Refine
Year of publication
- 2005 (157) (remove)
Document Type
- Article (111)
- Doctoral Thesis (40)
- Monograph/Edited Volume (3)
- Habilitation Thesis (1)
- Other (1)
- Postprint (1)
Is part of the Bibliography
- yes (157)
Keywords
- Arabidopsis (4)
- Modellierung (2)
- Redoxreaktion (2)
- Schmalwand <Arabidopsis> (2)
- phloem (2)
- phloem proteins (2)
- ABA (1)
- ADP-Glukosepyrophosphorylase (1)
- AMT (1)
- Abszisinsäure (1)
Institute
- Institut für Biochemie und Biologie (157) (remove)
We tested whether neighborhood density affects the clonal life history of the stoloniferous plant Ranunculus reptans through selection and genetic drift. After three generations of sexual reproduction of 16 low- and 16 high- density lines, we studied traits related to growth form and reproduction in a common competition free environment. A 7.7% lower branching frequency and slightly longer internodes indicated an evolutionary shift towards a less compact growth form under high neighborhood density, but because stolons grew also more vertically, horizontal spread per ramet was slightly decreased. Neighborhood density had no directional effects on the evolution of allocation to sexual and vegetative reproduction in R. reptans. Variation among replicated high-density lines was significantly lower than among replicated low-density lines in both growth form and reproductive characteristics, indicating less pronounced genetic drift under high neighborhood density. This study demonstrates that a clonal plant can respond to selection imposed by neighborhood density. Moreover, it shows that the effect of random genetic drift increases with decreasing neighborhood density. In a declining species, such as R. reptans in central Europe, this may lower the potential for adaptive evolutionary change and increase extinction risk
Electrochemical investigations of the blood oxygen carrier protein include both mediated and direct electron transfer. The reaction of haemoglobin (Hb) with typical mediators, e.g., ferricyanide, can be quantified by measuring the produced ferrocyanide which is equivalent to the Hb concentration. Immobilization of the mediator within the electrode body allows reagentless electrochemical measuring of Hb. On the other hand, entrapment of the protein within layers of polyclectrolytes, lipids, nanoparticles of clay or gold leads to a fast heterogeneous electron exchange of the partially denatured Hb. (c) 2005 Elsevier B.V. All rights reserved
The thermal unfolding of the wild-type lambda Cro repressor and of two designed variants, Cro K56-[DGEVK] and Cro K56-[DGEVK] Q16L, was studied by Fourier transform infrared spectroscopy and dynamic light scattering. The engineered Cro K56-[DGEVK] monomer has five additional amino acids inserted after position 56 of the wild-type sequence, while the K56-[DGEVK] Q16L variant differs only in one position (Gln-16 to Leu substitution) from the Cro K56-[DGEVK] sequence. The temperature dependence of selected protein backbone infrared `marker' bands revealed that Cro K56- [DGEVK] is slightly more stable than the wild-type protein, while the replacement of Gln-16 by Leu increases the thermal transition temperature by similar to 20 degrees C. Moreover, thermal unfolding of the two Cro variants was found to proceed through equilibrium unfolding intermediates and to involve the formation of oligomers. The first thermal transition of Cro K56-[DGEVK] involves the melting of major parts of its native secondary structure and is accompanied by the formation of dinners and non-native beta-sheet structures. These structures unfold during a second transition at higher temperatures, accompanied by the dissociation of the dimers. In contrast to the Cro K56-[DGEVK] protein, the intermediate state of the Cro K56-[DGEVK] Q16L variant is less well defined, and involves the formation of oligomers of different size. (c) 2005 Elsevier B.V. All rights reserved
The multiplication and antibody production of murine hybridoma cells cultured on five different polymer membranes were tested and compared with conventional tissue culture polystyrene (TCPS). Membranes were prepared from polyacrylonitrile (PAN) and acrylonitrile copolymerized with N-vinylpyrrolidone (NVP20, NVP30), Na-methallylsulfonate (NaMAS) and N-(3-amino-propyl-methacrylamide-hydrochloride) (APMA). Cell number and antibody concentration were quantified as criteria for viability and productivity. Adhesion of hybridoma cells was characterized by vital and scanning electron microscopy. The results suggest that a strong adhesion of cells, observed on APMA and TCPS, increased cell growth but reduced monoclonal antibody production. In contrast membranes with lowered adhesivity such as NVP20 provided favourable conditions for monoclonal antibody production. In addition it was shown that this membrane also possessed a minor fouling as indicated by the low decrease of water flux across the membrane after protein adsorption. It was concluded that NVP20 could be a suitable material for the development of hollow fibre membranes for bioreactors.
The present study aimed at assessing genetic purity of black wildebeest (Connochoetes gnou) at Abe Bailey Nature Reserve, Gauteng Province, South Africa, using a multitocus microsatellite approach. Five loci were studied in black and blue (C. taurinus) wildebeest, the latter being a closely related species and known to produce hybrids with the morphologically very similar black wildebeest. In fact, the entire national black wildebeest population of South Africa potentially contains a significant proportion of introgressed blue wildebeest genes. In our case, eight out of 39 alleles were unique to black and 22 to blue wildebeest, with nine alleles shared between pure populations of the two species in Line with their taxonomic proximity. A possible Limited past introgression of blue wildebeest genes into the Abe Bailey population, corresponding to documents on population history, was only supported by the presence of a single allele otherwise exclusively found in samples of four pure blue but not in samples of two pure black wildebeest control populations. However, an assignment test and coefficients of population divergence did not support an extended introgression of C. taurinus alleles into the C. gnou population under study. Average heterozygosity at Abe Bailey proved to be intermediate between black and blue wildebeest, the tatter species generally harbouring more genetic variation than the former owing to larger population sizes and the absence of population bottlenecks in historical times. The implications of our data are discussed with reference to the persistence of introgressed genes and the conservation of pure black wildebeest gene pools
Among plant remains from Mesolithic layers dating from 9249 to 7779 B.C. at the excavation site of Friesack IV in north-eastern Germany, nutlets of Urtica kioviensis were identified. Morphological studies have shown that they clearly differed from all other European Urtica species investigated. In contrast, pollen morphological investigations revealed only slight differences between the central European Urtica species, which could hardly have been noticed during routine or normal pollen analyses. The records of U. kioviensis nutlets are the first subfossil finds reported and prove the indigenous status of this taxon in north-eastern Germany. The records are discussed in the context of the overall species spectrum of the Mesolithic layers and consequences for the interpretation of pollen analytical studies concerning human impact are pointed out
After heterologous expression in Escherichia coli, the Azotobacter vinelandii rhodanese RhdA is purified in a persulfurated form (RhdA-SSH). We identified L-cysteine as the most effective sulfur source in producing RhdA-SSH. An E. coli soluble extract was required for in vitro persulfuration of RhdA, and the addition of pyridoxal-5'-phosphate increased RhdA-SSH production, indicating a likely involvement of a cysteine desulfurase. We were able to show the formation of a covalent complex between IscS and RhdA. By combining a time-course fluorescence assay and mass spectrometry analysis, we demonstrated the transfer of sulfur from E. coli IscS to RhdA. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved
Testing for ecological and genetic Allee effects in the invasive shrub Senna didymobotrya (Fabaceae)
(2005)
For an introduced plant species to become invasive, it must be able to reproduce even in initially small populations We tested for Aliee effects (reduced reproductive performance of individuals in small populations) in the nonclonal, NW-pollinated shrub Senna didymobotrya in its invasive range in South Africa. The species is self-compatible. but we found that in its invasive range in South Africa it requires pollinators to set seed. Nearly all stigmas (90%) received pollen. but natural fruit set has very low (3-20%), Pollen receipt and fruit set were not significantly correlated with population size. We thus found no evidence for an ecological Alice effect arising from pollen limitation in small populations. Offspring seedling performance, measured in terms of stern volume and leaf area, was also not significantly correlated with the number of plants in the source population. indicating that genetic Alice effects, such as inbreeding depression, are either absent or of such a small magnitude that they would be unlikely to limit further spread of S. didymobotrya in South Africa
Molybdenum cofactor deficiency (MIM#252150) is a severe autosomal- recessive disorder with a devastating outcome. The cofactor is the product of a complex biosynthetic pathway involving four different genes (MOCS1, MOCS2, MOCS3 and GEPH). This disorder is caused almost exclusively by mutations in the MOCS1 or MOCS2 genes. Mutations affecting this biosynthetic pathway result in a lethal phenotype manifested by progressive neurological damage via the inactivation of the molybdenum cofactor-dependent enzyme, sulphite oxidase. Here we describe a total of ten novel disease-causing mutations in the MOCS1 and MOCS2 genes. Nine out of these ten mutations were classified as pathogenic in nature, since they create a stop codon, affect constitutive splice site positions, or change strictly conserved motifs. The tenth mutation abolishes the stop codon of the MOCS2B gene, thus elongating the corresponding protein. The mutation was expressed in vitro and was found to abolish the binding affinities of the large subunit of molybdopterin synthase (MOCS2B) for both precursor Z and the small subunit of molybdopterin synthase (MOCS2A)