| 1. |
- Bergqvist, Ewa, Docent, et al.
(författare)
-
How mathematical symbols and natural language are integrated in textbooks
- 2020
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In mathematical text and talk, natural language is a constant companion to mathematical symbols. The purpose of this study is to identify different types of relations between natural language and symbolic language in mathematics textbooks. Here we focus on the level of integration. We have identified examples of high integration (e.g., when symbols are part of a sentence), medium integration (e.g., when the shifts between natural and symbolic language occurs when switching to a new line), and low integration (e.g., when symbols and written words are connected by the layout).
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Hörnberg, Andreas, 1972-, et al.
(författare)
-
The effect of iodide and chloride on transthyretin structure and stability
- 2005
-
Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 44:26, s. 9290-9299
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Transthyretin amyloid formation occurs through a process of tetramer destabilization and partial unfolding. Small molecules, including the natural ligand thyroxine, stabilize the tetrameric form of the protein, and serve as inhibitors of amyloid formation. Crucial for TTR's ligand-binding properties are its three halogen-binding sites situated at the hormone-binding channel. In this study, we have performed a structural characterization of the binding of two halides, iodide and chloride, to TTR. Chlorides are known to shield charge repulsions at the tetrameric interface of TTR, which improve tetramer stability of the protein. Our study shows that iodides, like chlorides, provide tetramer stabilization in a concentration-dependent manner and at concentrations approximately 15-fold below that of chlorides. To elucidate binding sites of the halides, we took advantage of the anomalous scattering of iodide and used the single-wavelength anomalous dispersion (SAD) method to solve the iodide-bound TTR structure at 1.8 A resolution. The structure of chloride-bound TTR was determined at 1.9 A resolution using difference Fourier techniques. The refined structures showed iodides and chlorides bound at two of the three halogen-binding sites located at the hydrophobic channel. These sites therefore also function as halide-binding sites.
|
|
| 5. |
- Wikström Hultdin, Ulrika, et al.
(författare)
-
Applying a new framework of connections between mathematical symbols and natural language
- 2023
-
Ingår i: Journal of Mathematical Behavior. - : Elsevier. - 0732-3123 .- 1873-8028. ; 72
-
Tidskriftsartikel (refereegranskat)abstract
- A reader of mathematical text must often switch between reading mathematical symbols and reading words. In this study, five different categories of structural connections between symbols and language, which invite such switches, are presented in a framework. The framework was applied in a study of Swedish mathematics textbooks, where 180 randomly selected pages from different educational stages were analyzed. The results showed a significant change in communication patterns as students progress through school. From a predomination of connections based on proximity found in year two, there is a gradual change to a predomination of symbols interwoven in sentences in year eight. Furthermore, more qualitative investigations of the different connections complemented the quantification, both through further explanations of the quantitative results, and through more examples of differences in communication patterns. The implications for readers of mathematics texts are discussed.
|
|
| 6. |
- Wikström Hultdin, Ulrika, 1977-
(författare)
-
Between symbols and words : structural connections in mathematics texts and their effect on reading
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- While students progress through their school years, they are expected to develop reading skills in all academic subjects, including mathematics. Mathematics texts, being multisemiotic, require readers to make meaning not only from written language but also from mathematical symbols and visualizations. Integrating content presented through different sign systems is essential for creating coherence. Thus, the organizational structure of these texts becomes critically important when designing texts for learning. The purpose of this thesis is to build knowledge of the organization of mathematical symbols and written language, and to achieve better understanding of how this organization influences the reading of mathematics texts. First, the structural connections between mathematical symbols and written language in mathematics texts designed for students are characterized. Five distinct categories of such connections—Interwoven, Chunked, Marked, Adjoined, and Referenced—are identified, ranging from connections in which mathematical symbols are integrated into sentences (Interwoven), to those based solely on the proximity between two text sequences (Adjoined). The prevalence of these connection categories in textbooks from different school levels is also investigated. The results indicate a progression in the use of structural connections, with a shift from reliance on proximity in early school years towards a preference for symbols interwoven in sentences between years 2 and 5, suggesting that all students eventually need to navigate texts with interwoven symbols. Additionally, changes can be seen in how symbols are being connected to more detailed meanings. Second, the reading of mathematics texts employing two distinct text designs inspired by the new framework is compared: one design features only sentences with interwoven symbols, whereas the other uses a graphic to highlight key connections between symbols and words. The reading processes and experiences of students are investigated by analyzing gaze measurements and interviews. The results indicate that the two designs have different advantages depending on the situation. While the graphic design can facilitate reading and interpretation by drawing attention to the connections between symbols and words, enabling quicker content matching, the symbols interwoven in sentences might provide better access to details or allow more efficient reading in other contexts. Moreover, individual differences in processing and experiences were noted: while some readers benefitted from the graphic design, others did not. Yet, as reading becomes more complex, the graphic is increasingly appreciated. It is concluded that while readers generally prefer text designs that enhance readability, the optimal design varies based on the reader and the context. The discussion includes what text design benefits whom and under what circumstances.
|
|
| 7. |
|
|
| 8. |
- Wikström Hultdin, Ulrika, et al.
(författare)
-
Purification, crystallization and preliminary data analysis of FocB, a transcription factor regulating fimbrial adhesin expression in uropathogenic Escherichia coli
- 2010
-
Ingår i: Acta Crystallographica. Section F. - 1744-3091 .- 1744-3091. ; 66:Pt 3, s. 337-341
-
Tidskriftsartikel (refereegranskat)abstract
- The transcription factor FocB belongs to a family of regulators encoded by several different fimbriae gene clusters in uropathogenic Escherichia coli. Recent findings suggest that FocB-family proteins may form different protein-protein complexes and that they may exert both positive and negative effects on the transcription of fimbriae genes. However, little is known about the actual role and mode of action when these proteins interact with the fimbriae operons. The 109-amino-acid FocB transcription factor from the foc gene cluster in E. coli strain J96 has been cloned, expressed and purified. The His6-tagged fusion protein was captured by Ni2+-affinity chromatography, cleaved with tobacco etch virus protease and purified by gel filtration. The purified protein is oligomeric, most likely in the form of dimers. NMR analysis guided the crystallization attempts by showing that probable conformational exchange or oligomerization is reduced at temperatures above 293 K and that removal of the highly flexible His6 tag is advantageous. The protein was crystallized using the hanging-drop vapour-diffusion method at 295 K. A native data set to 2.0 Å resolution was collected at 100 K using synchrotron radiation.
|
|
| 9. |
|
|
| 10. |
- Wikström Hultdin, Ulrika, 1977-
(författare)
-
Structural studies of FocB and Transthyretin
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The molecular structure of a protein decides its function, its way to interact with other molecules. Using X-ray crystallography methods, a 3-dimensional, atomic model of a macromolecule can be determined. In this thesis work, the X-ray structures of two different proteins involved in human diseases were studied: FocB, which is associated with urinary tract infections, and transthyretin, which is the causative of hereditary systemic transthyretin amyloidosis. FocB is a 12 kDa protein which binds DNA in an oligomeric fashion. It is involved in the regulation of the expression of bacterial surface organelles (fimbriae), responsible for the adhesion to specific receptors in host tissue. Specifically, FocB regulates the expression of one fimbrial type found in uropathogenic E. coli (UPEC): F1C. Our FocB structure revealed it to be an all-alpha helical protein with an atypical helix-turn-helix (HTH) motif. Residues previously found important for DNA-binding in the FocB homologue PapB, were not located in the putative “recognition helix” of the HTH-motif. FocB was also found to bind to the minor groove of the DNA. Together with homology searches showing that the DNA-interactions possible for FocB are greatly diversified, these findings indicated a DNA-interaction different from the typical DNA-interaction of a HTH-protein. Transthyretin (TTR) is a plasma protein involved in transport of thyroxin (T4) and retinol. Mutated TTR is also the cause of the neurodegenerative disease hereditary systemic transthyretin amyloidosis, which is characterized by systemic deposition of TTR amyloid fibrils. The amyloid occurs through a process of TTR tetramer destabilization and partial unfolding. A common way to inhibit amyloid formation is to design small molecules that bind unoccupied thyroxin binding sites and stabilize the tetrameric form of the protein. The structural characterization of the binding of chloride and iodide ions to TTR revealed that two of three previously identified halogen binding pockets in the T4-binding site were just as optimal for halide binding. In addition, a third halide-binding site, bridging two TTR subunits, was found. In biochemical experiments, chloride and iodide ions were shown to stabilize the TTR structure and inhibit the TTR aggregation and/or amyloid formation, with iodide ions doing so more efficiently than the chloride ions. In the search for new TTR amyloid-inhibiting drugs, the identified halide-binding sites in the T4-binding pocket are possible starting points for structure-based drug design.
|
|
