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| 2. |
- Andersson Trojer, Markus, 1981, et al.
(författare)
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Synthesis and polymerisation of maleolyl-L-histidine monomers and addition of histidine to an ethylene-alt-maleic co-polymer
- 2012
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Ingår i: Journal of Polymer Research. - : Springer Science and Business Media LLC. - 1572-8935 .- 1022-9760. ; 19:2, s. 9821-9829
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Tidskriftsartikel (refereegranskat)abstract
- This work has investigated two routes of synthesising polymers containing L-histidine using maleimide chemistry; grafting of histidine onto an ethylene-alt-maleic anhydride copolymer and AIBN (azobisisobutyronitrile) initiated radical polymerisation of the monomer maleoyl-L-histidine. The grafting technique and monomer synthesis are utilising the maleimide formation between the primary amine of histidine and maleic anhydride. The reactions are conveniently carried out in one step with good yields. The copolymers containing L-histidine were prepared by reacting L-histidine or L-histidine methyl ester with poly(ethylene-alt maleic anhydride) in DMSO at 50 °C for 8–16 h with 80% yields independent of the degree of substitution. The monomer maleoyl-L-histidine was synthesised by reacting histidine and maleic anhydride in acetic acid and the monomer was subsequently polymerised by AIBN radical initiation in DMSO at 80 °C for 48 h to yield poly(N-histidyl maleimide). The resulting polymer had a different optical rotation ([α]D20 = −11) than the monomer ([α]D20 = +25), which is ascribed to the threo-diisotactic and/or threo-disyndiotactic stereoregularity of the polymer.
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| 3. |
- Braesch-Andersen, Anna, et al.
(författare)
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Application of phase-field fracture theories and digital volume correlation to synchrotron X-ray monitored fractures in human trabecular bone : A case study
- 2022
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 135
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Tidskriftsartikel (refereegranskat)abstract
- Fracture processes of trabecular bone have been studied using various approaches over the years. However, reliable methods to analyse fracture at the single trabecula level are limited. In this study, a digital volume correlation (DVC) and a phase-field fracture model are applied and contrasted for human trabecular bone to analyse its failure under global compression at high resolution.A human trabecular bone sample was fractured in situ under synchrotron-based X-ray micro computed to-mography (CT). Reconstructed CT data was then used in DVC algorithms to obtain high-resolution displacement fields in the bone at different load steps. A high-resolution specimen-specific structural mesh was discretized from the CT data and used for the phase-field simulation of the fracturing bone.The DVC analysis showed opening mode cracks as well as shear mode cracks. Strains in cracked regions were analysed. The load distribution in the trabecular structure resulted in two completely separated fracture regions in the sample body. A phenomenon that was also captured in the phase-field model. The results encourage us to believe improvements in boundary conditions and material models are worthwhile pursuing. Findings in this study support further development of a phase-field method to analyse fracture in samples with complex morphology, such as trabecular bone, and the capacity of DVC to quantify strains and slowly growing stable fractures during step-wise loading of trabecular bone.
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| 4. |
- Ganachaud, C., et al.
(författare)
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An anomalous behavior of trypsin immobilized in alginate network
- 2013
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 97:10, s. 4403-4414
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Tidskriftsartikel (refereegranskat)abstract
- Alginate is a biopolymer used in drug formulations and for surgical purposes. In the presence of divalent cations, it forms solid gels, and such gels are of interest for immobilization of cells and enzymes. In this work, we entrapped trypsin in an alginate gel together with a known substrate, N (alpha)-benzoyl-l-arginine-4-nitroanilide hydrochloride (l-BAPNA), and in the presence or absence of d-BAPNA, which is known to be a competitive inhibitor. Interactions between alginate and the substrate as well as the enzyme were characterized with transmission electron microscopy, rheology, and nuclear magnetic resonance spectroscopy. The biocatalysis was monitored by spectrophotometry at temperatures ranging from 10 to 42 A degrees C. It was found that at 37 and 42 A degrees C a strong acceleration of the reaction was obtained, whereas at 10 A degrees C and at room temperature, the presence of d-BAPNA leads to a retardation of the reaction rate. The same effect was found when the reaction was performed in a non-cross-linked alginate solution. In alginate-free buffer solution, as well as in a solution of carboxymethylcellulose, a biopolymer that resembles alginate, the normal behavior was obtained; however, with d-BAPNA acting as an inhibitor at all temperatures. A more detailed investigation of the reaction kinetics showed that at higher temperature and in the presence of alginate, the curve of initial reaction rate versus l-BAPNA concentration had a sigmoidal shape, indicating an allosteric behavior. We believe that the anomalous behavior of trypsin in the presence of alginate is due to conformational changes caused by interactions between the positively charged trypsin and the strongly negatively charged alginate.
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| 5. |
- Gustafsson, Dan, et al.
(författare)
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Tissue zinc levels in a child with hypercalprotectinaemia and hyperzincaemia : a case report and a review of the literature
- 2012
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - London, United Kingdom : Informa Healthcare. - 0036-5513 .- 1502-7686. ; 72:1, s. 34-38
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Forskningsöversikt (refereegranskat)abstract
- Background: A girl suffering from a rare syndrome of unknown aetiology, termed hypercalprotectinaemia, was evaluated for tissue zinc status, because calprotectin is a protein which chelates Zn at multiple binding-sites, which might have affected the distribution of Zn in her body.Methods: Measurement of serum, urine, hair and nail zinc (Zn) concentration, complemented with measurement of total Zn in ultrafiltrates of plasma.Results: Her serum Zn concentration was 105-133 mu mol/L. Zn levels in her hair (102 mu g/g), nail (90 mu g/g) and urine (3-12 mu mol/L; 20-80 mu g/dL) were all at the lower end of the reference intervals described in the sparse literature. Zn concentrations in ultrafiltrates of plasma were below the detection limit (<100 nmol/L). Thus, the elevated serum Zn did not translate into a similarly increased level of Zn in any of the tissues tested, nor in free Zn concentrations. Instead it appeared to be a result of Zn being chelated to binder proteins, most probably calprotectin.Conclusion: Her grossly elevated serum calprotectin concentration is probably able to raise circulating total Zn concentrations without raising ionized concentrations, but this Zn remains confined to the circulating blood as well as to excreted body fluids, particularly faeces.
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| 6. |
- Gylle, A. Maria, et al.
(författare)
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Seasonal variations in photosynthetic capacity and osmotic adjustment in Fucus vesiculosus and F. radicans (Phaeophyceae) with respect to salinity
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The marine intertidal Fucus vesiculosus from the Norwegian Sea (34 practical salinity units, psu) and the sublittoral F. vesiculosus and F. radicans from the brackish Bothnian Sea (5 psu) have been compared physiologically with respect to changes in salinity and seasons. The initial maximum quantum yield of photosystem II photochemistry (Fv/Fm) did not vary between the marine and brackish ecotypes or between the seasons but showed different responses to the experiment condition at different seasons. In general, there were no differences in the ability to withstand salinity changes, measured as Fv/Fm, between the marine and brackish ecotype. The tolerance is in a broad range for both of the ecotypes. The marine ecotype of F. vesiculosus had 30 % more mannitol than the brackish F. vesiculosus and there was 35 % more mannitol in May compared to November. The mannitol content in the marine ecotype responded differently to salinity changes in May compared to November, probably partly due to different initial concentrations. No changes in mannitol content could be detected in brackish F. vesiculosus. No significant differences were shown in Fv/Fm and mannitol content between brackish F. vesiculosus and F. radicans.
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| 7. |
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| 8. |
- Gylle, A. Maria, et al.
(författare)
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The relation between water soluble organic compounds and salinity in marine and brackish Fucus vesiculosus L. (Phaeophyceae)
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The marine intertidal Fucus vesiculosus from the Norwegian Sea (34 practical salinity units, psu) and the sublittoral F. vesiculosus from the brackish Bothnian Sea (5 psu) have been compared with respect to the production of water soluble organic compounds during treatment in varying salinities. Nuclear magnetic resonance (NMR) 13C spectra revealed that there were differences in the content of water soluble organic compounds between the marine and the brackish F. vesiculosus and that production of these compounds was independent of salinity.
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| 9. |
- Gylle, Maria, et al.
(författare)
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Research note: Ecotype differentiation in qualitative content of water soluble organic compounds between marine and brackish Fucus vesiculosus L. (Phaeophyceae)
- 2009
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Ingår i: Phycological Research. - : Wiley. - 1322-0829 .- 1440-1835. ; 57:2, s. 127-130
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we compared the contents of water soluble organic compounds of the marine intertidal ecotype of Fucus vesiculosus (Phaeophyceae) from the Norwegian Sea (34 practical salinity units, psu) with the sublittoral ecotype of F. vesiculosus from the brackish Bothnian Sea (5 psu). Nuclear magnetic resonance spectra revealed that marine F. vesiculosus had additional types of water soluble organic compounds compared with brackish F. vesiculosus. The results suggested that glycine betaine in the marine ecotype could be the reason for this ecotype differentiation. Furthermore, the qualitative differences between the ecotypes were the same after one week's treatment of marine algae in brackish water and of brackish algae in marine water. These suggest that the additional types of water soluble organic compounds in marine F. vesiculosus are not caused by the salinity conditions at the growth sites. Further research concerning other environmental factors that may influence ecotype differentiation of water soluble organic compounds qualitative content and adaptation in F. vesiculosus is recommended.
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| 10. |
- Hedin, Jesper, 1980, et al.
(författare)
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Bi-Layer Formation of Imidazole- Modified Ethyl(HydroxyEthyl)Cellulose at a Hydrophobic Surface as monitored by QCM-D
- 2009
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 336:2, s. 388-392
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption behaviour of ethyl(hydroxyethyl)cellulose chemically modified with imidazole (Im-EHEC) at hydrophobic surfaces has been studied with QCM-D. The very slow adsorption isotherm was due to a continuous polymer film reconfiguration and exchange of different sized polymers. The thickness of the film was about 30 nm. The polymers adsorbed Cu2+ ions into the film from a CuCl2 solution and a bi-layer was formed when Im-EHEC was added a second time. The second polymer film was only 7 nm thick but highly viscoelastic. After rinsing with water the metal ions was flushed away and the second Im-EHEC layer was released. The imidazole modification of EHEC enables interaction with transition metal ions and opens up for new applications for cellulose based materials.
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