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  • 1. Almstrand, A-C
    et al.
    Ljungström, E
    Lausmaa, J
    YKI – Ytkemiska institutet.
    Bake, B
    Sjövall, P
    YKI – Ytkemiska institutet.
    Olin, A-C
    Airway Monitoring by Collection and Mass Specrometric Analysis of Exhaled Particles2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 2, p. 662-668Article in journal (Refereed)
    Abstract [en]

    We describe a new method for simultaneously collecting particles in exhaled air for subsequent chemical analysis and measuring their size distribution. After forced exhalation, particles were counted and collected in spots on silicon wafers with a cascade impactor. Several phospholipids were identified by time-of-flight secondary ion mass spectrometric analysis of the collected spots, suggesting that the particles originated from the lower airways. The amount of particles collected in ten exhalations was sufficient for characterizing the phospholipid composition. The feasibility of the technique in respiratory research is demonstrated by analysis of the phospholipid composition of exhaled particles from healthy controls, patients with asthma, and patients with cystic fibrosis. We believe this technology will be useful for monitoring patients with respiratory disease and has a high potential to detect new biomarkers in exhaled air.

  • 2.
    Arrhenius, Karine
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Organisk kemi (Kmo).
    Kühnemuth, Daniel
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Kemi.
    Traceable reference gas mixtures for sulfur-free natural gas odorants2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 13, no 1, p. 6695-6702Article in journal (Refereed)
  • 3. Bosvik, R.
    et al.
    Knutsen, K.V.
    von Sydow, Erik
    SIK – Svenska institutet för konserveringsforskning.
    Chromatographic separation and identification of normal aliphatic alcohols as esters of p-nitrophenyl-azobenzoic acid by infrared and x-ray diffraction1961In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 33, no 9, p. 1162-1164Article in journal (Refereed)
    Abstract [en]

    Alcohols in fruit flavors can be separated and identified as esters of p-nitrophenylazobenzoic acid by combined paper partition chromatography, infrared analysis, and x-ray diffraction. Both infrared spectra and x-ray diffraction patterns show marked differences among the esters.

  • 4.
    Gunnarsson, A
    et al.
    YKI – Ytkemiska institutet.
    Bally, M
    Jonsson, P
    Medard, N
    Hook, F
    Time-resolved surface-enhanced ellipsometric contrast imaging for label-free analysis of biomolecular recognition reactions on glycolipid domains2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 15, p. 6538-6545Article in journal (Refereed)
    Abstract [en]

    We have applied surface-enhanced ellipsometry contrast (SEEC) imaging for time-resolved label-free visualization of biomolecular recognition events on spatially heterogeneous supported lipid bilayers (SLB). Using a conventional inverted microscope equipped with total internal reflection (TIR) illumination, biomolecular binding events were monitored with a lateral resolution near the optical diffraction limit at an acquisition rate of ∼1 Hz with a sensitivity in terms of surface coverage of ∼1 ng/cm2. Despite the significant improvement in spatial resolution compared to alternative label-free surface-based imaging technologies, the sensitivity remains competitive with surface plasmon resonance (SPR) imaging and imaging ellipsometry. The potential of the technique to discriminate local differences in protein binding kinetics was demonstrated by time-resolved imaging of anti-GalCer antibodies binding to phase-separated lipid bilayers consisting of phosphatidylcholine (POPC) and galactosylceramide (GalCer). A higher antibody binding capacity was observed on the GalCer-diluted fluid region in comparison to the GalCer-rich gel phase domains. This observation is tentatively attributed to differences in the presentation of the GalCer epitope in the two phases, resulting in differences in availability of the ligand for antibody binding. The complementary information obtained by swiftly switching between SEEC and fluorescence (including TIR fluorescence) imaging modes was used to support the data interpretation. The simplicity and generic applicability of the concept is discussed in terms of microfluidic applications.

  • 5. Gunnarsson, A
    et al.
    Kollmer, F
    Sohn, S
    Höök, F
    Sjövall, P
    YKI – Ytkemiska institutet.
    Spatial-resolution limits in mass spectrometry imaging of supported lipid bilayers and individual lipid vesicles2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 6, p. 2426-2433Article in journal (Refereed)
    Abstract [en]

    The capabilities of time-of-flight secondary ion mass spectrometry (TOF-SIMS) with regards to limits in lateral resolution for biological samples are examined using supported lipid bilayers and individual lipid vesicles, both being among the most commonly used cell membrane mimics. Using supported 1-palmitoyl-2-oleoyl-sn-glycero3-phosphocholine (POPC) bilayers confined to a SiO2 substrate by a chemically modified gold surface, the edge of the lipid bilayer was analyzed by imaging TOFSIMS to assess the lateral resolution. The results using 80 keV Bi32+ primary ions show that, under optimized conditions, mass spectrometry imaging of specific unlabeled lipid fragments is possible with sub-100 nm lateral resolution. Comparison of the secondary ion yields for the phosphocholine ion (m/z 184) from a POPC bilayer using C60+ or Bi3+ primary ions showed similar results, indicating an advantage of Bi3+ primary ions for high-resolution imaging of lipid membranes, due to their better demonstrated focusing capability. Moreover, using 300 nm vesicles of different lipid composition, the capability to detect and chemically identify individual submicrometer lipid vesicles at separations down to ~ 1 μm is demonstrated.

  • 6. Knox, RJ
    et al.
    Burns, NL
    YKI – Ytkemiska institutet.
    Van Alstine, JM
    Milton Harris, J
    Seaman, GVF
    Automated analytical microelectrophoresis: Modeling and control of adverse chamber surface properties1998In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 70, p. 2268-2279Article in journal (Refereed)
    Abstract [en]

    Electrophoretic analysis of colloidal particles is adversely affected by a host of surface phenomena including electroosmosis, phase wall wetting, and sample or air bubble adsorption. Neutral, hydrophilic polymer coatings significantly control such phenomena on a variety of surfaces. Readily adsorbed poly(ethylene glycol)-poly(ethylene imine) conjugates were found to form coatings whichsignificantly reduce electroosmosis, and positively control adsorption and wetting, in the standard glass sample chambers (5 x 3 x 1 mm i.d.) employed in a representative commercial electrophoresis apparatus (Coulter DELSA 440+). The reduction in electroosmosis was similar to that exhibited by coated quartz capillaries (2 mm i.d.) in a manual apparatus (Rank MK 1). The coatings significantly reduced electroosmosis over a wide range of pH (2 to 11) and ionic strength (1 to 100 mM) and were stable for many weeks under normal laboratory conditions. They greatly enhanced ease of operation and accurancy (sample mean electrophoretic mobility _+ S.D.) of the DELSA 440. Enhanced mobility determination appeared related to reducing electroosmosis gradient flow profiles near the chamber center-axis stationary levels, where particle mobility is typically measured. Such flow profiles also appeared to be affected by asymmetries in the surface properties of DELSA chamber walls. A hydronamic description of electroosmotic fluid flow in rectangular chambers was adapted to analyze the propagation of errors due to nonideal focusing and chamber asymmetries. This analysis indicated that rectangular chambered devices may gain accuracy by measuring particle mobility at stationary levels removed from the chamber center-axes, and that the hydrodynamics of some rectangular chambers may confer accuracy advantages over cylindrical chambers.

  • 7.
    Lyvén, Benny
    et al.
    SP - Sveriges Tekniska Forskningsinstitut / Oorganisk kemi (Kmoo).
    Haraldsson, Conny
    SP - Sveriges Tekniska Forskningsinstitut / Oorganisk kemi (Kmoo).
    Hassellöv, M
    Determination of continuous size and trace element distribution of colloidal material in natural water by online coupling of flow field-flow fractionation with ICP MS1999In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 71, no 16, p. 3497-3502Article in journal (Other academic)
  • 8. Malm, J
    et al.
    Giannaras, D
    Riehle, MO
    Gadagaard, N
    Sjövall, P
    YKI – Ytkemiska institutet.
    Fixation and drying protocols for the preparation of cell samples for time-of-flight secondary ion mass spectrometry analysis2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 17, p. 7197-7205Article in journal (Refereed)
    Abstract [en]

    Time-of-flight secondary ion mass spectrometry (TOFSIMS) is a promising tool for subcellular chemical analysis of biological cells. However, to obtain relevant information, the method used for sample preparation is critical. In this work, we have used TOF-SIMS, scanning electron microscopy (SEM), and interference reflection microscopy (IRM) to study the effects of different fixation and drying methods on the morphology and chemical structure of human fibroblast cells (hTERT) adhered to a silicon surface. Specifically, two fixation techniques (chemical fixation with glutaraldehyde and cryofixation by plunge freezing) and two drying techniques (freeze drying and alcohol substitution drying) were investigated. Cryofixation followed by freeze drying was determined to produce dried cells with preserved cell morphology, intact cell membranes, and retained sodium/potassium ion concentration gradients across the plasma membrane. By washing samples in an aqueous solution of ammonium formate (AF) before cryofixation, the accumulation of salts on the sample surface during drying could be suppressed. IRM measurements showed that the cell morphology was preserved during washing with ammonium formate, although some swelling occurred. Compared with cryofixation, cells fixed with glutaraldehyde showed finer structures on the cell surface in SEM and similar lipid distributions in TOF-SIMS, but the sodium/potassium ion gradients were not retained. Alcohol drying was determined to remove cell membrane phospholipids significantly, although the use of osmium tetroxide as a post-fixative was shown to decrease this effect.

  • 9.
    Sjövall, Peter
    Funktionella material (KMf).
    Imaging of distribution of topically applied drug molecules in mouse skin by combination of time-of-flight secondary ion mass spectrometry and scanning electron microscopy2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 7, p. 3443-3452Article in journal (Refereed)
  • 10.
    Sjövall, Peter
    Funktionella material (KMf).
    Relative quantification of phospholipid accumulation in the PC12 cell plasma membrane following phospholipid incubation using TOF-SIMS imaging2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 13, p. 5337-5343Article in journal (Refereed)
  • 11. Solé-Domènech, S
    et al.
    Johansson, B
    Schalling, M
    Malm, J
    Sjövall, P
    YKI – Ytkemiska institutet.
    Analysis of opoid and amyloid peptides using time-of-flight secondary ion mass spectrometry2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 5, p. 1964-1974Article in journal (Refereed)
    Abstract [en]

    The imaging capability and high detection sensitivity of time-of-flight secondary ion mass spectrometry (ToF-SIMS) makes it a potentially attractive complement to other mass spectrometry methods, such as ESI and MALDI, for the analysis of proteins and peptides. We have explored this possibility by performing a systematic analysis of synthetic opioid and amyloid peptides with ToF-SIMS using Bi3+ and Au3 + primary ions. In the low mass region of the spectra, a number of single amino acid ion peaks were detected, providing information about the amino acid content in each peptide. In the medium and high mass range of the spectra, peaks corresponding to multiple amino acid ions (backbone cleavage ions) as well as molecular ions were detected, allowing for the determination of the amino acid sequence and the molecular mass of the entire peptide, respectively. Detection efficiencies were determined for the molecular ions of some of the peptides, indicating detection limits in the attomole range. The fragmentation patterns observed in the ToF-SIMS analysis of opioid and amyloid peptides showed interesting similarities with collision-induced dissociation (CID) studies using other mass spectrometry methods. The present work provides important progress toward ToFSIMS proteomics..

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