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  • 1.
    Alvehus, Malin
    et al.
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Burén, Jonas
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Goedecke, Julia
    Olsson, Tommy
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    The human visceral fat depot has a unique inflammatory profile2010In: Obesity, ISSN 1930-7381, E-ISSN 1930-739X, Vol. 18, no 5, p. 879-883Article in journal (Refereed)
    Abstract [en]

    Obesity can be considered as a low-grade inflammatory condition, strongly linked to adverse metabolic outcomes. Obesity-associated adipose tissue inflammation is characterized by infiltration of macrophages and increased cytokine and chemokine production. The distribution of adipose tissue impacts the outcomes of obesity, with the accumulation of fat in visceral adipose tissue (VAT) and deep subcutaneous adipose tissue (SAT), but not superficial SAT, being linked to insulin resistance. We hypothesized that the inflammatory gene expression in deep SAT and VAT is higher than in superficial SAT. A total of 17 apparently healthy women (BMI: 29.3 +/- 5.5 kg/m2) were included in the study. Body fat (dual-energy X-ray absorptiometry) and distribution (computed tomography) were measured, and insulin sensitivity, blood lipids, and blood pressure were determined. Inflammation-related differences in gene expression(real-time PCR) from VAT, superficial and deep SAT biopsies were analyzed using univariate and multivariate data analyses. Using multivariate discrimination analysis, VAT appeared as a distinct depot in adipose tissue inflammation,while the SAT depots had a similar pattern, with respect to gene expression. A significantly elevated (P < 0.01)expression of the CC chemokine receptor 2 (CCR2) and macrophage migration inhibitory factor (MIF) in VAT contributed strongly to the discrimination. In conclusion, the human adipose tissue depots have unique inflammatory patterns, with CCR2 and MIF distinguishing between VAT and the SAT depots.

  • 2.
    Andersson, Per M
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Torbjörn
    Comparison between physicochemical and calculated molecular descriptors2000In: Journal of Chemometrics: Special Issue: Proceedings of the SSC6, August 1999, HiT/TF, Norway . Issue Edited by Kim Esbensen, Vol. 14, no 5-6, p. 629-42Article in journal (Refereed)
    Abstract [en]

    It has earlier been proven that measured physicochemical properties are useful in the selection of building blocks for combinatorial chemistry as well as for investigation of the scope and limitations of organic reactions. However, measured physicochemical properties are only available for small subsets of reagents, starting materials or building blocks; therefore it is necessary to use calculated descriptors and it is essential that the descriptors are relevant. The objective was to investigate whether three different descriptor data sets contained similar information about the chemical structure, with the major aim to investigate whether calculated descriptors contain similar information as experimental data. A total of 205 heterogeneous primary amines were characterized using three different data sets of molecular descriptor variables. The first set consisted of four physicochemical variables compiled from the literature and commercially available chemicals in chemical catalogues. From these four descriptors together with molecular weight, three additional descriptors could be calculated, resulting in a total of eight descriptor variables in the first data set. The second data set consisted of 81 calculated molecular descriptor variables relating to size, connectivity, atom count, topology and electrotopology indices. The third data set consisted of 10 semi-empirical variables (AM1). All the calculated variables were generated using the software Tsar 3.11. The descriptor variable sets were compared using principal component analysis (PCA) and partial least squares projections to latent structures (PLS). The following result shows that the different descriptor sets do contain similar latent information and that the different types of calculated variables do correlate well with the experimental data, making them suitable to use for e.g. combinatorial library design.

  • 3.
    Andersson, Per M
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Torbjörn
    Strategies for subset selection of parts of an in-house chemical library2001In: Journal of Chemometrics, Vol. 15, no 4, p. 353-69Article in journal (Refereed)
    Abstract [en]

    When a company decides to perform biological testing of their in-house library, i.e. compounds which have been synthesized or purchased over the years, it is usually not feasible or desirable to test all of them using e.g. high-throughput screening (HTS). The limitation is the usually high number of compounds to test (104-106) leading to practical limitations and high costs in terms of both material costs and disposal considerations. Therefore it is often desirable to make a selection of which compounds to include in the biological testing. A challenge is how to make this selection in order to cover the structural space of the in-house library as well as possible. Here we present and discuss different selection strategies based mainly on statistical molecular design (SMD). These methods require different prior information about the compounds under investigation, e.g. characterization of the chemical structure, affinity/biological activity data or neither of these. Which method to be used is largely problem-dependent, i.e. the composition and origin of the library, and hence the structural space, are of great importance. Chemical and biological knowledge about the system under investigation should as far as possible be considered when making the final decision on which method to apply.

  • 4.
    Antti, Henrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Alexandersson, Daniel
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wallbäcks, Lars
    Detection of kappa number distributions in kraft pulps using nir spectroscopy and multivariate calibration2000In: TAPPI Journal, Vol. 83, no 3, p. 102-8Article in journal (Refereed)
    Abstract [en]

    Chemical pulp is characterized by its average lignin content, commonly expressed as the pulp-kappa number. However, this average kappa number provides no information about the distribution of kappa number within the pulp . This study proposes a new method of pulp characterization using near-infrared reflectance (NIR) spectroscopy to measure distributions of kappa numbers within pulp samples. Pure pulps with different kappa numbers were mixed to create blended samples with a known nonuniformity of kappa number distribution. NIR spectroscopy-combined with multi-variate calibration methods was used to detect distributions of kappa numbers in the pulps. Models calculated from these data gave good predictions of the average kappa number as well as the standard deviation around the average. The results imply that NIR spectroscopy can provide information about the average kappa number as well as the distribution of kappa number within the pulp.

  • 5. Artursson, Tom
    et al.
    Eklöv, Tomas
    Lundström, Ingemar
    Mårtensson, Per
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Holmberg, Martin
    Drift correction for gas sensors using multivariate methods2000In: Journal of Chemometrics, Vol. 14, no 5-6, p. 711-23Article in journal (Refereed)
    Abstract [en]

    Drift is one of the most serious impairments afflicting gas sensors. It can be seen as a gradual change in the sensor response over a long period of time when the external conditions are constant. This paper presents a new simple drift counteraction method based on PCA and PLS. The basic idea is to remove the drift direction component from the measurements. The direction of the drift, p, is calculated from measurements for a reference gas. Projecting the sample gas measurements on this vector gives the score vector t. The drift component tp T can then be removed from the sample gas data, which we call component correction (CC). The method is tested on a data set based on a reduced factorial design with four gases and a concentration gradient of hydrogen. It is found that the method works efficiently for both cases.

  • 6.
    Berglind, Rune
    et al.
    Umeå University, Faculty of Science and Technology, European CBRNE Center.
    Leffler, Per
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Interactions between pH, potassium, calcium, bromide, and phenol and their effects on the bioluminescence of Vibrio fischeri2010In: Journal of Toxicology and Environmental Health, ISSN 1528-7394, E-ISSN 1087-2620, Vol. 73, no 16, p. 1102-1112Article in journal (Refereed)
    Abstract [en]

    Little attention has been paid to how the light produced by the bacterium Vibrio fischeri in the Microtox assay is dependent on the concentration of essential ions such as sodium and potassium, and whether the concentrations of these ions affect the sensitivity of the test system to toxic chemicals. Five selected factors, pH, potassium (K(+)), calcium (Ca(2+)), bromide (Br(-)), and phenol (Phe), were simultaneously varied over a set of systematically planned experiments according to a D-optimal design that supported the estimation of a model with linear, quadratic, and two-factor interatcions of the studied factors. The bacterial light production represented by the gamma values in the Microtox assay for the 24 selected combinations of factors was measured at 5 and 15 min. The gamma values varied from negative to positive values greater than 1, indicating stimulation and inhibition of bacterial light production, respectively. The relationship between the gamma values and the factor settings was investigated with multiple linear regression. After 5 min of exposure, the light production was significantly affected by linear and quadratic terms for K(+), pH, and Phe and an interaction between pH and Phe. The situation was more complex after 15 min of exposure, since in addition significant interactions were found for K x Phe and Ca x pH. The tolerance of V. fischeri to Phe was enhanced by increasing the K and Ca concentrations. Data indicate that the ion composition and pH of the sample, as well as the diluents, need to be considered when the toxicity of salts, water samples, and extracts of sediments and soils are tested using commercially certified toxicity test kits.

  • 7.
    Bylesjö, Max
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Eriksson, Daniel
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sjödin, Andreas
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    MASQOT: a method for cDNA microarray spot quality control.2005In: BMC Bioinformatics, ISSN 1471-2105, E-ISSN 1471-2105, Vol. 6, p. 250-Article in journal (Refereed)
    Abstract [en]

    Background

    cDNA microarray technology has emerged as a major player in the parallel detection of biomolecules, but still suffers from fundamental technical problems. Identifying and removing unreliable data is crucial to prevent the risk of receiving illusive analysis results. Visual assessment of spot quality is still a common procedure, despite the time-consuming work of manually inspecting spots in the range of hundreds of thousands or more.

    Results

    A novel methodology for cDNA microarray spot quality control is outlined. Multivariate discriminant analysis was used to assess spot quality based on existing and novel descriptors. The presented methodology displays high reproducibility and was found superior in identifying unreliable data compared to other evaluated methodologies.

    Conclusion

    The proposed methodology for cDNA microarray spot quality control generates non-discrete values of spot quality which can be utilized as weights in subsequent analysis procedures as well as to discard spots of undesired quality using the suggested threshold values. The MASQOT approach provides a consistent assessment of spot quality and can be considered an alternative to the labor-intensive manual quality assessment process.

  • 8. Clothier, Richard
    et al.
    Dierickx, Paul
    Lakhanisky, Thaly
    Fabre, Myriam
    Betanzos, Monica
    Curren, Rodger
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Raabe, Hans
    Bourne, Nicola
    Hernandez, Vanessa
    Mainez, Jessica
    Owen, Monika
    Watts, Sarah
    Anthonissen, Roel
    A database of IC50 values and principal component analysis of results from six basal cytotoxicity assays, for use in the modelling of the in vivo and in vitro data of the EU ACuteTox project.2008In: Altern Lab Anim, ISSN 0261-1929, Vol. 36, no 5, p. 503-19Article in journal (Refereed)
    Abstract [en]

    The main aim of the ACuteTox project (part of the EU 6th Framework programme) is to demonstrate that animal tests for acute systemic toxicity can be replaced by alternative in vitro assays. In this project, data for 97 reference chemicals were collected in the AcuBase database, designed to handle deposited in vitro and in vivo (human and animal) data. To demonstrate the applicability of in vitro basal cytotoxicity tests and in vitro-in vivo modelling, it was deemed necessary to obtain data that were generated via defined standard operating procedures. The molar basal cytotoxicity IC50 values (the 50% inhibitory concentrations for the endpoint measured) for a mouse fibroblast cell line (3T3), a human hepatic cell line (HepG2), a rat hepatic cell line (Fa32), and a human neutrophil cell line (HL-60), were compared, and gave an R(2) correlation of 0.83. To identify chemicals that showed differential cytotoxicity to the various cell types involved, principal component analysis (PCA) was undertaken independently, once all the results had been returned. This showed that colchicine, cycloheximide, digoxin, 5-fluorouracil and hexachlorobenzene gave the lowest correlations with the first score vector of the PCA. The results presented are to be used to identify outliers that need to be further studied via the use of tissue-specific in vitro assays.

  • 9. Ekwall, Björn
    et al.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    MEIC evaluation of acute systemic toxicity: Part VIII. Multivariate partial least squares evaluation, including the selection of a battery of cell line tests with a good prediction of human acute lethal peak blood concentrations for 50 chemicals2000In: Atla-Alternatives to Laboratory Animals, ISSN 0261-1929, Vol. 28, p. 201-34Article in journal (Refereed)
    Abstract [en]

    The Multicenter Evaluation of In vitro Cytotoxicity (MEIC) programme was set up to evaluate the relevance for human acute toxicity of in vitro cytotoxicity tests. A total of 61 assays were used to test all 50 reference chemicals. The results of all the tests and the human database were presented in the first five papers of this series. An evaluation of the relevance for human acute toxicity of all submitted test results with use of hard linear regression modelling was presented in the next two papers, and demonstrated a high relevance of in vitro tests, notably tests involving human cell lines. In the present study, multivariate partial least square (PLS) modelling with latent variables analysis has been used to reach two objectives. The first objective was to study the prediction of human acute toxicity by the 61 assays. The second objective was to select a practical battery from the 61 assays, with an optimal prediction of lethal blood concentrations from human acute poisonings of the chemicals. A two-component PLS model of all 61 assays predicted three sets of lethal blood concentrations (clinical, forensic and peak concentrations) very well (R-2 = 0.77, 0.76 and 0.83, Q(2) = 0.74, 0.72 and 0.81, respectively), providing correlative evidence for a high relevance for human acute toxicity of most of the assays. The assays with human cells were highly predictive, whereas assays with Very short incubation times and non-fish ecotoxicological assays were least predictive. These findings confirm the previous results from linear regression analysis. To select an optimal battery, 24 successive PLS models of in vitro data were compared with lethal peak concentrations. The battery selection was based on 38 chemicals with reliable and relevant lethal peak concentrations. An initial PLS model of all 61 assays was used to select the 15 most predictive and most distinct assays. Subsequent PLS models were used to measure the decrease in prediction when assays were deleted from the 15-test battery, as well as the increase in prediction when some extra-predictive assays (as identified by the deletion process) were added later to an optimal two-test battery. The most predictive three-test battery (R-2 = 0.79 and Q(2) = 0.78 for all 50 chemicals) included two circumstantial assays. The most predictive and most cost-effective battery consisted of three human cell line assays, with four endpoints and two exposure times, i.e. protein content (24 hours), ATP content (24 hours), inhibition of elongation of cells (24 hours), and pH-change (7 days). This 1, 5, 9, 16 battery exclusively measures basal cytotoxicity, and is highly predictive (R-2 = 0.77 and Q(2) = 0.76 for 50 chemicals) of the actual lethal peak blood concentrations from acute poisonings in humans. The battery prediction compares favourably with the prediction of human lethal dose by a PLS model of rat and mouse 50% lethal dose (LD50) values for the 50 chemicals (R-2 = 0.65 and Q(2) = 0.64). The three assays of the battery and other promising MEIC assays should be formally validated as soon as possible. The battery can be used immediately for several non-regulatory purposes, including the high-throughput screening of potential pharmaceuticals.

  • 10.
    Elg Christoffersson, Kristina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hauksson, Jón
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Dolk, Matti
    Characterisation of dissolving pulp using designed process variables, NIR and NMR spec-troscopy, and multivariate analysis1999In: Cellulose, Vol. 6, p. 233-249Article in journal (Refereed)
  • 11.
    Elg Christoffersson, Kristina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Agnemo, Roland
    Chemical properties and cellulose su-permolecular structure of dissolving pulps with different reac-tivity revealed by solid state NMR, NIR spectra and multivari-ate data analysisManuscript (Other academic)
  • 12.
    Elg Christoffersson, Kristina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindgren, Åsa
    Dolk, Matti
    Reactivity of dissolving pulp: characterisation using chemical properties, NMR spectroscopy and multivariate data analysis2002In: Cellulose, Vol. 9, no 2, p. 159-70Article in journal (Refereed)
    Abstract [en]

    The reactivity of dissolving pulp was experimentally determined in termsof residual cellulose in viscose. The correlations between 11 chemicalproperties of pulp and filter values and residual cellulose contents of viscosewere then investigated by multivariate data analysis. Both the viscose filtervalue and the residual cellulose were well modelled from the 11 propertiesby partial least squares regression. The results show that pulps with highacetone extractable fractions, high magnesium contents, low alkali resistanceand low viscosity, gave low viscose filter values and low residual cellulosecontents. Pulps with low residual cellulose contents also had low carboxylgroupcontents and low polydispersity. The results are interpreted as that in pulpwith high reactivity, the hemicellulose content is low and that the cellulosechains are shorter and more soluble in alkali. An explanation of the positiveeffect from the high extractive content is that the extractives facilitate thediffusion of carbon disulfide. A principal component analysis of CP/MAS13C-NMR spectral data of six pulp samples showed that differences inreactivity between the pulps could be explained by variations in the hydrogenbonds in the cellulose and/or changes in the glucosidic bonds. In a separatestudy electron beam processing enhanced the reactivity, i.e. lowered theresidual cellulose content, of the investigated pulps. The magnitude of theelectron dose, within the tested range (5.4–23.7 kGy), didnotseem to be important, but the reactivity within pulp sheets tended to be ratherinhomogeneous.

  • 13.
    Elg Christoffersson, Kristina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindgren, Åsa
    Dolk, Matti
    Reactivity of dissolving pulp: characterisation using chemical properties, NMR spectros-copy and multivariate data analysis2002In: Cellulose, Vol. 9, p. 159-170Article in journal (Refereed)
  • 14. Eriksson, Lennart
    et al.
    Johansson, Erik
    Lindgren, Fredrik
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Megavariate analysis of hierarchical QSAR data2002In: Journal of Computer-Aided Molecular Design, Vol. 16, no 10, p. 711-26Article in journal (Refereed)
    Abstract [en]

    Multivariate PCA- and PLS-models involving many variables are often difficult to interpret, because plots and lists of loadings, coefficients, VIPs, etc, rapidly become messy and hard to overview. There may then be a strong temptation to eliminate variables to obtain a smaller data set. Such a reduction of variables, however, often removes information and makes the modelling efforts less reliable. Model interpretation may be misleading and predictive power may deteriorate.

    A better alternative is usually to partition the variables into blocks of logically related variables and apply hierarchical data analysis. Such blocked data may be analyzed by PCA and PLS. This modelling forms the base-level of the hierarchical modelling set-up. On the base-level in-depth information is extracted for the different blocks. The score vectors formed on the base-level, here called `super variables', may be linked together in new matrices on the top-level. On the top-level superficial relationships between the X- and the Y-data are investigated.

    In this paper the basic principles of hierarchical modelling by means of PCA and PLS are reviewed. One objective of the paper is to disseminate this concept to a broader QSAR audience. The hierarchical methods are used to analyze a set of 10 haloalkanes for which K = 30 chemical descriptors and M = 255 biological responses have been gathered. Due to the complexity of the biological data, they are sub-divided in four blocks. All the modelling steps on the base-level and the top-level are reported and the final QSAR model is interpreted thoroughly.

  • 15.
    Gabrielsson, Jon
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindberg, Nils-Olof
    Pålsson, Magnus
    Nicklasson, Fredrik
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Torbjörn
    Multivariate Methods in the Development of a New Tablet Formulation2003In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 29, no 10, p. 1053-1075Article in journal (Refereed)
    Abstract [en]

    The overall objective of this article is to use an efficient approach to find a suitable tablet formulation for direct compression. By using traditional approaches to statistical experimental design in tablet formulation, the number of experiments quickly grows when many descriptive variables or many excipients are included. To facilitate the screening process, a multivariate design, which allows a systematical evaluation of a large number of excipients with a limited number of experiments, was implemented. Formulations with acceptable values for disintegration time and crushing strength were obtained with some of the formulations in the present study. The multivariate experimental design strategy yielded PLS models that will be used to identify a region of interest for the optimization. The strategy is general and can be applied in many different areas of pharmaceutical research and development.

  • 16.
    Gabrielsson, Jon
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindberg, Nils-Olof
    Pharmacia AB, Consumer Healthcare, Helsingborg, Sweden.
    Pålsson, Magnus
    Nicklasson, Fredrik
    Pharmacia AB, Consumer Healthcare, Helsingborg, Sweden.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Torbjörn
    Department of Medicinal Chemistry, Uppsala University, Uppsala, Sweden.
    Multivariate methods in the development of a new tablet formulation: optimization and validation2004In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 30, no 10, p. 1037-1049Article in journal (Refereed)
    Abstract [en]

    In a previous study of the development of a tablet formulation approximately 100 excipients were characterized in screening experiments using multivariate design. Acceptable values for important responses were obtained with some of the formulations. The relationships between the properties of the excipients and the responses were evaluated using PLS. In this study additional experiments were performed in order to validate models obtained from the screening study and to find a formulation of suitable composition with desired tablet properties. A formulation with the desired disintegration time was found with the additional experiments and the agreement between observed and predicted values was fair for the tablets that did disintegrate. A limitation of this study was that tablets from four experiments did not disintegrate within the set time limit. The lack of agreement between observed and predicted values of these four experiments was probably due to the nature of one of the factors in the design. Considering the reduced experimental design the results are still encouraging.

  • 17.
    Gabrielsson, Jon
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pihl, Ann-Christin
    Lindberg, Nils-Olof
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lundstedt, Torbjörn
    Multivariate Methods in the Development of a New Tablet Formulation: Excipient Mixtures and Principal Properties2006In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 32, no 1, p. 7-20Article in journal (Refereed)
    Abstract [en]

    A tablet formulation for direct compression has previously been studied using multivariate design. An optimization study of one of the most important tablet properties, disintegration time, revealed that excipients with Principal Properties (PP's) that were predicted as suitable by the model were not represented within the studied material.

    The feasibility of using mixtures of excipients in the multivariate approach to tablet formulation to solve this problem has been investigated in the present study. By mixing different excipients of the same excipient class, it should be possible to obtain mixtures with the predicted PP's, which in turn should give a formulation with the desired properties. In order to investigate the utility of this approach, separate mixture designs were applied to both binders and fillers (diluents).

    As reported here, the Partial Least Squares Projections to Latent Structures (PLS) model developed in the previously published screening study has been validated in the sense that the interesting region of the PP space identified in it has been shown to contain excipients, pure or mixed, that give the formulation suitable properties. Formulations with suitable properties were found with the mixture experiments. The local models also offer several alternatives for the composition of the formulation that yield the desired disintegration time.

  • 18.
    Gabrielsson, Jon
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindberg, Nils-Olof
    Pihl, Ann-Christin
    Lundstedt, Torbjörn
    Robustness testing of a tablet formulation using multivariate design2006In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 32, no 3, p. 297-307Article in journal (Refereed)
    Abstract [en]

    A total of 45 experiments were carried out to evaluate the robustness of two similar tablet formulations--a product of two strengths--with respect to normal batch-to-batch variation of the excipients and the active pharmaceutical ingredient. The formulations consist of 10 ingredients. Because of the differing amounts of active pharmaceutical ingredients, the two formulations also differ in the amounts of two of the diluents and one of the binders. The excipients and active pharmaceutical ingredient were characterized in terms of multiple variables, and principal properties were calculated with principal component analysis. A Plackett and Burman design was applied to the principal properties. The relationships between the design factors and two responses, mean disintegration time and mean crushing strength, were evaluated by using regression methods. Both formulations were found to be robust under controlled conditions.

  • 19. Georgiev, Alexander
    et al.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wieslander, Åke
    Binding specificities of the GYF domains from two Saccharomyces cerevisiae Paralogs2007In: Protein Engineering, Design & Selection, Vol. 20, no 9, p. 443-52Article in journal (Refereed)
    Abstract [en]

    We have used multivariate statistics and z-scales to represent peptide sequences in a PLS-QSAR model of previously studied binding affinities [ Kofler,M., Motzny,K. and Freund,C. (2005b) Mol. Cell. Proteomics, 4, 1797–1811.] of two GYF domains to an array of immobilized synthetic peptides. As a result, we established structural determinants of the binding specificities of the two proteins. Our model was used to define new sets of yeast proteins potentially interacting with Syh1 (YPL105C) and Smy2 (YBR172C). These sets were subsequently examined for co-occurrence of Gene Ontology terms, leading to suggest a group of likely interacting proteins with a common function in mRNA catabolism. Finally, subcellular localization of a GFP-fused Syh1 and Smy2 reinforced the possibility that these proteins reside in cytoplasmic sites of mRNA degradation, thereby providing experimental confirmation to the predictions from the model.

  • 20. Goodacre, Royston
    et al.
    Broadhurst, David
    Smilde, Age K
    Kristal, Bruce S
    Baker, J David
    Beger, Richard
    Bessant, Conrad
    Connor, Susan
    Capuani, Giorgio
    Craig, Andrew
    Ebbels, Tim
    Kell, Douglas B
    Manetti, Cesare
    Newton, Jack
    Paternostro, Giovanni
    Somorjai, Ray
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wulfert, Florian
    Proposed minimum reporting standards for data analysis in metabolomics2007In: Metabolomics, Vol. 3, p. 231-41Article in journal (Refereed)
    Abstract [en]

    The goal of this group is to define the reporting requirements associated with the statistical analysis (including univariate, multivariate, informatics, machine learning etc.) of metabolite data with respect to other measured/collected experimental data (often called metadata). These definitions will embrace as many aspects of a complete metabolomics study as possible at this time. In chronological order this will include: Experimental Design, both in terms of sample collection/matching, and data acquisition scheduling of samples through whichever spectroscopic technology used; Deconvolution (if required); Pre-processing, for example, data cleaning, outlier detection, row/column scaling, or other transformations; Definition and parameterization of subsequent visualizations and Statistical/Machine learning Methods applied to the dataset; If required, a clear definition of the Model Validation Scheme used (including how data are split into training/validation/test sets); Formal indication on whether the data analysis has been Independently Tested (either by experimental reproduction, or blind hold out test set). Finally, data interpretation and the visual representations and hypotheses obtained from the data analyses.

  • 21.
    Gullberg, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Jonsson, Pär
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nordström, Anders
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Moritz, Thomas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Design of experiments: an efficient strategy to identify factors influencing extraction and derivatization of Arabidopsis thaliana samples in metabolomic studies with gas chromatography/mass spectrometry2004In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 331, no 2, p. 283-295Article in journal (Refereed)
    Abstract [en]

    The usual aim in metabolomic studies is to quantify the entire metabolome of each of a series of biological samples. To do this for complex biological matrices, e.g., plant tissues, efficient and reproducible extraction protocols must be developed. However, derivatization protocols must also be developed if GC/MS (one of the mostly widely used analytical methods for metabolomics) is involved. The aim of this study was to investigate how different chemical and physical factors (extraction solvent, derivatization reagents, and temperature) affect the extraction and derivatization of the metabolome from leaves of the plant Arabidopsis thaliana. Using design of experiment procedures, variation was systematically introduced, and the effects of this variation were analyzed using regression models. The results show that this approach allows a reliable protocol for metabolomic analysis of Arabidopsis to be determined with a relatively limited number of experiments. Following two different investigations an extraction and derivatization protocol was chosen. Further, the reproducibility of the analysis of 66 endogenous compounds was investigated, and it was shown that both hydrophilic and lipophilic compounds were detected with high reproducibility.

  • 22.
    Hauksson, Jón B
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bergqvist, Göran
    Bergsten, Urban
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Prediction of basic wood properties for Norway spruce. Interpretation of Near Infrared Spectroscopy data using partial least squares regression2001In: Wood Science and Technology, ISSN 0043-7719 (Print) 1432-5225 (Online), Vol. 35, no 6, p. 475-85Article in journal (Refereed)
    Abstract [en]

    This work was undertaken to investigate the feasibility of using near infrared spectroscopy (NIR) and partial least squares regression (PLS) as a tool to characterize the basic wood properties of Norway Spruce (Picea abies (L.) Karst.). The wood samples originated from a trial located in the province of Västerbotten in Sweden. In this trial, the effects of birch shelterwoods (Betula pendula Roth) of different densities on growth and yield in Norway spruce understorey were examined. All Norway spruce trees in each shelterwood treatment were divided into three growth rate classes based on diameter at breast height (1.3 m) over bark. Five discs were cut from each tree (i.e. from the root stem, and at 20%, 40%, 60%, and 80% of the total height). The discs from 40% tree height were used (i.e., where the largest variations in annual ring widths and wood density were found). A total of 27 discs were selected. The discs were used for measuring annual ring widths, wood density, average fiber length and the fiber length distributions. Milled wood samples prepared from the discs were used for recording NIR spectra. PLS regression was used to generate prediction models for the wood properties (Y-matrix) and NIR spectra (X-matrix) as well as between the wood properties (Y-matrix) and the fiber length distributions (X-matrix). One set of models was generated using untreated spectra and fiber length distributions. For a second set of models the structure in the X-matrix, which was orthogonal to the matrix described by the wood properties, was eliminated using a soft target rotation technique called orthogonal signal correction (OSC). The PLS model obtained using "raw" untreated NIR spectra and fiber length distributions had a poor modeling power as evidenced by the cumulative Q2 values. For the PLS models based on untreated NIR spectra the cumulative Q2 values ranged from a minimum of 16% (wood density) to a maximum of 46% (no. of annual rings). Orthogonal signal correction of the X-matrix (NIR spectra or fiber length distributions) gave PLS models with a modeling power corresponding to cumulative Q2 values well in excess of 70%. The improvement in predictive ability accomplished by the OSC procedure was verified by placing four of the 27 observations in an external test set and comparing RMSEP values for the test set observations without OSC and with OSC.

  • 23. Héberger, K.
    et al.
    Görgényi, M.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Partial least squares modeling of retention data of oxo compounds in gas chromatography2000In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 51, no 9-10, p. 595-600Article in journal (Refereed)
    Abstract [en]

    Partial least squares modeling of latent structures were carried out on a data matrix consisting of Kováts retention indices of 35 aliphatic ketones and aldehydes and their physical characteristics. The retention indices were determined on capillary columns with 4 different stationary phases, namely bonded methyl-{HP-1}, methyl-phenyl- {HP-50} and trifluoropropyl-methyl siloxane {DB-210}, as well as polyethylene glycol {HP-Innovax} at four different temperatures. It was found that ketones and aldehydes cannot be classified on the basis of retention data solely, whereas the physical characteristics (boiling point, molar volume, molecular mass, molar refraction, octanol-water partition coefficient) contain the necessary information for differentiation of the two classes of compounds. The retention index of but-2-enal does not fit into the general trend of aliphatic aldyhydes and ketones. A predictive PLS model was built to estimate retention data of oxo compounds at different temperatures and various stationary phases of different polarity. Cross-validation suggests a good reliability of the results. Characteristic plots (PLS weights, scores) show the similar retention behavior of oxo compounds (Figures 3 and 4).

  • 24.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bruce, Stephen J
    Moritz, Thomas
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Plumb, Robert
    Granger, Jennifer
    Maibaum, Elaine
    Nicholson, Jeremy K
    Holmes, Elaine
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Extraction, interpretation and validation of information for comparing samples in metabolic LC/MS data sets2005In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 130, no 5, p. 701-707Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

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

  • 25.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gullberg, Jonas
    Nordström, Anders
    Kusano, Miyako
    Kowalczyk, Mauriusz
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Moritz, Thomas
    A strategy for identifying differences in large series of metabolomic samples analyzed by GC/MS2004In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 76, no 6, p. 1738-1745Article in journal (Refereed)
    Abstract [en]

    In metabolomics, the purpose is to identify and quantify all the metabolites in a biological system. Combined gas chromatography and mass spectrometry (GC/MS) is one of the most commonly used techniques in metabolomics together with 1H NMR, and it has been shown that more than 300 compounds can be distinguished with GC/MS after deconvolution of overlapping peaks. To avoid having to deconvolute all analyzed samples prior to multivariate analysis of the data, we have developed a strategy for rapid comparison of nonprocessed MS data files. The method includes baseline correction, alignment, time window determinations, alternating regression, PLS-DA, and identification of retention time windows in the chromatograms that explain the differences between the samples. Use of alternating regression also gives interpretable loadings, which retain the information provided by m/z values that vary between the samples in each retention time window. The method has been applied to plant extracts derived from leaves of different developmental stages and plants subjected to small changes in day length. The data show that the new method can detect differences between the samples and that it gives results comparable to those obtained when deconvolution is applied prior to the multivariate analysis. We suggest that this method can be used for rapid comparison of large sets of GC/MS data, thereby applying time-consuming deconvolution only to parts of the chromatograms that contribute to explain the differences between the samples.

  • 26.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johansson, Annika I.
    Gullberg, Jonas
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jiye, A
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
    Grung, Björn
    Marklund, Stefan
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    High-throughput data analysis for detecting and identifying differences between samples in GC/MS-based metabolomic analyses2005In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 17, p. 5635-5642Article in journal (Refereed)
    Abstract [en]

    In metabolomics, the objective is to identify differences in metabolite profiles between samples. A widely used tool in metabolomics investigations is gas chromatography-mass spectrometry (GC/MS). More than 400 compounds can be detected in a single analysis, if overlapping GC/ MS peaks are deconvoluted. However, the deconvolution process is time-consuming and difficult to automate, and additional processing is needed in order to compare samples. Therefore, there is a need to improve and automate the data processing strategy for data generated in GC/MS-based metabolomics; if not, the processing step will be a major bottleneck for high-throughput analyses. Here we describe a new semiautomated strategy using a hierarchical multivariate curve resolution approach that processes all samples simultaneously. The presented strategy generates (after appropriate treatment, e.g., multivariate analysis) tables of all the detected metabolites that differ in relative concentrations between samples. The processing of 70 samples took similar time to that of the GC/TOFMS analyses of the samples. The strategy has been validated using two different sets of samples: a complex mixture of standard compounds and Arabidopsis samples.

    KeyWords Plus: CHROMATOGRAPHY MASS-SPECTROMETRY; PRINCIPAL COMPONENT ANALYSIS; SYSTEMS BIOLOGY; ARABIDOPSIS-THALIANA; CHEMOMETRIC ANALYSIS; 2-WAY DATA; MS; REGRESSION; RESOLUTION; ALIGNMENT

  • 27.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wallbäcks, Lars
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Strategies for implementation and validation of on-line models for multivariate monitoring and control of wood chip properties2004In: Journal of Chemometrics, Vol. 18, no 3-4, p. 203-7Article in journal (Refereed)
    Abstract [en]

    Here we present an approach for on-line control and monitoring of pulpwood chip properties based on near infrared (NIR) spectroscopy and multivariate data analysis. In addition, this paper suggests how to deal with large multivariate data sets in order to extract information which can be used as a basis for changes in raw material or process conditions in the drive towards more optimal intermediate or end product properties within the pulp and paper industry. The pulpwood chips used as raw material in a pulp and paper making process were characterized at- and on-line using NIR spectroscopic measurements. Collected NIR spectra were used in multivariate calibration models for prediction of the moisture content as well as the between- and within-species variation in the studied raw material. Statistical experimental design was used to form a calibration data set including most of the variation occurring in a real on-line situation. NIR spectra for all designed samples were measured at-line and the estimated calibration models were used for carrying out predictions on-line. Predictions of the moisture content (% dry weight) as well as the percentage contents of pine and sawmill chips in the raw material were carried out using partial least squares projections to latent structures (PLS) methodology. NIR spectra were collected subsequently on-line once every minute, and, to reduce the problem with noise in the time series predictions, the measured signals were filtered using a moving average of 100 predicted values. This provided smoother predictions more suitable for process monitoring and control. To validate the quality of the predictions, wood chips from the studied process were sampled and analysed in the laboratory before being subjected to predictions in the on-line model. Comparison of the filtered on-line predictions with the results obtained from the laboratory measurements indicated that moisture and pine chip contents could be well predicted by the on-line model, while predictions of sawmill chip content showed less promising results.

  • 28.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjövik-Johansson, Elin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wuolikainen, Anna
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindberg, Johan
    Schuppe-Koistinen, Ina
    Kusano, Miyako
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Moritz, Thomas
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Predictive metabolite profiling applying hierarchical multivariate curve resolution to GC-MS data: a potential tool for multi-parametric diagnosis2006In: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 5, no 6, p. 1407-1414Article in journal (Refereed)
    Abstract [en]

    A method for predictive metabolite profiling based on resolution of GC-MS data followed by multivariate data analysis is presented and applied to three different biofluid data sets (rat urine, aspen leaf extracts, and human blood plasma). Hierarchical multivariate curve resolution (H-MCR) was used to simultaneously resolve the GC-MS data into pure profiles, describing the relative metabolite concentrations between samples, for multivariate analysis. Here, we present an extension of the H-MCR method allowing treatment of independent samples according to processing parameters estimated from a set of training samples. Predictions or inclusion of the new samples, based on their metabolite profiles, into an existing model could then be carried out, which is a requirement for a working application within, e.g., clinical diagnosis. Apart from allowing treatment and prediction of independent samples the proposed method also reduces the time for the curve resolution process since only a subset of representative samples have to be processed while the remaining samples can be treated according to the obtained processing parameters. The time required for resolving the 30 training samples in the rat urine example was approximately 13 h, while the treatment of the 30 test samples according to the training parameters required only approximately 30 s per sample (approximately 15 min in total). In addition, the presented results show that the suggested approach works for describing metabolic changes in different biofluids, indicating that this is a general approach for high-throughput predictive metabolite profiling, which could have important applications in areas such as plant functional genomics, drug toxicity, treatment efficacy and early disease diagnosis.

  • 29.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stenlund, Hans
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Moritz, Thomas
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Verheij, Elwin R
    Lindberg, Johan
    Schuppe-Koistinen, Ina
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A strategy for modelling dynamic responses in metabolic samples characterized by GC/MS2006In: Metabolomics, Vol. 2, no 3, p. 135-143Article in journal (Refereed)
    Abstract [sv]

    A multivariate strategy for studying the metabolic response over time in urinary GC/MS data is presented and exemplified by a study of drug-induced liver toxicity in the rat. The strategy includes the generation of representative data through hierarchical multivariate curve resolution (H-MCR), highlighting the importance of obtaining resolved metabolite profiles for quantification and identification of exogenous (drug related) and endogenous compounds (potential biomarkers) and for allowing reliable comparisons of multiple samples through multivariate projections. Batch modelling was used to monitor and characterize the normal (control) metabolic variation over time as well as to map the dynamic response of the drug treated animals in relation to the control. In this way treatment related metabolic responses over time could be detected and classified as being drug related or being potential biomarkers. In summary the proposed strategy uses the relatively high sensitivity and reproducibility of GC/MS in combination with efficient multivariate curve resolution and data analysis to discover individual markers of drug metabolism and drug toxicity. The presented results imply that the strategy can be of great value in drug toxicity studies for classifying metabolic markers in relation to their dynamic responses as well as for biomarker identification.

  • 30.
    Jonsson, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stenlund, Hans
    Moritz, Thomas
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Verheij, Elwin R
    Lindberg, Johan
    Schuppe-Koistinen, Ina
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Modeling of time dependent toxicological responses in urinary GC/MS dataArticle in journal (Refereed)
  • 31. Kinsner-Ovaskainen, Agnieszka
    et al.
    Coecke, Sandra
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    van Vliet, Erwin
    Prieto, Pilar
    Optimisation and pre-validation of an in Vitro test strategy for predicting human acute toxicity: Progress of the “A-Cute-Tox” project2008In: Proceedings of the Annual Congress of The British Toxicology Society, Elsevier Ireland Ltd. , 2008Conference paper (Other academic)
  • 32. Kusano, Miyako
    et al.
    Jonsson, Pär
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fukushima, Atsushi
    Gullberg, Jonas
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Moritz, Thomas
    Metabolite signature during short-day induced growth cessation in populus2011In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 2, article id 29Article in journal (Refereed)
    Abstract [en]

    The photoperiod is an important environmental signal for plants, and influences a wide range of physiological processes. For woody species in northern latitudes, cessation of growth is induced by short photoperiods. In many plant species, short photoperiods stop elongational growth after a few weeks. It is known that plant daylength detection is mediated by Phytochrome A (PHYA) in the woody hybrid aspen species. However, the mechanism of dormancy involving primary metabolism remains unclear. We studied changes in metabolite profiles in hybrid aspen leaves (young, middle, and mature leaves) during short-day-induced growth cessation, using a combination of gas chromatography–time-of-flight mass spectrometry, and multivariate projection methods. Our results indicate that the metabolite profiles in mature source leaves rapidly change when the photoperiod changes. In contrast, the differences in young sink leaves grown under long and short-day conditions are less distinct. We found short daylength induced growth cessation in aspen was associated with rapid changes in the distribution and levels of diverse primary metabolites. In addition, we conducted metabolite profiling of leaves of PHYA overexpressor (PHYAOX) and those of the control to find the discriminative metabolites between PHYAOX and the control under the short-day conditions. The metabolite changes observed in PHYAOX leaves, together with those in the source leaves, identified possible candidates for the metabolite signature (e.g., 2-oxo-glutarate, spermidine, putrescine, 4-amino-butyrate, and tryptophan) during short-day-induced growth cessation in aspen leaves.

  • 33.
    Lloyd, Scott A
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Sara
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Wolf-Watz, Hans
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Molecular characterization of type III secretion signals via analysis of synthetic N-terminal amino acid sequences2002In: Molecular Microbiology, Vol. 43, no 1, p. 51-9Article in journal (Refereed)
    Abstract [en]

    Yersinia species utilize a type III secretion system to inject toxins, called Yops (Yersinia outer proteins), into eukaryotic cells. The N-termini of the Yops serve as type III secretion signals, but they do not share a consensus sequence. To simplify the analysis of type III secretion signals, we replaced amino acids 2–8 of the secreted protein YopE with all permutations (27 or 128) of synthetic serine/isoleucine sequences. The results demonstrate that amphipathic N-terminal sequences, containing four or five serine residues, have a much greater probability than hydrophobic or hydrophilic sequences to target YopE for secretion. Multiple linear regression analysis of the synthetic sequences was used to obtain a model for N-terminal secretion signals. The model accurately classifies the N-terminal sequences of native type III substrates as efficient secretion signals.

  • 34.
    Malm, Linus
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Larsson, Göran
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Predicting amyloid aggregation rates of proteins using multivariate analysisManuscript (preprint) (Other academic)
    Abstract [en]

    Several diseases have been linked to the presence of extracellular protein deposits of β-rich aggregates, known as amyloid fibrils. The formation of these fibrils and their precursors has been identified as key players in the development of these diseases. It is therefore desirable to gain a deeper understanding of the mechanism of amyloid aggregation.In this study we have used multivariate analysis to elucidate the most important physicochemical and structural factors of amino acids that are important for the amyloid aggregation. We used a combination of principal component analysis, orthogonal partial least squares and auto- and cross-covariance to investigate a database consisting of amyloid aggregation rate measurements of 77 AcP mutants.Our results show that changes in hydrophobic patterns, charge and β-sheet propensity is common for mutants with the largest changes in amyloid propensity. In addition, we can also, with reasonable accuracy, predict the amyloid aggregation rate of a test set of AcP mutants that were not used to create the initial aggregation model. Thus, the multivariate approach used in this study is shown to be powerful tools to extract important factors of protein amyloid aggregation that are hidden in the growing pool of available experimental data of amyloid aggregation.

  • 35.
    Nilsson, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Elg-Christofferson, Kristina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Agnemo, Roland
    The effect of designed wood storage on the brightness of bleached and unbleached thermo mechanical pulp2003In: Nordic Pulp & Paper Research Journal, Vol. 18, no 4, p. 369-76Article in journal (Refereed)
    Abstract [en]

    60 Norway Spruce (Picea abies) logs were stored in climate chambers for 14 weeks in order to investigate the effect of wood storage on the brightness of thermo mechanical pulp. The storage conditions were altered according to an experimental design comprised of five factors; light, watering, temperature, tree growth and debarking. Wood samples were collected during the storage period and refined into thermo mechanical pulp. ISO brightness values were measured for the unbleached, the dithionite bleached and the hydrogen peroxide bleached thermo mechanical pulp samples that were refined from the stored wood. The decrease in ISO brightness after 14 weeks of wood storage was significant for some of the samples bleached with dithionite. It was found that the interaction between watering and light had a significant negative effect on the brightness of the unbleached and dithionite bleached samples. The samples bleached with hydrogen peroxide generally showed a more consistent ISO brightness. Only watering and temperature had a significant effect on the brightness of peroxide bleached thermo, mechanical pulp.

  • 36.
    Nilsson, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edlund, Ulf
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Agnemo, Roland
    Prediction of thermo mechanical pulp brightness using NIR spectroscopy on wood raw material2005In: Paperi ja puu, ISSN 0031-1243, Vol. 87, no 2, p. 102-109Article in journal (Refereed)
    Abstract [en]

    Partial Least Squares regression to latent structures was used to find a correlation between near-infrared reflectance spectra of samples of milled Norway Spruce (Picea abies) and ISO brightness of bleached thermo mechanical pulp. Logs of spruce were stored in climate chambers with different conditions for 14 weeks. A factorial design based on five variables was constructed to control the storage and to provide different brightness properties of the stored spruce logs. Wood samples were collected during the storage and they were analysed with near-infrared reflectance spectroscopy and later refined to thermo mechanical pulp. The pulp was bleached with both hydrogen peroxide and sodium dithionite. The ISO brightness of the bleached pulp was correlated to the near-infrared spectra of the untreated samples using Partial Least Squares regression to latent structures. The modelling showed that it is possible to predict the ISO brightness of bleached thermo mechanical pulp from near-infrared spectra of original wood raw material.

  • 37.
    Nordlund, Åke
    et al.
    Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
    Johansson, Ingegerd
    Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
    Källestål, Carina
    Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
    Ericson, Thorild
    Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Strömberg, Nicklas
    Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
    Improved ability of biological and previous caries multimarkers to predict caries disease as revealed by multivariate PLS modelling2009In: BMC Oral Health, ISSN 1472-6831, E-ISSN 1472-6831, Vol. 9, no 28Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Dental caries is a chronic disease with plaque bacteria, diet and saliva modifying disease activity. Here we have used the PLS method to evaluate a multiplicity of such biological variables (n=88) for ability to predict caries in a cross-sectional (baseline caries) and prospective (2-year caries development) setting. METHODS: Multivariate PLS modelling was used to associate the many biological variables with caries recorded in thirty 14-year-old children by measuring the numbers of incipient and manifest caries lesions at all surfaces. RESULTS: A wide but shallow gliding scale of one fifth caries promoting or protecting, and four fifths non-influential, variables occurred. The influential markers behaved in the order of plaque bacteria > diet > saliva, with previously known plaque bacteria/diet markers and a set of new protective diet markers. A differential variable patterning appeared for new versus progressing lesions. The influential biological multimarkers (n=18) predicted baseline caries better (ROC area 0.96) than five markers (0.92) and a single lactobacilli marker (0.7) with sensitivity/specificity of 1.87, 1.78 and 1.13 at 1/3 of the subjects diagnosed sick, respectively. Moreover, biological multimarkers (n=18) explained 2-year caries increment slightly better than reported before but predicted it poorly (ROC area 0.76). By contrast, multimarkers based on previous caries predicted alone (ROC area 0.88), or together with biological multimarkers (0.94), increment well with a sensitivity/specificity of 1.74 at 1/3 of the subjects diagnosed sick. CONCLUSION: Multimarkers behave better than single-to-five markers but future multimarker strategies will require systematic searches for improved saliva and plaque bacteria markers.

  • 38.
    Pommer, Linda
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sundell, J
    Nilsson, C
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stenberg, Berndt
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Dermatology and Venerology.
    Andersson, Barbro
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Class separation of buildings with high and low prevalence of SBS by principal component analysis2004In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 14, no 1, p. 16-23Article in journal (Refereed)
    Abstract [en]

    In this study, we were able to separate buildings with high and low prevalence of sick building syndrome (SBS) using principal component analysis. The prevalence of SBS was defined by the presence of at least one typical skin, mucosal and general (headache and fatigue) symptom. Data from the Swedish Office Illness Study describing the presence and level of chemical compounds in outdoor, supply, and room air, respectively, were evaluated together with information about the buildings in six models. When all data were included the most complex model was able to separate 71% of the high prevalence buildings from the low prevalence buildings. The most important variable that separates the high prevalence buildings from the low prevalence buildings was a more frequent occurrence or a higher concentration of compounds with shorter retention time in the high prevalence buildings. Elevated relative humidity in supply and room air and higher levels of total volatile organic compounds in outdoor and supply air were more common in high prevalence buildings. Ten building variables also contributed to the separation of the two classes of low and high prevalence buildings.

  • 39.
    Rajalahti, Tarja
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Huang, Fang
    Rosén Klement, Maria
    Pisareva, Tatiana
    Edman, Maria
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wieslander, Åke
    Norling, Birgitta
    Proteins in Different Synechocystis Compartments Have Distinguishing N-Terminal Features: A Combined Proteomics and Multivariate Sequence Analysis2007In: Journal of Proteome Research, Vol. 6, no 7, p. 2420-34Article in journal (Refereed)
    Abstract [en]

    Cyanobacteria have a cell envelope consisting of a plasma membrane, a periplasmic space with a peptidoglycan layer, and an outer membrane. A third, separate membrane system, the intracellular thylakoid membranes, is the site for both photosynthesis and respiration. All membranes and luminal spaces have unique protein compositions, which impose an intriguing mechanism for protein sorting of extracytoplasmic proteins due to single sets of translocation protein genes. It is shown here by multivariate sequence analyses of many experimentally identified proteins in Synechocystis, that proteins routed for the different extracytosolic compartments have correspondingly different physicochemical properties in their signal peptide and mature N-terminal segments. The full-length mature sequences contain less significant information. From these multivariate, N-terminal property-profile models for proteins with single experimental localization, proteins with ambiguous localization could, to a large extent, be predicted to a defined compartment. The sequence properties involve amino acids varying especially in volume and polarizability and at certain positions in the sequence segments, in a manner typical for the various compartment classes. Potential means of the cell to recognize the property features are discussed, involving the translocation channels and two Type I signal peptidases with different cellular localization, and charge features at their membrane interfaces.

  • 40. Rhen, Christofer
    et al.
    Gref, Rolf
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wästerlund, Iwan
    Effects of raw material moisture content, densification pressure and temperature on some properties of Norway spruce pellets2005In: FUEL PROCESSING TECHNOLOGY, ISSN 0378-3820, Vol. 87, no 1, p. 11-16Article in journal (Refereed)
    Abstract [en]

    In order to study the pelletising process, Norway spruce sawdust pellets were produced under strictly controlled conditions on a laboratory scale. The aim of the work was to investigate how the moisture content of raw material and the densification parameters, pressure and temperature, affect compression strength, dry density and moisture uptake of the formed pellets. In the experiments performed, temperature (26–144 °C), moisture content (6.3–14.7 wt.% of d.b.) and pressure (46–114 MPa) were the factors which varied according to a prescribed central composite design. The relationships between the factor settings and the responses (dry density, moisture uptake and compression strength) were evaluated by multiple linear regressions.

    In the present study, it was found that high compression strength was strongly correlated with the density of the pellets. High temperature (at least up to 144 °C) and low moisture content at the start of compression (down to 6.3 wt.% of d.b.) increased the dry density of the pellets. Remarkably, compression force had very little effect in the tested range of 46–114 MPa, indicating that pressure in the die does not need to be higher than 50 MPa.

    Similarly, compression force had very little effect on moisture uptake in the pellets. The least moisture uptake occurred when the pellets were produced at 90 °C.

  • 41. Rosén, Maria L
    et al.
    Edman, Maria
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wieslander, Åke
    Recognition of Fold and Sugar Linkage for Glycosyltransferases by Multivariate Sequence Analysis2004In: Journal of Biological Chemistry, Vol. 279, p. 38683-92Article in journal (Refereed)
    Abstract [en]

    Glycosyltransferases (GTs) are among the largest groups of enzymes found and are usually classified on the basis of sequence comparisons into many families of varying similarity (CAZy systematics). Only two different Rossman-like folds have been detected (GT-A and GT-B) within the small number of established crystal structures. A third uncharacterized fold has been indicated with transmembrane organization (GT-C). We here use a method based on multivariate data analyses (MVDAs) of property patterns in amino acid sequences and can with high accuracy recognize the correct fold in a large data set of GTs. Likewise, a retaining or inverting enzymatic mechanism for attachment of the donor sugar could be properly revealed in the GT-A and GT-B fold group sequences by such analyses. Sequence alignments could be correlated to important variables in MVDA, and the separating amino acid positions could be mapped over the active sites. These seem to be localized to similar positions in space for the // binding motifs in the GT-B fold group structures. Analogous, active-site sequence positions were found for the GT-A fold group. Multivariate property patterns could also easily group most GTs annotated in the genomes of Escherichia coli and Synechocystis to proper fold or organization group, according to benchmarking comparisons at the MetaServer. We conclude that the sequence property patterns revealed by the multivariate analyses seem more conserved than amino acid types for these GT groups, and these patterns are also conserved in the structures. Such patterns may also potentially define substrate preferences.

  • 42. Samuelsson, Robert
    et al.
    Thyrel, Mikael
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lestander, Torbjörn A
    Effect of biomaterial characteristics on pelletizing properties and biofuel pellet quality2009In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 90, no 9, p. 1129-1134Article in journal (Refereed)
    Abstract [en]

    Sawdust of conifers as a by-product from saw mills is the most commonly used biomaterial for pellet production in Sweden today. Experiences from the biofuel pellet industry indicate that different biomaterial properties influence the final pellet quality. A systematic study was conducted where five factors were varied according to a two level fractional factorial design. The factors were: tree species (Scots pine, Norway spruce); origin of growth-place (latitudes 57 and 64°N); storage time of sawdust (0 and 140 days), moisture content (9 and 12%) and steam treatment (2 and 6 kg/h). The measured responses bulk density and mechanical durability represented the pellet quality while the press current and the fines produced in the pelletizing process were measures of the pelletizing property.

    The results showed that low moisture content and long storage time resulted in increased bulk densities and press currents. For mechanical durability and fines, a long storage time and intermediate moisture contents were found favourable. In addition, indications were found that the reduction of fatty and resin acids during the storage also influenced the pelletizing properties and the pellet quality.

  • 43. Sjögren, Florence
    et al.
    Davidsson, Karin
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Anderson, Chris D
    Cutaneous Microdialysis: Cytokine Evidence for Altered Innate Reactivity in the Skin of Psoriasis Patients?2012In: AAPS Journal, ISSN 1550-7416, E-ISSN 1550-7416, Vol. 14, no 2, p. 187-195Article in journal (Refereed)
    Abstract [en]

    Cutaneous microdialysis demonstrates cytokine production in living human skin. In the present study, microdialysis samples taken from uninvolved and lesional skin in three test subjects with psoriasis over 24 h have been investigated for cytokine content with a bead-based multiplex immunoassay from Luminex. Concentration curves for a set of Th1/Th2 and pro-inflammatory cytokines measured differed from a reference group of ten subjects without psoriasis. The time to return to near baseline values after innate insertion reactivity is between 9 and 16 h. Post-equilibration levels (17-24 h) for the three main cytokines elevated in the reference group were differentially elevated outside the range of the reference group for interleukin-1β (IL1β) and IL8 but not so for IL6. Two further cytokines, granulocyte-macrophage colony-stimulating factor and tumor necrosis factor-α not generally elevated in the reference group, showed elevated values in the test subjects. Multivariate time series analysis (chemometry) showed that cytokine patterns for the individual test subjects often fell outside the 99% confidence intervals of a model generated from the reference group. In a clinical research situation, cutaneous microdialysis is feasible, gives generally higher cytokine levels than in the blood and generates interpretable data on an individual's reactivity compared with a reference group. This may well prove useful in delineation of pathogenetic issues, selection of appropriate therapy and monitoring of subsequent response in inflammatory dermatoses such as psoriasis.

  • 44.
    Sjöström, Michael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kolman, Ada
    Clemedson, Cecilia
    Clothier, Richard
    Estimation of human blood LC50 values for use in modeling of in vitro – in vivo data of the ACuteTox project2008In: Toxicology in Vitro, Vol. 22, no 5, p. 1405-11Article in journal (Refereed)
    Abstract [en]

    The main aim of the ACuteTox project, under EU 6th Framework programme, is to investigate whether animal toxicity tests for acute systemic toxicity could be replaced by a combination of alternative assays. Data for 97 reference chemicals was collected in the ACuteTox database (Acutoxbase), designed to handle in vitro and in vivo (human and animal) lodged data. The principal basis for demonstration of the applicability of in vitro tests is the in vitro–in vivo modeling, by using statistical correlation between in vitro IC50 molar values (the 50% inhibitory concentration for the endpoints measured) and human blood molar concentrations LC50 (50% lethal concentrations). The LC50 values were calculated from time-related sub-lethal and lethal blood concentrations determined from human acute poisoning cases. The 3T3 standard NRU assay (3T3 NRU) was chosen, among the various basal cytotoxicity assays, applied in the ACuteTox project, to demonstrate the applicability of the IC50/LC50 values for in vitro–in vivo modeling.

    Linear regression analysis between IC50 (x) and LC50 (y) gave an explained variance R2 = 0.56 for the 67 reference chemicals, for which both sets of data were available. The results demonstrated usefulness of human LC50 values for in vitro–in vivo evaluation of the predictability of basal cytotoxicity assays for human acute systemic toxicity.

    The R2 value of 0.56 shows, as in the MEIC study, that additional organ-specific and biokinetic tests are needed in order to improve the predictability.

  • 45. Sundblad, Lars-Göran
    et al.
    Andersson, Mikael
    Geladi, Paul
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Salomonson, Ann
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fast, nondestructive measurement of frost hardiness in conifer seedlings by VIS+NIR spectroscopy2001In: Tree Physiology, Vol. 21, p. 751–7-Article in journal (Refereed)
    Abstract [en]

    Frost hardiness development from mid-August to mid-November was evaluated in seedlings of three provenances of Norway spruce (Picea abies (L.) Karst.) and three provenances of Scots pine (Pinus sylvestris L.) raised at nurseries in north, central and south Sweden. Measurements of the visible + near infrared (VIS+NIR) spectra of shoots were made simultaneously with estimates of frost hardiness based on electrolyte leakage following artificial freezing. Nine physiological variables known to influence frost hardiness were measured throughout the experiment. Multivariate analysis showed that VIS+NIR spectra explained 69% and 72% of the variation in frost hardiness in Scots pine and Norway spruce, respectively. Stem lignification, dry weight fraction, and starch, glucose, fructose, galactose, sucrose, raffinose and stachyose concentrations together explained 80% and 85% of the variation in frost hardiness in Scots pine and Norway spruce, respectively when used as independent X variables in a partial least squares model. These physiological variables could be related to varying degrees with variation in the VIS+NIR spectra. We conclude that VIS+NIR spectroscopy provides a rapid nondestructive technique for measuring frost hardiness in conifer seedlings based on causal relationships between the spectra and the physiology of seedling frost hardiness.

  • 46. Sunesson, A-L
    et al.
    Rosén, I
    Stenberg, Berndt
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Dermatology and Venerology.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multivariate evaluation of VOCs in buildings where people with non-specific building-related symptoms perceive health problems and in buildings where they do not.2006In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 16, no 5, p. 383-391Article in journal (Refereed)
    Abstract [en]

    Volatile organic compounds (VOCs) were sampled in buildings where people with non-specific building-related symptoms perceive health problems and in buildings where they do not. In total, nine persons and 34 buildings were included in the study. The obtained VOC data was evaluated using multivariate methods, to investigate possible systematic differences in air quality of 'problem' and 'non-problem' buildings. All individual compounds were included as variables in a multivariate partial least squares (PLS) data analysis. 'Problem' and 'non-problem' buildings separated into two distinct groups, showing that air samples of the two groups of building were chemically different. PRACTICAL IMPLICATIONS: The study showed that there was an identifiable systematic difference in the collected VOC data between buildings causing and not causing problems for people with non-specific building-related symptoms (also called sick building syndrome, SBS). This is an important indication that even such volatile organic compounds that can be sampled by commonly used adsorbents are of importance for the presence of such symptoms. By coordination of procedures for sampling and analysis of VOCs in buildings between laboratories, to get large datasets and more general models, the method can become a useful diagnostic measure in evaluating indoor air and to identify chemical compounds and sources that contribute to SBS problems.

  • 47.
    Uppgård, Lise-Lott
    et al.
    Umeå University.
    Berglund, Anders
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johansson, Ingegärd
    Akzo Nobel Surface Chemistry AB, Stenungsund, Sweden.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Strandberg, Christine
    Akzo Nobel Surface Chemistry AB, Stenungsund, Sweden.
    A multivariate physicochemical characterisation of technical APGsManuscript (preprint) (Other academic)
  • 48.
    Uppgård, Lise-Lott
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindgren, Åsa
    Akzo Nobel Surface Chemistry AB, Stenungsund, Sweden.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Improving cellulose reactivity by addition of nonionic surfactantsManuscript (preprint) (Other (popular science, discussion, etc.))
  • 49.
    Uppgård, Lise-Lott
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindgren, Åsa
    Akzo Nobel Surface Chemistry AB, Stenungsund, Sweden.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multivariate quantitative structure-activity relationships for the aquatic toxicity of technical nonionic surfactants2000In: Journal of Surfactants and Detergents, ISSN 1097-3958 (Print) 1558-9293 (Online), Vol. 3, no 1, p. 33-41Article in journal (Refereed)
    Abstract [en]

    The aquatic toxicity of 36 technical nonionic surfactants (ethoxylated fatty alcohols) was examined toward two freshwater animal species, the fairy shrimp Thamnocephalus playtyurus and the rotifer Brachionus calyciflorus. Responses of the two species to the surfactants were generally similar. A multivariate-quantitative structure-activity relationship (M-QSAR) model was developed from the data. The M-QSAR model consisted of a partial least squares model with three components and explained 92.4% of the response variance and had a predictive capability of 89.1%. The most important physicochemical variables for the M-QSAR model were the number of carbon atoms in the longest chain of the surfactant hydrophobe (redC), the molecular hydrophobicity (log P), the number of carbon atoms in the hydrophobe (C), the hydrophilic-lipophilic balance according to Davis (Davis), the critical packing parameter with respect to whether the hydrophobe was branched or not (redCPP), and the critical micelle concentration. Surfactant toxicity tended to increase with increasing alkyl chain lengths.

  • 50.
    Uppgård, Lise-Lott
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöström, Michael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multivariate quantitative structure-activity relationships for the aquatic toxicity of alkyl polyglucosides2000In: Tenside Surfactants Detergents:, Vol. 37, no 2, p. 131-8Article in journal (Refereed)
    Abstract [en]

    The aquatic toxicity of 34 alkyl polyglucosides (APGs) towards two fresh-water species, Thamnocephalus platyurus and Brachionus calyciflorus were studied. The toxicity tests were performed using so-called toxkits, and for each surfactant the results are presented as (10)log (mean LC50) values. The toxicity data were combined with physico-chemical data for the APGs, and a Multivariate Quantitative Structure-Activity Relationship (M-QSAR) model was calculated. Partial Least Squares (PLS) regression was used to develop the M-QSAR model. The resulting linear M-QSAR model explained 93.6% of the variance in the biological response and had a predictability of 86.6% according to cross-validation. The physico-chemical properties with the strongest influences on the toxicity of the surfactants were the critical micelle concentration (c.m.c.), wetting, contact angle, and number of carbon atoms in their hydrophobic parts (C and redC).

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