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| 2. |
- Larsson, Karin M., et al.
(författare)
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Enzymatic catalysis in microemulsions : Enzyme reuse and product recovery
- 1990
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290. ; 36:2, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- A technique for enzyme reuse and product recovery from enzymatic catalysis in microemulsions is demonstrated. The enzymatic reaction is performed in a homogeneous isotropic microemulsion; AOT (sodium bis‐(2‐ethyl‐ hexyl)sulfosuccinate)/isooctane/buffer or C12E5(penta ethylene glycol dodecyl ether)/heptane/buffer. By small temperature changes the systems are shifted to two phase regions, where an oil‐rich phase, containing the product, coexists with a water‐rich phase containing surfactant and enzyme. The oil‐rich phase may be replaced by an oil solution containing new substrate. Thus, the reaction may be continued and the enzyme reused. This procedure was repeated nine times in the present study. Data on phase behavior in presence and in absence of protein, partitioning of the components and a radioactive‐labelled protein between the phases, and the repeated use of horse liver alcohol dehydrogenase (HLADH) in the microemulsions are presented.
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| 3. |
- Larsson, Karin M., et al.
(författare)
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Enzyme catalysis in uni- and bi-continuous microemulsions : Dependence of kinetics on substrate partitioning
- 1991
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Ingår i: Journal of the Chemical Society, Faraday Transactions. - 0956-5000. ; 87:3, s. 465-471
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of enzymatic conversion in a microemulsion have been investigated. Racemic 3-methylcyclohexanone was oxidized by horse-liver alcohol dehydrogenase (HLADH, E.C. 1.1.1.1.) using a coupled substrate-coenzyme regenerating cycle in a sodium bis-(2-ethylhexyl) sulphosuccinate (AOT)-isooctane-buffer microemulsion. Initial enzyme activity was measured as a function of the oil volume fraction in the range 0 ≤ Φ ≤ 0.83 for a constant surfactant concentration. The change in composition is followed by a change in microstructure from oil-in-water (O/W) to water-in-oil (W/O) via a bicontinuous structure as determined by self-diffusion measurements using the pulsed-gradient NMR technique. The variation of the initial rate with composition is well described by modifying the rate equation, valid in pure buffer, by simply taking into account the partitioning of the substrates between the polar and apolar microdomains in the structured solvent. Also the enzyme stability was investigated at various compositions of the microemulsion. The stability was found to increase with increasing Φ.
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| 4. |
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| 5. |
- Larsson, Karin M., et al.
(författare)
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Three systems used for biocatalysis in organic solvents a comparative study
- 1990
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422. ; 4:2-3, s. 163-175
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Tidskriftsartikel (refereegranskat)abstract
- The activity and operational stability of horse liver alcohol dehydrogenase (HLADH) and αchymotrypsin were investigated in three systems commonly used for biocatalysis in organic solvents: 1. enzyme adsorbed on a solid support (celite) and added to the organic solvent (isooctane) 2. enzyme powder directly added to the organic solvent (isooctane). 3. enzyme dissolved in a microemulsion (AOT/isooctane). The activity and the operational stability in all systems were strongly dependent on the water content. The initial reaction rate was high in both the microemulsion and the celite system, but was much lower when adding the enzymes directly to the organic solvent. HLADH was observed to be more stable when added directly to the organic solvent or dissolved in the microemulsion than when adsorbed on celite, whereas for αchymotrypsin stability was higher when adsorbed on celite or added directly to the organic solvent. For a hydrolytic reaction, a microemulsion was preferred due to the high water content. When adding the enzymes directly to the organic solvent both HLADH and chymotrypsin were adsorbed strongly to the glass walls of the reaction vessel. None of the systems were superior in all respects for the two enzymes studied.
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| 6. |
- Lindgren, Karin, et al.
(författare)
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Major Armed Conflicts (1989)
- 1990
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Ingår i: SIPRI Yearbook 1990. - : Oxford: Oxford University Press.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Nordenström, J, et al.
(författare)
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Hyperparathyroidism associated with treatment of manic-depressive disorders by lithium.
- 1992
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Ingår i: European Journal of Surgery. - 1102-4151 .- 1741-9271. ; 158:4, s. 207-211
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To clarify the association between treatment of affective psychiatric disorders with lithium, and the development of secondary hyperparathyroidism.DESIGN: Retrospective review of medical records, 1973-89.SUBJECTS: 17 patients with affective psychiatric disorders who were treated with lithium (n = 6) or with tricyclic antidepressant, or neuroleptic, drugs (n = 11) all of whom were operated on for hyperparathyroidism.MAIN OUTCOME MEASURE: Duration of lithium therapy and parathyroid histology.RESULTS: Parathyroid hyperplasia was present in 5 patients who had taken lithium during a median period of 13 years. A parathyroid adenoma was found in one patient treated with lithium for three years. Ten of the 11 patients who had been treated with tricyclic antidepressant, or neuroleptic drugs had a parathyroid adenoma and the remaining one had an adenoma as an underlying cause of hyperparathyroidism.CONCLUSION: Hyperparathyroidism in patients who have undergone long term treatment with lithium is associated with parathyroid hyperplasia. This indicates that lithium may exert a chronic stimulus that results in secondary hyperparathyroidism.
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| 8. |
- Wårdell, Karin, et al.
(författare)
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Spatial heterogeity in normal skin perfusion recorded with laser Doppler imaging and flowmetry
- 1994
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Ingår i: Microvascular Research. - 0026-2862 .- 1095-9319. ; 48:1, s. 26-38
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Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal variations in forearm skin perfusion captured by laser Doppler perfusion imaging (LDI) have been compared with topographic maps recorded by laser Doppler flowmetry. In order to determine the shortest LDI sampling time required at each measurement site, with an adequate signal-to-noise ratio and with the ability to display the heterogeneity in skin perfusion, the noise-limited resolution of the LDI system as well as various sampling times were tested. The noise-limited resolution for medium and high light intensities were less than 0.5% (temporal) and 0.3% (spatial) of full scale. A sampling time of 1 sec was selected and image presentation was made by performing bilinear interpolation between perfusion values. The same area (10 x 10 mm) was mapped with LDI and topographic mapping at seven different sites. In addition, a larger area covering the surrounding skin was recorded with LDI. The small area recordings with LDI and topographic mapping could be identified in the larger LDI image. High-and low-perfusion spots coincided between the two systems. Temporal variations were studied by repeated LDI recordings of the same areas as above. Small spots were selected in the areas and plotted versus time. Without provocation, the total perfusion changes at each spot showed large variations, but the relative perfusion levels between neighboring spots persisted. Provocation with heat increased the perfusion in all spots.
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