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  • 1. Acero Sanchez, Josep Ll.
    et al.
    Joda, Hamdi
    Henry, Olivier Y. F.
    Solnestam, Beata W.
    Kvastad, Linda
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Sahlén, Pelin
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Lundeberg, Joakim
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Laddach, Nadja
    Ramakrishnan, Dheeraj
    Riley, Ian
    Schwind, Carmen
    Latta, Daniel
    O'Sullivan, Ciara K.
    Electrochemical Genetic Profiling of Single Cancer Cells2017In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 89, no 6, p. 3378-3385Article in journal (Refereed)
    Abstract [en]

    Recent understandings in the development and spread of cancer have led to the realization of novel single cell analysis platforms focused on circulating tumor cells (CTCs). A simple, rapid, and inexpensive analytical platform capable of providing genetic information on these rare cells is highly desirable to support clinicians and researchers alike to either support the selection or adjustment of therapy or provide fundamental insights into cell function and cancer progression mechanisms. We report on the genetic profiling of single cancer cells, exploiting a combination of multiplex ligation-dependent probe amplification (MLPA) and electrochemical detection. Cells were isolated using laser capture and lysed, and the mRNA was extracted and transcribed into DNA. Seven markers were amplified by MLPA, which allows for the simultaneous amplification of multiple targets with a single primer pair, using MLPA probes containing unique barcode sequences. Capture probes complementary to each of these barcode sequences were immobilized on a printed circuit board (PCB) manufactured electrode array and exposed to single-stranded MLPA products and subsequently to a single stranded DNA reporter probe bearing a HRP molecule, followed by substrate addition and fast electrochemical pulse amperometric detection. We present asimple, rapid, flexible, and inexpensive approach for the simultaneous quantification of multiple breast cancer related mRNA markers, with single tumor cell sensitivity.

  • 2. Adler, Belinda
    et al.
    Boström, Tove
    KTH, School of Biotechnology (BIO), Proteomics.
    Ekström, Simon
    Hober, Sophia
    KTH, School of Biotechnology (BIO), Proteomics.
    Laurell, Thomas
    Miniaturized and Automated High-Throughput Verification of Proteins in the ISET Platform with MALDI MS2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 20, p. 8663-8669Article in journal (Refereed)
    Abstract [en]

    A major bottleneck in high-throughput protein production is the validation step, which is why parallel and automated sample processing methods are highly desirable. Also, a miniaturized sample preparation format is preferred, as the reduction of reagent volumes significantly decreases the analysis cost per sample. We have developed an automated and miniaturized protein sequence verification protocol for recombinant proteins utilizing peptide mass fingerprinting and MS/MS analysis. The integrated selective enrichment target (ISET) platform, previously developed in our group, with its dual functionality, being both a sample preparation platform and a MALDI target plate, is employed. All steps including immobilized metal ion affinity chromatography of protein on cobalt-loaded beads, tryptic digestion, and MALDI MS analysis are performed in an array format, without any sample transfers, on the same ISET chip. The automated configuration reduced the sample preparation time significantly. Starting with crude lysate, a full plate of 48 purified, digested samples prepared for MALDI-MS can be generated in 4 h, with only 30 min of operator involvement. This paper demonstrates the utility of the method by parallel analysis of 45 His-tagged human recombinant proteins.

  • 3.
    Aeppli, Christoph
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Holmstrand, Henry
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Andersson, Per
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Direct compound-specific stable chlorine isotope analysis of organic compounds with quadrupole GC/MS using standard isotope bracketing2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 1, p. 420-426Article in journal (Refereed)
    Abstract [en]

    A method has been developed for the direct determination of the stable chlorine isotope composition (delta(37)Cl) of organochlorines that eliminates sample preparation, achieves precision comparable to earlier techniques while improving the sensitivity, and makes use of benchtop gas chromatography-quadrupole mass spectrometry instruments (GCqMS). The method is based on the use of multiple injections (n = 8-10) of the sample, bracketed by a molecularly identical isotopic standard with known delta(37)Cl, determined using off-line thermal ionization mass spectrometry (TIMS). Mass traces of two isotopologues differing by one chlorine isotope were used to calculate delta(37)Cl values. Optimization of mass spectrometry and peak integration parameters as well as method validation was achieved using tetrachloroethene (PCE), p,p'-dichlorodiphenyltrichloroethane (DDT), and pentachlorophenol (PCP), spanning a delta(37)Cl range of -5.5 to +3.2 per thousand vs SMOC. Injecting 1.6-1100 pmol resulted in standard deviations (1sigma) of 0.6-1.3 per thousand, and the delta(37)Cl results agreed with values independently measured with TIMS. The method was tested by determining the Rayleigh fractionation during evaporation of pure liquid PCE, resulting in a chlorine isotopic enrichment factor of epsilon(Cl) = -1.1 +/- 0.4 per thousand. Furthermore, position-specific delta(37)Cl analysis based on analysis of DDT mass fragments was evaluated. The GCqMS-delta(37)Cl method offers a simplified yet sensitive approach for compound-specific chlorine isotope analysis.

  • 4. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Coulometric Calcium Pump for Thin Layer Sample Titrations2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 19, p. 10125-10130Article in journal (Refereed)
  • 5. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Direct Ion Speciation Analysis with Ion-Selective Membranes Operated in a Sequential Potentiometric/Time Resolved Chronopotentiometric Sensing Mode2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 20, p. 8813-8821Article in journal (Refereed)
  • 6. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 7, p. 3945-3952Article in journal (Refereed)
  • 7. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Xie, Xiaojiang
    Bakker, Eric
    Direct Alkalinity Detection with Ion-Selective Chronopotentiometry2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 13, p. 6461-6470Article in journal (Refereed)
  • 8.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Reijmar, Karin
    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.
    Label-Free Characterization of Peptide-Lipid Interactions Using Immobilized Lipodisks2013In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 85, no 15, p. 7377-7384Article in journal (Refereed)
    Abstract [en]

    Lipodisks, planar lipid bilayer structures stabilized by PEG-ylated lipids, were in the present study covalently bound and immobilized onto sensors for quartz crystal microbalance with dissipation monitoring (QCM-D) studies. It is shown that the modified sensors can be used to characterize the interaction of lipodisks with α-helical amphiphilic peptides with an accuracy similar to that obtained with well established fluorimetric approximations. The method presented has the great advantage that it can be used with peptides in their native form even if no fluorescent residues are present. The potential of the method is illustrated by determining the parameters describing the association of melittin, mastoparan X, and mastoparan with immobilized lipodisks. Both thermodynamic and kinetic analyses are possible. The presented method constitutes a useful tool for fundamental studies of peptide–membrane interactions and can also be applied to optimize the design of lipodisks, for example, for sustained release of antimicrobial peptides in therapeutic applications.

  • 9. Akter, Farhima
    et al.
    Mie, Masayasu
    Grimm, Sebastian
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Nygren, Per-Åke
    KTH, School of Biotechnology (BIO), Molecular Biotechnology.
    Kobatake, Eiry
    Detection of Antigens Using a Protein-DNA Chimera Developed by Enzymatic Covalent Bonding with phiX Gene A2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 11, p. 5040-5046Article in journal (Refereed)
    Abstract [en]

    The chemical reactions used to make antibody DNA conjugates in many immunoassays diminish antigen-binding activity and yield heterogeneous products. Here, we address these issues by developing an antibody-based rolling circle amplification (RCA) strategy using a fusion of phi X174 gene A* protein and Z(mab2s) (A*-Zmab). The phi X174 gene A* protein is an enzyme that can covalently link with DNA, while the Z(mab2s) protein moiety can bind to specific species of antibodies. The DNA in an A*-Zmab conjugate was attached to the A* protein at a site chosen to not interfere with protein function, as determined by enzyme-linked immunosorbent assay (ELISA) and gel mobility shift analysis. The novel A*-Zmab-DNA conjugate retained its binding capabilities to a specific class of murine immunoglobulin gamma 1 (IgG1) but not to rabbit IgG. This indicates the generality of the A*-Zmab-based immuno-RCA assay that can be used in-sandwich ELISA format. Moreover, the enzymatic covalent method dramatically increased the yields of A*-Zmab-DNA conjugates up to 80% after a 15 min reaction. Finally, sensitive detection of human interferon-gamma (IFN-gamma) was achieved by immuno-RCA using our fusion protein in sandwich ELISA format. This new approach of the use of site-specific enzymatic DNA conjugation to proteins should be applicable to fabrication of novel immunoassays for biosensing.

  • 10.
    Allard, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Bäckström, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Sjöberg, Per J.R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Comparing capillary electrophoresis: mass spectrometry fingerprints of urine samples obtained after intake of coffee, tea, or water.2008In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 80, no 23, p. 8946-8955Article in journal (Refereed)
    Abstract [en]

    Metabolomic fingerprinting is a growing strategy for characterizing complex biological samples without detailed prior knowledge about the metabolic system. A two-way analysis system with liquid separation and mass spectrometric detection provides detail-rich data suitable for such fingerprints. As a model study, human urine samples, obtained after intake of coffee, tea, or water, were analyzed with capillary electrophoresis electrospray ionization time-of-flight mass spectrometry (CE−ESI-TOF-MS). In-house-developed software (in Matlab) was utilized to manage and explore the large amount of data acquired (230 CE−MS runs, each with 50−100 million nonzero data points). After baseline and noise reduction, followed by suitable binning in time and m/z, the data sets comprised 9 and 14 million data points in negative and positive ESI mode, respectively. Finally, a signal threshold was applied, further reducing the number to about 100 000 data points per data set. A set of interactive exploratory tools, utilizing principal component analysis (PCA) and analysis of variance (ANOVA) results based on a general linear model, facilitated visual interpretation with score plots (for group assessment) and differential fingerprints (for “hot spot” detection). In the model study highly significant differences due to beverage intake were obtained among the 10 first principal components (p < 10−6 for two of the components in both ESI modes). Especially, the contrasts between “coffee” and “tea or water” indicated several “hot spots” with highly elevated intensities (e.g., for uncharged masses 93, 94, 109, 119, 123, 132, 148, 169, 178, 187, 190, and 193) suitable for further analysis, for example, with tandem MS.

  • 11.
    Alleso, Morten
    et al.
    Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, and Department of Food Science, Faculty of Life Sciences, University of Copenhagen.
    Velaga, Sitaram
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Alhalaweh, Amjad
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Cornett, Claus
    Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, and Department of Food Science, Faculty of Life Sciences, University of Copenhagen.
    Rasmussen, Morten A.
    Department of Food Science, Faculty of Life Sciences, University of Copenhagen.
    Berg, Frans van den
    Department of Food Science, Faculty of Life Sciences, University of Copenhagen.
    Diego, Heidi Lopez de
    Analytical R and D, H. Lundbeck A/S.
    Rantanen, Jukka
    Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen.
    Near-infrared spectroscopy for cocrystal screening: a comparative study with Raman spectroscopy2008In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 80, no 20, p. 7755-7764Article in journal (Refereed)
    Abstract [en]

    Near-infrared (NIR) spectroscopy is a well-established technique for solid-state analysis, providing fast, noninvasive measurements. The use of NIR spectroscopy for polymorph screening and the associated advantages have recently been demonstrated. The objective of this work was to evaluate the analytical potential of NIR spectroscopy for cocrystal screening using Raman spectroscopy as a comparative method. Indomethacin was used as the parent molecule, while saccharin and L-aspartic acid were chosen as guest molecules. Molar ratios of 1:1 for each system were subjected to two types of preparative methods. In the case of saccharin, liquid-assisted cogrinding as well as cocrystallization from solution resulted in a stable 1:1 cocrystalline phase termed IND-SAC cocrystal. For L-aspartic acid, the solution-based method resulted in a polymorphic transition of indomethacin into the metastable a form retained in a physical mixture with the guest molecule, while liquid-assisted cogrinding did not induce any changes in the crystal lattice. The good chemical peak selectivity of Raman spectroscopy allowed a straightforward interpretation of sample data by analyzing peak positions and comparing to those of pure references. In addition, Raman spectroscopy provided additional information on the crystal structure of the IND-SAC cocrystal. The broad spectral line shapes of NIR spectra make visual interpretation of the spectra difficult, and consequently, multivariate modeling by principal component analysis (PCA) was applied. Successful use of NIR/PCA was possible only through the inclusion of a set of reference mixtures of parent and guest molecules representing possible solid-state outcomes from the cocrystal screening. The practical hurdle related to the need for reference mixtures seems to restrict the applicability of NIR spectroscopy in cocrystal screening.

  • 12. Almstrand, A-C
    et al.
    Ljungström, E
    Lausmaa, J
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Bake, B
    Sjövall, Peter
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, 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.

  • 13.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsen, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk (Addition/Correction)2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, p. 631-631Article in journal (Refereed)
  • 14.
    Amini, Nahid
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Shariatgorji, Mohammadreza
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Crescenzi, Carlo
    Thorsén, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 1, p. 290-296Article in journal (Refereed)
    Abstract [en]

    A simple platform for combining solid phase extraction (SPE) and surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) of extracted analytes, using disks prepared by embedding graphitized carbon black (GCB-4) particles in a network of polytetrafluoroethylene (PTFE), is presented. The system provides a convenient approach for rapid SALDI-MS screening of substances in aqueous samples, which can be followed by robust quantitative and/or structural analyses by liquid chromatography (LC)/MS/MS of positive samples. The extraction discs are easily transferred between gaskets where the sample extraction and desorption of selected samples is performed and the mass spectrometer. The SPE and SALDI properties of the new GCB-4 disc have been characterized for 15 pesticides with varying chemical properties, and the screening strategy has been applied to the analysis of pesticides in agricultural drainage water. Atrazine and atrazine-desethyl-2-hydroxy were detected in the sampled water by SALDI-MS screening and subsequently confirmed and quantified using LC/MS/MS.

  • 15.
    Andersson, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Svensson, Karolina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A microfluidic control board for high-pressure flow, composition, and relative permittivity2018In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, no 21, p. 12601-12608Article in journal (Refereed)
    Abstract [en]

    Flow control is central to microfluidics and chromatography. With decreasing dimensions and high pressures, precise fluid flows are often needed. In this paper, a high-pressure flow control system is presented, allowing for the miniaturization of chromatographic systems and the increased performance of microfluidic setups by controlling flow, composition and relative permittivity of two-component flows with CO2. The system consists of four chips: two flow actuator chips, one mixing chip and one relative permittivity sensor. The actuator chips, throttling the flow, required no moving parts as they instead relied on internal heaters to change the fluid resistance. This allows for flow control using miniaturized fluid delivery systems containing only a single pump or pressure source. Mobile phase gradients between 49% to 74% methanol in CO2 were demonstrated. Depending on how the actuator chips were dimensioned, the position of this range could be set for different method-specific needs. With the microfluidic control board, both flow and composition could be controlled from constant pressure sources, drift could be removed, and variations in composition could be lowered by 84%, resulting in microflows of CO2 and methanol with a variation in the composition of 0.30%.

  • 16.
    Appelblad, Patrik
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Sciences. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jonsson, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bäckström, Torbjörn
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Obstetrics and Gynaecology.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Determination of C-21 ketosteroids in serum using trifluoromethanesulfonic acid catalyzed precolumn dansylation and 1,1’-oxalyldiimidazole postcolumn peroxyoxalate chemiluminescence detection1998In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 70, no 23, p. 5002-5009Article in journal (Refereed)
    Abstract [en]

    A new procedure for the quantitation of C-21 ketosteroids using trifluoromethanesulfonic acid-catalyzed precolumn dansylation and coupled column liquid chromatographic separation, followed by postcolumn 1,1‘-oxalyldiimidazole peroxyoxalate chemiluminescence detection is presented. In the simultaneous optimization of chromatographic resolution and chemiluminescence intensity, a coupled column chromatographic system and a stopped-flow system were used. An eluent containing 20 mM phosphate buffer at pH 6.7 accomplished an efficient separation of 3α-hydroxy-5β-pregnan-20-one from a mixture containing 10 C-21 ketosteroids. Phosphate buffer also proved to be the most advantageous, among the six buffers tested, for sensitive detection. Experimental design and multivariate data analysis were used to characterize and optimize the postcolumn reaction chemistry in the chromatographic system. A valid full factorial design with excellent predictability showed that the flow rates for both 1,1‘-oxalyldiimidazole and hydrogen peroxide were the factors most strongly affecting the sensitivity of the system. The theoretical plate numbers were above 11 000 for all 10 dansylated ketosteroids. The 3σ detection limit estimated from 3α-hydroxy-5β-pregnan-20-one calibration curve data was 1.6 pmol (n = 4, 125 μL injected) and spiked serum containing 0−74 pmol of this compound showed overall recoveries of 73 ± 9% (n = 12). Quantitation of 3α-hydroxy-5β-pregnan-20-one was finally carried out on 45 serum samples and the results compared to those from a radioimmunoassay (RIA) method. The data acquired with the procedure described in this work compare well with the results from RIA, which confirms the reliability of the new analytical procedure.

  • 17. Appelblad, P.K.
    et al.
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Baxter, Douglas
    Sources of uncertainty in isotope ratio measurements by inductively coupled plasma mass spectrometry2001In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 73, no 13, p. 2911-2919Article in journal (Refereed)
    Abstract [en]

    A model is presented describing the effects of dead time and mass bias correction factor uncertainties, flicker noise, and counting statistics on isotope ratio measurement precision using inductively coupled plasma mass spectrometry (ICPMS) with a single collector. Noise spectral analysis is exploited to enable estimation of the flicker noise parameters. For the instrument used, the flicker noise component exhibited a fairly weak frequency (f) dependence ( f -0.33±0.12), but was directly proportional to the total number of counts, Q. As white noise, determined by counting statistics, is given by Q0.5, the isotope ratio measurement uncertainties will actually cease to improve when Q exceeds a certain threshold. This would suggest that flicker noise could become the limiting factor for the precision with which isotope ratios can be determined by ICPMS. However, under most experimental conditions, uncertainties associated with mass discrimination and dead time correction factors are decisive. For ratios up to ~22 (115In/113In), optimum major isotope count rates are generally below 0.3 MHz, for which precision in the mass discrimination factor is limiting. The model derived could be used as a starting point for determining optimum conditions and understanding the limitations of single-collector ICPMS for precise isotope ratio measurements.

  • 18.
    Araújo, Ana Catarina
    et al.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Song, Yajing
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Lundeberg, Joakim
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Ståhl, Patrik L.
    Brumer, Harry, III
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Activated Paper Surfaces for the Rapid Hybridization of DNA through Capillary Transport2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 7, p. 3311-3317Article in journal (Refereed)
    Abstract [en]

    The development of low-cost, accurate, and equipment-free diagnostic tests is crucial to many clinical, laboratory, and field applications, including forensics and medical diagnostics. Cellulose fiber-based paper is an inexpensive, biodegradable, and renewable resource, the use of which as a biomolecule detection matrix and support confers several advantages compared to traditional materials such as glass. In this context, a new, facile method for the preparation of surface functionalized papers bearing single-stranded probe DNA (ssDNA) for rapid target hybridization via capillary transport is presented. Optimized reaction conditions were developed that allowed the direct, one-step activation of standard laboratory filters by the inexpensive and readily available bifunctional linking reagent, 1,4-phenylenediisothiocyanate. Such papers were thus amenable to subsequent coupling of amine-labeled ssDNA under standard conditions widely used for glass-based supports. The intrinsic wicking ability of the paper matrix facilitated rapid sample elution through arrays of probe DNA, leading to significant, detectable hybridization in the time required for the sample liquid to transit the vertical length of the strip (less than 2 min). The broad applicability of these paper test strips as rapid and specific diagnostics in "real-life" situations was exemplified by the discrimination of amplicons generated from canine and human mitochondrial and genomic DNA in mock forensic samples.

  • 19.
    Arnell, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Validation of the Tracer-Pulse Method for Multi-Component Liquid Chromatography. A Classical Paradox Revisited2006In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 78, no 13, p. 4615-4623Article in journal (Refereed)
    Abstract [en]

    The tracer-pulse method was extended and validated for the determination of multicomponent adsorption isotherms in liquid chromatography. Competitive adsorption isotherms can be determined for any number of solutes, up to the column resolution limit. The basic principle is to equilibrate the column with an eluent containing a mixture of the solutes and then measure the migration velocity of each of them through the column. It is easy to calculate the stationary phase concentrations from these velocities, given the eluent composition. As in frontal analysis, real competitive isotherm data are measured using this method, unlike other methods, which only produce parametric estimates. The method was used to measure the binary isotherms of beta-blockers on a Kromasil C8 column. The data were fitted to competitive bi-Langmuir adsorption isotherm functions and was found to agree well with the results of frontal analysis and the perturbation method. Computer simulations based on the isotherm parameters were performed and displayed very good agreement with the experimental chromatograms. An intriguing and seemingly paradoxical property is visualized and discussed: the fact that the injected molecules are not found in the detected peaks.

  • 20.
    Arnell, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Forssén, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Tuneable Peak Deformations in Chiral Liquid Chromatography2007In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 79, p. 5838-5847Article in journal (Refereed)
  • 21.
    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)
    Abstract [en]

    The first reference gas mixtures of sulfur-free natural gas odorants that are traceable to the International System of Units (SI) have been produced and their compositions validated. These mixtures, which contain methyl acrylate and ethyl acrylate at amount fractions between 1.1 and 2.1 μmol mol-1, can be used to underpin measurements of sulfur-free odorants, which are increasingly being used to odorize natural gas in transmission networks as they have less harmful properties than traditional sulfur-containing odorants. The reference gas mixtures produced have been shown to be stable in passivated aluminum cylinders for at least 8 months and have been validated (to within 6% or less) by interlaboratory measurements at three National Measurement Institutes. The stability of methyl acrylate and ethyl acrylate in gas sampling bags has been investigated, and the challenges of analyzing 2-ethyl-3- methylpyrazine, which is used as a stabilizer in sulfur-free odorants, are also briefly discussed.

  • 22.
    Artemenko, Konstantin A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Zubarev, Alexander R.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Samgina, Yu
    Lebedev, T
    Savitski, Mikhail M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Zubarev, Roman A.
    Two dimensional mass mapping as a general method of data representation in comprehensive analysis of complex molecular mixtures.2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 10, p. 3738-3745Article in journal (Refereed)
    Abstract [en]

    A recent proteomics-grade (95%+ sequence reliability) high-throughput de novo sequencing method utilizes the benefits of high resolution, high mass accuracy, and the use of two complementary fragmentation techniques collision-activated dissociation (CAD) and electron capture dissociation (ECD). With this high-fidelity sequencing approach, hundreds of peptides can be sequenced de novo in a single LC-MS/MS experiment. The high productivity of the new analysis technique has revealed a new bottleneck which occurs in data representation. Here we suggest a new method of data analysis and visualization that presents a comprehensive picture of the peptide content including relative abundances and grouping into families. The 2D mass mapping consists of putting the molecular masses onto a two-dimensional bubble plot, with the relative monoisotopic mass defect and isotopic shift being the axes and with the bubble area proportional to the peptide abundance. Peptides belonging to the same family form a compact group on such a plot, so that the family identity can in many cases be determined from the molecular mass alone. The performance of the method is demonstrated on the high-throughput analysis of skin secretion from three frogs, Rana ridibunda, Rana arvalis, and Rana temporaria. Two dimensional mass maps simplify the task of global comparison between the species and make obvious the similarities and differences in the peptide contents that are obscure in traditional data presentation methods. Even biological activity of the peptide can sometimes be inferred from its position on the plot. Two dimensional mass mapping is a general method applicable to any complex mixture, peptide and nonpeptide alike.

  • 23. Athavale, Rohini
    et al.
    Kokorite, Ilga
    Dinkel, Christian
    Bakker, Eric
    Wehrli, Bernhard
    Crespo, Gaston A.
    Brand, Andreas
    In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic Lakes2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 24, p. 11990-11997Article in journal (Refereed)
  • 24.
    Bellucci, J. J.
    et al.
    Swedish Museum Nat Hist, Sweden.
    Whitehouse, M. J.
    Swedish Museum Nat Hist, Sweden.
    Aleshin, M.
    IAEA, Austria.
    Eriksson, Mats
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Swedish Radiat Safety Author, Sweden.
    Simultaneous Pu and U Isotope Nuclear Forensics on an Environmentally Recovered Hot Particle2019In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 91, no 9, p. 5599-5604Article in journal (Refereed)
    Abstract [en]

    An environmentally recovered, mixed Pu-U hot particle from the Thule accident, Greenland has been analyzed by Scanning Electron Microscopy and a large-geometry Secondary Ion Mass Spectrometry based Scanning Ion Imaging (SII) method for simultaneous U-235,U-236,U-238 and Pu-239,Pu-240 isotope compositions. This SII technique permits the visual assessment of the spatial distribution of the isotopes of U and Pu and can be used to obtain quantitative isotope ratios in any user-defined square region up to a few 100 itm in size. The particle measured here has two resolvable U isotopic compositions with a single composition of weapons grade Pu. The bulk of the particle has,, enriched U and weapons-grade Pu with U-235/U-238, U-236/U-238 and Pu-240/Pu-239 of 1.12 +/- 0.04, 0.006 +/- 0.002, 0.054 +/- 0.004, respectively (2 sigma). The Pu isotopic ratio was consistent across the Pu-239/U-238(raw) sample but decreased from 1.99 +/- 0.07 to 0.11 +/- 0.04 (2 sigma) corresponding to the area of the particle with a resolvably different U isotope composition. This portion of the particle has U-235/U-238 U-236/U-238 and Pu-240/Pu-239 ratios of 0.11 +/- 0.04, 0.001 +/- 0.002, and 0.05 +/- 0.04, respectively (2 sigma). The origin of the less enriched U could be environmental that mixed with the particle or heterogeneously enriched U from the weapons. The heterogeneity of hot particles on a micrometer scale highlights the need for spatially resolved techniques to avoid mixing during a bulk or whole particle analysis, as the mixing end members here would have been lost, and the measured ratios would have been inaccurate.

  • 25.
    Bellucci, Jeremy
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Joshua, Snape
    Swedish Museum of Natural History, Department of Geology.
    Whitehouse, Martin
    Swedish Museum of Natural History, Department of Geology.
    Nemchin, Alexander
    Direct Pb Isotopic Analysis of a Nuclear Fallout Debris Particle from the Trinity Nuclear Test2017In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 89, p. 1887-1891Article in journal (Refereed)
    Abstract [en]

    The Pb isotope composition of a nuclear fallout debris particle has been directly measured in post-detonation materials produced during the Trinity nuclear test by a secondary ion mass spectrometry (SIMS) scanning ion image technique (SII). This technique permits the visual assessment of the spatial distribution of Pb and can be used to obtain full Pb isotope compositions in user-defined regions in a 70 μm × 70 μm analytical window. In conjunction with backscattered electron (BSE) and energy-dispersive spectroscopy (EDS) mapping of the same particle, the Pb measured in this fallout particle cannot be from a major phase in the precursor arkosic sand. Similarly, the Pb isotope composition of the particle is resolvable from the surrounding glass at the 2σ uncertainty level (where σ represents the standard deviation). The Pb isotope composition measured in the particle here is in excellent agreement with that inferred from measurements of green and red trinitite, suggesting that these types of particles are responsible for the Pb isotope compositions measured in both trinitite glasses. 

  • 26.
    Bergquist, Jonas
    et al.
    Department of Clinical Neuroscience, Section of Psychiatry and Neurochemistry, Goteborg University,.
    Gilman, S D
    Chemistry, Pennsylvania State university.
    Ewing, A G
    Chemistry, Pennsylvania State university.
    Ekman, R
    Department of Clinical Neuroscience, Section of Psychiatry and Neurochemistry, Goteborg University,.
    Analysis of human cerebrospinal fluid by capillary electrophoresis with laser-induced fluorescence detection.1994In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 66, no 20, p. 3512-8Article in journal (Refereed)
    Abstract [en]

    Capillary electrophoresis with laser-induced fluorescence detection is used to analyze 10 microL samples of human cerebrospinal fluid. Primary amine-containing compounds in untreated cerebrospinal fluid are labeled with 3-(4-carboxybenzoyl)-2-quinolinecarboxaldehyde prior to analysis, producing fluorescent isoindoles. Electropherograms containing approximately 50 peaks are obtained in less than 35 min from cerebrospinal fluid samples. Ten peaks in the electropherograms have been identified and quantitated: arginine, glutamine, threonine, valine, gamma-amino-n-butyric acid, serine, alanine, glycine, glutamic acid, and aspartic acid. Detection limits for these 10 amino acids range from 0.29 nM for gamma-amino-n-butyric acid to 100 nM for threonine, and separation efficiencies as high as 190,000 theoretical plates are obtained for these analytes. Electropherograms of cerebrospinal fluid samples from patients with Alzheimer's disease and from children with different neurological disorders are compared to those of healthy controls. Differences in individual amino acid levels are observed between the patient groups, and these differences appear to be disease and age related. These results indicate that analysis of cerebrospinal fluid by capillary electrophoresis will be useful as a selective, rapid, and sensitive tool for both diagnosis of central nervous system disorders and for study of the mechanisms of these disorders.

  • 27.
    Bergström, Sara K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Edenwall, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Lavén, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Velikyan, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Polyamine deactivation of integrated poly(dimethylsiloxane) structures investigated by radionuclide imaging and capillary electrophoresis experiments2005In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 3, p. 938-942Article in journal (Refereed)
    Abstract [en]

    The poly(dimethylsiloxane) (PDMS) material provides a number of advantageous features, such as flexibility, elasticity, and transparency, making it useful in integrated analytical systems. Hard fused-silica capillary structures and soft PDMS channels can easily be combined by a tight fit, which offers many alternatives for structure combinations. PDMS and fused silica are in different ways prone to adsorption of low levels of organic compounds. The need for modification of the inner wall surface of PDMS channels may often be necessary, and in this paper, we describe an easy and effective method using the amine-containing polymer PolyE-323 to deactivate both fused-silica and PDMS surfaces. The adsorption of selected peptides to untreated surfaces was compared to PolyE-323-modified surfaces, using both radionuclide imaging and capillary electrophoresis experiments. The polyamine modification displayed a substantially reduced adsorption of three hydrophobic test peptides compared to the native PDMS surface. Filling and storage of aqueous solution were also possible in PolyE-323-modified PDMS channels. In addition, hybrid microstructures of fused silica and PDMS could simultaneously be deactivated in one simple coating procedure.

  • 28.
    Bergström, Sara K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Samskog, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Markides, Karin E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Development of a Poly(dimethylsiloxane) Interface for On-Line Capillary Column Liquid Chromatography: Capillary Electrophoresis Coupled to Sheathless Electrospray Ionization Time-of-Flight Mass Spectrometry2003In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 75, no 20, p. 5461-5467Article in journal (Refereed)
    Abstract [en]

    An interface in elastomeric poly(dimethylsiloxane) (PDMS) for on-line orthogonal coupling of packed capillary liquid chromatography (LC) (i.d. = 0.2 mm) with capillary electrophoresis (CE) in combination with sheathless electrospray ionization (ESI) time-of-flight mass spectrometric (TOFMS) detection is presented. The new interface has a two-level design, which in combination with a continuous CE electrolyte flow through the interface provides integrity of the LC effluent and the CE separation until an injection is desired. The transparent and flexible PDMS material was found to have a number of advantages when combined with fused silica column technology, including ease to follow the process and ease to exchange columns. By combining conventional microscale systems of LC, CE, and ESI−MS, respectively, the time scales of the individual dimensions were harmonized for optimal peak capacity per unit time. The performance of the LC−CE−TOFMS system was evaluated using peptides as model substances. A S/N of about 330 was achieved for leucine-enkephaline from a 0.5 μL LC injection of 25 μg/mL peptide standard.

  • 29.
    Betson, Tatiana R
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Augusti, Angela
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Schleucher, Jürgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance.2006In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 78, no 24, p. 8406-8411Article in journal (Refereed)
    Abstract [en]

    Stable isotopes in tree rings are important tools for reconstruction of past climate. Deuterium (D) is of particular interest since it may contain climate signals and report on tree physiology. Measurements of the D/H ratio of tree-ring cellulose have proven difficult to interpret, presumably because the D/H ratio of the whole molecule blends the abundances of the seven D isotopomers of cellulose. Here we present a method to measure the abundance of the D isotopomers of tree-ring cellulose by nuclear magnetic resonance spectroscopy (NMR). The method transforms tree-ring cellulose into a glucose derivative that gives highly resolved, quantifiable deuterium NMR spectra. General guidelines for measurement of D isotopomers by NMR are described. The transformation was optimized for yield and did not alter the original D isotopomer abundances, thus, conserving the original signals recorded in wood cellulose. In the tree-ring samples tested, the abundances of D isotopomers varied by approximately ±10% (2% standard error). This large variability can only be caused by biochemistry processes and shows that more information is present in D isotopomer abundances, compared to the D/H ratio. Therefore, measurements of the D isotopomer distribution of tree rings may be used to obtain information on long-term adaptations to environmental changes and past climate change.

  • 30.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Petoral Jr, Rodrigo M.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Electrochemical impedance spectroscopy for investigations on ion permeation in ?-functionalized self-assembled monolayers2007In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 79, no 21, p. 8391-8398Article in journal (Refereed)
    Abstract [en]

    Electrochemical impedance spectroscopy was employed to explore the possibility of relating the permeation of electrolyte ions in ?-functionalized self-assembled monolayers to structural or polarity changes induced by interaction with metal ions. The monolayers were based on alkanethiols modified with a phosphorylated tyrosine analogue, which from previous work are known to drastically change their organization on gold surfaces upon interaction with aluminum and magnesium ions. The ion permeation was evaluated by using relatively low excitation frequencies, 1000 to 2 Hz, and quantified by an extra resistive component in the equivalent circuit (R SAM). The extent of ion permeation influenced by the dc potential, the electrolyte concentration, the functional group, and the thiol length were also investigated. It was, for example, found that RSAM decreased ~20% when the thiol organization collapsed and that RSAM increased ~4-5 times when the electrolyte concentration was decreased by 1 order of magnitude. Interesting observations were also made regarding the potential dependence of RSAM and the double layer capacitance. The evaluation of the ion permeation can be used to indirectly detect whether the organization of a SAM is influenced by, for example, electric fields or chemical and biological interactions. This analysis can be performed without addition of redox species, but is on the other hand complicated by the fact that other factors also influence the presence of ions within the monolayer. In addition, a second parallel RC process was obtained in some of the impedance spectra when using even lower frequencies, and its resistive component revealed different results compared to RSAM. Such data may be useful for the understanding of complex double layer phenomena at modified electrodes. © 2007 American Chemical Society.

  • 31. Blab, Gerhard A.
    et al.
    Schmidt, Thomas
    Nilsson, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Genetics and Pathology.
    Homogeneous detection of single rolling circle replication products2004In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 2, p. 495-8Article in journal (Refereed)
    Abstract [en]

    We describe a simple and straightforward approach for homogeneous and isothermal detection of individual rolling circle replication (RCR) products, which represent individual padlock probe circularization events. The RCR products constitute tens of kilobases long single-stranded tandem repeated copies of the probe sequence, and in solution, they fold into micrometer-sized random coils. The method is based on the local enrichment of fluorescence-labeled probes that hybridize to the coiled RCR products compared to the concentration of free probes in solution. We present a detailed characterization of the fluorescence-labeled products using a highly sensitive and fast microscopy setup. At a 10(4)-fold excess of free label, we were able to detect and follow individual RCR products at a signal-to-background noise ratio of 27. This high signal-to-background noise ratio leaves room for analysis in a simple detection device at higher speeds or at lower labeling ratios.

  • 32. Bogdal, Christian
    et al.
    Alsberg, Tomas
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Diefenbacher, Pascal S.
    MacLeod, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berger, Urs
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Fast Quantification of Chlorinated Paraffins in Environmental Samples by Direct Injection High-Resolution Mass Spectrometry with Pattern Deconvolution2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 5, p. 2852-2860Article in journal (Refereed)
    Abstract [en]

    Chlorinated paraffins (CPs) are high production volume chemicals, but data about their environmental fate are scarce. CP mixtures composed of thousands of isomers represent a major challenge for quantification at low levels in environmental samples. Here, we present a novel analytical method for analysis of short-chain, medium-chain, and long-chain CPs in a single injection, that also yields information about congener group pattern. Our detection method is based on direct injection into an atmospheric pressure chemical ionization source operated in negative ion mode under chlorine-enhanced conditions, followed by quadrupole time-of-flight high-resolution mass spectrometry (APCI-qTOF-HRMS) operated in full-scan mode. A mathematical algorithm is applied to deconvolute the CP patterns in the analyzed samples into a linear combination of patterns of technical CP mixtures and to quantify CPs using technical mixtures as external calibration standards. For CP mixtures with known composition, the new method provided concentrations that were within a factor of 1.2 of the target value. Accuracies for CPs spiked to sediment and fish extracts were between 91% and 123%. Concentrations determined in unspiked field samples were within a factor of 5 for short-chain CPs and a factor of 16 for medium-chain CPs of results obtained with an independent method based on gas chromatography/electron capture negative ionization high-resolution mass spectrometry (GC/ECNI-HRMS). The presented APCI-qTOF-HRMS pattern deconvolution method is an interesting alternative for CP analysis in environmental samples. It is particularly sensitive for medium- and long-chain CPs and has the advantage of being extremely fast (instrumental analysis time, less than 1 min).

  • 33.
    Bondza, Sina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. Ridgeview Instruments AB, Uppsala.
    Björkelund, Hanna
    Ridgeview Instruments AB, Uppsala.
    Nestor, Marika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science.
    Andersson, Karl
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. Ridgeview Instruments AB, Uppsala.
    Buijs, Jos
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. Ridgeview Instruments AB, Uppsala.
    Novel Real-Time Proximity Assay for Characterizing Multiple Receptor Interactions on Living Cells2017In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 89, no 24, p. 13212-13218Article in journal (Refereed)
    Abstract [en]

    Cellular receptor activity is often controlled through complex mechanisms involving interactions with multiple molecules, which can be soluble ligands and/or other cell surface molecules. In this study, we combine a fluorescence-based technology for real-time interaction analysis with fluorescence quenching to create a novel time-resolved proximity assay to study protein-receptor interactions on living cells. This assay extracts the binding kinetics and affinity for two proteins if they bind in proximity on the cell surface. One application of real-time proximity interaction analysis is to study relative levels of receptor dimerization. The method was primarily evaluated using the HER2 binding antibodies Trastuzumab and Pertuzumab and two EGFR binding antibodies including Cetuximab. Using Cetuximab and Trastuzumab, proximity of EGFR and HER2 was investigated before and after treatment of cells with the tyrosine-kinase inhibitor Gefitinib. Treated cells displayed 50% increased proximity signal, whereas the binding characteristics of the two antibodies were not significantly affected, implying an increase in the EGFR-HER2 dimer level. These results demonstrate that real-time proximity interaction analysis enables determination of the interaction rate constants and affinity of two ligands while simultaneously quantifying their relative colocalization on living cells.

  • 34.
    Bonn, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Pettersson Redeby, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Electrostatic Sample Nebulization for Improved Sample Vaporization in the Split/Splitless Gas Chromatography Inlet2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 13, p. 5327-5332Article in journal (Refereed)
    Abstract [en]

    The split/splitless inlet system has basically the same fundamental drawbacks it had when it was introduced: poor repeatability of the injected amount of sample and discrimination of high-boiling analytes. Hot needle injection improves the repeatability of the sample transfer but suffers from in-needle discrimination. Injection with a fast autosampler, resulting in minimal heating of the needle, solves this problem but usually requires a glass wool packing in the inlet liner to assist in vaporization of the sample. As glass wool has been reported to cause degradation of labile analytes, it cannot be applied as a general remedy for improving incomplete vaporization. In this paper, a novel concept, based on electrostatic nebulization of the injected sample, is presented. The resulting fine droplets promote a more effective heat transfer and a rapid vaporization. Evaluation of the electrospray inlet in the split mode, using a straight, empty glass liner and a cold needle, showed an improvement in peak area repeatability by about 1 order of magnitude, compared with the results obtained when no electrostatic field was applied, Splitless injection of a series of hydrocarbons up to C-28 in the electrospray inlet with an empty, tapered liner, using a cold needle, showed no measurable analyte discrimination. The relative standard deviation in terms of area count for the largest hydrocarbon (C-28) was < 1.5%, compared to similar to 30% for injections where no high voltage was applied.

  • 35.
    Bossi, A
    et al.
    Cranfield Institute Technology, Institute Biosci and Technology, Cranfield MK43 0AL, Beds, England; University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; .
    Piletsky, SA
    Cranfield Institute Technology, Institute Biosci and Technology, Cranfield MK43 0AL, Beds, England; University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; .
    Piletska, EV
    Cranfield Institute Technology, Institute Biosci and Technology, Cranfield MK43 0AL, Beds, England; University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; .
    Righetti, PG
    Cranfield Institute Technology, Institute Biosci and Technology, Cranfield MK43 0AL, Beds, England; University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; .
    Turner, APF
    Cranfield University, UK.
    An assay for ascorbic acid based on polyaniline-coated microplates2000In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 72, no 18, p. 4296-4300Article in journal (Refereed)
    Abstract [en]

    A technique for modification of the microtiter reader plates well with a polyaniline (PANI) film sensitive for ascorbic acid is presented. The principle of the analyte detection is based on monitoring the changes in optical absorption of the PANI film resulting from the reduction process initiated by ascorbic acid. The detection limit for ascorbic acid is 1 mg/L. Testing with real samples (soft drinks, fruit juices) gave good correlation of the method with iodimetric titration. High sensitivity, stability, and good reproducibility of the measurements make the proposed system an attractive alternative to traditional assays, used in medicine, ecology and biotechnology.

  • 36.
    Bossi, A
    et al.
    University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Piletsky, SA
    University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Piletska, EV
    University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Righetti, PG
    University Verona, Dipartimento Science and Tecnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Turner, APF
    Cranfield University, UK.
    Surface-grafted molecularly imprinted polymers for protein recognition2001In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 73, no 21, p. 5281-5286Article in journal (Refereed)
    Abstract [en]

    A technique for coating microplate wells with molecularly imprinted polymers (MIPs) specific for proteins is presented. 3-Aminophenylboronic acid was polymerized in the presence of the following templates: microperoxidase, horseradish peroxidase, lactoperoxidase, and hemoglobin, via oxidation of the monomer by ammonium persulfate. This process resulted in the grafting of a thin polymer layer to the polystyrene surface of the microplates. Imprinting resulted in an increased affinity of the polymer toward the corresponding templates. The influence of the washing procedure, template concentration, and buffer pH on the polymer affinity was analyzed. It was shown that the stabilizing function of the support and spatial orientation of the polymer chains and template functional groups are the major factors affecting the imprint formation and template recognition. Easy preparation of the MIPs, their high stability, and their ability to recognize small and large proteins, as well as to discriminate molecules with small variations in charge, make this approach attractive and broadly applicable in biotechnology, assays and sensors.

  • 37. 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.

  • 38. Burman, Jan-Ola
    et al.
    Boström, Kurt
    Luleå tekniska universitet.
    Comparison of different plasma excitation and calibration methods in the analysis of geological materials by optical emission spectrometry1979In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 51, no 4, p. 516-520Article in journal (Refereed)
    Abstract [en]

    A comparative study has been made of different dissolution and calibration methods for analyses by optical emission spectrometry (OES) utilizing inductively coupled plasma (ICP) and capacitively coupled microwave plasma (MWP) as excitation sources. The test substances were geological standard rocks, in which SlO2, Al2O3, TiO2, Fe2O3, MnO, MgO CaO, Na2O, Ba, and some traces were determined. The results show that analyses by MWP-OES are severely disturbed by matrix effects; only in the presence of large quantities of ionization buffers e.g., [Sr(NO3)2] can MWP-OES yield rock analyses of very good quality. No buffers are needed for analyses by ICP-OES, for which the matrix effects are remarkably low. ICP-OES may suffer from annoying nebulizer disturbances when concentrated solutions are used but, with properly diluted solutions, all major and many trace elements can routinely be analyzed in 50-mg rock samples. MWP-OES on the other hand is poorly suited for trace element determinationsA comparative study has been made of different dissolution and calibration methods for analyses by optical emission spectrometry (OES) utilizing inductively coupled plasma (ICP) and capacitively coupled microwave plasma (MWP) as excitation sources. The test substances were geological standard rocks, in which SlO2, Al2O3, TiO2, Fe2O3, MnO, MgO CaO, Na2O, Ba, and some traces were determined. The results show that analyses by MWP-OES are severely disturbed by matrix effects; only in the presence of large quantities of ionization buffers e.g., [Sr(NO3)2] can MWP-OES yield rock analyses of very good quality. No buffers are needed for analyses by ICP-OES, for which the matrix effects are remarkably low. ICP-OES may suffer from annoying nebulizer disturbances when concentrated solutions are used but, with properly diluted solutions, all major and many trace elements can routinely be analyzed in 50-mg rock samples. MWP-OES on the other hand is poorly suited for trace element determinations. © 1979 American Chemical Society.

  • 39. Burman, Jan-Ola
    et al.
    Ponter, Christer
    Luleå tekniska universitet.
    Boströn, Kurt
    Luleå tekniska universitet.
    Metaborate digestion procedure for inductively coupled plasma-optical emission spectrometry1978In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 50, no 4, p. 679-680Article in journal (Refereed)
  • 40.
    Butorin, Sergei M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Modin, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Vegelius, Johan R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Suzuki, Michi-To
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. RIKEN Ctr Emergent Matter Sci, 2-1 Hirosawa, Wako, Saitama 3510198, Japan..
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Andersson, David A.
    Los Alamos Natl Lab, Div Mat Sci & Technol, Mat Sci Radiat & Dynam Extremes, Los Alamos, NM 87545 USA..
    Shuh, David K.
    Lawrence Berkeley Natl Lab, Div Chem Sci, MS 70A1150,One Cyclotron Rd, Berkeley, CA 94720 USA..
    Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 8, p. 4169-4173Article in journal (Refereed)
    Abstract [en]

    A systematic X-ray absorption study at actinide N-6,(7) (4f -> 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO2, PuO2 and UO3. The measurements were supported by ab initio calculations based on local-density approximation. with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L-2,L-3 (2p -> 6d transitions) edges allowed us to resolve the major structures of the 13 unoccupied 6d density of states (DOS) and estimate the crystal-field 116) splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N-6,N-7, spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO2 which is in agreement with the tentative Np-O phase diagram.

  • 41.
    Butorin, Sergei M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Shuh, David K.
    Kvashnina, Kristina O.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Guo, Jinghua
    Werme, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Chemical Reduction of Actinides Probed by Resonant Inelastic X-ray Scattering2013In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 85, no 23, p. 11196-11200Article in journal (Refereed)
    Abstract [en]

    The study addresses the possibilities of immobilizing the mobile species of actinides in the geosphere using metallic iron. Sorption on corroding iron is well-known, but there have been uncertainties with regard to the possibilities of reducing the actinyl species to sparingly soluble oxides and, thereby, permanently immobilizing them. Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d edges on Fe foils exposed to uranium(VI) and neptunium(V) solutions in groundwater unambigiously indicate reduction of actinides to, respectively, uranium(IV) and neptunium(IV) on iron surfaces. The reduction manifests itself in an appearance of distinct specific signatures of uranium(IV) and neptunium(IV) in the RIXS profile of 5f-5f excitations. Such signatures and RIXS intensity/cross-section behavior with varying energy of incident photons can be reproduced by model atomic-multiplet calculations of the RIXS spectra. By normalizing the RIXS signal of corresponding 5f-5f excitations to core-to-core 6p-to-5d characteristic fluorescence transitions of actinides, their reduction rates on Fe samples with different exposure to actinide solutions can be estimated. Observed reduction implies similar processes in the nuclear waste canister thus suggesting reduced probability of nuclear waste release with ground waters from the canister.

  • 42.
    CASS, AEG
    et al.
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    DAVIS, G
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    FRANCIS, GD
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    HILL, HAO
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    ASTON, WJ
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    HIGGINS, IJ
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    PLOTKIN, EV
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    SCOTT, LDL
    UNIV OXFORD,INORGAN CHEM LAB,OXFORD OX1 3QR,ENGLAND; CRANFIELD INST TECHNOL,CTR BIOTECHNOL,CRANFIELD MK43 0AL,BEDS,ENGLAND; .
    TURNER, APF
    Cranfield University, UK.
    FERROCENE-MEDIATED ENZYME ELECTRODE FOR AMPEROMETRIC DETERMINATION OF GLUCOSE1984In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 56, no 4, p. 667-671Article in journal (Refereed)
    Abstract [en]

    n/a

  • 43.
    Castillo, S.
    et al.
    VTT Technical Research Centre of Finland, Espoo, Finland.
    Mattila, I.
    VTT Technical Research Centre of Finland, Espoo, Finland.
    Miettinen, J.
    VTT Technical Research Centre of Finland, Espoo, Finland.
    Oresic, Matej
    VTT Technical Research Centre of Finland, Espoo, Finland.
    Hyötyläinen, Tuulia
    VTT Technical Research Centre of Finland, Espoo, Finland.
    Data analysis tool for comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 8, p. 3058-3067Article in journal (Refereed)
    Abstract [en]

    Data processing and identification of unknown compounds in comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC x GC/TOFMS) analysis is a major challenge, particularly when large sample sets are analyzed. Herein, we present a method for efficient treatment of large data sets produced by GC x GC/TOFMS implemented as a freely available open source software package, Guineu. To handle large data sets and to efficiently utilize all the features available in the vendor software (baseline correction, mass spectral deconvolution, peak picking, integration, library search, and signal-to-noise filtering), data preprocessed by instrument software are used as a starting point for further processing. Our software affords alignment of the data, normalization, data filtering, and utilization of retention indexes in the verification of identification as well as a novel tool for automated group-type identification of the compounds. Herein, different features of the software are studied in detail and the performance of the system is verified by the analysis of a large set of standard samples as well as of a large set of authentic biological samples, including the control samples. The quantitative features of our GC x GC/TOFMS methodology are also studied to further demonstrate the method performance and the experimental results confirm the reliability of the developed procedure. The methodology has already been successfully used for the analysis of several thousand samples in the field of metabolomics.

  • 44.
    Cedergren, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nordmark, Ulrika
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Determination of water in NIST reference material for mineral oils2000In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 72, no 14, p. 3392-3395Article in journal (Refereed)
    Abstract [en]

    The accuracy of the reference concentrations of moisture in electrical insulating oil RM 8506 and lubricating oil RM 8507 (both of mineral type) and specified by the National institute of Standards and Technology (NIST) as containing 39.7 and 76.8 ppm (w/w) water, respectively, has recently been the subject of debate in this journal. To shed some further light on this controversy, we report in this correspondence results for these oils obtained by two additional methods, one based on specially designed reagents for diaphragm-free Karl Fischer (KF) coulometry and the other based on the concept of stripping at elevated temperature/continuous KF coulometry. A positive interference effect was shown to take place for RM 8506 when the direct coulometric method was used. If the results are corrected for this, the values including six different procedures varied in the range 13.5-15.6 ppm (w/w). For RM 8507, all values were between 42.5 and 47.2 ppm (w/w), which means that the values recommended by NIST for both reference oils using volumetric titration are about twice as high as those obtained with the other techniques. A possible explanation for this discrepancy is presented.

  • 45. Chabert, Max
    et al.
    Dorfman, Kevin D.
    de Cremoux, Patricia
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Viovy, Jean-Louis
    Automated microdroplet platform for sample manipulation and polymerase chain reaction2006In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 78, no 22, p. 7722-7728Article in journal (Refereed)
    Abstract [en]

    We present a fully automated system performing continuous sampling, reagent mixing, and polymerase chain reaction (PCR) in microdroplets transported in immiscible oil. Sample preparation and analysis are totally automated, using an original injection method from a modified 96-well plate layered with three superimposed liquid layers and in-capillary laser-induced fluorescence endpoint detection. The process is continuous, allowing sample droplets to be carried uninterruptedly into the reaction zone while new drops are aspirated from the sample plate. Reproducible amplification, negligible cross-contamination, and detection of low sample concentrations were demonstrated on numerous consecutive sample drops. The system, which opens the route to strong reagents and labor savings in high-throughput applications, was validated on the clinically relevant quantification of progesterone receptor gene expression in human breast cancer cell lines.

  • 46.
    Chan, Yang-Hsiang
    et al.
    Department of Chemistry, University of Washington, Seattle, USA.
    Gallina, Maria Elena
    Department of Chemistry, University of Washington, Seattle, USA.
    Zhang, Xuanjun
    Department of Chemistry, University of Washington, Seattle, USA.
    Wu, I-Che
    Department of Chemistry, University of Washington, Seattle, USA.
    Jin, Yuhui
    Department of Chemistry, University of Washington, Seattle, USA.
    Sun, Wei
    Department of Chemistry, University of Washington, Seattle, USA.
    Chiu, Daniel T.
    Department of Chemistry, University of Washington, Seattle, USA.
    Reversible Photoswitching of Spiropyran-Conjugated Semiconducting Polymer Dots2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 21, p. 9431-9438Article in journal (Refereed)
    Abstract [en]

    Semiconducting polymer dots (Pdots) recently have emerged as a new class of ultrabright fluorescent probes with promising applications in biological detection and imaging. We developed photoswitchable Pdots by conjugating photochromic spiropyran molecules onto poly[9,9-dioctylfluorenyl-2,7-diyl)-co-1,4-benzo-{2,1′-3}-thiadiazole)] (PFBT). The modulation of fluorescence was achieved by ultraviolet irradiation, which converted spiropyran into its visible-absorbing merocyanine form. The merocyanine efficiently quenched the fluorescence of PFBT via Förster resonance energy transfer (FRET). We then reversed the quenching by subsequent irradiation with visible light to get back the fluorescence of PFBT. This FRET-based photomodulation of Pdot fluorescence could be repeated multiple times. We next conjugated biomolecules onto the surface of these photoswitchable Pdots and demonstrated their specific cellular and subcellular labeling to different types of cells without any noticeable nonspecific binding. We anticipate these photoswitchable and biocompatible Pdots will be useful in developing bioimaging techniques in the future.

  • 47.
    Chen, Hu
    et al.
    Nanyang Technology University, Singapore; Nanyang Technology University, Singapore; University of Loughborough, England.
    Chen, Peng
    Nanyang Technology University, Singapore; Centre Biomimet Sensor Science, Singapore.
    Huang, Jingfeng
    Nanyang Technology University, Singapore; Nanyang Technology University, Singapore.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Platt, Mark
    University of Loughborough, England.
    Palaniappan, Alagappan
    Nanyang Technology University, Singapore; Centre Biomimet Sensor Science, Singapore.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Iing Yoong Tok, Alfred
    Nanyang Technology University, Singapore; Nanyang Technology University, Singapore.
    Liedberg, Bo
    Nanyang Technology University, Singapore; Centre Biomimet Sensor Science, Singapore.
    Detection of Matrilysin Activity Using Polypeptide Functionalized Reduced Graphene Oxide Field-Effect Transistor Sensor2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 6, p. 2994-2998Article in journal (Refereed)
    Abstract [en]

    A novel approach for rapid and sensitive detection of matrilysin (MMP-7, a biomarker involved in the degradation of various macromolecules) based on a polypeptide (JR2EC) functionalized reduced graphene oxide (rGO) field effect transistor (FET) is reported. MMP-7 specifically digests negatively charged JR2EC immobilized on rGO, thereby modulating the conductance of rGO-FET. The proposed assay enabled detection of MMP-7 at clinically relevant concentrations with a limit of detection (LOD) of 10 ng/mL (400 pM), attributed to the significant reduction of the net charge of JR2EC upon digestion by MMP-7. Quantitative detection of MMP-7 in human plasma was further demonstrated with a LOD of 40 ng/mL, illustrating the potential for the proposed methodology for tumor detection and carcinoma diagnostic (e.g., lung cancer and salivary gland cancer). Additionally, excellent specificity of the proposed assay was demonstrated using matrix metallopeptidase 1 (MMP-1), a protease of the same family. With appropriate selection and modification of polypeptides, the proposed assay could be extended for detection of other enzymes with polypeptide digestion capability.

  • 48.
    Chen, Peng
    et al.
    Nanyang Technol Univ, Singapore.
    Liu, Xiaohu
    Nanyang Technol Univ, Singapore; Tsinghua Univ, Peoples R China.
    Goyal, Garima
    Nanyang Technol Univ, Singapore.
    Tran, Nhung Thi
    Nanyang Technol Univ, Singapore; Ho Chi Minh City Univ Technol and Educ, Vietnam.
    Ho, James Chin Shing
    Nanyang Technol Univ, Singapore.
    Wang, Yi
    Nanyang Technol Univ, Singapore; Wenzhou Med Univ, Peoples R China.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Liedbereg, Bo
    Nanyang Technol Univ, Singapore; Nanyang Technol Univ, Singapore.
    Nanoplasmonic Sensing from the Human Vision Perspective2018In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, no 7, p. 4916-4924Article in journal (Refereed)
    Abstract [en]

    Localized surface plasmon resonance (LSPR) constitutes a versatile technique for biodetection, exploiting the sensitivity of plasmonic nanostructures to small changes in refractive index. The optical shift in the LSPR band caused by molecular interactions in the vicinity of the nanostructures are typically amp;lt;5 nm and can readily be detected by a spectrophotometer. Widespread use of LSPR-based sensors require cost-effective devices and would benefit from sensing schemes that enables use of very simple spectrophotometers or even naked-eye detection. This paper describes a new strategy facilitating visualization of minute optical responses in nanoplasmonic bioassays by taking into account the physiology of human color vision. We demonstrate, using a set of nine different plasmonic nanoparticles, that the cyan to green transition zone at similar to 500 nm is optimal for naked-eye detection of color changes. In this wavelength range, it is possible to detect a color change corresponding to a wavelength shift of similar to 2-3 nm induced by refractive index changes in the medium or by molecular binding to the surface of the nanoparticles. This strategy also can be utilized to improve the performance of aggregation-based nanoplasmonic colorimetric assays, which enables semiquantitative naked-eye detection of matrix metalloproteinase 7 (MMP7) activity at concentrations that are at least 5 times lower than previously reported assays using spherical gold nanoparticles. We foresee significant potential of this strategy in medical diagnostic and environmental monitoring, especially in situations where basic laboratory infrastructure is sparse or even nonexistent. Finally, we demonstrate that the developed concept can be used in combination with cell phone technology and red-green-blue (RGB) analysis for sensitive and quantitative detection of MMP7.

  • 49.
    Chen, Si
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Contacting versus Insulated Gate Electrode for Si Nanoribbon Field-Effect Sensors Operating in Electrolyte2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 24, p. 9546-9551Article in journal (Refereed)
    Abstract [en]

    Electric response to pH variations is employed to investigate Si nanoribbon field-effect transistors (SiNRFETs) operating in electrolyte with different gate configurations. For devices with a concluding gate electrode for direct metal electrolyte contact, a well-defined electrode reaction leading to a stable electrode potential is essential for retaining a stable electrical potential of the electrolyte. However, noble metals such as Pt do not meet the stability requirement and consequently bring severe distortions to the electronic response. For devices with an insulated gate electrode relying on the principle of capacitive gate coupling, the capacitance between the gate electrode and the electrolyte should be made much larger than the gate capacitance established between the SiNR and the electrolyte. In this case, an efficient gate control as well as a high stability against external disturbances can be ensured. Further studies show that surface charging of the gate insulator is the main cause responsible for the pH response of the SiNRFETs. Hence, devices with different gate configurations give rise to a comparable pH sensitivity.

  • 50.
    Chianella, I
    et al.
    Cranfield University, Institute Biosci and Technology, Bedford MK45 4DT, England; .
    Lotierzo, M
    Cranfield University, Institute Biosci and Technology, Bedford MK45 4DT, England; .
    Piletsky, SA
    Cranfield University, Institute Biosci and Technology, Bedford MK45 4DT, England; .
    Tothill, IE
    Cranfield University, Institute Biosci and Technology, Bedford MK45 4DT, England; .
    Chen, BN
    Cranfield University, Institute Biosci and Technology, Bedford MK45 4DT, England; .
    Karim, K
    Cranfield University, Institute Biosci and Technology, Bedford MK45 4DT, England; .
    Turner, APF
    Cranfield University, UK.
    Rational design of a polymer specific for microcystin-LR using a computational approach2002In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 74, no 6, p. 1288-1293Article in journal (Refereed)
    Abstract [en]

    A computational approach for the design of a molecularly imprinted polymer (MIP) specific for Cyanobacterial toxin microcystin-LR is presented. By using molecular modeling software, a virtual library of functional monomers was designed and screened against the target toxin, employed as a template. The monomers giving the highest binding energy were selected and used in a simulated annealing (molecular dynamics) process to investigate their interaction with the template. The stoichiomettic ratio observed from the simulated annealing study was used in MIP preparation for microcystin-LR. The monomers were copolymerized with a cross-linker in the presence of the template. A control (blank) polymer was prepared under the same conditions but in the absence of template. A competitive assay with microcystin-horseradish peroxidase conjugate was optimized and used to evaluate the affinity and cross-reactivity of the polymer. The performance of the artificial receptor was compared to the performance of monoclonal and polyclonal antibodies raised against the toxin. The results indicate that imprinted polymer has affinity and sensitivity comparable to those of polyclonal antibodies (die detection limit for microcystin-LR using the MIP-based assay was found to be 0.1 mug L-1), while superior chemical and thermal stabilities were obtained. Moreover, cross-reactivity to other toxin analogues was very low for the imprinted polymer, in contrast to the results achieved for antibodies. It is anticipated that the polymer designed could be used in assays, sensors, and solid-phase extraction.

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