| 1. |
- Lönnberg, Maria, 1953-
(författare)
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Membrane-Assisted Isoform ImmunoAssay : Separation and determination of protein isoforms
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proteins exist in a variety of isoforms with minor differences, mostly due to their glycosylation patterns, which can modulate their biological functions. It seems to be of clinical relevance to measure the isoform-distribution.Thesis describes a novel technology named Membrane-Assisted Isoform ImmunoAssay (MAIIA). This technique allows rapid (< 15 min.) isoform determination. It is based on a chromatographic separation combined with immunoassay detection. These steps are performed along a thin, disposable micro-porous chip in which capillary forces maintain the flow. By using anion-exchange as a chromatographic principle the technology has been utilized for the determination of transferrin isoforms in ten minutes. In one variant (the one-dimensional), selected isoforms (carbohydrate-deficient transferrin) are quantified. In a more elaborate variant (the two-dimensional) it was possible to determine the entire isoform profile of transferrin. Isoforms differing by only 0.1 pH unit in isoelectric point could be distinguished.The chromatography along the microporous bed of nitrocellulose showed very good separation performance with plate heights of 10-20 µm and only minor flow rate variations between individual devices. The quantitative determination of antibody-captured molecules was performed by using antibodies labelled with carbon black particles. Combined with a detection procedure by means of a flatbed scanner, a highly sensitive and specific immunoassay with a detection limit of 0.13 pM was obtained upon using IgE as a model analyte.This technology can thus be used to rapidly distinguish proteins with minor structure differences and specifically determine protein isoforms in complex environments, e.g., blood, down in the pM (10-12 M) concentration range.
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| 2. |
- Magnusson, Klas E. G., 1985-
(författare)
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Segmentation and tracking of cells and particles in time-lapse microscopy
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In biology, many different kinds of microscopy are used to study cells. There are many different kinds of transmission microscopy, where light is passed through the cells, that can be used without staining or other treatments that can harm the cells. There is also fluorescence microscopy, where fluorescent proteins or dyes are placed in the cells or in parts of the cells, so that they emit light of a specific wavelength when they are illuminated with light of a different wavelength. Many fluorescence microscopes can take images on many different depths in a sample and thereby build a three-dimensional image of the sample. Fluorescence microscopy can also be used to study particles, for example viruses, inside cells. Modern microscopes often have digital cameras or other equipment to take images or record time-lapse video.When biologists perform experiments on cells, they often record image sequences or sequences of three-dimensional volumes to see how the cells behave when they are subjected to different drugs, culture substrates, or other external factors. Previously, the analysis of recorded data has often been done manually, but that is very time-consuming and the results often become subjective and hard to reproduce. Therefore there is a great need for technology for automated analysis of image sequences with cells and particles inside cells. Such technology is needed especially in biological research and drug development. But the technology could also be used clinically, for example to tailor a cancer treatment to an individual patient by evaluating different treatments on cells from a biopsy.This thesis presents algorithms to find cells and particles in images, and to calculate tracks that show how they have moved during an experiment. We have developed a complete system that can find and track cells in all commonly used imaging modalities. We selected and extended a number of existing segmentation algorithms, and thereby created a complete tool to find cell outlines. To link the segmented objects into tracks, we developed a new track linking algorithm. The algorithm adds tracks one by one using dynamic programming, and has many advantages over prior algorithms. Among other things, it is fast, it calculates tracks which are optimal for the entire image sequence, and it can handle situations where multiple cells have been segmented incorrectly as one object. To make it possible to use information about the velocities of the objects in the linking, we developed a method where the positions of the objects are preprocessed using a filter before the linking is performed. This is important for tracking of some particles inside cells and for tracking of cell nuclei in some embryos. We have developed an open source software which contains all tools that are necessary to analyze image sequences with cells or particles. It has tools for segmentation and tracking of objects, optimization of settings, manual correction, and analysis of outlines and tracks. We developed the software together with biologists who used it in their research. The software has already been used for data analysis in a number of biology publications. Our system has also achieved outstanding performance in three international objective comparisons of systems for tracking of cells.
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| 3. |
- Magnusson, Monika, 1965-
(författare)
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Adoption av elektronisk handel : Innehåll, kontext, process och samspelet mellan dessa
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- E-commerce is far more common in large firms than in small and medium-sized enterprises (SMEs). As a result SMEs risk competitive disadvantages. A growing body of research has attended to this problem but few studies examine the adoption of e-commerce from a broader contextual perspective. To be able to understand SMEs’ adoption of e-commerce it is desirable to study their contextual preconditions, approaches and effects.The purpose of this study is to contribute to the theory building in the e-commerce area by forming a conceptual framework over SMEs’ adoption of e-commerce: the ECA (Electronic Commerce Adoption) framework. A central starting point for the study is Pettigrew’s (1985) contextual framework for strategic changes. The analysis dimensions in Pettigrew’s framework − content, context and process − are adapted to adoption of e-commerce. Thus, the ECA framework consists of analysis models that focus on a) the content, b) the context and c) the process of e-commerce adoption in SMEs. Further, the ECA framework includes an analysis model over the interplay between content, context and process and a typology over adoption situations. The SME in its role as a supplier is the unit of analysis. The study uses an abductive approach where results from previous studies in areas such as e-commerce, information systems and decision making are used as sources for forming the ECA framework. The ECA framework is then applied to the collection, interpretation and analyze of empirical data from the case studies of two small and one medium-sized enterprise. The case studies lead to the identification of additional elements that are added to the analysis models.One contribution from the study is the typology over adoption situations. The typology, which builds on studies of Junghagen (1998) and Engsbo et al. (2001), divides the adoption of e-commerce in SMEs into five categories of adoption situations: proactive adoption situations, adaptive adoption situations, pragmatic adoption situations, forced adoption situations and enabled adoption situations. An adoption situation describes what is being adopted (content), why (context) and how (process).Another contribution is the so called adoption guides. These are contextual conditions whose states indicate if a SME will adopt e-commerce or not and if so, which adoption situation they are likely to find themselves in. The adoption guides are: the relative dependence on individual customers, the degree of customer pressure, the strategic needs of e-commerce, the information complexity and, the CEO’s extent of aversion towards risk-taking. Consequently two major conclusions from this study are that SMEs’ e-commerce adoption can be divided into five different adoption situations and a small number of contextual conditions – here called adoption guides – determine which of them a SME tend to go through. The typology enables organizations that educate SMEs or support their development of e-commerce to design their efforts more efficiently and researchers to diversify the studied population. As the study is theory building the contributions and conclusions are propositions that need to be tested empirically in future studies.
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| 4. |
- Sörme, Pernilla, et al.
(författare)
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Design and Synthesis of Galectin Inhibitors
- 2003
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Ingår i: Recognition of Carbohydrates in Biological Systems, Part B: Specific Applications (Methods in Enzymology; 263). - 0121822664 ; 363, s. 157-169
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Galectins, a lectin family, have shown binding affinities towards b-galactosides. Galectins have been proposed to be involved in a wide range of functions like for example, cell growth, adhesion, migration, chemo taxis and apoptosis. They have also been associated with various cancer types. However, the detailed functions of galectins are still very much unknown. High affinity inhibitors towards the galectins would thus be of value as research tools, as well as possible future pharmaceutical agents. Existing inhibitors have undesirable properties, for example high molecular weight and instability. This thesis concerns the synthesis of small high affinity galectin inhibitors. A previously published X-ray structure of galectin-3 together with LacNAc revealed an extended binding pocket close to 3´-C of the galactoside residue. Filling this pocket with additional chemical entities was hypothesized to allow for further interactions and hence creating higher affinity ligands as compared to the naturally occurring ligand. The hypothesis was probed by substituting the 3´-hydroxyl group on the galactose unit of LacNAc with an amine, which enables the introduction of functional groups under mild reaction conditions. We synthesised a collection of more than 60 LacNAc derivatives with various functional groups at 3´-C of the galactose unit. The measurements of inhibitor potencies towards galectins were made in a novel fluorescence polarisation (FP) assay, which is a solution phase method, as well as a general technique that do not need major re-optimisation to enable the study of other galectins. Hence, it enabled us to study the panel of synthetic inhibitors towards galectin-1, -3 and –4. Selective and high affinity inhibitors were discovered, which is of value as often more than one galectin is present in one and the same system. We found that aromatic amides in particular showed high affinity towards galectin-3. In addition, the X-ray structure of one of the best inhibitors (Kd 0.9 mM) revealed that Arg-144 on galectin-3 had moved 3.5 Å to enable a face-to-face stacking interaction with a 4-methoxy-2,3,5,6-tetrafluorobenzamido substituent. The best inhibitor synthesised as of yet, carried a 2-naphthamido functionality at 3´of the galactose residue. This inhibitor had a Kd of 0.3 mM, which the strongest binding affinity achieved as compared to any monovalent inhibitor. It shows over 200 times higher affinity towards galectin-3 than the unfunctionalised LacNAc.
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