| 65701. |
|
|
| 65702. |
- Lundberg, Mathias, et al.
(författare)
-
Methodological Aspects of ELISA Analysis of Thioredoxin 1 in Human Plasma and Cerebrospinal Fluid
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:7, s. e103554-
-
Tidskriftsartikel (refereegranskat)abstract
- Thioredoxin-1 (Trx1) is a protein antioxidant involved in major cellular processes. Increased plasma levels of Trx1 have been associated with human diseases suggesting that Trx1 is a marker for oxidative stress with putative clinical use. However, the reported mean levels of Trx1 in the control cohorts vary a hundred-fold between studies (0.8-87 ng/ml), possibly due to methodological differences between the capture ELISA used in the different studies. The aim of this study was to investigate methodological aspects related to the ELISA measurement of Trx1. ELISAs utilizing different capture and detection combinations of antibodies to Trx1 and as well as recombinant human (rh) Trx1 standards from two sources were characterized. The different ELISAs were subsequently used to measure Trx1 in human plasma and cerebrospinal fluid samples (CSF) from healthy donors and from patients with various neurological diagnoses. The Trx1 standards differed in their content of monomeric and oligomeric Trx1, which affected the ELISAs composed of different antibody combinations. Thus, the levels of Trx1 determined in human plasma and CSF samples varied depending on the antibody used in the ELISAs and on the rhTrx1 standard. Furthermore, the relevance of preventing interference by heterophilic antibodies (HA) in human plasma and CSF was investigated. The addition of a HA blocking buffer to human samples drastically reduced the ELISA signals in many samples showing that HA are likely to cause false positive results unless they are blocked. In conclusion, the study shows that the design of a Trx1 ELISA in regards to antibodies and standards used has an impact on the measured Trx1 levels. Importantly, analyses of human plasma and CSF without preventing HA interference may obscure the obtained data. Overall, the results of this study are crucial for the improvement of future studies on the association of Trx1 levels with various diseases.
|
|
| 65703. |
|
|
| 65704. |
|
|
| 65705. |
- Lundberg, Magnus, 1976-, et al.
(författare)
-
New insights into polyploid evolution in Fragaria (Rosaceae) based on the single/low copy nuclear intergenic region RGA1-Subtilase
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A phylogenetic study of the genus Fragaria (Rosaceae) was performed based on the nuclear low/singlecopy intergenic region between the two genes Resistance Gene Analogue 1 (RGA1) and Subtilase(Subt). Potential diploid progenitors of the polyploid Fragaria species were detected and autopolyploid species were distinguished from allopolyploid. Our analyses indicate nine separate events of polyploidization in the evolution of Fragaria, of which three are of autopolyploid and six are of allopolyploid origin. Three tetraploid Fragaria have a probable autopolyploid origin, while a fourth one is most likely an allopolyploid. Fragaria nipponica is the diploid progenitor of autotetraploid F. tibetica, a diploid of the F. nipponica lineage is the progenitor of autotetraploid F. gracilis and F. vesca or more likely F. mandshurica is the diploid progenitor of autotetraploid F. orientalis. The progenitorsof the allotetraploid F. corymbosa are a diploid of the F. nipponica lineage and a diploid sister to the F.nipponica lineage. The hexaploid F. moschata originated after two events of allopolyploidization. First,a hybridization event involving the two diploids F. vesca and F. viridis took place, resulting in an undescribed allotetraploid and secondly, this allotetraploid hybridized with a diploid of the F. iinumae lineage. The octoploid lineage that gave rise to the two species F. virginiana and F. chiloensis was formed after an allopolyploidization event between F. moschata and a diploid of the F. iinumae lineage.The decaploid F. iturupensis originated after an allopolyploidization event between the octoploid lineage and a diploid of the F. iinumae lineage. The potential new species, formerly known as F.virginiana ssp. platypetala, originated after an allopolyploidization event between F. virginiana and a diploid Fragaria basally placed in our phylogeny, close to F. daltoniana.
|
|
| 65706. |
|
|
| 65707. |
- Lundberg, Marcus, 1974-, et al.
(författare)
-
Optimized spin crossings and transition states for short-range electron transfer in transition metal dimers
- 2005
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 109:20, s. 10513-10520
-
Tidskriftsartikel (refereegranskat)abstract
- Electron-transfer reactions in eight mixed-valence manganese dimers are studied using B3LYP. One of the dimers is a model of the active site of manganese catalase, while another represents a basic building block of the oxygen-evolving complex in photosystem II. The adiabatic reactions are characterized by fully optimized transition states where the single imaginary frequency represents the electron-transfer coordinate. When there is antiferromagnetic coupling between different high-spin centers, electron transfer must be accompanied by a spin transition. Spin transitions are characterized by minimum-energy crossing points between spin surfaces. Three reaction mechanisms have been investigated. First, a single-step reaction where spin flip is concerted with electron transfer. Second, an initial transition to a center with intermediate spin that can be followed by electron transfer. Third, an initial transition to a ferromagnetic state from which the electron can be transferred adiabatically. The complexes prefer the third route with rate-determining barriers ranging from 5.7 kcal/mol to 17.2 kcal/mol for different complexes. The origins of these differences are discussed in terms of oxidation states and ligand environments. Many DFT functionals overestimate charge-transfer interactions, but for the present complexes, the error should be limited because of short Mn-Mn distances.
|
|
| 65708. |
|
|
| 65709. |
- Lundberg, Marcus, 1974-, et al.
(författare)
-
Quantifying the Effects of the Self-interaction Error in DFT : When do the delocalized states appear?
- 2005
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 122:22, s. 221403-
-
Tidskriftsartikel (refereegranskat)abstract
- The self-interaction error in density-functional theory leads to artificial stabilization of delocalized states, most evident in systems with an odd number of electrons. Clear examples are dissociations of carbocation radicals that often give delocalized states at long distances and large errors in computed binding energies. On the other hand, many mixed-valence transition-metal dimers known to exhibit valence trapping are correctly predicted to be localized. To understand the effects of the self-interaction error on these different systems, energy differences between delocalized and localized states are calculated with B3LYP. In the dissociation of radicals into symmetric fragments at infinite distance, this energy difference equals the error of the density-functional treatment. The energy difference decreases with increasing size of the system, from 55 kcal/mol in H2+ to 15 kcal/mol for C12H26+. Solvent corrections stabilize the localized state and result in smaller errors. Most reactions are asymmetric and this decreases the effect of the self-interaction error. In many systems, delocalization will not occur if the cost to move the electron from one fragment to the other is 70–80 kcal/mol (3.0–3.5 eV). This estimate refers to a situation where the distance between the fragments is infinite. The limit decreases with decreasing fragment distance. B3LYP calculations on the ferromagnetic state of a Mn(III,IV) dimer predict that the correct localized state is 22 kcal/mol more stable than the incorrect delocalized state. At short metal–metal distances the effect of the self-interaction error is predicted to be small. However, as the distance between the two manganese centers is increased to 7 Å, the dimer starts to delocalize and the energy artificially decreases. In the dissociation limit, the error is 10 kcal/mol. This is interpreted as an artifact originating from the self-interaction error. Delocalization is not encountered in many systems due to relatively short metal–metal distances and asymmetric ligand environments. However, some charge-transfer complexes cannot be properly calculated and delocalized states may become a problem in large models of enzyme systems with multiple transition-metal complexes.
|
|
| 65710. |
- Lundberg, Magnus, 1976-
(författare)
-
Systematics and polyploid evolution in Potentilleae (Rosaceae)
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis comprises studies of the phylogenetic relationships in the flowering plant clade Potentilleae in Rosaceae. The relationships were elucidated by using DNA sequence data from the nuclear genome as well as from the plastid genome. In particular, the focus of the studies was the investigation of allopolyploidy, i.e. speciation as a result of hybridization and subsequent chromosome doubling. A phylogenetic method was used for identifying allopolyploidy through comparison of trees resulting from the analyses of different DNA sequences. Five sub-clades were investigated. First, both the sister clades that together contain all of Potentilleae: Fragariinae and Potentilla. Secondly, three subclades of Fragariinae, namely Alchemilla in wide sense, Sibbaldia and relatives, and Fragaria. The aim was to unravel the phylogenetic relationships, including instances of allopolyploidy. Classification issues were discussed in relation to the phylogenetic results. The split between Potentilla (=Potentillinae) and Fragariinae received better support than in previous studies. The phylogeny of Fragariinae was found to be consistent with classifying ten genera: Alchemilla in wide sense (incl. Aphanes and Lachemilla), Comarum, Sibbaldia, Sibbaldianthe, Sibbaldiopsis, Chamaerhodos, Drymocallis, Dasiphora, Potaninia, Fragaria, and also including a few orphan Potentilla species. The segregated genera Ivesia, Horkelia, Horkeliella and Duchesnea were found to be nested within Potentilla, corroborating earlier studies, while the segregated genus Argentina (P. anserina and close relatives) showed an ambiguous position. Plastid and nuclear (ribosomal) phylogenies were compared and incongruences were detected as potential instances of allopolyploid speciation. Five strongly supported incongruences were detected in Fragariinae and four of them were considered to be potentially caused by allopolyploidy. In addition, five supported incongruences were found in Potentilla. Alchemilla in the wide sense was found to contain four major clades, African Alchemilla, Eurasian Alchemilla, Lachemilla and Aphanes. Both Lachemilla and Aphanes were nested within Alchemilla and it was suggested that the name Alchemilla should be used in the wide sense, i.e. including both the genera Lachemilla and Aphanes. The genus Sibbaldia as commonly classified was shown to be polyphyletic in five different places in Potentilleae. Three Sibbaldia clades ended up in Fragariinae and two in Potentilla. A phylogeny of Fragaria, based on a nuclear low/single copy DNA region was estimated. The gene copy phylogeny was used to construct a reticulate tree hypothesizing allopolyploid speciation events. The evolution of Fragaria was shown to have been shaped by polyploidy.
|
|
