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| 3. |
- Ahl, Ing-Marie, 1974-, et al.
(författare)
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Coexpression of yeast copper chaperone (yCCS) and CuZn-superoxide dismutases in Escherichia coli yields protein with high copper contents
- 2004
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Ingår i: Protein Expression and Purification. - : Elsevier BV. - 1046-5928 .- 1096-0279. ; 37:2, s. 311-319
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Tidskriftsartikel (refereegranskat)abstract
- To fully understand the function of the Cu- and Zn-containing superoxide dismutases in normal and disordered cells, it is essential to study protein variants with full metal contents. We describe the use of an Escherichia coli-based expression system for the overproduction of human intracellular wild type CuZn-superoxide dismutase (SOD), the CuZnSOD variant F50E/G51E (monomeric), two amyotrophic lateral sclerosis-related mutant CuZnSOD variants (D90A and G93A), and PseudoEC-SOD, all with high Cu contents. This system is based on coexpression of the SOD variants with the yeast copper chaperone yCCS during growth in a medium supplemented with Cu2+ and Zn2+. The recombinant SOD enzymes were all found in the cytosol and represented 30-50% of the total bacterial protein. The enzymes were purified to homogeneity and active enzymes were obtained in high yield. The resulting proteins were characterized through immunochemical reactivity and specific activity analyses, in conjunction with mass-, photo-, and atomic absorption-spectroscopy. © 2004 Elsevier Inc. All rights reserved.
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| 4. |
- Ahl, Ing-Marie, et al.
(författare)
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Thermodynamic Characterization of the Interaction between the C-Terminal Domain of Extracellular Superoxide Dismutase and Heparin by Isothermal Titration Calorimetry
- 2009
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Ingår i: BIOCHEMISTRY. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 48:41, s. 9932-9940
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular superoxide dismutase (ECSOD) interacts with heparin through its C-terminal domain. In this study we used isothermal titration calorimetry (ITC) to get detailed thermodynamic information about the interaction. We have shown that the interaction between ECSOD and intestinal mucosal heparin (M-w 6000-30000 Da) is exothermic and driven by enthalpy at physiological salt concentration. However, the contribution from entropy is favorable for binding or small isolated heparin fragments. By studying different size-defined heparin fragments, we also concluded that it hexasaccharide moiety is sufficient for strong binding to ECSOD. The binding involves proton transfer from the buffer to the ECSOD-heparin complex, and the results indicate that the number of ionic interactions made between ECSOD and heparin upon binding varies from three to five for heparin and an octasaccharide fragment, respectively. Surprisingly and despite the many charges found oil both the protein and the polysaccharide, our results indicate that the nonionic contribution to the binding is large. From the temperature dependence we have calculated the constant pressure heat capacity change (Delta C-p) of the interaction to -644 J K-1 mol(-1) and -306 J K-1 mol(-1) for heparin and all octasaccharide, respectively
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| 5. |
- Andersson, Johanna, 1972-
(författare)
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Barns teckningar som utgångspunkt i det naturvetenskapliga samtalet
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Barns föreställningar utgör en viktig del i deras begreppsbildning inom naturvetenskap vilket betonas inom konstruktivismen. I denna avhandling utgör en socialkonstruktivistisk syn på lärande det teoretiska ramverket. Det övergripande syftet med avhandlingen är att i samtal med barn i åldrarna 4–13 år och med utgångspunkt i deras teckningar, utveckla kunskap om de föreställningar de ger uttryck för inom fyra naturvetenskapliga områden: värme, blandning, människokroppen och vad som är levande/inte levande. Två forskningsfrågor behandlas i avhandlingen: Vilka föreställningar ger barn uttryck för i teckningar och i samtal om naturvetenskapliga fenomen? Vilka metodologiska förutsättningar och utmaningar finns det när det gäller att använda teckningar som utgångspunkt och som meningsskapande redskap för att fånga barns föreställningar? En multimodal metod bestående av teckningar, samtal och barnens aktivitet användes vid datainsamlingen, vilket är i linje med ett socialsemiotiskt perspektiv.Avhandlingen består av fyra studier. Resultatet i de två första studierna visar att barns föreställningar om blandningar var något mer utvecklade än vad som visats i tidigare studier, medan deras föreställningar gällande värme överensstämde med vad som tidigare rapporterats.Den tredje studien visar att barnen känner till fler organ i människokroppen och visar, till skillnad från vad som framkommit i tidigare forskning, förmåga att rita kopplingar mellan organen. I den fjärde studien talar en majoritet av barnen om död som en motsats till liv och några ritade att det som inte lever tidigare har levt. Barn som är medvetna om mikroskopiska objekt klassificerar dem som levande. Förklaringarna visar på en inkonsekvens i barnens resonemang om växter lever eller inte.Metodologiskt framkom att barns föreställningar med fördel fångas genom deras egna teckningar tillsammans med deras förklaringar av dessa. Teckningarna fungerar även som hjälpmedel för att föra fram och delge olika resonemang. I avhandlingen diskuteras barns lösningar på rittekninska problem som de mötte vid sidan av den naturvetenskapliga uppgiften. I studien om människokroppen handlar dessa problem om svårigheten i att överföra den tredimensionella människokroppen till två dimensioner. En annan svårighet var att kroppens organ, skelett, muskler och vävnader ligger ovanpå varandra. Där använde barnen strategin att rita röntgenbilder för att visa det som ligger dolt. Barn i olika åldrar löste ofta dessa rittekniska problem på ett mycket kreativt sätt i kombination med deras muntliga/skriftliga kommentarer. Förutom teckningarnas betydelse diskuteras skillnaden mellan kontextualiserade och dekontextualiserade uppgifter. De olika områdena som studerats i avhandlingens artiklar befinner sig på olika abstraktionsnivåer vilket påverkar barnens föreställningar och hur detta uttrycks in bilder. Naturvetenskap innefattar olika dimensioner där det handlar om att både lära sig strukturell och processuell kunskap. Den multimodala metoden gav barnen hjälp med att samla, strukturera och uttrycka sina tankar
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| 6. |
- Andersson, Johanna, et al.
(författare)
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Children's reasoning and representations about living and non-living things
- 2013
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Konferensbidrag (refereegranskat)abstract
- Understanding of the concept ‘life’ and what characterise ‘living things’ is important as a foundation for learning in biology. In a more general view, this understanding can make children develop awareness, respect and responsibility for life as members of a society and in decision making for sustainable development. The present pilot study aim to investigate 5-6 year old pre-school children’s reasoning and representations about living and nonliving things. In cognitive developmental research, the concept of life is well investigated but, questions still remain regarding how children reason around and represent these concepts. Previous research has found that children have difficulties in including plants as living things. Moreover, it is found that young children include e.g. the sun, clouds and rocks as living things. The methods that have been used are often quantitative and use picture-cards with different objects for the children to categorize. In the present pilot study a modified methodology was applied. Children’s drawings of what they consider as living and non-living were collected and picture-cards were used as point of departure for reasoning. In interviews the children were encouraged to explain and express their ideas. The drawings and the cards mainly worked as a meaning making tool for the children. Results from the study will be presented and discussed.
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| 7. |
- Andersson, Johanna, et al.
(författare)
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Exploring childrens' views of what's inside the body
- 2012
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Konferensbidrag (refereegranskat)abstract
- The importance of living a healthy life in an everyday context is promoted in schools and preschools. The discussion often focuses on what food is healthy, and that one should eat enough but not too much. The connection between food and beverages and their role in the body is seldom discussed. Students’ ideas about how the human body functions have been investigated in several studies but few have focused on young children. In this study, we investigate young children’s conceptions related to this topic and how their ideas develop. Seventy-nine pre- and primary school children, aged 4-11, participated in individual focus interviews wherein the children were asked to draw and explain their understanding. Our results confirm several findings observed by other workers. However, in contrast with earlier studies, 10 of seventeen 4-5 year-old children indicated the stomach, and more than half of those children described how food can be utilized in the body to extract energy. Furthermore, the brain was among the most commonly mentioned organs cross all age groups. Interestingly, the level of expertise varied and did not covariate with age. For example, five of eight of the 4 year-old children draw 5-8 organs, while a single 10 year-old child could only mention three. Similarly, two of thirteen 7-year old children provided an almost completely correct description of the digestive tract and its function, while most of the older children expressed a much less developed understanding. The results reflect the wide range of different conceptual ideas that teachers confront in a day-to-day classroom context.
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| 8. |
- Andersson, Johanna, 1972-, et al.
(författare)
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What’s in the body? Children’s annotated drawings
- 2020
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Ingår i: Journal of Biological Education. - : Routledge. - 0021-9266 .- 2157-6009. ; :2, s. 176-190
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study of children’s ideas of the body’s internal structure. Children between four and 13 years (N = 170) individually produced drawings. During each drawing session the children explained their drawings to a facilitator and added written labels either by them- selves or, if they were too young to write, with the facilitator’s help. The results provide an updated comprehensive picture of children in differ- ent age groups and their views on the internal structure of the body. The type and numbers of organs drawn are similar to those documented in previous studies. However, in comparison to recent studies, the children drew more organs, the brain was indicated almost as often as the heart, and the Valentine heart was frequently used as a symbol. In contrast with previous research, children drew connections between organs. This result calls for caution regarding conclusions made from decontextua- lized questions. The importance of providing children with the opportu- nity to clarify their drawings is emphasised since it otherwise becomes a question of the researcher’s interpretation. The connections they draw, and explanations they give to their drawings, have interesting implica- tions for understanding children’s ideas, and hence both for teaching and learning and for science education research.
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| 9. |
- Berg, Anders, et al.
(författare)
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Benefiting from an open-ended experiment? A comparison of attitudes to, and outcomes of, an expository versus an open-inquiry version of the same experiment
- 2003
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Ingår i: International Journal of Science Education. - : Informa UK Limited. - 0950-0693 .- 1464-5289. ; 25:3, s. 351-372
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Tidskriftsartikel (refereegranskat)abstract
- In this article we compare outcomes of an open-inquiry and an expository version of a chemistry laboratory experiment at university level for 190 students. The aim of the study was to investigate if these two versions would result in different outcomes depending on the students' attitudes towards learning. We used a questionnaire to find out their attitude position prior to the laboratory experiment. The outcome in the different version of the experiment was evaluated by interviews, questions asked during the experiment and students self-evaluations. The main findings were that the open-inquiry version shows the most positive outcomes regarding learning outcome, preparation time, time spent in the laboratory and student perception of the experiment. The students with low attitude position needed more support to meet the challenge of an open-inquiry experiment, the support being a clearer explanation of the aims, and feedback from the instructor during the experiment.
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| 10. |
- Bergendahl, Christina, et al.
(författare)
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Boosting complex learning by strategic assessment and course design
- 2005
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Ingår i: Journal of Chemical Education. - 0021-9584 .- 1938-1328. ; 82:4, s. 645-651
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Tidskriftsartikel (refereegranskat)abstract
- A strategic selection of instruction and assessment methods geared to higher cognition levels was used to foster increasingly complex learning. Assessment results from the redesigned course show that students are capable of mastering higher-order cognitive skills relative to these objectives, however the synthesis category constitutes a threshold in students' cognitive development. No single assessment method was found to be clearly the best, yet careful selection of the method that allows higher-order thinking made it possible to develop a combination of assessments that meet objectives.
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