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  • 1.
    Andersson, Henrik
    et al.
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden/The Ångström Laboratory, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden.
    Myrskog, Annika
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ingemarsson, Björn
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden.
    Pei, Zhichao
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden.
    Optimizing immobilization conditions on a two dimensional carboxylbiosensor surface: pH dependence of antibody orientation andantigen binding capacity2009In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309Article in journal (Other academic)
    Abstract [en]

    The performance of immunosensors is highly dependent on the amount of immobilized antibodies and their remaining antigen binding capacity. In this work, a method for immobilization of antibodies on a two dimensional carboxyl surface has been optimized using quartz crystal microbalance biosensors. We have shown that successful immobilization is highly dependent on surface pKa, antibody pI and pH of immobilization buffer. By use of EDC/sulfo-NHS activation reagents, the effect of the intrinsic surface pKa is avoided and immobilization also at very low pH has been made possible which is of importance for immobilization of acidic proteins. Generic immobilization conditions were demonstrated on a panel of antibodies which resulted in an average coefficient of variation of 4% for the immobilization of these antibodies.

    Antigen binding capacity as a function of immobilization pH was studied. In most cases the antigen binding capacity followed the immobilization response. However, the antigen to antibody binding ratio differed between the antibodies investigated, and for one of the antibodies, the antigen binding capacity was significantly lower than expected from immobilization in a certain pH range. Tests with anti-Fc and anti-Fab antibodies on different antibody surfaces showed that the orientation of the antibodies on the surface had a profound effect on the antigen binding capacity of the immobilized antibodies.

  • 2.
    Banerjee, S
    et al.
    Department of Polymer Science and Technology, University of Calcutta, India.
    Sarkar, Priya
    Department of Polymer Science and Technology, University of Calcutta, India.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Amperometric Biosensor for estimation of Glucose-6-phosphate Using Prussian Blue Nanoparticles.2013In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 439, no 2, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Glucose-6-phosphateplays an important role in carbohydrate metabolism of all living organisms.Compared to the conventional analytical methods available for estimation of glucose-6-phosphate,the biosensors having relative simplicity, specificity, low-cost and fastresponse time are a promising alternative. We have reported a glucose-6-phosphatesensor based on screen-printed electrode utilizing Prussian blue nanoparticlesand enzymes, glucose-6-phosphate dehydrogenase and glutathione reductase. The Prussianblue nanoparticles acted as a mediator enhancing the rate of electrochemical responses.The Fourier transforminfrared spectroscopy and energy-dispersiveX-ray spectroscopy study confirmed the formation of Prussian blue, whereas, the atomic forced microscopy revealed that Prussian bluenanoparticles were about 25-30 nm in diameter. To obtainmaximum amperometric response, optimization studies were conducted for pH,enzyme and cofactor loading. The proposed glucose-6-phosphate biosensor showed goodstability, rapid response time and broad linear response in the range of 0.01-1.25mM and detection limit of 6.3 mM. The biosensor also worked well for serum samples and exhibitedexcellent anti-interference ability.

  • 3.
    Duong-Thi, Minh-Dao
    et al.
    Linnaeus Univ, Dept Chem & Biomed Sci, SE-39182 Kalmar, Sweden.
    Bergström, Gunnar
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, The Institute of Technology.
    Mandenius, Carl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, The Institute of Technology.
    Bergstrom, Maria
    Linnaeus University, Sweden .
    Fex, Tomas
    University of Gothenburg, Sweden .
    Ohlson, Sten
    Nanyang Technology University, Singapore .
    Comparison of weak affinity chromatography and surface plasmon resonance in determining affinity of small molecules2014In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 461, p. 57-59Article in journal (Refereed)
    Abstract [en]

    In this study, we compared affinity data from surface plasmon resonance (SPR) and weak affinity chromatography (WAC), two established techniques for determination of weak affinity (mM-mu M) small molecule-protein interactions. In the current comparison, thrombin was used as target protein. In WAC the affinity constant (K-D) was determined from retention times, and in SPR it was determined by Langmuir isotherm fitting of steady-state responses. Results indicate a strong correlation between the two methods (R-2 = 0.995, P less than 0.0001).

  • 4.
    Ghafouri, Bijar
    et al.
    Linköping University, Department of Molecular and Clinical Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    Karlsson, Helen
    Linköping University, Department of Molecular and Clinical Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    Mörtstedt, Harriet
    Linköping University, Department of Molecular and Clinical Medicine. Linköping University, Faculty of Health Sciences.
    Lewander, Andreas
    Linköping University, Department of Biomedicine and Surgery. Linköping University, Faculty of Health Sciences.
    Tagesson, Christer
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Molecular and Clinical Medicine, Occupational and Environmental Medicine. Östergötlands Läns Landsting, Pain and Occupational Centre, Occupational and Environmental Medicine Centre.
    Lindahl, Mats
    Linköping University, Department of Molecular and Clinical Medicine, Occupational and Environmental Medicine. Linköping University, Faculty of Health Sciences.
    Note: 2,5-Dihydroxybenzoic acid instead of α-cyano-4-hydroxycinnamic acid as matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for analyses of in-gel digests of silver-stained proteins: in Analytical Biochemistry(ISSN 0003-2697), vol 371, issue 1, pp 121-1232007In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 371, no 1, p. 121-123Article in journal (Other academic)
    Abstract [en]

    [No abstract available]

  • 5.
    Hedman, Johannes
    et al.
    Department of Applied Microbiology, Lund University, Sweden.
    Nordgaard, Anders
    Swedish National Laboratory of Forencis Sciences, Linkoping, Sweden.
    Dufva, Charlotte
    National Laboratory of Forensic Sciences, Linkoping, Sweden.
    Rasmusson, Birgitta
    National Laboratory of Forensic Sciences, Linkoping, Sweden.
    Ansell, Ricky
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics. Linköping University, The Institute of Technology.
    Rådström, Peter
    Department of Applied Microbiology, Lund University, Sweden.
    Synergy between DNA polymerases increases polymerase chain reaction inhibitor tolerance in forensic DNA analysis2010In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 405, p. 192-200Article in journal (Refereed)
    Abstract [en]

    The success rate of diagnostic polymerase chain reaction (PCR) analysis is lowered by inhibitory substancespresent in the samples. Recently, we showed that tolerance to PCR inhibitors in crime scene salivastains can be improved by replacing the standard DNA polymerase AmpliTaq Gold with alternative DNApolymerase–buffer systems (Hedman et al., BioTechniques 47 (2009) 951–958). Here we show thatblending inhibitor-resistant DNA polymerase–buffer systems further increases the success rate of PCRfor various types of real crime scene samples showing inhibition. For 34 of 42 ‘‘inhibited” crime scenestains, the DNA profile quality was significantly improved using a DNA polymerase blend of ExTaq HotStart and PicoMaxx High Fidelity compared with AmpliTaq Gold. The significance of the results was confirmedby analysis of variance. The blend performed as well as, or better than, the alternative DNA polymerasesused separately for all tested sample types. When used separately, the performance of the DNApolymerases varied depending on the nature of the sample. The superiority of the blend is discussed interms of complementary effects and synergy between the DNA polymerase–buffer systems.

  • 6.
    Joda, Hamdi
    et al.
    Universitat Rovira i Virgili, Tarragona, Spain.
    Beni, Valerio
    INTERFIBIO Research Group, Departament d’Enginyeria Quimica, Universitat Rovira i Virgili, Tarragona, Spain.
    Katakis, Ioanis
    Universitat Rovira i Virgili, Tarragona, Spain.
    O´Sullivan, Ciara K.
    Universitat Rovira i Virgili, Tarragona, Spain.
    DNA biosensor based on hybridization refractory mutation system approach for single mismatch detection2015In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 474, p. 66-68Article in journal (Refereed)
    Abstract [en]

    We report on a simple approach to enhance solid-phase hybridization-based single base mismatch discrimination at high ionic strength based on the deliberate insertion of a natural DNA base mismatch in the surface-tethered probe. A large drop in hybridization signal of single base mismatched alleles using the designed probe as compared with the conventional probe, from 80% to less than 25% of the signal obtained with the fully complementary, non-mutation-containing sequence, when using colorimetric detection was further improved to 20% when using electrochemical detection, attributable to a difference of spacing of immobilized probes. Finally, the designed probe was used for the electrochemical detection of the DQA1*05:05 allele amplified from real human blood samples.

  • 7.
    Jungar, Christina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, Faculty of Science & Engineering.
    Strandh, M
    University of Kalmar, Kalmar, Sweden.
    Ohlson, S
    University of Kalmar, Kalmar, Sweden.
    Mandenius, Carl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biotechnology.
    Analysis of carbohydrates using liquid chromatography-surface plasmon resonance immunosensing systems2000In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 281, no 2, p. 151-158Article in journal (Refereed)
    Abstract [en]

    An immunosensing system based on surface plasmon resonance (SPR) was used for on-line detection and characterization of carbohydrate molecules separated by high-performance liquid chromatography. These analytes, with or without serum, were continuously separated and analyzed in the combined liquid chromatography-surface plasmon resonance (LC-SPR) system. By using weak and readily reversible monoclonal antibodies, the SPR system allowed specific on-line monitoring of the substances. To increase the specificity of the immunosensor, nonrelevant antibodies were used as reference in a serial flow cell. The sensitivity of the LC-SPR system was dependent on molecular weight of the carbohydrate, affinity of binding, and design of the sensor. (C) 2000 Academic Press.

  • 8.
    Liljeblad, Mathias
    et al.
    Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Rydén, Ingvar
    Department of Clinical Chemistry, Kalmar County Hospital, Kalmar, Sweden.
    Ohlson, Sten
    Division of Biochemistry/Biotechnology, Department of Chemistry and Biomedical Sciences, University of Kalmar, Kalmar, Sweden.
    Lundblad, Arne
    Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Påhlsson, Peter
    Linköping University, Department of Biomedicine and Surgery, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    A Lectin Immunosensor Technique for Determination of α1-Acid Glycoprotein Fucosylation2001In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 288, no 2, p. 216-224Article in journal (Refereed)
    Abstract [en]

    The fucosylation of α1-acid glycoprotein (AGP), an acute-phase protein, is known to change in association with inflammatory diseases. Thus, fucosylation of AGP could be a potential diagnostic or prognostic marker. The change in fucosylation has previously been investigated using crossed affinoimmunoelectrophoresis, high-pH anion-exchange chromatography, and lectin ELISA. This study describes a surface plasmon resonance-based affinity biosensor assay for quantification of the fucosylation of AGP. Diluted EDTA plasma or serum was injected directly in a BIACORE 2000 biosensor. AGP was captured on the sensor surface using immobilized antibodies and a fucose-binding lectin from Aleuria aurentia was then used for the detection of fucosylation. The feature of the biosensor makes it possible to determine both the amount of bound AGP and the amount of bound lectin. Using a calibration curve it was possible to obtain a fucosylation ratio that was independent of AGP concentration. The assay was validated against a lectin ELISA and used to follow inflammation in patients with severe burns.

  • 9.
    Lundberg, Peter
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Harmsen, Eef
    Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Ho, Clinton
    Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Vogel, Hans J.
    Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Nuclear magnetic resonance studies of cellular metabolism1990In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 191, no 2, p. 193-222Article in journal (Refereed)
    Abstract [en]

    Nuclear magnetic resonance (NMR) spectroscopy was described in 1946 (1,2), initially as a method that had appeal only for nuclear physicists who used it to accurately determine nuclear magnetic moments. Thissituation changed rapidly, however, when it was demonstrated that the NMR frequency for the same nucleus in different chemical compounds was different (3). For example, two separate signals are observed in a 14N NMR spectrum of a solution of NH,NO,, representing the NH: and NO; ions, respectively (4). Since individual atoms within one molecule also give rise to resolved signals (5) it became clear that the NMR technique held great analytical potential, in particular since the spectra can be recorded in such a way that the area under a signal is directly proportional to its concentration. Such phenomena and various theoretical aspects of NMR are currently quite well understood (6,7). Because of these features NMR has become the foremost spectroscopic method for the analysis of all sorts of chemical compounds.

  • 10.
    Nasef, Hany
    et al.
    Universitat Rovira i Virgili, Tarragona, Spain.
    Cengiz, Ozalp
    Universitat Rovira i Virgili, Tarragona, Spain.
    Beni, Valerio
    Universitat Rovira i Virgili, Tarragona, Spain.
    O´Sullivan, Ciara K.
    Universitat Rovira i Virgili, Tarragona, Spain.
    Melting temperature of surface-tethered DNA2010In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 406, no 1, p. 34-40Article in journal (Refereed)
    Abstract [en]

    A method for the accurate determination of the melting temperature (Tm) of surface-immobilized DNAduplexes that exploits the fluorescence-quenching properties of gold is reported. A thiolated singlestrandedDNA probe is chemisorbed onto a gold surface and then hybridized to a fluorophore-labeledcomplementary sequence. On formation of the duplex, the fluorescence of the label is effectivelyquenched by the gold surface. As the temperature is increased and the duplex denatures, the fluorophorelabel moves away from the gold surface and the fluorescence signal is again observed. The increase influorescence is measured as the temperature is ramped, and using first-derivative plots, the Tm is determined.To demonstrate the approach, the Tm of the cystic fibrosis DF508 mutation was determined inthree different phases: in solution, in suspension immobilized on gold nanoparticles, and immobilizedon gold film-coated substrate. The technique was further applied to optimize conditions for differentiationbetween a surface-immobilized DF508 mutant probe and a mutant/wild-type target exploitingincreasing stringency in varying salt and formamide concentrations. The approach has application inoptimization of assay conditions for biosensors that use gold substrates as well as in melting curveanalysis.

  • 11.
    Speda, Jutta
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Johansson, Mikaela A.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Carlsson, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Karlsson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. InZymes Biotech AB, Linköping, Sweden.
    Assessment of sample preparation methods for metaproteomics of extracellular proteins2017In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 516, p. 23-36Article in journal (Refereed)
    Abstract [en]

    Enzyme discovery in individual strains of microorganisms is compromised by the limitations of pure culturing. In principle, metaproteomics allows for fractionation and study of different parts of the protein complement but has hitherto mainly been used to identify intracellular proteins. However, the extracellular environment is also expected to comprise a wealth of information regarding important proteins. An absolute requirement for metaproteomic studies of protein expression, and irrespective of downstream methods for analysis, is that sample preparation methods provide clean, concentrated and representative samples of the protein complement. A battery of methods for concentration, extraction, precipitation and resolubilization of proteins in the extracellular environment of a constructed microbial community was assessed by means of 2D gel electrophoresis and image analysis to elucidate whether it is possible to make the extracellular protein complement available for metaproteomic analysis. Most methods failed to provide pure samples and therefore negatively influenced protein gel migration and gel background clarity. However, one direct precipitation method (TCA-DOC/acetone) and one extraction/precipitation method (phenol/methanol) provided complementary high quality 2D gels that allowed for high spot detection ability and thereby also spot detection of less abundant extracellular proteins.

  • 12.
    Svedhem, Sofia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Karlsson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Sjöbom, Hans
    Biacore AB, Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Löfås, Stefan
    Biacore AB, Uppsala, Sweden.
    Mårtensson, Lars-Göran
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Sjöstrand, Sven-Erik
    Linköping University, Department of Biomedicine and Surgery, Cell biology. Linköping University, Faculty of Health Sciences.
    Svensson, Stefan
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Carlsson, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Subtle differences in dissociation rates of interactions between destabilized human carbonic anhydrase II mutants and immobilized benzenesulfonamide inhibitors probed by a surface plasmon resonance biosensor2001In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 296, no 2, p. 188-196Article in journal (Refereed)
    Abstract [en]

    The development of commercial biosensors based on surface plasmon resonance has made possible careful characterization of biomolecular interactions. Here, a set of destabilized human carbonic anhydrase II (HCA II) mutants was investigated with respect to their interaction kinetics with two different immobilized benzenesulfonamide inhibitors. Point mutations were located distantly from the active site, and the destabilization energies were up to 23 kJ/mol. The dissociation rate of wild-type HCA II, as determined from the binding to the inhibitor with higher affinity, was 0.019 s−1. For the mutants, dissociation rates were faster (0.022–0.025 s−1), and a correlation between faster dissociation and a high degree of destabilization was observed. We interpreted these results in terms of increased dynamics of the tertiary structures of the mutants. This interpretation was supported by entropy determinations, showing that the entropy of the native structure significantly increased upon destabilization of the protein molecule. Our findings demonstrate the applicability of modern biosensor technology in the study of subtle details in molecular interaction mechanisms, such as the long-range effect of point mutations on interaction kinetics.

  • 13.
    Testorf, Martin
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Kronstrand, Robert
    Linköping University, Department of Medical and Health Sciences, Forensic Science and Toxicology . Linköping University, Faculty of Health Sciences.
    Svensson, Samuel
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ahlner, Johan
    Linköping University, Department of Medical and Health Sciences, Forensic Science and Toxicology . Linköping University, Faculty of Health Sciences.
    Characterization of [3H]flunitrazepam binding to melanin2001In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 298, no 2, p. 259-264Article in journal (Refereed)
    Abstract [en]

    In both clinical and forensic toxicology, the analysis of hair for drugs is an important tool to determine drug use in the past or to verify abstinence from illegal drugs during extended periods. Melanin is proposed as one of the factors that influences drug incorporation to hair and we have characterized the binding of the drug flunitrazepam to melanin in vitro. The drug was 3H labeled and melanin granules from cuttlefish, Sepia officinalis, were used according to the suggested standard for melanin studies. We observed a rapid Langmuir-like binding followed by a slower diffusion-limited binding that may be interpreted as an initial surface binding followed by deeper bulk binding. From three concentrations of melanin, with a 60-min incubation time, a mean saturation value of 180 ± 20 pmol/mg was calculated. The binding of a group of benzodiazepines and tranquilizers was compared to the binding of [3H]flunitrazepam by means of displacement experiments. These drugs showed binding characteristics similar to [3H]flunitrazepam except phenobarbital, which had a lower affinity to melanin. The method presented in this study allowed measurements with low melanin and drug concentrations and it has the strength of directly measuring the amount of drug bound to melanin, in contrast to previous indirect methods.

  • 14. Vostiar, I.
    et al.
    Tkac, J.
    Mandenius, Carl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biotechnology .
    Intracellular monitoring of superoxide dismutase expression in an Escherichia coli fed-batch cultivation using on-line disruption with at-line surface plasmon resonance detection2005In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 342, no 1, p. 152-159Article in journal (Refereed)
    Abstract [en]

    An on-line cell disruption system for at-line monitoring of the intracellular concentration of recombinant human superoxide dismutase (rhSOD) in a genetically modified Escherichia coli strain, HMS174(DE3) (pET11a/rhSOD), in bioreactor cultivations is described. The sampled bacteria were disrupted on-line by rapid mixing with a nonionic detergent. The recombinant protein content of the lysed bacterial sample was quantitated by a subsequent surface plasmon resonance biosensor with a specific monoclonal antibody. Extraction efficiency of the monitoring system was optimized with respect to the flow rate ratio of the cell suspension and the detergent at relevant cell densities with the aim to attain rapid monitoring. Monitoring was demonstrated for a shake flask culture and a glucose-limited fed-batch cultivation. The results are compared with a traditional enzyme-linked immunosorbent assay method showing a correlation coefficient of R2 = 0.97. Extraction efficiency of rhSOD reached 95-99% at a total processing time of 1.8-2.6 min and a contact time of 0.8-1.4 min. The possibility of extending the monitoring system to other intracellular proteins is discussed. © 2005 Elsevier Inc. All rights reserved.

  • 15. Vostiar, I.
    et al.
    Tkac, J.
    Mandenius, Carl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biotechnology .
    Monitoring of the heat-shock response in Escherichia coli using an optical biosensor2003In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 322, no 2, p. 156-163Article in journal (Refereed)
    Abstract [en]

    A surface plasmon resonance (SPR) method for monitoring the concentration of the chaperone DnaK and its relation to physiological stress response in a recombinant Escherichia coli strain subjected to heat shock is described. The DnaK protein, an abundantly occurring representative of the heat-shock proteins, was used as a marker of physiological stress. The SPR biosensor instrument was used for label-free immunoaffinity detection directly in cell culture lysates using an anti-DnaK monoclonal IgG antibody immobilized on the sensor surface. The SPR method provides a fast response (<8min) and a reproducible (RSD<2%), accurate (comparison to the direct enzyme-linked immunosorbent assay), and sensitive (LOD<1nM) assay for determination of the DnaK level in cell culture lysates. The operational stability of the method was high compared to that of other SPR assays, the sensitivity decreased at only 2.7%/h. This allowed measurement of more than 220 samples per sensor surface. Storage stability was determined at 25°C (100% after 17h) and 10°C (101% after 1month). The method was validated by standard additions of DnaK (30, 60, and 120nM) with recovery indices in the range 95.7-103.7%. © 2003 Elsevier Inc. All rights reserved.

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