| 1. |
- Aaltonen, Emil, et al.
(author)
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Transmembrane topology of the Acr3 family arsenite transporter from Bacillus subtilis.
- 2008
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In: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736. ; 1778:4, s. 963-973
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Journal article (peer-reviewed)abstract
- The transmembrane topology of the Acr3 family arsenite transporter Acr3 from Bacillus subtilis was analysed experimentally using translational fusions with alkaline phosphatase and green fluorescent protein and in silico by topology modelling. Initial topology prediction resulted in two models with 9 and 10 TM helices respectively. 32 fusion constructs were made between truncated forms of acr3 and the reporter genes at 17 different sites throughout the acr3 sequence to discriminate between these models. Nine strong reporter protein signals provided information about the majority of the locations of the cytoplasmic and extracellular loops of Acr3 and showed that both the N- and the C-termini are located in the cytoplasm. Two ambiguous data points indicated the possibility of an alternative 8 helix topology. This possibility was investigated using another 10 fusion variants, but no experimental support for the 8 TM topology was obtained. We therefore conclude that Acr3 has 10 transmembrane helices. Overall, the loops which connect the membrane spanning segments are short, with cytoplasmic loops being somewhat longer than the extracellular loops. The study provides the first ever experimentally derived structural information on a protein of the Acr3 family which constitutes one of the largest classes of arsenite transporters.
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| 2. |
- Arndt, D. S., et al.
(author)
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STATE OF THE CLIMATE IN 2017
- 2018
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In: Bulletin of The American Meteorological Society - (BAMS). - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 99:8, s. S1-S310
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Research review (peer-reviewed)
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| 3. |
- Berggård Silow, Maria
(author)
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Rate Limiting Factors For Protein Folding.
- 2000
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Doctoral thesis (other academic/artistic)abstract
- Abstract. This thesis describes factors that are rate limiting for the folding of two small proteins, U1A and CI2 which fold without accumulating intermediates. The [GdnHCl] dependencies of the unfolding- and refolding kinetics of U1A display downward curvatures. However, as the curvatures are precisely matched and no indications of formation of partially structured intermediates are seen, the folding behaviour is still consistent with a two-state model. Instead, the curvatures seem related to Hammond behaviour, i.e. movements of the transition state on the reaction coordinate. This implies that the free energy barrier is broad and rather flat. Consequently the search for productive interactions in the folding protein does not take place at ground state level but at high energy. Analysis of mutants of CI2 shows, that to a larger extent than previously thought, these mutants also display transition state movements. Possibly, the activation barrier for folding is generally broad but with a more or less rugged surface. When the ruggedness involves localised features that are much higher than the surrounding barrier, the protein will appear to have a localised transition state. Mutations that lower these localised features will then set free movements of the transition state. One way to monitor diffusive events in protein folding is to measure the rate of folding as a function of solvent viscosity. Unfortunately the viscogens (osmolytes) added in these studies also tend to stabilise the protein and thus have dual effects on the folding rate. When CI2 is refolded in the presence of several different osmolytes we find no viscosity dependence on the refolding kinetics. However, we find that the osmolytes, in addition to their other effects also induce a collapse of the denatured protein. The collapse increases the reconfiguration time of the protein and thereby retards folding. At [protein]>1mM, U1A aggregates early in kinetic refolding experiments. This leads to a retardation of folding at low [denaturant], which resembles the accumulation of an intermediate. The retardation results from kinetic competition: at high [protein] the fraction of protein that aggregates increases and eventually dominates the refolding amplitude. As the rate of folding after aggregation is slower than direct folding, this results in an apparent decrease of the folding rate. Similar experiments with CI2 show that also this protein undergoes transient aggregation. Furthermore, as both U1A and CI2 fold without accumulating intermediates the protein aggregates likely form directly from the coil.
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| 4. |
- Björklund, Maria, 1980-, et al.
(author)
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Institutionsetnologi : en inledning
- 2019
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In: Kulturella perspektiv - Svensk etnologisk tidskrift. - : Föreningen Kulturella Perspektiv. - 1102-7908. ; 28:3-4, s. 2-12
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Journal article (other academic/artistic)
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| 5. |
- Björklund, Maria, 1980-, et al.
(author)
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Institutionsetnologi
- 2022. - 1
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In: Etnologiskt fältarbete. - Lund : Studentlitteratur AB. - 9789144153261 ; , s. 69-83
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Book chapter (other academic/artistic)
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| 6. |
- Falk, Magnus, et al.
(author)
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Miniature biofuel cell as a potential power source for glucose-sensing contact lenses
- 2013
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:13, s. 6342-6348
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Journal article (peer-reviewed)abstract
- A microscale membrane-less biofuel cell, capable of generating elec. energy from human lachrymal liq., was developed by using the ascorbate and oxygen naturally present in tears as fuel and oxidant. The biodevice is based on three-dimensional nanostructured gold electrodes covered with abiotic (conductive org. complex) and biol. (redox enzyme) materials functioning as efficient anodic and cathodic catalysts, resp. Three-dimensional nanostructured electrodes were fabricated by modifying 100 μm gold wires with 17 nm gold nanoparticles, which were further modified with tetrathiafulvalene-tetracyanoquinodimethane conducting complex to create the anode and with Myrothecium verrucaria bilirubin oxidase to create the biocathode. When operated in human tears, the biodevice exhibited the following characteristics: an open circuit voltage of 0.54 V, a maximal power d. of 3.1 μW cm-2 at 0.25 V and 0.72 μW cm-2 at 0.4 V, with a stable c.d. output of over 0.55 μA cm-2 at 0.4 V for 6 h of continuous operation. These findings support the authors' proposition that an ascorbate/oxygen biofuel cell could be a suitable power source for glucose-sensing contact lenses to be used for continuous health monitoring by diabetes patients.
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| 7. |
- Gustavsson, Niklas, et al.
(author)
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A peptide methionine sulfoxide reductase highly expressed in photosynthetic tissue in Arabidopsis thaliana can protect the chaperone-like activity of a chloroplast-localized small heat shock protein.
- 2002
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In: Plant Journal. - 1365-313X. ; 29:5, s. 545-553
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Journal article (peer-reviewed)abstract
- The oxidation of methionine residues in proteins to methionine sulfoxides occurs frequently and protein repair by reduction of the methionine sulfoxides is mediated by an enzyme, peptide methionine sulfoxide reductase (PMSR, EC 1.8.4.6), universally present in the genomes of all so far sequenced organisms. Recently, five PMSR-like genes were identified in Arabidopsis thaliana, including one plastidic isoform, chloroplast localised plastidial peptide methionine sulfoxide reductase (pPMSR) that was chloroplast-localized and highly expressed in actively photosynthesizing tissue (Sadanandom A et al., 2000). However, no endogenous substrate to the pPMSR was identified. Here we report that a set of highly conserved methionine residues in Hsp21, a chloroplast-localized small heat shock protein, can become sulfoxidized and thereafter reduced back to methionines by this pPMSR. The pPMSR activity was evaluated using recombinantly expressed pPMSR and Hsp21 from Arabidopsis thaliana and a direct detection of methionine sulfoxides in Hsp21 by mass spectrometry. The pPMSR-catalyzed reduction of Hsp21 methionine sulfoxides occurred on a minute time-scale, was ultimately DTT-dependent and led to recovery of Hsp21 conformation and chaperone-like activity, both of which are lost upon methionine sulfoxidation (Härndahl et al., 2001). These data indicate that one important function of pPMSR may be to prevent inactivation of Hsp21 by methionine sulfoxidation, since small heat shock proteins are crucial for cellular resistance to oxidative stress.
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| 8. |
- Krikstolaityte, Vida, et al.
(author)
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Mediatorless Carbohydrate/Oxygen Biofuel Cells with Improved Cellobiose Dehydrogenase Based Bioanode
- 2014
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In: Fuel Cells. - : John Wiley & Sons. - 1615-6846 .- 1615-6854. ; 14:6, s. 792-800
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Journal article (peer-reviewed)abstract
- Direct electron transfer (DET) between cellobiose dehydrogenase from Humicola insolens ascomycete (HiCDH) and gold nanoparticles (AuNPs) was achieved by modifying AuNPs with a novel, pos. charged thiol N-(6-mercapto)hexylpyridinium (MHP). The DET enabled the use of the HiCDH enzyme as an anodic biocatalyst in the design of a mediatorless carbohydrate/oxygen enzymic fuel cell (EFC). A biocathode of the EFC was based on bilirubin oxidase from Myrothecium verrucaria (MvBOx) directly immobilized on the surface of AuNPs. The following parameters of the EFC based on Au/AuNP/MHP/HiCDH bioanode and Au/AuNP/MvBOx biocathode were obtained in quiescent air satd. PBS, pH 7.4, contg.: (i) 5 mM glucose-open-circuit voltage (OCV) of 0.65 ± 0.011 V and the maximal power d. of 4.77 ± 1.34 μW cm-2 at operating voltage of 0.50 V; or (ii) 10 mM lactose-OCV of 0.67 ± 0.006 V and the maximal power d. of 8.64 ± 1.91 μW cm-2 at operating voltage of 0.50 V. The half-life operation times of the EFC were estd. to be at least 13 and 44 h in air satd. PBS contg. 5 mM glucose and 10 mM lactose, resp. Among advantages of HiCDH/MvBOx FCs are (i) simplified construction, (ii) relatively high power output with glucose as biofuel, and (iii) the absence of the inhibition of the HiCDH based bioanode by lactose, when compared with the best previously reported CDH based bioanode.
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| 9. |
- Oliveberg, Mikael, et al.
(author)
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The Changing Nature of the Protein Folding Transition State: Implications for the Shape of the Free-energy Profile for Folding
- 1998
-
In: Journal of Molecular Biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 277:4, s. 933-943
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Journal article (peer-reviewed)abstract
- According to landscape theory proteins do not fold by localised pathways, but find their native conformation by a progressive organisation of an ensemble of partly folded structures down a folding funnel. Here, we use kinetics and protein engineering to investigate the shape of the free-energy profile for two-state folding, which is the macroscopic view of the funnel process for small and rapidly folding proteins. Our experiments are based mainly on structural changes of the transition state of chymotrypsin inhibitor 2 (CI2) upon destabilisation with temperature and GdnHCl. The transition state ensemble of CI2 is a localised feature in the free-energy profile that is sharply higher than the other parts of the activation barrier. The relatively fixed position of the CI2 transition state on the reaction coordinate makes it easy to characterise but contributes also to overshadow the rest of the free-energy profile, the shape of which is inaccessible for analysis. Results from mutants of CI2 and comparison with other two-state proteins, however, point at the possibility that the barrier for folding is generally broad and that localised transition states result from minor ripples in the free-energy profile. Accordingly, variabilities in the folding kinetics may not indicate different folding mechanisms, but could be accounted for by various degrees of ruggedness on top of very broad activation barriers for folding. The concept is attractive since it summarises a wide range of folding data which have previously seemed unrelated. It is also supported by theory. Consistent with experiment, broad barriers predict that new transition state ensembles are exposed upon extreme destabilisation or radical mutations.
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| 10. |
- Ortiz, Roberto, et al.
(author)
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Engineering of Cellobiose Dehydrogenases for Improved Glucose Sensitivity and Reduced Maltose Affinityydrogenases for Improved Glucose Sensitivity and Reduced Maltose Affinity
- 2017
-
In: ChemElectroChem. - : Wiley. - 2196-0216. ; 4:4, s. 846-855
-
Journal article (peer-reviewed)abstract
- Cellobiose dehydrogenase (CDH) is a fungal extracellular flavocytochrome capable of direct electron transfer (DET). Unlike other CDHs, the pH optimum for CDHs from Corynascus thermophilus (CtCDH) and Humicola insolens (HiCDH) is close to the human physiological pH in blood (7.4). These are, therefore, interesting candidates for glucose measurements in human blood and the application in enzymatic fuel cells is, however, limited by their relatively low activity with this substrate. In this work, the substrate specificities of CtCDH and HiCDH have been altered by a single cysteine to tyrosine substitution in the active sites of CtCDH (position 291) and HiCDH (position 285), which resulted in improved kinetic constants with glucose while decreasing the activity with several disaccharides, including maltose. The DET properties of the generated CDH variants were tested in the absence and in the presence of substrates, on graphite electrodes and thiolic self-assembled monolayer (SAM)-modified Au electrodes. Seven different thiols with different spacer lengths were used, containing -COOH, -OH, and -NH2 end groups. The length and head functionality of the thiol govern the efficiency of the DET reaction and indicate different DET properties of CtCDH and HiCDH
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