Change search
Refine search result
12 1 - 50 of 91
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ahlford, Annika
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Molecular Medicine.
    Kjeldsen, Bastian
    Reimers, Jakob
    Lundmark, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Molecular Medicine.
    Romani, Massimo
    Wolff, Anders
    Syvänen, Ann-Christine
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Molecular Medicine.
    Brivio, Monica
    Dried reagents for multiplex genotyping by tag-array minisequencing to be used in microfluidic devices2010In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 135, no 9, p. 2377-2385Article in journal (Refereed)
    Abstract [en]

    We present an optimized procedure for freeze-drying and storing reagents for multiplex PCR followed by genotyping using a tag-array minisequencing assay with four color fluorescence detection which is suitable for microfluidic assay formats. A test panel was established for five cancer mutations in three codons (175, 248 and 273) of the tumor protein gene (TP53) and for 13 common single nucleotide polymorphisms (SNPs) in the TP53 gene. The activity of DNA polymerase was preserved for six months of storage after freeze-drying, and the half-life of activities of exonuclease I and shrimp alkaline phosphatase were estimated to 55 and 200 days, respectively. We conducted a systematic genotyping comparison using freeze-dried and liquid reagents. The accuracy of successful genotyping was 99.1% using freeze-dried reagents compared to liquid reagents. As a proof of concept, the genotyping protocol was carried out with freeze-dried reagents stored in reaction chambers fabricated by micromilling in a cyclic olefin copolymer substrate. The results reported in this study are a key step towards the development of an integrated microfluidic device for point-of-care DNA-based diagnostics.

  • 2.
    Artemenko, Konstantin A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Lind, Sara Bergström
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology.
    Elfineh, Lioudmila
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Genomics.
    Mayrhofer, Corina
    Zubarev, Roman A.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Pettersson, Ulf
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Genomics.
    Optimization of immunoaffinity enrichment and detection: toward a comprehensive characterization of the phosphotyrosine proteome of K562 cells by liquid chromatography-mass spectrometry2011In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 136, no 9, p. 1971-1978Article in journal (Refereed)
    Abstract [en]

    Phosphorylation of protein tyrosine residues regulates many cell functions and has also been proved to be involved in oncogenesis. Thus, the identification of the phosphotyrosine (pTyr) proteome of cells is a very important task. Since tyrosine phosphorylation represents only around 1% of the total human phosphoproteome, the study of pTyr proteins is rather challenging. Here we report the optimization study of the phosphotyrosine proteome using K562 cells as a model system. A substantial segment of the phosphotyrosine proteome of K562 cells was characterized by immunoaffinity enrichment with 4G10 and PYKD1 antibodies followed by LC-MS/MS analysis. 480 non-redundant pTyr peptides corresponding to 342 pTyr proteins were found. 141 pTyr peptides were not described elsewhere. The mass spectrometry approach involving high-resolving FTMS analysis of precursor ions and subsequent detection of CID fragments in a linear ion trap was considered as optimal. For detection of low abundant pTyr peptides pooling of individual immunoaffinity enrichments for one LC-MS/MS analysis was crucial. The enrichment properties of the monoclonal PYKD1 antibody were presented for the first time, also in comparison to the 4G10 antibody. PYKD1 was found to be more effective for protein enrichment (1.2 and 5% efficiency at peptide and protein level correspondingly), while 4G10 showed better results when peptide enrichment was performed (15% efficiency versus 3.6% at protein level). Substantially different subsets of the phosphoproteome were enriched by these antibodies. This finding together with previous studies demonstrates that comprehensive pTyr proteome characterization by immunoprecipitation requires multiple antibodies to be used for the affinity enrichment.

  • 3.
    Axelsson, Mikael
    et al.
    Luleå tekniska universitet.
    Rodushkin, Ilya
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Multielemental analysis of Mn-Fe nodules by ICP-MS: optimisation of analytical method2002In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 127, no 1, p. 76-82Article in journal (Refereed)
    Abstract [en]

    Two acid digestion procedures (microwave-assisted and room temperature) were developed for the quantitative analysis of ferromanganese nodules by inductively coupled plasma double focusing sector field mass spectrometry (ICP-SFMS). Different compositions of the acid mixture, dilution factors and corrections for spectral interferences were tested. A combination of nitric, hydrochloric and hydrofluoric acids is necessary for complete sample digestion, with lowest acid to sample ratios (v/m) of 15 and 1.5. respectively, for the last two acids. Sample dilution factors higher than 2 X 104 should be used in order to decrease matrix effects and provide robust long-term instrumental operation. In spite of high dilution. method detection limits in the sub-mug g(-1) range were obtained for 54 out of 71 elements tested. due to the high detection capability of ICP-SFMS, as well as the special care taken to ensure the purity of reagents, to clean the instrument sample introduction system and to minimise sample handling. Owing to the presence of unresolved (at the resolution available) spectral interferences, accurate determination of Au, Hg, Os, Pd, Re and Rh is impossible without matrix separation. The accuracy of the entire analytical method was tested by the analysis of two nodule reference materials. The results generated agreed to within +/-2% for about 10, within +/-10% for more than 40 and within +/-20% for about 50 of 53 elements for which certified, recommended or literature values are available. A precision better than 3%, expressed as the between-digestion relative standard deviation (n=4). was obtained for the majority of elements, except in cases limited by low analyte concentrations

  • 4.
    Bailly-Chouriberry, Ludovic
    et al.
    Laboratoire des Courses Hippiques (LCH), France.
    Cormant, Florence
    Laboratoire des Courses Hippiques (LCH), France.
    Garcia, Patrice
    Laboratoire des Courses Hippiques (LCH), France.
    Lönnberg, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Szwandt, Simon
    Thermo Fisher Scientific, Hemel Hempstead, UK.
    Bondesson, Ulf
    Dept. of Chemistry, Environment and Feed Hygiene, The National Veterinary Institute (SVA), Uppsala, Sweden.
    Popot, Marie-Agnes
    Laboratoire des Courses Hippiques (LCH), France.
    Bonnaire, Yves
    Laboratoire des Courses Hippiques (LCH), France.
    A new analytical method based on anti-EPO monolith column and LC-FAIMS-MS/MS for the detection of rHuEPOs in horse plasma and urine samples2012In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 137, no 10, p. 2445-2453Article in journal (Refereed)
    Abstract [en]

    Recombinant human erythropoietin (rHuEPO) is a 30-34 kDa glycoprotein banned by the racing authorities. For some years this molecule has been detected in race horses in USA and in Europe, and even in racing camels. Although direct methods to differentiate horse endogenous EPO and rHuEPO have been developed either by LC-MS/MS or by isoelectric focusing (IEF) with double-blotting, the short confirmation time of such prohibited hormone in plasma remains a problem for horseracing doping control laboratories. In order to improve the rHuEPOs confirmation process in horse plasma or urine in terms of reliability and delay, a small anti-EPO monolith membrane contained in a disposable column (anti-EPO monolith column) has been successfully used and validated (n = 10). This new sample preparation, combined with LC-FAIMS-MS/MS, has been performed on plasma and urine samples collected from one horse which received an Eprex[registered sign] treatment during six consecutive days and a second one with a single injection of Aranesp[registered sign]. This inventive technology allowed the possibility to confirm the presence of rHuEPO within one day with a limit of detection validated for both urine and plasma at 250 pg mL-1 by means of a disposable, ready to use immunoaffinity column. The lower limit of detection (LLOD) obtained for each matrix was 100 pg mL-1. These results provide an important improvement for rHuEPO doping control in horseracing especially the possibility to confirm these banned molecules in both matrices, urine and plasma, with a confidence of two specific target peptides.

  • 5.
    Baldassarre, Maurizio
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Pushing the detection limit of infrared spectroscopy for structural analysis of dilute protein samples.2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 21, p. 5393-5399Article in journal (Refereed)
    Abstract [en]

    Fourier-transform infrared spectroscopy is a powerful and versatile tool to investigate the structure and dynamics of proteins in solution. The intrinsically low extinction coefficient of the amide I mode, the main structure-related oscillator, together with the high infrared absorptivity of aqueous media, requires that proteins are studied at high concentrations (>10 mg L(-1)). This may represent a challenge in the study of aggregation-prone proteins and peptides, and questions the significance of structural data obtained for proteins physiologically existing at much lower concentrations. Here we describe the development of a simple experimental approach that increases the detection limit of protein structure analysis by infrared spectroscopy. Our approach relies on custom-made filters to isolate the amide I region (1700-1600 cm(-1)) from irrelevant spectral regions. The sensitivity of the instrument is then increased by background attenuation, an approach consisting in the use of a neutral density filter, such as a non-scattering metal grid, to attentuate the intensity of the background spectrum. When the filters and grid are combined, a 2.4-fold improvement in the noise level can be obtained. We have successfully tested this approach using a highly diluted solution of pyruvate kinase in deuterated medium (0.2% w/v), and found that it provides spectra of a quality comparable to those recorded with a 10-fold higher protein concentration.

  • 6.
    Baldassarre, Maurizio
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    The carbonate/bicarbonate system as a pH indicator for infrared spectroscopy2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 9, p. 2167-2176Article in journal (Refereed)
    Abstract [en]

    Caged compounds capable of inducing large pH-jumps upon UV illumination have represented a breakthrough in time-resolved infrared spectroscopy of acidification-triggered phenomena, but their use is hampered by the inability to control the initial pH as well as to measure the final pH in mu L volumes. We have developed an experimental approach that accurately measures the initial and final pH values in pH-jump experiments. Our approach exploits the concomitant presence of two or more inorganic ions, such as carbonate and bicarbonate, that are added to the sample at a known concentration. The difference spectrum obtained in the infrared measurement is fitted to isolate the bands arising from the appearance or disappearance of either protonation state, and is then compared to a synthetic library of difference spectra generated using both qualitative (band position and width, extinction coefficient, pK) and quantitative (concentration, pathlength) parameters of the reporter ions. We have tested this approach in UV-photolysis experiments of 1-(2-nitrophenyl)ethyl sulfate in the presence of different concentrations of Na2CO3 and successfully used the infrared absorption of the carbonate and the bicarbonate ions to determine the initial and final pH values before and after the pH-jump, respectively.

  • 7.
    Baldassarre, Maurizio
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Bennett, Matthew
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Simultaneous acquisition of infrared, fluorescence and light scattering spectra of proteins: direct evidence for pre-fibrillar species in amyloid fibril formation2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 3, p. 963-973Article in journal (Refereed)
    Abstract [en]

    Different spectroscopic approaches are often used to probe specific aspects of amyloid fibril formation but are usually performed separately and under different conditions. This makes it problematic to relate different aspects of the aggregation process when these are monitored by different methods. We report on a multispectral approach for simultaneous acquisition of infrared, fluorescence and light scattering spectra of proteins undergoing aggregation. We have applied our approach to study beta-lactoglobulin, a milk protein known to form amyloid fibrils under well-established conditions. Our real-time multispectral measurements show that unfolding of this protein is followed by formation of early aggregates consisting of intermolecular beta-sheets with a typical infrared absorption at similar to 1619 cm(-1) in (H2O)-H-2. These aggregates, which lead to an increase in the light scattering signal, do not bind the amyloid-specific fluorophore ThT and therefore consist of oligomers or protofibrils. Fibril growth is then observed as a sigmoidal increase in ThT fluorescence. After similar to 25 h, a plateau is observed in the intensities of ThT emission and of the band at 1619 cm(-1), indicating that no new fibrils are forming. However, a second phase in the light scattering signal taking place after similar to 25 h suggests that the fibrils are assembling into larger structures, known as mature fibrils. This is associated with an upshift of the main beta-sheet band in the infrared spectrum. TEM analyses confirmed the existence of thick fibrils comprising 3-5 filaments.

  • 8.
    Bergman, Hilde-Marlene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lanekoff, Ingela
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Profiling and quantifying endogenous molecules in single cells using nano-DESI MS2017In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 142, no 19, p. 3639-3647Article in journal (Refereed)
    Abstract [en]

    Molecular profiling of single cells has the potential to significantly advance our understanding of cell function and cellular processes of importance to health and disease. In particular, small molecules with rapid turn-over rates can reveal activated metabolic pathways resulting from an altered chemical environment or cellular events such as differentiation. Consequently, techniques for quantitative metabolite detection acquired in a higher throughput manner are needed to characterize the biological variability between seemingly homogenous cells. Here, we show that nanospray desorption electrospray ionization (nano-DESI) mass spectrometry ( MS) enables sensitive molecular profiling and quantification of endogenous species in single cells in a higher throughput manner. Specifically, we show a large number of detected amino acids and phospholipids, including plasmalogens, readily detected from single cheek cells. Further, by incorporating a phosphatidylcholine ( PC) internal standard into the nano-DESI solvent, we determined the total amount of PC in one cell to be 1.2 pmoles. Finally, we describe a higher throughput approach where molecules in single cells are automatically profiled. These developments in single cell analysis provide a basis for future studies to understand cellular processes related to drug effects, cell differentiation and altered chemical microenvironments.

  • 9.
    Bergman, Hilde-Marléne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lundin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Andersson, Malin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Lanekoff, Ingela
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Quantitative mass spectrometry imaging of small-molecule neurotransmitters in rat brain tissue sections using nanospray desorption electrospray ionization2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 12, p. 3686-3695Article in journal (Refereed)
    Abstract [en]

    Small molecule neurotransmitters are essential for the function of the nervous system, and neurotransmitter imbalances are often connected to neurological disorders. The ability to quantify such imbalances is important to provide insights into the biochemical mechanisms underlying the disorder. This proof-of-principle study presents online quantification of small molecule neurotransmitters, specifically acetylcholine, γ-aminobutyric acid (GABA) and glutamate, in rat brain tissue sections using nanospray desorption electrospray ionization (nano-DESI) mass spectrometry imaging. By incorporating deuterated internal standards in the nano-DESI solvent we show identification, accurate mapping, and quantification of these small neurotransmitters in rat brain tissue without introducing any additional sample preparation steps. We find that GABA is about twice as abundant in the medial septum-diagonal band complex (MSDB) as in the cortex, while glutamate is about twice as abundant in the cortex as compared to the MSDB. The study shows that nano-DESI is well suited for imaging of small molecule neurotransmitters in health and disease.

  • 10.
    Bergman, Nina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Recent developments in proteomic methods and disease biomarkers2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, p. 3836-3851Article in journal (Refereed)
    Abstract [en]

    Proteomic methodologies for identification and analysis of biomarkers have gained more attention during recent years and have evolved rapidly. Identification and detection of disease biomarkers are important to foresee outbreaks of certain diseases thereby avoiding surgery and other invasive and expensive medical treatments for patients. Thus, more research into discovering new biomarkers and new methods for faster and more accurate detection is needed. It is often difficult to detect and measure biomarkers because of their low concentrations and the complexity of their respective matrices. Therefore it is hard to find and validate methods for accurate screening methods suitable for clinical use. The most recent developments during the last three years and also some historical considerations of proteomic methodologies for identification and validation of disease biomarkers are presented in this review.

  • 11.
    Bergström, Sara K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Dahlin, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Ramström, Margareta
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Andersson, Marit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Markides, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    A simplified multidimensional approach for analysis of complex biological samples: on-line LC-CE-MS2006In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 131, no 7, p. 791-798Article in journal (Refereed)
    Abstract [en]

    Information on protein expression, disease biomarkers or surrogate markers and genetic disorders can nowadays be achieved from analysis of complex biological samples by liquid separation coupled to mass spectrometric (MS) detection. This paper describes fast multidimensional separation by on-line liquid chromatography (LC) and capillary electrophoresis (CE), followed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) MS detection. This detector provides ultrahigh resolution of the detected ions, mass accuracy at the ppm-level and high sensitivity. Most of the challenge of this system lies in the development of a new interface for the on-line coupling of LC to CE. The interface developed in poly(dimethylsiloxane) provides a RSD for injection repeatability of <3.5% and surface control for unspecific binding by deactivation with a cationic polymer, PolyE-323. We have evaluated the interface, as well as the overall system, with respect to robustness and deconvolution ability. Sequence coverage for bovine serum albumin (BSA) of 93% showed a high recovery of sample in the different transfer steps through the system. The detection limit for identification is 277 ng mL−1 (or 280 nM) on average for peptides. In the future, we expect LC-CE-MS to be a novel strategy for elucidating the chemistry of biological matrices.

  • 12.
    BRADLEY, J
    et al.
    DISTILLERS CO YEAST LTD,DEPT RES and QUAL ASSURANCE,MENSTRIE FK11 7ES,CLACK,SCOTLAND; .
    KIDD, AJ
    DISTILLERS CO YEAST LTD,DEPT RES and QUAL ASSURANCE,MENSTRIE FK11 7ES,CLACK,SCOTLAND; .
    ANDERSON, PA
    DISTILLERS CO YEAST LTD,DEPT RES and QUAL ASSURANCE,MENSTRIE FK11 7ES,CLACK,SCOTLAND; .
    DEAR, AM
    DISTILLERS CO YEAST LTD,DEPT RES and QUAL ASSURANCE,MENSTRIE FK11 7ES,CLACK,SCOTLAND; .
    ASHBY, RE
    DISTILLERS CO YEAST LTD,DEPT RES and QUAL ASSURANCE,MENSTRIE FK11 7ES,CLACK,SCOTLAND; .
    TURNER, APF
    Cranfield University, UK.
    RAPID-DETERMINATION OF THE GLUCOSE CONTENT OF MOLASSES USING A BIOSENSOR1989In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 114, no 3, p. 375-379Article in journal (Refereed)
    Abstract [en]

    n/a

  • 13. Candefjord, Stefan
    et al.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Effects of snap-freezing and near-infrared laser illumination on porcine prostate tissue as measured by Raman spectroscopy2009In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 134, no 9, p. 1815-1821Article in journal (Refereed)
    Abstract [en]

    Most Raman spectroscopic studies on tissue are performed in vitro. To assure that the results are applicable to in vivo examinations, preparation protocols and measurement procedures of tissue for in vitro studies should preserve tissue characteristics close to the native state. This study had two aims. The first was to elucidate if photoinduced effects arise during 5 minutes' continuous illumination of tissue with an 830 nm laser at an irradiance of 3 × 1010 W/m2. The second was to investigate the effects of snap-freezing of porcine prostate tissue in liquid nitrogen and subsequent storage at -80 °C, by means of multivariate analysis. 830 nm laser illumination of the specified irradiance did not affect the Raman spectra. A decrease of the spectral background was observed, likely due to photobleaching of tissue fluorophores. Snap-freezing and subsequent storage at -80 °C gave rise to subtle but significant alterations in Raman spectra, most likely related to changes in the protein conformations

  • 14.
    Chinnasamy, Thiruppathiraja
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Segerink, Loes I.
    Nystrand, Mats
    Gantelius, Jesper
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Andersson Svahn, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    A lateral flow paper microarray for rapid allergy point of care diagnostics2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 10, p. 2348-2354Article in journal (Refereed)
    Abstract [en]

    There is a growing need for multiplexed specific IgE tests that can accurately evaluate patient sensitization profiles. However, currently available commercial tests are either single/low-plexed or require sophisticated instrumentation at considerable cost per assay. Here, we present a novel convenient lateral flow microarray-based device that employs a novel dual labelled gold nanoparticle-strategy for rapid and sensitive detection of a panel of 15 specific IgE responses in 35 clinical serum samples. Each gold nanoparticle was conjugated to an optimized ratio of HRP and anti-IgE, allowing significant enzymatic amplification to improve the sensitivity of the assay as compared to commercially available detection reagents. The mean inter-assay variability of the developed LFM assay was 12% CV, and analysis of a cohort of clinical samples (n = 35) revealed good general agreement with ImmunoCAP, yet with a varying performance among allergens (AUC = [0.54-0.88], threshold 1 kU). Due to the rapid and simple procedure, inexpensive materials and read-out by means of a consumer flatbed scanner, the presented assay may provide an interesting low-cost alternative to existing multiplexed methods when thresholds > 1 kU are acceptable.

  • 15. Crespo, Gaston A.
    et al.
    Bakker, Eric
    Ionophore-based ion optodes without a reference ion: electrogenerated chemiluminescence for potentiometric sensors2012In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 137, no 21, p. 4988-4994Article in journal (Refereed)
  • 16.
    Dennison, MJ
    et al.
    CRANFIELD UNIV,CRANFIELD BIOTECHNOL CTR,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    Hall, JM
    CRANFIELD UNIV,CRANFIELD BIOTECHNOL CTR,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    Turner, APF
    Cranfield University, UK.
    Direct monitoring of formaldehyde vapour and detection of ethanol vapour using dehydrogenase-based biosensors1996In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 121, no 12, p. 1769-1773Article in journal (Refereed)
    Abstract [en]

    Biosensors capable of directly detecting low levels of formaldehyde and ethanol vapour were constructed, Both biosensors are based on dehydrogenase enzymes which produce reduced nicotinamide adenine dinucleotide as part of the oxidation of formaldehyde and ethanol, The enzymes were immobilized in a reverse micelle medium which did not dehydrate significantly over time, and allowed direct gas-phase monitoring, A screen-printed electrode was used as transducer. Formaldehyde and ethanol vapour partitioned into the reverse micelle media, where it was acted upon by the relevant enzyme, Reduced nicotinamide adenine dinucleotide was oxidized at the working electrode at a potential of 800 mV versus an Ag/AgCl reference electrode, Formaldehyde could be measured over the concentration range 1 ppb-1.3 ppm and ethanol could be detected over the range 50-250 ppm.

  • 17. Dorokhin, Denis
    et al.
    Crespo, Gaston A.
    Afshar, Majid Ghahraman
    Bakker, Eric
    A low-cost thin layer coulometric microfluidic device based on an ion-selective membrane for calcium determination2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 1, p. 48-51Article in journal (Refereed)
  • 18.
    Duncan, Kyle D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Bergman, Hilde-Marlene
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Andersson, Ingela
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    A pneumatically assisted nanospray desorption electrospray ionization source for increased solvent versatility and enhanced metabolite detection from tissue2017In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 142, no 18, p. 3424-3431Article in journal (Refereed)
    Abstract [en]

    Nanospray desorption electrospray ionization (nano-DESI) has been established as a powerful technique for mass spectrometry imaging (MSI) of biomolecules from tissue samples. The direct liquid extraction of analytes from a surface at ambient pressure negates the need for significant sample preparation or matrix application. Although many recent studies have applied nano-DESI to new and exciting applications, there has not been much work in the development and improvement of the nano-DESI source. Here, we incorporate a nebulizer to replace the self-aspirating secondary capillary in the conventional nano-DESI setup, and characterize the device by use of rat kidney tissue sections. We find that the pneumatically assisted nano-DESI device offers improved sensitivity for metabolite species by 1-3 orders of magnitude through more complete desolvation and reduced ionization suppression. Further, the pneumatically assisted nano-DESI device reduces the dependence on probe-to-surface distance and enables sampling and imaging using pure water as the nano-DESI solvent. This provides exclusive detection and imaging of many highly polar endogenous species. Overall, the developed pneumatically assisted nano-DESI device provides more versatile solvent selection and an increased sensitivity for metabolites, which generates ion images of higher contrast - allowing for more intricate studies of metabolite distribution.

  • 19.
    Duncan, Kyle D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Fyrestam, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lanekoff, Ingela
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Advances in mass spectrometry based single-cell metabolomics2019In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 144, no 3, p. 782-793Article, review/survey (Refereed)
    Abstract [en]

    Metabolomics has grown into a prominent field contributing to the molecular understanding of complex biological processes in both health and disease. Furthermore, single-cells are known to display metabolic differences between seemingly homogeneous populations of cells. Single-cell metabolomics attempts to analyze many cellular metabolites from single cells to understand phenotypic heterogeneity, which is a significant challenge due to the low analyte abundances and limited sample volumes. Label-free metabolite detection can be achieved with mass spectrometry, which is capable of simultaneously analyzing hundreds of metabolites. Herein, we review the recent advances in mass spectrometry based single-cell metabolomics, highlighting the current state-of-the-art within the last three years, and identify the challenges to move the field forward.

  • 20.
    Duner, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Anderson, Henrik
    Pei, Zhichao
    Ingemarsson, Bjorn
    Aastrup, Teodor
    Ramstrom, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Signal enhancement in ligand-receptor interactions using dynamic polymers at quartz crystal microbalance sensors2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 13, p. 3993-3996Article in journal (Refereed)
    Abstract [en]

    The signal enhancement properties of QCM sensors based on dynamic, biotinylated poly(acrylic acid) brushes has been studied in interaction studies with an anti-biotin Fab fragment. The poly (acrylic acid) sensors showed a dramatic increase in signal response with more than ten times higher signal than the carboxyl-terminated self-assembled monolayer surface.

  • 21.
    Dunér, Gunnar
    et al.
    Department of Chemistry, KTH.
    Anderson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Attana AB.
    Pei, Zhichao
    Attana AB.
    Ingemarsson, Björn
    Attana AB.
    Aastrup, Teodor
    Attana AB.
    Ramström, Olof
    Department of Chemistry, KTH.
    Signal Enhancement in Ligand-Receptor Interactions using Dynamic Polymers at Quartz Crystal Microbalance Surfaces2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 13, p. 3993-3996Article in journal (Refereed)
    Abstract [en]

    The potential for signal amplification on QCM sensors by use of in situ polymerized poly(acrylic acid) brushes has been studied. A biotin derivative was immobilized on these surfaces and the interaction with anti-biotin Fabs was evaluated. Interaction data was found to be specific for the studied binding events, and the level of non-specific binding was shown to be low. The surface was proven to be suitable for regeneration, of importance for biomolecular interaction analysis and repetitive immunoassays.

    For comparison, the same interaction system was tested using commercial sensor surfaces with carboxylated self-assembled monolayers. The poly(acrylic acid) surface showed a dramatic increase in signal response with more than ten times the signal of the carboxylated self-assembled monolayer surface. Thus, the present study shows that polymers can be successfully applied to amplify responses on QCM sensors, valuable for studies of interactions between receptors and low molecular weight compounds.

  • 22.
    Duong-Thi, Minh-Dao
    et al.
    Linnaeus University, Department of Chemistry and Biomedical Sciences, SE-39182 Kalmar, Sweden.
    Bergström, Maria
    Linnaeus University, Department of Chemistry and Biomedical Sciences, SE-39182 Kalmar, Sweden.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Eriksson, Jonny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Ohlson, Sten
    Nanyang Technological University, School of Biological Sciences, Singapore 637551, Republic of Singapore.
    To Yiu Ying, Janet
    Nanyang Technological University, School of Biological Sciences, Singapore 637551, Republic of Singapore.
    Torres, Jaume
    Nanyang Technological University, School of Biological Sciences, Singapore 637551, Republic of Singapore.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lipodisks integrated with weak affinity chromatography enable fragment screening of integral membrane proteins2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 3, p. 981-988Article in journal (Refereed)
    Abstract [en]

    Membrane proteins constitute the largest class of drug targets but they present many challenges in drug discovery. Importantly, the discovery of potential drug candidates is hampered by the limited availability of efficient methods for screening drug-protein interactions. In this work we present a novel strategy for rapid identification of molecules capable of binding to a selected membrane protein. An integral membrane protein (human aquaporin-1) was incorporated into planar lipid bilayer disks (lipodisks), which were subsequently covalently coupled to porous derivatized silica and packed into HPLC columns. The obtained affinity columns were used in a typical protocol for fragment screening by weak affinity chromatography (WAC), in which one hit was identified out of a 200 compound collection. The lipodisk-based strategy, which ensures a stable and native-like lipid environment for the protein, is expected to work also with other membrane proteins and screening procedures.

  • 23.
    Duong-Thi, Minh-Dao
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences. Nanyang Technol University, Singapore.
    Bergström, Maria
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Edwards, Katarina
    Uppsala University.
    Eriksson, Jonny
    Uppsala University.
    Ohlson, Sten
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    To Yiu Ying, Janet
    Nanyang Technol University, Singapore.
    Torres, Jaume
    Nanyang Technol University, Singapore.
    Agmo Hernández, Víctor
    Uppsala University.
    Lipodisks integrated with weak affinity chromatography enable fragment screening of integral membrane proteins2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 3, p. 981-988Article in journal (Refereed)
    Abstract [en]

    Membrane proteins constitute the largest class of drug targets but they present many challenges in drug discovery. Importantly, the discovery of potential drug candidates is hampered by the limited availability of efficient methods for screening drug-protein interactions. In this work we present a novel strategy for rapid identification of molecules capable of binding to a selected membrane protein. An integral membrane protein (human aquaporin-1) was incorporated into planar lipid bilayer disks (lipodisks), which were subsequently covalently coupled to porous derivatized silica and packed into HPLC columns. The obtained affinity columns were used in a typical protocol for fragment screening by weak affinity chromatography (WAC), in which one hit was identified out of a 200 compound collection. The lipodisk-based strategy, which ensures a stable and native-like lipid environment for the protein, is expected to work also with other membrane proteins and screening procedures.

  • 24.
    Ekman, Jenny
    et al.
    National Institute for Working Life, Umeå.
    Levin, Jan-Olof
    National Institute for Working Life, Umeå.
    Lindahl, Roger
    National Institute for Working Life, Umeå.
    Sundgren, Margit
    National Institute for Working Life, Umeå.
    Ostin, Anders
    National Institute for Working Life, Umeå.
    Comparison of sampling methods for 1,6-hexamethylene diisocyanate, (HDI) in a commercial spray box2002In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 127, no 1, p. 169-173Article in journal (Refereed)
    Abstract [en]

    In this study three different types of samplers for the determination of 1,6-hexamethylene diisocyanate in air were compared. The experimental set up was a simulation of real life conditions with spray painting operations performed inside a commercial, full sized, spray box. The sampling methods were 1-(2-methoxyphenyl)-piperazine impregnated on glass fibre filter, and the same reagent in impinger, and also dibutylamine in impinger. All analyses were performed by LC-MS-MS. The determined concentrations varied between 20 and 90 microg m(-3) with relative standard deviations from 7 to 17% for each method. No significant difference was found between the three methods using ANOVA with a significance level of alpha = 0.05.

  • 25.
    Emteborg, Håkan
    et al.
    Umea University, Department of Analytical Chemistry.
    Björklund, Erland
    Ödman, Fredrik
    Karlsson, Lars
    Lund University.
    Mathiasson, Lennart
    Fresh, Wolfgang
    Baxter, Douglas
    Determination of methylmercury in sediments using supercritical fluid extraction and gas chromatography coupled with microwave-induced plasma atomic emission spectrometry1996In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 121, no 1, p. 19-29Article in journal (Refereed)
  • 26.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Cooperative adsorption behavior of phosphopeptides on TiO2 leads to biased enrichment, detection and quantification2015In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, no 1, p. 303-312Article in journal (Refereed)
    Abstract [en]

    The adsorption behavior of phosphopeptides onto TiO2 surfaces was studied using the quartz crystal microbalance with dissipation monitoring (QCM-D) as the main experimental technique. The main focus is the characterization of the emergence of positive cooperativity under conditions where the peptides have a positively charged C-term. It is shown that when carrying no net charge, small water-soluble peptides as a rule develop positive cooperativity. The impact of the adsorption mechanism on the outcome of TiO2 based enrichment methods was investigated with the help of matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS). The data presented illustrate how the phosphopeptide profile in the enriched material may deviate from that in the native sample, as cooperative phosphopeptides are overrepresented in the former. Furthermore, commonly employed washing and elution solutions may facilitate preferential release of certain peptides, leading to further bias in the recovered sample. Taken together, the results of the present study demonstrate that thorough understanding of the mechanisms behind the adsorption of phosphopeptides on the enrichment material is necessary in order to develop reliable qualitative and quantitative methods for phosphoproteomics.

  • 27.
    Fernandes, Daniel L. A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pavliuk, Maria V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sa, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    A 3D printed microliquid jet with an adjustable nozzle diameter2015In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 140, no 18, p. 6234-6238Article in journal (Refereed)
    Abstract [en]

    Microliquid jets have many applications, in particular in the fields of spectroscopy/analysis of samples susceptible to beam damage. Herein, we report a microliquid jet, manufactured with 3D printing technology, with a tuneable nozzle diameter output. This strategy increases the breadth of techniques that can be covered with a single microliquid jet.

  • 28.
    Filippini, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Effect of fingerprint conformation and spectral scaling on the performance of computer screen photo-assisted experiments2006In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 131, no 1, p. 118-125Article in journal (Refereed)
    Abstract [en]

    The use of computer screens as controlled light sources and web cameras as image detectors (the so-called computer screen photo-assisted technique, CSPT) is an ubiquitous alternative for the evaluation of colorimetric quick tests at homes or in primary care units. The performance of CSPT for such evaluations depends on several factors, from which the most relevant are the composition of illuminating sequences and the conformation of CSPT substance signatures. In this work, with the aid of a CSPT model, the effect of the construction of the substance signatures on the classification performance of different representative substance sets is studied. The correlation of illuminating colors with such classification is investigated, allowing one to determine redundancy and limitations with respect to visible spectroscopy. The concept of spectral scaling is introduced and its properties compared with standard procedures. © The Royal Society of Chemistry 2006.

  • 29.
    Filippini, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Measurement strategy and instrumental performance of a computer screen photo-assisted technique for the evaluation of a multi-parameter colorimetric test strip2006In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 131, no 1, p. 111-117Article in journal (Refereed)
    Abstract [en]

    A measuring strategy for the evaluation of a seven parameters colorimetric test using a computer screen photo-assisted technique (CSPT) is demonstrated. CSPT is a versatile approach aimed at point of care or home tests that uses regular computer sets and web cameras as the whole instrument. Issues such as the stability and the equivalency on different platforms of the determinations have been addressed in the present work. The method uses an embedded local reference simultaneously measured with the tests and solves the evaluation as a classification problem. The achieved performance tested along 580 classifications covering all the ranges of the assay, using synthetic samples, yielded 97.2% correct determinations compared with 89.7% for the case of colorimetric determinations. The errors were concentrated in only two parameters that show a significant correlation with a set of quality indices used to assess the performance of the classification. © The Royal Society of Chemistry 2006.

  • 30. Guinovart, Tomas
    et al.
    Parrilla, Marc
    Crespo, Gaston A.
    Rius, F. Xavier
    Andrade, Francisco J.
    Potentiometric sensors using cotton yarns, carbon nanotubes and polymeric membranes2013In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 138, no 18, p. 5208-5215Article in journal (Refereed)
    Abstract [en]

    A simple and generalized approach to build electrochemical sensors for wearable devices is presented. Commercial cotton yarns are first turned into electrical conductors through a simple dyeing process using a carbon nanotube ink. These conductive yarns are then partially coated with a suitable polymeric membrane to build ion-selective electrodes. Potentiometric measurements using these yarn-potentiometric sensors are demonstrated. Examples of yarns that can sense pH, K+ and NH4+ are presented. In all cases, these sensing yarns show limits of detection and linear ranges that are similar to those obtained with lab-made solid-state ion-selective electrodes. Through the immobilization of these sensors in a band-aid, it is shown that this approach could be easily implemented in a wearable device. Factors affecting the performance of the sensors and future potential applications are discussed.

  • 31.
    Haas, Julian
    et al.
    Ulm University, Germany.
    Vargas Catalán, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Piron, Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Molecular Fingerprint Sweden AB, Eksätravägen 130, SE-756 55 Uppsala, Sweden .
    Mizaikoff, Boris
    Ulm University, Germany.
    Infrared Spectroscopy Based on Broadly Tunable Quantum Cascade Lasers and Polycrystalline Diamond Waveguides2018In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 143, no 21, p. 5112-5119Article in journal (Refereed)
    Abstract [en]

    Recently emerging broadly tunable quantum cascade lasers (tQCL) emitting in the mid-infrared (MIR) are a versatile alternative to well established thermal emitters in combination with interferometers as applied in Fourier transform infrared (FTIR) spectroscopy. The wide and highly spectrally resolved wavelength tuning characteristics along with superior spectral energy density renders laser-based vibrational spectroscopy methods an efficient alternative vs. conventional molecular spectroscopies. Using diamond in attenuated total reflection (ATR) sensing formats benefits from the physical robustness and chemical resistivity of the internal reflective element (IRE) material. While inherent material absorption frequently limits the optical path length within diamond ATR elements, the herein presented design combining bright tQCLs with a multi-reflection polycrystalline diamond (PCD) ATR element enables an optical beam path length of approximately 5 cm. Thereby, sensitive spectroscopic measurements in the MIR are enabled. As an example, non-invasive glucose monitoring in human saliva is examined, highlighting the potential benefits of the proposed analytical concept with regards to exquisite sensitivity and selectivity in combination with a robust sensing interface, i.e., diamond. This approach paves the way towards directly analyzing molecular constituents in complex and potentially corrosive biomedical and biochemical matrices.

  • 32.
    Hagenbjörk-Gustafsson, Annika
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine. National Institute for Working Life, Programme for Chemical Exposure Assessment, Umeå.
    Lindahl, Roger
    Umeå University, Faculty of Science and Technology, Department of Chemistry. National Institute for Working Life, Programme for Chemical Exposure Assessment, Umeå.
    Levin, Jan-Olof
    Umeå University, Faculty of Science and Technology, Department of Chemistry. National Institute for Working Life, Programme for Chemical Exposure Assessment, Umeå.
    Karlsson, Doris
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Validation of the Willems badge diffusive sampler for nitrogen dioxide determinations in occupational environments2002In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 127, no 1, p. 163-168Article in journal (Refereed)
    Abstract [en]

    The Willems badge, a diffusive sampler for nitrogen dioxide, has previously been validated for ambient air measurements. This paper describes the laboratory and field validation of the Willems badge for personal sampling under working environment conditions. The mean sampling rate in the laboratory tests was 46 ml min(-1), with an RSD of 12%. No statistically significant effects on sampling rate of the sampling time, concentration of NO2 or relative humidity were found. A slightly decreased sampling rate was observed at low wind velocity. This was also confirmed during static sampling, which makes the sampler less appropriate for static sampling indoors. No back diffusion was observed. Storage of the samplers for two weeks before or after exposure did not affect the sampling rate. Our analysis is based on a modified colorimetric method, performed by FIA (flow injection analysis). This technique was compared to ion chromatography analysis. The use of ion chromatography lowered the detection limit from 11 to 2 microg m(-3) for an 8 h sample, and furthermore enabled the detection of other anions. In conclusion, the diffusive sampler was found to perform well for personal measurements in industrial environments.

  • 33. Hartfelder, Urs
    et al.
    Szlachetko, Jakub
    Sá, Jacinto
    van Bokhoven, Jeroen A
    Determination of catalytic reaction mechanisms by isotopic frequency response.2012In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 137, no 22, p. 5374-81Article in journal (Refereed)
    Abstract [en]

    Efficient catalysts are of extraordinary importance for the development of efficient chemical processes as well as applications such as energy storage. Rational development of catalysts requires a mechanistic understanding of the catalytic reaction. Since steady-state investigations are insufficient to gain mechanistic understanding, transient methods such as SSITKA and frequency response have been developed. In this paper we provide a theoretical basis for a frequency response method based on variations in the isotopic composition of the reactant. This approach is particularly useful, since it permits transient investigations under quasi-steady state conditions and because the response is linear.

  • 34.
    Herr, Amy E.
    et al.
    Univ Calif Berkeley, Berkeley, CA 94720 USA.
    Kitamori, Takehiko
    Univ Tokyo, Tokyo, Japan.
    Landegren, Ulf
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Kamali-Moghaddam, Masood
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Next wave advances in single-cell analyses2019In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 144, no 3, p. 735-737Article in journal (Other academic)
  • 35.
    Isetun, Sindra
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic field sampling of airborne organophosphate triesters using solid-phase microextraction under equilibrium and non-equilibrium conditions2005In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 30, p. 94-98Article in journal (Refereed)
    Abstract [en]

     

    A simple setup for dynamic air sampling using a solid-phase microextraction (SPME) device

    designed for use in the field was evaluated for organophosphate triester vapour under both

    equilibrium and non-equilibrium conditions. The effects of varying the applied airflows in the

    sampling device were evaluated in order to optimise the system with respect to the Reynolds

    number and magnitude of the boundary layer that developed near the surface. Further, the

    storage stability of the analytes was studied for both capped and uncapped 100-

     

     

    m

    m PDMS fibres.

    Organophosphate triesters are utilized on large scales as flame-retardants and/or plasticizers, for

    instance in upholstered furniture. In indoor working environments these compounds have become

    common components in the surrounding air. Measurements were performed in a recently

    furnished working environment and the concentration of tris(2-choropropyl) phosphate was

    found to be 7

     

     

    mg m23

    .

  • 36.
    Johansson, Ursula
    et al.
    Luleå tekniska universitet.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Frost, Ray L.
    Queensland University of Technology.
    Isotopic exchange of kaolinite hydroxyl protons: a diffuse reflectance infrared Fourier transform spectroscopy study1998In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 123, no 4, p. 641-645Article in journal (Refereed)
    Abstract [en]

    Specific surface reactions on kaolinite were investigated by deuterium exchange of the hydroxyl protons of kaolinite, The kaolinite samples were reacted with deuterium oxide for 48 h and 2.5 and 5 weeks, at various pH values (3, natural and 8) and at different temperatures (ambient, and 30, 60 and 100 degrees C), Analyses were performed using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The spectral results show that it is very difficult at room temperature to exchange the hydroxyl protons isotopically with deuterons at the surface of kaolinite, The temperature and the reaction time must be increased for successful exchange. It was found that the most suitable temperature for isotopic exchange was 60 degrees C. The pH did not significantly influence the deuteration, Only at high pH were changes of the OD bands in the DRIFT spectra observed, This study shows that it is possible to deuterate kaolinite without using intercalation. All three types of hydroxyl protons from the inner, inner surface and edge were exchanged.

  • 37.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bruce, Stephen J
    Moritz, Thomas
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Plumb, Robert
    Granger, Jennifer
    Maibaum, Elaine
    Nicholson, Jeremy K
    Holmes, Elaine
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Extraction, interpretation and validation of information for comparing samples in metabolic LC/MS data sets2005In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 130, no 5, p. 701-707Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    LC/MS is an analytical technique that, due to its high sensitivity, has become increasingly popular for the generation of metabolic signatures in biological samples and for the building of metabolic data bases. However, to be able to create robust and interpretable ( transparent) multivariate models for the comparison of many samples, the data must fulfil certain specific criteria: (i) that each sample is characterized by the same number of variables, (ii) that each of these variables is represented across all observations, and (iii) that a variable in one sample has the same biological meaning or represents the same metabolite in all other samples. In addition, the obtained models must have the ability to make predictions of, e. g. related and independent samples characterized accordingly to the model samples. This method involves the construction of a representative data set, including automatic peak detection, alignment, setting of retention time windows, summing in the chromatographic dimension and data compression by means of alternating regression, where the relevant metabolic variation is retained for further modelling using multivariate analysis. This approach has the advantage of allowing the comparison of large numbers of samples based on their LC/MS metabolic profiles, but also of creating a means for the interpretation of the investigated biological system. This includes finding relevant systematic patterns among samples, identifying influential variables, verifying the findings in the raw data, and finally using the models for predictions. The presented strategy was here applied to a population study using urine samples from two cohorts, Shanxi (People's Republic of China) and Honolulu ( USA). The results showed that the evaluation of the extracted information data using partial least square discriminant analysis (PLS-DA) provided a robust, predictive and transparent model for the metabolic differences between the two populations. The presented findings suggest that this is a general approach for data handling, analysis, and evaluation of large metabolic LC/MS data sets.

  • 38. Kelly, Orla
    et al.
    Duffy, Martin J
    King, Raymond B
    Belshaw, Louise
    Williams, Ian D
    Sá, Jacinto
    Calvert, Chris R
    Greenwood, Jason B
    Femtosecond lasers for mass spectrometry: proposed application to catalytic hydrogenation of butadiene.2012In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 137, no 1, p. 64-9Article in journal (Refereed)
    Abstract [en]

    Mass spectra from the interaction of intense, femtosecond laser pulses with 1,3-butadiene, 1-butene, and n-butane have been obtained. The proportion of the fragment ions produced as a function of intensity, pulse length, and wavelength was investigated. Potential mass spectrometry applications, for example in the analysis of catalytic reaction products, are discussed.

  • 39.
    Kjeldsen, Frank
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
    Savitski, Mikhail M.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
    Nielsen, Michael L.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
    Shi, L.
    Zubarev, Roman A.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences, MMS, Medical Mass Spectrometry.
    On studying protein phosphorylation patterns using bottom-up LC-MS/MS: the case of human alpha-casein2007In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 132, no 8, p. 768-776Article in journal (Refereed)
    Abstract [en]

    Most proteomics studies involving mapping post-translational modifications, such as the phosphorylation of serine and threonine, are performed today using the 'bottom-up' approach. This approach involves enzymatic cleavage of proteins, most often by trypsin, with subsequent nano-LC-MS/MS. The occupancy rates of phosphosites in proteins may differ by orders of magnitude, and thus the occupancy rate must be reported for each occupied phosphosite. To highlight potential pitfalls in quantifying the occupancy rates, αs1- casein from human milk was selected as a model molecule representing moderately phosphorylated proteins. For this purpose, human milk from one Caucasian woman in the eighth month of lactation was used. The phosphorylation level of caseins is believed to have major implications for the formation of micelles that are involved in delivering valuable calcium phosphate and other minerals to the new-born. Human αs1-casein has been reported to be much less phosphorylated than ruminant caseins, which may indicate a different function of caseins in humans. Revealing the phosphorylation pattern in human casein can thus shed light on its function. The current study found that the sequence region between the residues Ser70 and Ser76 in human αs1-casein is in fact phosphorylated, contrary to previous knowledge. The site of the most abundant phosphorylation is Ser75, in agreement with the known action of the mammary gland casein kinase. There is evidence for the second phosphorylation in that region, possibly at Ser73. Earlier reported positions of phosphorylations at Ser18 and Ser26 are also confirmed, but not the dominance of Ser18 phosphorylation. The occupancy rates at Ser18, Ser26 and Ser75 are estimated to be (7 ± 2), (20 ± 6) and (27 ± 9)%, respectively. Owing to differences in the ionization efficiency between phosphorylated and unphosphorylated peptides a 30% error margin is added to the occupancy rates. The highlighted pitfalls of the bottom-up strategy include the sensitivity of enzymes to proximal acidic and phosphorylated residues and the presence of multiple isoforms, including unexpected ones, of the tryptic peptides. The utility of the earlier introduced PhosTS_hunter and ModifiComb approaches for evading the latter pitfall is demonstrated.

  • 40.
    Kumar, Keshav
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Cava, Felipe
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Constraint randomised non-negative factor analysis (CRNNFA): an alternate chemometrics approach for analysing the biochemical data sets2017In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 142, no 11, p. 1916-1928Article in journal (Refereed)
    Abstract [en]

    The present work introduces an alternate chemometrics approach constraint randomised non-negative factor analysis (CRNNFA) for analysing the bioanalytical data sets. The CRNNFA algorithm provides the outputs that are easy to interpret and correlate with the real chromatograms. The CRNNFA algorithm achieves termination when the iteration limit is reached circumventing the premature convergence. Theoretical and computational aspects of the proposed method are also described. The analytical and computational potential of CRNNFA are successfully tested by analysing the complex chromatograms of the peptidoglycan samples belonging to the Alphaproteobacterium members. The obtained results clearly show that CRNNFA can easily trace the compositional variability of the peptidoglycan samples. In summary, the proposed method in general can be a potential alternate approach for analysing the data sets obtained from different analytical and clinical fields.

  • 41.
    Kumar, Saroj
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Milani, Gloria
    University of Padova, Italy.
    Takatsuki, Hideyo
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Lana, Tobia
    University of Padova, Italy.
    Persson, Malin
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Frasson, Chiara
    University of Padova, Italy.
    te Kronnie, Geertruy
    University of Padova, Italy.
    Månsson, Alf
    Linnaeus University, Faculty of Health and Life Sciences, Department of Chemistry and Biomedical Sciences.
    Sensing protein antigen and microvesicle analytes using high-capacity biopolymer nano-carriers2016In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 141, no 3, p. 836-846Article in journal (Refereed)
    Abstract [en]

    Lab-on-a-chip systems with molecular motor driven transport of analytes attached to cytoskeletal filament shuttles (actin filaments, microtubules) circumvent challenges with nanoscale liquid transport. However, the filaments have limited cargo-carrying capacity and limitations either in transportation speed (microtubules) or control over motility direction (actin). To overcome these constraints we here report incorporation of covalently attached antibodies into self-propelled actin bundles (nanocarriers) formed by cross-linking antibody conjugated actin filaments viafascin, a natural actin-bundling protein. We demonstrate high maximum antigen binding activity and propulsion by surface adsorbed myosin motors. Analyte transport capacity is tested using both protein antigens and microvesicles, a novel class of diagnostic markers. Increased incubation concentration with protein antigen in the 0.1–100 nM range (1 min) reduces the fraction of motile bundles and their velocity but maximum transportation capacity of >1 antigen per nm of bundle length is feasible. At sub-nanomolar protein analyte concentration, motility is very well preserved opening for orders of magnitude improved limit of detection using motor driven concentration on nanoscale sensors. Microvesicle-complexing to monoclonal antibodies on the nanocarriers compromises motility but nanocarrier aggregation via microvesicles shows unique potential in label-free detection with the aggregates themselves as non-toxic reporter elements.

  • 42.
    Källsten, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Recipharm OT Chem AB, Uppsala, Sweden.
    Hartmann, Rafael
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preparative Medicinal Chemistry.
    Artemenko, Konstantin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Bergström Lind, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lehmann, Fredrik
    Recipharm OT Chem AB, Uppsala, Sweden.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Qualitative analysis of antibody-drug conjugates (ADCs): an experimental comparison of analytical techniques of cysteine-linked ADCs.2018In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 143, no 22, p. 5487-5496Article in journal (Refereed)
    Abstract [en]

    Antibody-drug conjugates (ADCs) are an emerging type of biotherapeutics that utilize multiple tissue-specific antibodies combined with a range of linker designs to enable the transportation and selective release of cytotoxic drugs in close proximity to tumours. Consisting of antibodies conjugated to small drug molecules through a variety of linkers, ADCs are chemically complex analytes. Here we present a unique experimental comparison of four techniques for ADC analysis: hydrophobic interaction chromatography (HIC-UV/Vis), reversed phase liquid chromatography mass spectrometry (RPLC-MS), using either a QToF or an Orbitrap analyser, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Four different ADCs consisting of Trastuzumab, monomethyl auristatin E (MMAE) and a peptidic linker moiety differing in their respective stoichiometric ratios in regard to drug-to-antibody ratio (DAR) were used for the comparison. We found that the determined DAR from all techniques was comparable, while the accuracy of the molecular weights for the conjugated light and heavy chain differed more extensively. This indicates that the choice of a mass analyser is more crucial for determining the accurate weights of the light and heavy chains than to evaluate the DAR of a given batch. However, ambiguous DAR assignment in HIC-UV/Vis or bias for either the light or heavy chain fragments in the mass spectrometry-based techniques can influence the obtained average DAR value and the use of complementary techniques is advisable. Out of the four techniques evaluated, HIC-UV/Vis and MALDI required less time to obtain an average DAR value and would therefore be good for initial screenings in the early stages of the discovery phase of new ADCs.

  • 43. Lanekoff, Ingela
    et al.
    Geydebrekht, Oleg
    Pinchuk, Grigoriy E
    Konopka, Allan E
    Laskin, Julia
    Spatially resolved analysis of glycolipids and metabolites in living Synechococcus sp. PCC 7002 using nanospray desorption electrospray ionization2013In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 138, no 7, p. 1971-1978Article in journal (Refereed)
    Abstract [en]

    Microorganisms release a diversity of organic compounds that couple interspecies metabolism, enable communication, or provide benefits to other microbes. Increased knowledge of microbial metabolite production will contribute to understanding of the dynamic microbial world and can potentially lead to new developments in drug discovery, biofuel production, and clinical research. Nanospray desorption electrospray ionization (nano-DESI) is an ambient ionization technique that enables detailed chemical characterization of molecules from a specific location on a surface without special sample pretreatment. Due to its ambient nature, living bacterial colonies growing on agar plates can be rapidly analyzed without affecting the viability of the colony. In this study we demonstrate for the first time the utility of nano-DESI for spatial profiling of chemical gradients generated by microbial communities on agar plates. We found that despite the high salt content of the agar used in this study (~350 mM), nano-DESI analysis enables detailed characterization of metabolites produced by the Synechococcus sp. PCC 7002 colonies. High resolution mass spectrometry and MS/MS analysis of the living Synechococcus sp. PCC 7002 colonies allowed us to detect metabolites and lipids on the colony and on the surrounding agar, and confirm their identities. High sensitivity of nano-DESI enabled identification of several glycolipids that have not been previously reported by extracting the cells using conventional methods. Spatial profiling demonstrated that a majority of lipids and metabolites were localized on the colony while sucrose and glucosylglycerol, an osmoprotective compound produced by cyanobacteria, were secreted onto agar. Furthermore, we demonstrated that the chemical gradients of sucrose and glucosylglycerol on agar depend on the age of the colony. The methodology presented in this study will facilitate future studies focused on molecular-level characterization of interactions between bacterial colonies.

  • 44. Lanekoff, Ingela
    et al.
    Stevens, Susan L
    Stenzel-Poore, Mary P
    Laskin, Julia
    Matrix effects in biological mass spectrometry imaging: identification and compensation2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 14, p. 3528-3532Article in journal (Refereed)
    Abstract [en]

    Matrix effects in mass spectrometry imaging (MSI) may affect the observed molecular distribution in chemical and biological systems. In this study, we use mouse brain tissue of a middle cerebral artery occlusion (MCAO) stroke model to examine matrix effects in nanospray desorption electrospray ionization MSI (nano-DESI MSI). This is achieved by normalizing the intensity of the sodium and potassium adducts of endogenous phosphatidylcholine (PC) species to the intensity of the corresponding adduct of the PC standard supplied at a constant rate with the nano-DESI solvent. The use of MCAO model with an ischemic region localized to one hemisphere of the brain enables immediate comparison of matrix effects within one ion image. Furthermore, significant differences in sodium and potassium concentrations in the ischemic region in comparison with the healthy tissue allowed us to distinguish between two types of matrix effects. Specifically, we discuss matrix effects originating from variations in alkali metal concentrations and matrix effects originating from variations in the molecular composition of the tissue. Compensation for both types of matrix effects was achieved by normalizing the signals corresponding to endogenous PC to the signals of the standards. This approach, which does not introduce any complexity in sample preparation, efficiently compensates for signal variations resulting from differences in the local concentrations of sodium and potassium in tissue sections and from the complexity of the extracted analyte mixture derived from local variations in molecular composition.

  • 45.
    Larsson, Tom
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Frech, Wolfgang
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Dybdahl, Björn
    Studies of transport and collection characteristics of gaseous mercury in natural gases using amalgamation and isotope dilution analysis2007In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 132, no 6, p. 579-586Article in journal (Refereed)
    Abstract [en]

    Transport and collection characteristics were studied for gaseous elemental mercury (Hg0(g)) in natural gases using newly developed methodology based on amalgamation, isotope dilution with permeation tubes and inductively coupled plasma mass spectrometry. The study involved different Au–Pt collection tube designs, tubing materials and gaseous matrices, including air, natural and sales gas, as well as methane and sales gas to which hydrogen sulfide (H2S) had been added. The Hg0(g) capacity of the Au–Pt tubes was determined to 3.5 ± 0.1 µg. Blanks and detection limits of gaseous mercury (Hg(g)) were 58 ± 17 pg m–3 and 50 pg m–3, respectively, for a 60 L sample volume. For the gases tested, added Hg0(g) tracers could be collected with 90% or higher efficiency at flow rates and volumes of up to 10 L min–1 and 100 L, respectively. The collection efficiency was found to be independent of the type of gas tested, even in the presence of H2S. However, for the gases containing H2S, the apparent transport efficiency of added Hg0(g) tracers through stainless steel tubing varied from 50 to 150% upon changing the temperature from 25 to 100 °C. The interaction of stainless steel with Hg0(g) leading to either a sink, or source of Hg, was not observed in the absence of H2S, nor was it observed for PTFE tubing in the presence of H2S. These observations raise questions about the applicability of currently used sampling procedures for determination of Hg(g) in H2S rich natural gases, including the 6978-2 ISO standard method, in which stainless steel is a prescribed material for tubing and valves of the sampling apparatus.

  • 46. Li, C. Y.
    et al.
    Zhang, X. B.
    Han, Z. X.
    Akermark, B.
    Sun, Licheng C.
    Shen, G. L.
    Yu, R. Q.
    A wide pH range optical sensing system based on a sol-gel encapsulated amino-functionalised corrole2006In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 131, no 3, p. 388-393Article in journal (Refereed)
    Abstract [en]

    The synthesis of a new compound, 10-(4-aminophenyl)-5,15-dimesitylcorrole, and its application for the preparation of optical chemical pH sensors is described. The dye materials were immobilized in a sol - gel glass matrix and characterised upon exposure to aqueous buffer solutions. The response of the sensor is based on the fluorescence intensity changing of corrole owing to multiple steps of protonation and deprotonation. Due to its containing several proton sensitive centers, the 10-(4-aminophenyl)- 5,15-dimesitylcorrole based optode shows a wider response range toward pH than that of tetraphenylporphyrin (TPPH2) and 5,10,15-tris( pentafluorophenyl) corrole (H-3(tpfc)). It shows a linear pH response in the range of 2.17 - 10.30. The effect of the composition of the sensor membrane has been studied and the experimental conditions were optimized. The optode showed good reproducibility and reversibility, and common co-existing inorganic ions did not show obvious interference to its pH measurement.

  • 47.
    Li, Chenge
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Kumar, Saroj
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Montigny, Cedric
    le Mairebcd, Marc
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Quality assessment of recombinant proteins by infrared spectroscopy. Characterisation of a protein aggregation related band of the Ca2+-ATPase2014In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 139, no 17, p. 4231-4240Article in journal (Refereed)
    Abstract [en]

    Infrared spectroscopy was used to characterise recombinant sarcoplasmic reticulum Ca2+-ATPase (SERCA1a). In the amide I region, its spectrum differed from that of Ca2+-ATPase prepared from rabbit fast twitch muscle below 1650 cm(-1). A band at 1642 cm(-1) is reduced in the spectrum of the recombinant protein and a band at 1631 cm(-1) is more prominent. By comparison of amide 1 band areas with the known secondary structure content of the protein, we assigned the 1642 cm(-1) band to beta-sheet structure. Further investigation revealed that the 1642 cm(-1) band decreased and the 1631 cm-1 band increased upon storage at room temperature and upon repeated washing of a protein film with water. Also protein aggregates obtained after solubilisation of the rabbit muscle enzyme showed a prominent band at 1631 cm(-1), whereas the spectrum of solubilised ATPase resembled that of the membrane bound protein. The spectral position of the 1631 cm(-1) band is similar to that of a band observed for inclusion bodies of other proteins. The findings show that the absence of the 1642 cm(-1) band and the presence of a prominent band at 1631 cm(-1) indicate protein aggregation and can be used as a quality marker for the optimisation of recombinant protein production. We conclude that recombinant production of SERCA1a, storage at room temperature, repeated washing and aggregation after solubilisation all modify existing beta-sheets in the cytosolic domains so that they become similar to those found in inclusion bodies of other proteins.

  • 48. Lidén, H.
    et al.
    Bachinger, T.
    Gorton, L.
    Mandenius, Carl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biotechnology .
    On-line determination of non-volatile or low-concentration metabolites in a yeast cultivation using an electronic nose2000In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 125, no 6, p. 1123-1128Article in journal (Refereed)
    Abstract [en]

    An electronic nose was used for on-line gas phase monitoring of key metabolites in a Saccharomyces cerevisiae cultivation. The metabolites were either non-volatile or present at very low concentrations and therefore not detectable in the gas phase by the sensors in the electronic nose. It was found that it is still possible to make a prediction based on the off-gas emission. Artificial neural networks (ANNs) were trained using data acquired by the gas sensors and reference data obtained from on-line HPLC analyses, from a total of six cultivations to estimate concentrations of the metabolites glucose, glycerol, acetate and acetaldehyde. The ANNs were subsequently validated on an independent set of cultivation data resulting in a prediction accuracy described by the root mean square error (RMSE) of 0.13 (in the range 0-7.33), 0.015 (0.08-0.15), 0.012 (0-0.20) and 0.004 (0-0.11) g L-1, respectively. Data from a cultivation with higher initial glucose concentration were added to the original data and the extended set was used for training an ANN to determine concentration variables at higher concentration ranges than in the first study. The RMSE was 1.2 (0-9.31), 0.016 (0.09-0.20), 0.026 (0-0.19) and 0.010 (0-0.15) g L-1, respectively, when validating the ANNs.

  • 49.
    Lindahl, R
    et al.
    National Institute for Working Life, Umeå.
    Wästerby, A
    National Institute for Working Life, Umeå.
    Levin, Jan-Olof
    National Institute for Working Life, Umeå.
    Determination of morpholine in air by derivatisation with 1-naphthylisothiocyanate and HPLC analysis2001In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 126, no 2, p. 152-154Article in journal (Refereed)
    Abstract [en]

    A method for the determination of morpholine in air was developed. Samples were collected with adsorbent tubes containing XAD-2 resin coated with 1-naphthylisothiocyanate (NIT). The thiourea derivative formed was subsequently desorbed with acetonitrile and analysed by HPLC with UV detection. The recovery after gas phase spiking with morpholine (2.2-1570 micrograms) was 91% (86-100%) with a relative standard deviation of 5.5%. No effect on recovery from relative humidity or amount of morpholine was seen. The lowest level tested corresponded to 7 mg m-3 (1/10 threshold limit value) for a 15 min sampling period with a sampling rate of 20 ml min-1. Exposed NIT-coated XAD-2 tubes were stable at room temperature for at least 2 weeks.

  • 50. Liu, Wei
    et al.
    Chen, Yi
    Yan, Mingdi
    Portland State University.
    Surface plasmon resonance imaging of limited glycoprotein samples2008In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 133, no 9, p. 1268-1273Article in journal (Refereed)
    Abstract [en]

    A surface plasmon resonance imaging method has been developed for high throughput recognition and determination of low level glycoproteins with limited sample volume at least down to 50 nL. Chicken ovalbumin and immunoglobulin G were chosen as model compounds while bovine serum albumin and lysozyme were used as control. Each protein, at a concentration of 0.0080-1.0 mg mL(-1), was printed on one gold sensing film, and the films were simultaneously reacted with a probe solution and viewed using a laboratory-built surface plasmon resonance imaging system. The imaging signals were dependent on the concentration and the type of analyte, with a limit of detection down to at least 0.5 ng. The glycoproteins dotted at either 1.0 mg mL(-1) or 0.010 mg mL(-1) were easily differentiated from the non-glycoproteins by reaction with 200 nM concanavalin A (con A), giving a limit of recognition down also to 0.5 ng glycoprotein. This imaging method was hence considered a new tool for analyzing glycoproteins.

12 1 - 50 of 91
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf