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131.
The effect of pertussis toxin (PT) on the aggregation of pigment granules in melanophores from cuckoo wrasse (Labrus ossifagus L.) was studied. The results indicate the presence of a PT resistant alpha 2-adrenoceptor signal transduction mechanism. 相似文献
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133.
We present a model for the activity of protein clusters based on a simultaneous desorption of an activator (agonist, substrate molecule, etc.) and an inactivator (antagonist, inhibitor, etc.) caused by the collision or interaction between two effector molecules (e.g. receptors, enzymes). This model gives rise to switch-like dose-response curves, which are difficult to explain by ordinary co-operativity. It fits with recent experimental results obtained on single cells. Some other interesting aspects of the model are also pointed out. The model is similar to the model used to explain steep 'dose-response curves' in heterogeneous catalysis, caused by the reaction between two different molecules or atoms on the surface of the catalyst. 相似文献
134.
Previous studies have revealed that chlorine participates in a complex biogeochemical cycle in soil, which suggests that the
transport of chloride through catchments may also be influenced. The present study is based on field observations of organic
carbon, chloride (Clin), and chlorinated organic carbon (Clorg) in precipitation, soil, and runoff over a 2-year period from a small, forested catchment in southeast Sweden. The study
reveals that (1) the soil pool is dominated by Clorg, (2) the input via wet deposition and output of Clin via runoff is 30 times smaller than the total storage of chlorine (Clin + Clorg) in soil, and (3) the transport is dominated by Clin. The organic matter that entered the outlet of the catchment was more chlorinated in the autumn than during the rest of the
year, and rain events taking place in low-flow periods had a greater influence on TOC, Clorg, and Clin than did rain events taking place in high-flow periods. The seasonal pattern in combination with the low-flow versus high-flow
pattern and previous findings of increasing chlorine-to-carbon ratios with soil depth suggests that the chlorine-to-carbon
ratio variation in the leached organic matter is due that water preferentially comes from deeper layers in low-flow conditions.
This study provides well-founded estimates of Clorg and Clin storage and fluxes for the studied catchment; however, the processes underlying the observed seasonal Clorg variations and transportation processes need further study. 相似文献
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136.
Neha Pant Harold Marcotte Harald Brüssow Lennart Svensson Lennart Hammarström 《BMC microbiology》2007,7(1):86
Background
Rotavirus is a worldwide cause of infectious infantile diarrhea that claims over 600,000 lives annually. Recently, two new vaccine candidates have been developed but their efficacy in developing countries, still remains to be proven. Oral delivery of specific immunoglobulins provides passive immunity and is a fast acting treatment for rotavirus diarrhea. Probiotic bacteria have also gained considerable attention lately as treatment for rotavirus diarrhea. Here we report an evaluation of the therapeutic potential of different probiotics and their combination with anti - rotavirus antibodies in a mouse model of rotavirus diarrhea. 相似文献137.
138.
Sex pheromone of the cloaked pug moth,Eupithecia abietaria (Lepidoptera: Geometridae), a pest of spruce cones 下载免费PDF全文
H. L. Wang G. P. Svensson J. Jakobsson E. V. Jirle O. Rosenberg W. Francke O. Anderbrant J. G. Millar C. Löfstedt 《Journal of Applied Entomology》2015,139(5):352-360
The sex pheromone of the cloaked pug moth, Eupithecia abietaria Götze, an important cone‐feeding pest in spruce seed orchards in Europe, was investigated. Chemical and electrophysiological analyses of pheromone gland extracts of female moths and analogous analyses of synthetic hydrocarbons and epoxides of chain length C19 and C21 revealed (3Z,6Z,9Z)‐3,6,9‐nonadecatriene (3Z,6Z,9Z‐19:H) and 3Z,6Z‐cis‐9,10‐epoxynonadecadiene (3Z,6Z‐cis‐9,10‐epoxy‐19:H) as candidate pheromone components, which were found in a gland extract in a ratio of 95 : 5. In field trapping experiments, conspecific males were only attracted to a combination of 3Z,6Z,9Z‐19:H and the (9S,10R)‐enantiomer of 3Z,6Z‐cis‐9,10‐epoxy‐19:H. The (9R,10S)‐enantiomer was not attractive, which is in agreement with studies on other Eupithecia species, for which males have only been attracted by the (9S,10R)‐enantiomer of epoxides. Subsequent experiments showed that E. abietaria males were attracted to a wide range of ratios of the two active compounds and that trap catches increased with increasing dose of the binary blend. A two‐component bait containing 300 μg 3Z,6Z,9Z‐19:H and 33 μg of the (9S,10R)‐enantiomer of 3Z,6Z‐cis‐9,10‐epoxy‐19:H was efficient for monitoring E. abietaria in spruce seed orchards in southern Sweden, where this species has probably been overlooked as an important pest in the past. With sex pheromones recently identified for two other moths that are major pests on spruce cones, the spruce seed moth, Cydia strobilella L., and the spruce coneworm, Dioryctria abietella Denis & Schiffermüller, pheromone‐based monitoring can now be achieved for the whole guild of cone‐feeding moths in European spruce seed orchards. 相似文献
139.
Marie S. M?ller Malene B. Vester-Christensen Johanne M. Jensen Maher Abou Hachem Anette Henriksen Birte Svensson 《The Journal of biological chemistry》2015,290(20):12614-12629
Molecular details underlying regulation of starch mobilization in cereal seed endosperm remain unknown despite the paramount role of this process in plant growth. The structure of the complex between the starch debranching enzyme barley limit dextrinase (LD), hydrolyzing α-1,6-glucosidic linkages, and its endogenous inhibitor (LDI) was solved at 2.7 Å. The structure reveals an entirely new and unexpected binding mode of LDI as compared with previously solved complex structures of related cereal type family inhibitors (CTIs) bound to glycoside hydrolases but is structurally analogous to binding of dual specificity CTIs to proteases. Site-directed mutagenesis establishes that a hydrophobic cluster flanked by ionic interactions in the protein-protein interface is vital for the picomolar affinity of LDI to LD as assessed by analysis of binding by using surface plasmon resonance and also supported by LDI inhibition of the enzyme activity. A phylogenetic analysis identified four LDI-like proteins in cereals among the 45 sequences from monocot databases that could be classified as unique CTI sequences. The unprecedented binding mechanism shown here for LDI has likely evolved in cereals from a need for effective inhibition of debranching enzymes having characteristic open active site architecture. The findings give a mechanistic rationale for the potency of LD activity regulation and provide a molecular understanding of the debranching events associated with optimal starch mobilization and utilization during germination. This study unveils a hitherto not recognized structural basis for the features endowing diversity to CTIs. 相似文献
140.
Efficient secretory expression of functional barley limit dextrinase inhibitor by high cell-density fermentation of Pichia pastoris 总被引:1,自引:0,他引:1
Jensen JM Vester-Christensen MB Møller MS Bønsager BC Christensen HE Hachem MA Svensson B 《Protein expression and purification》2011,79(2):217-222
The limit dextrinase inhibitor (LDI) from barley seeds acts specifically on limit dextrinase (LD), an endogenous starch debranching enzyme. LDI is a 14 kDa hydrophobic protein containing four disulfide bonds and one unpaired thiol group previously found to be either glutathionylated or cysteinylated. It is a member of the so-called CM-protein family that includes α-amylase and serine protease inhibitors, which have been extremely challenging to produce recombinantly in functional form and in good yields. Here, LDI is produced in very high yields by secretory expression by Pichia pastoris applying high cell-density fermentation in a 5L fed-batch bioreactor. Thus about 200mg of LDI, which showed twofold higher inhibitory activity towards LD than LDI from barley seeds, was purified from 1L of culture supernatant by His-tag affinity chromatography and gel filtration. Electrospray ionization mass spectrometry verified the identity of the produced glutathionylated LDI-His(6). At a 1:1M ratio the recombinant LDI completely inhibited hydrolysis of pullulan catalyzed by 5-10 nM LD. LDI retained stability in the pH 2-12 range and at pH 6.5 displayed a half-life of 53 and 33 min at 90 and 93°C, respectively. The efficient heterologous production of LDI suggests secretory expression by P. pastoris to be a promising strategy to obtain other recombinant CM-proteins. 相似文献