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51.
K. Chandrasekhar A. Patricia Campbell Mei-Fen Jeng Arne Holmgren H. Jane Dyson 《Journal of biomolecular NMR》1994,4(3):411-432
Summary As a prelude to complete structure calculations of both the oxidized and reduced forms of Escherchia coli thioredoxin (Mr 11 700), we have analyzed the NMR data obtained for the two proteins under identical conditions. The complete aliphatic 13C assignments for both oxidized and reduced thioredoxin are reported. Correlations previously noted between 13C chemical shifts and secondary structure are confirmed in this work, and significant differences are observed in the C and C shifts between cis- and trans-proline, consistent with previous work that identifies this as a simple and unambiguous method of identifying cis-proline residues in proteins. Reduction of the disulfide bond in the active-site Cys32-Gly-Pro-Cys35 sequence causes changes in the 1H, 15N and 13C chemical shifts of residues close to the active site, some of them quite far distant in the amino acid sequence. Coupling constants, both backbone and side chain, show some differences between the two proteins, and the NOE connectivities and chemical shifts are consistent with small changes in the positions of several side chains, including the two tryptophan rings (Trp28 and Trp31). These results show that, consistent with the biochemical behavior of thioredoxin, there are minimal differences in backbone configuration between the oxidized and reduced forms of the protein. 相似文献
52.
Einar Lystad Arne T. Høstmark Cecilie Kiserud Aage Haugen 《In vitro cellular & developmental biology. Animal》1994,30(9):568-573
Summary The protective influence of bovine serum albumin against growth inhibition caused by fatty acids was studied in human hepatoma
(HepG2) and immortalized human kidney epithelial (IHKE) cells. In general, growth inhibition by unsaturated fatty acids (0.15
mmol/liter) increased with increasing number of double bonds. For HepG2 cells crude albumin (1g/100 ml) did not greatly modify growth inhibition by arachidonic, eicosapentaenoic, and docosahexaenoic acid. With oleic,
linoleic, and linolenic acids, crude and defatted albumin stimulated cell growth. In contrast, for IHKE cells both albumins
counteracted growth inhibition by unsaturated fatty acids to approximately the same extent. When HepG2 cells were cultured
in the presence of saturated fatty acids (0.3 mmol/liter), C2, C6, and C8 had no or little inhibitory effect. C10 and C12
inhibited cell growth appreciably, whereas C14, and especially C16, had poor inhibitory effects. Crude albumin counteracted
growth inhibition by all these fatty acids. In contrast, defatted albumin had little or no effect (except against C10 and
C12), and even increased the growth inhibition by C14 and C16. With unsaturated fatty acids there seemed to be an inverse
relationship between cell growth and the concentration of thiobarbituric acid reactive substances (TBARS) in media. Vitamin
E abolished growth inhibition (and the increase in TBARS concentration) by unsaturated fatty acids. The complex interaction
between fatty acids and albumins calls for great caution when interpreting data on growth effects. 相似文献
53.
Petra Sumasgutner Susan J. Cunningham Arne Hegemann Arjun Amar Hannah Watson Johan F. Nilsson Martin N. Andersson Caroline Isaksson 《Global Change Biology》2023,29(9):2399-2420
Climate change and urbanisation are among the most pervasive and rapidly growing threats to biodiversity worldwide. However, their impacts are usually considered in isolation, and interactions are rarely examined. Predicting species' responses to the combined effects of climate change and urbanisation, therefore, represents a pressing challenge in global change biology. Birds are important model taxa for exploring the impacts of both climate change and urbanisation, and their behaviour and physiology have been well studied in urban and non-urban systems. This understanding should allow interactive effects of rising temperatures and urbanisation to be inferred, yet considerations of these interactions are almost entirely lacking from empirical research. Here, we synthesise our current understanding of the potential mechanisms that could affect how species respond to the combined effects of rising temperatures and urbanisation, with a focus on avian taxa. We discuss potential interactive effects to motivate future in-depth research on this critically important, yet overlooked, aspect of global change biology. Increased temperatures are a pronounced consequence of both urbanisation (through the urban heat island effect) and climate change. The biological impact of this warming in urban and non-urban systems will likely differ in magnitude and direction when interacting with other factors that typically vary between these habitats, such as resource availability (e.g. water, food and microsites) and pollution levels. Furthermore, the nature of such interactions may differ for cities situated in different climate types, for example, tropical, arid, temperate, continental and polar. Within this article, we highlight the potential for interactive effects of climate and urban drivers on the mechanistic responses of birds, identify knowledge gaps and propose promising future research avenues. A deeper understanding of the behavioural and physiological mechanisms mediating species' responses to urbanisation and rising temperatures will provide novel insights into ecology and evolution under global change and may help better predict future population responses. 相似文献
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56.
The desmid Staurastrum luetkemuellerii Donat et Ruttner and the cyanobacterium Microcystis aeruginosa Kütz. were grown in mixed cultures with various phosphate (Pi) additions. One pulse of Pi each day (semi-continuous cultures) favored M. aeruginosa whereas S. luetkemuellerii was favored when the same quantity of Pi was supplied continuously (chemostats). Both species coexisted under P limitation provided that the nutrient was supplied in an appropriate mode. The ability of each species to compete for P depended on their Pi uptake characteristics and their capability to retain the accumulated Pi. High affinity in uptake at low Pi concentrations contributed considerably to the growth eficiency of S. luetkemuellerii under continuous supply of PiM. aeruginosa was, however, consistently superior to S. luetkemuellerii in accuniulatiug the newly added P, but had a high rate of Pi release. In both -types of cultures, a net high of P went from M. aeruginosa to S. luetkemuellerii. The kinetic characteristics of the two species were used to simulate the outcome of competition experiments. Simulations agreed with the experimental data f both uptake and Pi release were considered in the model. The zlariable P*(the concentration of Pi at which the net uptake is equal to μ·QP is a function of uptake and release of Pi but could not explain the chemostat results. S. luetkemuellerii was the winner in many experiments even if its P*was higher thou that of M. aeruginosa. Thus, in the present case Pc (the concentration at which the net uptake is zero) was a better predictor of the ability to compete for Pi under steady state as well as transient conditions in the Pi supply. 相似文献
57.
Sigrun Skjelseth Arne Moksnes Eivin Røskaft H. Lisle Gibbs Michael Taborsky Barbara Taborsky Marcel Honza Oddmund Kleven 《Journal of avian biology》2003,35(1):21-24
Microsatellite DNA markers were used to investigate parentage relationships in a population of common cuckoo Cuculus canorus . Thirty adults and 55 nestlings were genotyped at six loci from blood samples collected over a four-year period. To test whether each cuckoo female specialises in parasitising one single host species (Host Preference Hypothesis), the maternal relationships were used to record each female's host choice. The results supported the Host Preference Hypothesis since no female (N=3) was recorded to have parasitised more than one of four congeneric host species breeding in the area. In contrast, the males (N=4) did not show such specialisation since two of them sired offspring reared by different host species. 相似文献
58.
Nils Empacher Volker Mosbrugger Anita Roth Matthias Wolf Arne Wunderlin 《Journal of biological physics》1995,21(4):241-264
We shall present several qualitative mathematical models to describe the early evolution of water transport systems in plants. To perform this in a systematic way we apply methods which have been developed in phenomenological synergetics. These methods rest on the fact that it becomes possible to describe the macroscopic behavior of a complex system by a set of control and order parameters when they are suitably identified. Our presentation is addressed to community with interdisciplinary interests. 相似文献
59.
Anderberg, A. A. & Karis, P. O. 1995. Psednotrichia , a genus of the tribe Senecioneae hitherto misplaced in the Astereae (Asteraceae). — Nord. J. Bot. 15: 375–379. Copenhagen. ISSN 0107–055X.
The tribal position for the little known genus Psednorrichia , is established. This monotypic genus, hitherto placed in the tribe Astereae, is a congener of Xyridopsis of the tribe Senecioneae (Asteraceae). The two species of Xyridopsis are here transferred to Psednotrichia and the new combinations P. xyridopsis and P. newtonii are made. A brief discussion of the morphology of the genus, and its systematic position within the tribe Senecioneae is provided. 相似文献
The tribal position for the little known genus Psednorrichia , is established. This monotypic genus, hitherto placed in the tribe Astereae, is a congener of Xyridopsis of the tribe Senecioneae (Asteraceae). The two species of Xyridopsis are here transferred to Psednotrichia and the new combinations P. xyridopsis and P. newtonii are made. A brief discussion of the morphology of the genus, and its systematic position within the tribe Senecioneae is provided. 相似文献
60.
Malin Bäckström Vafa Shahabi Susanne Johansson Susann Teneberg ers Kjellberg Halina Miller-Podraza Jan Holmgren & Michael Lebens 《Molecular microbiology》1997,24(3):489-497
The closely related B-subunits of cholera toxin (CTB) and Escherichia coli heat-labile enterotoxin (LTB) both bind strongly to GM1 ganglioside receptors but LTB can also bind to additional glycolipids and glycoproteins. A number of mutant CT B-subunits were generated by substituting CTB amino acids with those at the corresponding positions in LTB. These were used to investigate the influence of specific residues on receptor-binding specificity. A mutated CTB protein containing the first 25 residues of LTB in combination with LTB residues at positions 94 and 95, bound to the same extent as native LTB to both delipidized rabbit intestinal cell membranes, complex glycosphingolipids (polyglycosylceramides) and neolactotetraosylceramide, but not to non-GM1 intestinal glycosphingolipids. In contrast, when LTB amino acid substitutions in the 1–25 region were combined with those in the 75–83 region, a binding as strong as that of LTB to intestinal glycosphingolipids was observed. In addition, a mutant LTB with a single Gly-33→Asp substitution that completely lacked affinity for both GM1 and non-GM1 glycosphingolipids could still bind to receptors in the intestinal cell membranes and to polyglycosylceramides. We conclude that the extra, non-GM1 receptors for LTB consist of both sialylated and non-sialylated glycoconjugates, and that the binding to either class of receptors is influenced by different amino acid residues within the protein. 相似文献