tandem Mass Spectrometry2011In: Analytical Chemistry Letters, ISSN 2229-7928, Vol. 1, no 1, p. 25-33Article in journal (Refereed)
    Abstract [en]

    A new simplified method for monitoring of cotinine in urine and saliva, based on hydrophilic interaction liquid chromatography (HILIC) and tandem mass spectrometry (MS) is presented. Work-up techniques based on filtration, using 0.45 μm pore sizepolypropylene filter, of crude urine and saliva and alkaline extraction of cotinine with methylene dichloride were studied. Multiple reaction monitoring (MRM) of the protonated molecular ions of cotinine and tri-deuterium labelled cotinine resulted in selective determinations with linear calibration graphs (correlation coefficients >0.999) The precision for 10 samples, containing 100 ng cotinine /ml, prepared from urine and saliva by methylene dichloride extraction or filtration were between 2 and 5 %. The detection limit for extracted and filtrated saliva was 2 fmol and for extracted and filtrated urine it was 5 and 9 fmol, respectively. Agreement was obtained for the two different work-up techniques. Extraction of urine/saliva enabled detection at lower levels (down to 5 pg cotinine/ml of urine) compared to filtration, since the possibility of enrichment of the sample but also due to reduction of interfering compounds present in the matrix. However, when performing large exposure studies with many samples to be analysed, the simplified and time saving work-up procedure obtained with filtration is valuable.

    The higher organic content of the effluent in the HILIC mode and a more efficient separation of polar compounds present in the matrix, favoured the electrospray ionisation compared to reversed phase (RP) LC, thus enabling lower detection limits.

  • 168. Karlsson, Oskar
    et al.
    Jiang, Liying
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Andersson, Marie
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Brittebo, Eva B.
    Protein association of the neurotoxin and non-protein amino acid BMAA (beta-N-methylamino-L-alanine) in the liver and brain following neonatal administration in rats2014In: Toxicology Letters, ISSN 0378-4274, E-ISSN 1879-3169, Vol. 226, no 1, p. 1-5Article in journal (Refereed)
    Abstract [en]

    The environmental neurotoxin beta-N-methylamino-L-alanine (BMAA) is not an amino acid that is normally found in proteins. Our previous autoradiographic study of H-3-labeled BMAA in adult mice unexpectedly revealed a tissue distribution similar to that of protein amino acids. The aim of this study was to characterize the distribution of free and protein-bound BMAA in neonatal rat tissues following a short exposure using autoradiographic imaging and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The autoradiographic imaging of C-14-L-BMAA demonstrated a distinct uptake of radioactivity that was retained following acid extraction in tissues with a high rate of cell turnover and/or protein synthesis. The UHPLC-MS/MS analysis conclusively demonstrated a dose-dependent increase of protein-associated BMAA in neonatal rat tissues. The level of protein-associated BMAA in the liver was more than 10 times higher than that in brain regions not fully protected by the blood-brain barrier which may be due to the higher rate of protein synthesis in the liver. In conclusion, this study demonstrated that BMAA was associated with rat proteins suggesting that BMAA may be mis-incorporated into proteins. However, protein-associated BMAA seemed to be cleared over time, as none of the samples from adult rats had any detectable free or protein-associated BMAA.

  • 169.
    Kempe, Henrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Advances in Separation Science: . Molecular Imprinting: Development of Spherical Beads and Optimization of the Formulation by Chemometrics.2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An intrinsic mathematical model for simulation of fixed bed chromatography was demonstrated and compared to more simplified models. The former model was shown to describe variations in the physical, kinetic, and operating parameters better than the latter ones. This resulted in a more reliable prediction of the chromatography process as well as a better understanding of the underlying mechanisms responsible for the separation. A procedure based on frontal liquid chromatography and a detailed mathematical model was developed to determine effective diffusion coefficients of proteins in chromatographic gels. The procedure was applied to lysozyme, bovine serum albumin, and immunoglobulin γ in Sepharose™ CL-4B. The effective diffusion coefficients were comparable to those determined by other methods.

    Molecularly imprinted polymers (MIPs) are traditionally prepared as irregular particles by grinding monoliths. In this thesis, a suspension polymerization providing spherical MIP beads is presented. Droplets of pre-polymerization solution were formed in mineral oil with no need of stabilizers by vigorous stirring. The droplets were transformed into solid spherical beads by free-radical polymerization. The method is fast and the performance of the beads comparable to that of irregular particles. Optimizing a MIP formulation requires a large number of experiments since the possible combinations of the components are huge. To facilitate the optimization, chemometrics was applied. The amounts of monomer, cross-linker, and porogen were chosen as the factors in the model. Multivariate data analysis indicated the influence of the factors on the binding and an optimized MIP composition was identified. The combined use of the suspension polymerization method to produce spherical beads with the application of chemometrics was shown in this thesis to drastically reduce the number of experiments and the time needed to design and optimize a new MIP.

  • 170.
    Kempe, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Axelsson, Anders
    Nilsson, Bernt
    Zacchi, Guido
    Simulation of chromatographic processes applied to separation of proteins1999In: Journal of Chromatography A, ISSN 00219673, Vol. 846, no 1, p. 1-12Article in journal (Refereed)
  • 171.
    Kempe, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Kempe, Maria
    Development and evaluation of spherical molecularly imprinted polymer beads2006In: Analytical Chemistry, ISSN 00032700, Vol. 78, no 11, p. 3659-3666Article in journal (Refereed)
  • 172.
    Kempe, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Kempe, Maria
    Novel Method for the synthesis of molecularly imprinted polymer bead libraries2004In: Macromolecular Rapid Communications, ISSN 10221336, Vol. 25, no 1, p. 315-320Article in journal (Refereed)
  • 173.
    Kempe, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Persson, Patrik
    Axelsson, Anders
    Nilsson, Bernt
    Zacchi, Guido
    Determination of diffusion coefficients of proteins in stationary phases by frontal chromatography2006In: Biotechnology and Bioengineering, ISSN 00063592, Vol. 93, no 4, p. 656-664Article in journal (Refereed)
  • 174.
    KM, Åberg
    et al.
    Stockholm University, Faculty of Science, Bergianska botaniska trädgården (tills m Kungl. Vet. Ak.).
    RJO, Torgrip
    Department of Analytical Chemistry.
    J, Kolmert
    I, Schuppe-Koistinen
    J, Lindberg
    Feature detection and alignment of hyphenated chromatographic-mass spectrometric data. Extraction of Pure Ion Chromatograms using Kalman tracking2008In: J Chromatogr A, Vol. 1192, no 1, p. 139-146Article in journal (Refereed)
  • 175. Kocbach Bølling, Anette
    et al.
    Totlandsdal, Annike Irene
    Sallsten, Gerd
    Braun, Artur
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Boman, Johan
    Dahlman, Hans Jørgen
    Sehlstedt, Maria
    Herseth, Jan Inge
    Wood smoke particles from different combustion phases induce similar pro-inflammatory effects in a co-culture of monocyte and pneumocyte cell lines2012In: Particle and Fibre Toxicology, ISSN 1743-8977, E-ISSN 1743-8977, Vol. 9, p. 45-Article in journal (Refereed)
    Abstract [en]

    Background: Exposure to particulate matter (PM) has been linked to several adverse cardiopulmonary effects, probably via biological mechanisms involving inflammation. The pro-inflammatory potential of PM depends on the particles' physical and chemical characteristics, which again depend on the emitting source. Wood combustion is a major source of ambient air pollution in Northern countries during the winter season. The overall aim of this study was therefore to investigate cellular responses to wood smoke particles (WSPs) collected from different phases of the combustion cycle, and from combustion at different temperatures. Results: WSPs from different phases of the combustion cycle induced very similar effects on pro-inflammatory mediator release, cytotoxicity and cell number, whereas WSPs from medium-temperature combustion were more cytotoxic than WSPs from high-temperature incomplete combustion. Furthermore, comparisons of effects induced by native WSPs with the corresponding organic extracts and washed particles revealed that the organic fraction was the most important determinant for the WSP-induced effects. However, the responses induced by the organic fraction could generally not be linked to the content of the measured polycyclic aromatic hydrocarbons (PAHs), suggesting that also other organic compounds were involved. Conclusion: The toxicity of WSPs seems to a large extent to be determined by stove type and combustion conditions, rather than the phase of the combustion cycle. Notably, this toxicity seems to strongly depend on the organic fraction, and it is probably associated with organic components other than the commonly measured unsubstituted PAHs.

  • 176. Kolmert, J
    et al.
    Bäckström, J
    Teiwik, P
    Linder, M
    Wahlström, E
    Åberg, K.M
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Torgrip, R.J.O
    Schuppe-Koistinen, I
    Lindberg, J
    Analysis of human plasma samples using a LC-ESI-MS based platform to screen for safety biomarkers2007In: Metabolomics Society 3rd Annual Conference, 2007Conference paper (Other (popular science, discussion, etc.))
  • 177.
    Kolmert, J.
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Forngren, B.
    Lindberg, J.
    Ohd, J.
    Åberg, Magnus
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, G.
    Moritz, T.
    Nordström, A.
    A quantitative LC/MS method targeting urinary 1-methyl-4-imidazoleacetic acid for safety monitoring of the global histamine turnover in clinical studies2014In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 6, p. 1751-1762Article in journal (Refereed)
    Abstract [en]

    Anaphylaxis is a potentially life-threatening condition triggered mainly by the release of inflammatory mediators, notably histamine. In pharmaceutical research, drug discovery, and clinical evaluation, it may be necessary to accurately assess the potential of a compound, event, or disorder to promote the release of histamine. In contrast to the measurement of plasma histamine, determination of the stable metabolite 1-methyl-4-imidazoleacetic acid (tele-MIAA) in urine provides a noninvasive and more reliable methodology to monitor histamine release. This study presents a repeatable high-performance liquid chromatography coupled to electrospray mass spectrometry (LC-ESI-MS) method where tele-MIAA is baseline separated from its structural isomer 1-methyl-5-imidazoleacetic acid (pi-MIAA) and an unknown in human urine. The ion-pairing chromatography method, in reversed-phase mode, based on 0.5 mM tridecafluoroheptanoic acid demonstrated high repeatability and was applied in a clinical development program that comprised a large number of clinical samples from different cohorts. The inter- and intra-run precision of the method for tele-MIAA were 8.4 and 4.3 %, respectively, at the mean urinary concentration level, while method accuracy was between -16.2 and 8.0 % across the linear concentration range of 22-1,111 ng mL(-1). Overall, method precision was greater than that reported in previously published methods and enabled the identification of gender differences that were independent of age or demography. The median concentration measured in female subjects was 3.0 mu mol mmol(-1) of creatinine, and for male subjects, it was 2.1 mu mol mmol(-1) of creatinine. The results demonstrate that the method provides unprecedented accuracy, precision, and practicality for the measurement of tele-MIAA in large clinical settings.

  • 178. Kubán, P
    et al.
    Karlberg, B
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Flow/sequential injection sample treatment coupled to capillary electrophoresis. A review2009In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 648, p. 129-145Article in journal (Refereed)
    Abstract [en]

    Various flow sample handling approaches coupled to capillary electrophoresis (CE) are reviewed, covering the research in this field in the 12 years since the milestone year of 1997, when practical interfaces to on-line couple flow injection (FI) and capillary electrophoresis were first developed independently by two research groups. Some previous attempts are also presented. Since 1997 a plethora of ingenious coupled systems have been developed. Although several reviews are available on various aspects of the topic, we have opted for a comprehensive overview of all FI-CE systems, as well as related and similar systems. This coupling has thus also led to the development of systems based on hybrids between the classical and microchip approaches. Truly microchip FI-CE systems are also included in this review. The developed systems have been used for various sample treatments, including on-line membrane-assisted sample treatment, column-based preconcentration, on-line derivatization and monitoring, to name just a few. The utility of coupling flow sampling to CE has been demonstrated in various practical applications that are discussed in detail. The current state-of-the-art and foreseeable future developments are also discussed.

  • 179.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Shariatgorji, Mohammadreza
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hansson, Örjan
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Light-Induced Water Oxidation by a Ru-complex Containing a Bio-Inspired Ligand2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 28, p. 7953-7959Article in journal (Refereed)
    Abstract [en]

    The new Ru-complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 could efficiently catalyze water oxidation using CeIV and RuIII as chemical oxidants. More importantly, this complex has sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.

  • 180.
    Kölhed, Malin
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Novel on-line mid infrared detection strategies in capillary electrophoretic systems2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Infrared absorption spectra can provide analytically useful information on a large variety of compounds, ranging from small ions to large biological molecules. In fact, all analytes that possess a dipole moment that changes during vibration are infrared-active. The infrared (IR) spectrum can be subdivided into far-, mid- and near- regions. The focus of attention in this thesis is the mid-IR region, in which the fundamental vibrations of most organic compounds are located, thus providing scope for positive structural identification. However, while such near-ubiquitous signals can be very useful for monitoring simple molecules in simple systems, they can be increasingly disadvantageous as the number of analytes and/or the complexity of the sample matrix increases. Thus, hyphenation to a separation system prior to detection is desirable. Paper I appended to this thesis presents (for the first time) the on-line hyphenation between Fourier transform infrared spectroscopy, FTIR, and capillary zone electrophoresis, CZE. CZE is a highly efficient separation technique that separates ionic analytes with respect to their charge-to-size ratio. It is most commonly performed in aqueous buffers in fused silica capillaries. Since these capillaries absorb virtually all infrared light an IR-transparent flow cell had to be developed. In further studies (Paper II) the applicability of CZE is expanded to include neutral analytes by the addition of micelles to the buffer, and micellar electrokinetic chromatography, MEKC, was successfully hyphenated to FTIR for the first time. Paper III describes an application of the on-line CZE-FTIR technique in which non-UV-absorbing analytes in a complex matrix were separated, identified and quantified in one run.

    Measuring aqueous solutions in the mid-IR region is not straightforward since water absorbs intensely in this region, sometimes completely, leaving no transmitted, detectable light. For this reason, quantum cascade lasers are interesting. These lasers represent a new type of mid-IR semiconducting lasers with high output power due to their ingenious design. The laser action lies within one conduction band (intersubband) and can be tailored to emit light in the entire mid-IR region using the same semiconducting material. To investigate their potential to increase the optical path length in aqueous solutions, these lasers were used with an aqueous flow system (Paper IV), and the experience gained in these experiments enabled hyphenation of such lasers to a CZE system (Paper V).

  • 181.
    Kölhed, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Haberkorn, Michael
    Pustogov, Viktor
    Mizaikoff, Boris
    Frank, Johannes
    Karlberg, Bo
    Lendl, Bernhard
    Assessment of quantum cascade lasers as mid infrared light sources for measurements of aqueous solutions2002In: Vibrational Spectroscopy, ISSN 0924-2031, Vol. 29, no 1-2, p. 283-289Article in journal (Refereed)
  • 182.
    Kölhed, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hinsmann, Peter
    Lendl, Bernhard
    Karlberg, Bo
    Micellar electrokinetic chromatography with on-line Fourier transform infrared detection2003In: Electrophoresis, ISSN 0173-0835, Vol. 24, no 4, p. 687-692Article in journal (Refereed)
  • 183.
    Kölhed, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hinsmann, Peter
    Svasek, Peter
    Frank, Johannes
    Karlberg, Bo
    Lendl, Bernhard
    On-line Fourier transform infrared detection in capillary electrophoresis2002In: Analytical Chemistry, ISSN 0003-2700, Vol. 74, no 15, p. 3843-3848Article in journal (Refereed)
  • 184.
    Kölhed, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Bo
    Capillary electrophoretic separation of sugars in fruit juices using on-line mid infrared Fourier transform detection2005In: Analyst, ISSN 0003-2654, Vol. 130, no 5, p. 772-778Article in journal (Refereed)
  • 185.
    Kölhed, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Schaden, Stefan
    Karlberg, Bo
    Lendl, Bernhard
    On-line hyphenation of quantum cascade laser and capillary electrophoresis2005In: Journal of Chromatography A, ISSN 0021-9673, Vol. 1083, no 1-2, p. 199-204Article in journal (Refereed)
  • 186.
    Larson, Tuula
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air2011In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 400, no 2, p. 449-458Article in journal (Refereed)
    Abstract [en]

    The monitoring of radioactive xenon isotopes is one of the principal methods for the detection of nuclear explosions in order to identify clandestine nuclear testing. In this work, a miniaturized, multiple-oven, six-column, preparative gas chromatograph was constructed in order to isolate trace quantities of radioactive xenon isotopes from ambient air, utilizing nitrogen as the carrier gas. The multidimensional chromatograph comprised preparative stainless steel columns packed with molecular sieves, activated carbon, and synthetic carbon adsorbents (e.g., AnasorbA (R)-747 and CarbosphereA (R)). A combination of purification techniques-ambient adsorption, thermal desorption, back-flushing, thermal focusing, and heart cutting-was selectively optimized to produce a well-defined xenon peak that facilitated reproducible heart cutting and accurate quantification. The chromatographic purification of a sample requires approximately 4 h and provides complete separation of xenon from potentially interfering components (such as water vapor, methane, carbon dioxide, and radon) with recovery and accuracy close to 100%. The preparative enrichment process isolates and concentrates a highly purified xenon gas fraction that is suitable for subsequent ultra-low-level gamma-, /gamma-spectroscopic or high-resolution mass spectrometric measurement (e.g., to monitor the gaseous fission products of nuclear explosions at remote locations). The Xenon Processing Unit is a free-standing, relatively lightweight, and transportable system that can be interfaced to a variety of sampling and detection systems. It has a relatively inexpensive, rugged, and compact modular (19-inch rack) design that provides easy access to all parts for maintenance and has a low power requirement.

  • 187.
    Leck, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gao, Qiuju
    Stockholm University, Faculty of Science, Department of Meteorology .
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-resolved atmospheric particulate polysaccharides in the high summer Arctic2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 24, p. 12573-12588Article in journal (Refereed)
    Abstract [en]

    Size-resolved aerosol samples for subsequent quantitative determination of polymer sugars (polysaccharides) after hydrolysis to their subunit monomers (monosaccharides) were collected in surface air over the central Arctic Ocean during the biologically most active summer period. The analysis was carried out by novel use of liquid chromatography coupled with highly selective and sensitive tandem mass spectrometry. Polysaccharides were detected in particle sizes ranging from 0.035 to 10 mu m in diameter with distinct features of heteropolysaccharides, enriched in xylose, glucose + mannose as well as a substantial fraction of deoxysugars. Polysaccharides, containing deoxysugar monomers, showed a bimodal size structure with about 70% of their mass found in the Aitken mode over the pack ice area. Pentose (xylose) and hexose (glucose + mannose) had a weaker bimodal character and were largely found with super-micrometer sizes and in addition with a minor sub-micrometer fraction. The concentration of total hydrolysable neutral sugars (THNS) in the samples collected varied over two orders of magnitude (1 to 160 pmol m(-3)) in the supermicrometer size fraction and to a somewhat lesser extent in sub-micrometer particles (4 to 140 pmol m(-3)). Lowest THNS concentrations were observed in air masses that had spent more than five days over the pack ice. Within the pack ice area, about 53% of the mass of hydrolyzed polysaccharides was detected in sub-micrometer particles. The relative abundance of sub-micrometer hydrolyzed polysaccharides could be related to the length of time that the air mass spent over pack ice, with the highest fraction (> 90 %) observed for > 7 days of advection. The aerosol samples collected onboard ship showed similar monosaccharide composition, compared to particles generated experimentally in situ at the expedition's open lead site. This supports the existence of a primary particle source of polysaccharide containing polymer gels from open leads by bubble bursting at the air-sea interface. We speculate that the occurrence of atmospheric surface-active polymer gels with their hydrophilic and hydrophobic segments, promoting cloud droplet activation, could play a potential role as cloud condensation nuclei in the pristine high Arctic.

  • 188.
    Leck, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Qiuju, Gao
    Stockholm University, Faculty of Science, Department of Meteorology .
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-resolved polysaccharides in summer high Arctic aerosol relevant to cloud formation.Manuscript (preprint) (Other academic)
  • 189.
    Leonova, Ekaterina
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Eden, Mattias
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Solid-state NMR investigations of Si-29 and N-15 enriched silicon nitride2009In: Solid State Nuclear Magnetic Resonance, ISSN 0926-2040, E-ISSN 1527-3326, Vol. 36, no 1, p. 11-18Article in journal (Refereed)
  • 190.
    Li, Hang
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Polycyclic aromatic compounds (PAC) in diesel fuels and exhaust emissions: aspects of sampling techniques, chemical determination, multivariate data interpretation and PAC emissions reduction1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The rapid growth in the number of motor vehicles has raised serious environmental health hazard problems in urban areas associated with vehicle exhaust emissions. Exhaust emissions from heavy duty diesel vehicles are very complex mixtures containing thousands of chemical components distributed between the particulate, semivolatile and gaseous phases. So far only those regulated pollutant are legislated, and it is important to be aware of the contribution of unregulated pollutants, as potential health effects can be linked to these pollutants. Polycyclic aromatic compounds (PAC) are an important group of unregulated compounds that exist in diesel exhaust emissions. Some PAC represent some of the most important chemical carcinogens known to humans today.

    This thesis addresses PAC in diesel fuels and exhaust emissions from heavy duty diesel vehicles. Sampling techniques associated with the particulate and semivolatile phases are discussed. For the particulate phase, Teflon coated glass fibre filters gave a good recovery of PAC; for the semivolatile phase, polyurethane foam (PUF) plugs gave the highest recovery of PAC. Chemical determination of PAC by capillary gas chromatography-mass spectrometry (GC-MS) was carried out. For Nitro-PAH determination, high performance liquid chromatography with chemiluminescence detection (HPLC-CL) technique was developed, high sensitivity is demonstrated. Nitro-PAH analysis using both HPLC with fluorescence detection (HPLC-FL) and HPLC-CL techniques were performed on the diesel exhaust emission sample matrix.

    Multivariate analysis methods such as principal component analysis (PCA) and partial least squares projection on latent structures (PLS) have been used to investigate and interpret the correlation of PAC in fuels with PAC in emissions, and the correlation of chemical data with biological (Ames test) data.

    The ability of diesel emission extracts fractions and subtractions concerning their PAC content, to compete with 2,3,7,8-tetrachloro[l,6-^H]dibenzo-p-dioxin (TCDD) for the dioxin (Ah) receptor was determined and interpreted.

    Particulate traps and catalytic converters used on heavy-duty diesel vehicles are powerful ways to reduce exhaust emissions. The pollutants emitted in the regeneration mode of a particulate trap are negligible. By an appropriate selection of fuel, the PAC emissions can be reduced from today's level by a factor up to 10. By using a particulate trap and catalytic converter the PAC emissions can also be reduced by a factor of 5-10. It is possible to further reduce PAC emissions by combining diesel fuel selection with the use of particulate traps and catalytic converters. 

  • 191.
    Lim, Hwanmi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Jarvis, Ian
    Mattsson, Åse
    Dreij, Kristian
    Stenius, Ulla
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Benzo[a]pyrene-specific online high-performance liquid chromatography fractionation of air particulate extracts–A tool for evaluating biological interactions2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1355, p. 100-106Article in journal (Refereed)
    Abstract [en]

    Benzo[a]pyrene (B[a]P) is a known human carcinogen and is commonly used as a surrogate for assessing the carcinogenic risk posed by complex mixtures of polycyclic aromatic hydrocarbons (PAHs) present in air particulate matter (PM). However, studies have shown that using B[a]P as a surrogate may underestimate the carcinogenic potential of PAH mixtures, as the risk assessment approach does not consider interaction effects. Thus, toxicological studies using B[a]P to assess its carcinogenic potential in environmentally derived complex mixtures, as opposed to single compound experiments, could improve risk assessment. The intention of the present study was to develop an online HPLC fractionation system for the selective removal of B[a]P from air PM extracts. Two serial pyrenylethyl (PYE) columns enabled selective separation of B[a]P from its isomers and other PAHs as well as a short fractionation cycle of 30 minutes. One run consisted of three collection steps: the first fraction contained PAHs eluting earlier than B[a]P, the second contained B[a]P and the last contained later-eluting PAHs. The selectivity and recovery of the system was investigated using extracts of Stockholm air PM samples. The overall recovery for all PAHs was approximately 80%, and the system proved to be selective, as it removed 94% of B[a]P and less than 3% of benzo[b]fluoranthene from the complex PAH mixture. Exposing human cells to blanks generated by the fractionation system did not induce cytotoxicity or DNA damage signalling. In conclusion, the online HPLC system was selective for B[a]P fractionation whilst minimising run-to-run variation and allowing repeated fractionations for larger samples due to its relatively short run time

  • 192. Lin, Yuan
    et al.
    Aldaeus, Fredrik
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Roeraade, Johan
    Amberg, Gustav
    Simulation of dielectrophoretic motion of microparticles using a molecular dynamics approach2006In: Proceedings of ICNMM 2006, no 96095Article in journal (Refereed)
  • 193.
    Luongo, Giovanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Quinolines in clothing textiles-a source of human exposure and wastewater pollution?2014In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 12, p. 2747-2756Article in journal (Refereed)
    Abstract [en]

    A production process in which the use of various types of chemicals seems to be ubiquitous makes the textile industry a growing problem regarding both public health as well as the environment. Among several substances used at each stage, the present study focuses on the quinolines, a class of compounds involved in the manufacture of dyes, some of which are skin irritants and/or classified as probable human carcinogens. A method was developed for the determination of quinoline derivatives in textile materials comprising ultrasound-assisted solvent extraction, solid phase extraction cleanup, and final analysis by gas chromatography/mass spectrometry. Quinoline and ten quinoline derivatives were determined in 31 textile samples. The clothing samples, diverse in color, material, brand, country of manufacture, and price, and intended for a broad market, were purchased from different shops in Stockholm, Sweden. Quinoline, a possible human carcinogen, was found to be the most abundant compound present in almost all of the samples investigated, reaching a level of 1.9 mg in a single garment, and it was found that quinoline and its derivatives were mainly correlated to polyester material. This study points out the importance of screening textiles with nontarget analysis to investigate the presence of chemicals in an unbiased manner. Focus should be primarily on clothing worn close to the body.

  • 194.
    Maddalo, Gianluca
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Strategies to explore the membrane proteome of a cell2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cell envelope plays key roles in numerous processes such as maintaining cellular integrity, communication with other cells, signal transduction, maintenance of cellular homeostasis, and regulation of the traffic of molecules between the cell and the extracellular milieu. Essential membrane components in many of these processes are proteins. It is estimated that ~20-30% of the predicted open reading frames (ORFs) of all organisms encode membrane proteins. Furthermore, two thirds of drug targets are membrane proteins. However, despite their importance, membrane proteins have so far been mostly neglected in most proteomic studies, due to the inherent challenges in analyzing them.

    The focus of this thesis is to devise strategies that allow investigation of membrane proteins and their associated complexes. Optimization of sample preparation in the underlying studies has allowed important goals to be reached in membrane protein analyses at various levels such as elucidation of their primary structure by collision-induced dissociation (CID) and electron-capture dissociation (ECD) mass spectrometry (MS), profiling membrane proteins and their complexes, the discovery of novel protein complexes, definition of their topology, and unambiguous identification of protein-bound ligand(s). This thesis paves the way for better characterization of membrane proteins and their assemblies hinting towards the crucial role(s) they play in maintaining normal cell physiology.

  • 195.
    Maddalo, Gianluca
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Chovanec, Peter
    Stenberg-Bruzell, Filippa
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Nielsen, Hailyn V
    Jensen-Seaman, Michael
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Kline, Kimberly
    Daley, Daniel
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A reference map of the membrane proteome of Enterococcus faecalis2011In: Proteomics, ISSN 1615-9853, E-ISSN 1615-9861, Vol. 11, no Special issue, p. 3935-3941Article in journal (Refereed)
    Abstract [en]

    Enterococcus faecalis is a gram-positive bacterium that is part of the indigenous microbiotica of humans and animals as well as an opportunistic pathogen. In this study, we have fractionated the membrane proteome of E. faecalis and identified many of its constituents by mass spectrometry. We present blue native-/SDS-PAGE reference maps that contain 102 proteins. These proteins are important for cellular homeostasis, virulence, and antibiotic intervention. Intriguingly, many proteins with no known function were also identified, indicating that there are substantial gaps in the knowledge of this organism's biology. On a more limited scale, we also provide insight into the composition of membrane protein complexes. This study is a first step toward elucidating the membrane proteome of E. faecalis, which is critical for a better understanding of how this bacterium interacts with a host and with the extracellular milieu.

  • 196.
    Maddalo, Gianluca
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Proteomic platform for the analysis of inner and outer membrane proteomes in Escherichia coli2009Conference paper (Other academic)
  • 197.
    Maddalo, Gianluca
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Adams, Christopher M.
    Fung, Eva
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Zubarev, Roman A.
    Sedzik, Jan
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Porcine P2 myelin protein primary structure and bound fatty acids determined by mass spectrometry2010In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 397, no 5, p. 1903-1910Article in journal (Refereed)
    Abstract [en]

    Complementary collision-induced/electron capture dissociation Fourier-transform ion cyclotron resonance mass spectrometry was used to fully sequence the protein P2 myelin basic protein. It is an antigenic fatty-acid-binding protein that can induce experimental autoimmune neuritis: an animal model of Guillain-Barre syndrome, a disorder similar in etiology to multiple sclerosis. Neither the primary structure of the porcine variant, nor the fatty acids bound by the protein have been well established to date. A 1.8-angstrom crystal structure shows but a bound ligand could not be unequivocally identified. A protocol for ligand extraction from protein crystals has been developed with subsequent gas chromatography MS analysis allowing determination that oleic, stearic, and palmitic fatty acids are associated with the protein. The results provide unique and general evidence of the utility of mass spectrometry for characterizing proteins from natural sources and generating biochemical information that may facilitate attempts to elucidate the causes for disorders such as demyelination.

  • 198.
    Maddalo, Gianluca
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Stenberg-Bruzell, Filippa
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Götzke, Hansjörg
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Toddo, Stephen
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Patrik, Björkholm
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Eriksson, Hanna
    Chovanec, Peter
    Genevaux, Pierre
    Lehtiö, Janne
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Daley, Daniel O.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Systematic Analysis of Native Membrane Protein Complexes in Escherichia coli2011In: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 10, no 4, p. 1848-1859Article in journal (Refereed)
    Abstract [en]

    The cell envelope of Escherichia coli is an essential structure that modulates exchanges between the cell and the extra-cellular milieu. Previous proteomic analyses have suggested that it contains a significant number of proteins with no annotated function. To gain insight into these proteins and the general organization of the cell envelope proteome, we have carried out a systematic analysis of native membrane protein complexes. We have identified 30 membrane protein complexes (6 of which are novel) and present reference maps that can be used for cell envelope profiling. In one instance, we identified a protein with no annotated function (YfgM) in a complex with a well-characterized periplasmic chaperone (PpiD). Using the guilt by association principle, we suggest that YfgM is also part of the periplasmic chaperone network. The approach we present circumvents the need for engineering of tags and protein overexpression. It is applicable for the analysis of membrane protein complexes in any organism and will be particularly useful for less-characterized organisms where conventional strategies that require protein engineering (i.e., 2-hybrid based approaches and TAP-tagging) are not feasible.

  • 199.
    Marand, Åsa
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Isocyanates and Amines – Sampling and Analytical Procedures2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis covers sampling and analytical procedures for isocyanates (R-NCO) and amines (R-NH2), two kinds of chemicals frequently used in association with the polymeric material polyurethane (PUR). Exposure to isocyanates may result in respiratory disorders and dermal sensitisation, and they are one of the main causes of occupational asthma. Several of the aromatic diamines associated with PUR production are classified as suspected carcinogens. Hence, the presence of these chemicals in different exposure situations must be monitored.

    In the context of determining isocyanates in air, the methodologies included derivatisation with the reagent di-n-butylamine (DBA) upon collection and subsequent determination using liquid chromatography (LC) and mass spectrometric detection (MS). A user-friendly solvent-free sampler for collection of airborne isocyanates was developed as an alternative to a more cumbersome impinger-filter sampling technique. The combination of the DBA reagent together with MS detection techniques revealed several new exposure situations for isocyanates, such as isocyanic acid during thermal degradation of PUR and urea-based resins. Further, a method for characterising isocyanates in technical products used in the production of PUR was developed. This enabled determination of isocyanates in air for which pure analytical standards are missing. Tandem MS (MS/MS) determination of isocyanates in air below 10-6 of the threshold limit values was achieved.

    As for the determination of amines, the analytical methods included derivatisation into pentafluoropropionic amide or ethyl carbamate ester derivatives and subsequent MS analysis. Several amines in biological fluids, as markers of exposure for either the amines themselves or the corresponding isocyanates, were determined by LC-MS/MS at amol level. In aqueous extraction solutions of flexible PUR foam products, toluene diamine and related compounds were found.

    In conclusion, this thesis demonstrates the usefulness of well characterised analytical procedures and techniques for determination of hazardous compounds. Without reliable and robust methodologies there is a risk that exposure levels will be underestimated or, even worse, that relevant compounds will be completely missed.

  • 200. Marand, Åsa
    et al.
    Dahlin, Jakob
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlsson, Daniel
    Skarping, Gunnar
    Dalene, Marianne
    Determination of technical grade isocyanates used in the production of polyurethane plastics2004In: Journal of Environmental Monitoring, ISSN 1464-0325, Vol. 6, no 7, p. 606-614Article in journal (Refereed)
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