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排序方式: 共有417条查询结果,搜索用时 19 毫秒
121.
Xylanase A from the phytopathogenic bacterium Erwinia chrysanthemi is classified as a glycoside hydrolase family 30 enzyme (previously in family 5) and is specialized for degradation of glucuronoxylan. The recombinant enzyme was crystallized with the aldotetraouronic acid β-D-xylopyranosyl-(1→4)-[4-O-methyl-α-D-glucuronosyl-(1→2)]-β-D-xylopyranosyl-(1→4)-D-xylose as a ligand. The crystal structure of the enzyme-ligand complex was solved at 1.39 ? resolution. The ligand xylotriose moiety occupies subsites -1, -2 and -3, whereas the methyl glucuronic acid residue attached to the middle xylopyranosyl residue of xylotriose is bound to the enzyme through hydrogen bonds to five amino acids and by the ionic interaction of the methyl glucuronic acid carboxylate with the positively charged guanidinium group of Arg293. The interaction of the enzyme with the methyl glucuronic acid residue appears to be indispensable for proper distortion of the xylan chain and its effective hydrolysis. Such a distortion does not occur with linear β-1,4-xylooligosaccharides, which are hydrolyzed by the enzyme at a negligible rate. DATABASE: Structural and experimental data are available in the Protein Data Bank database under accession number 2y24 [45]. 相似文献
122.
Background
Dendritic cells (DC), present in the skin, are the first target cells of dengue virus (DENV). Dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) is present on DC and recognizes N-glycosylation sites on the E-glycoprotein of DENV. Thus, the DC-SIGN/E-glycoprotein interaction can be considered as an important target for inhibitors of viral replication. We evaluated various carbohydrate-binding agents (CBAs) against all four described serotypes of DENV replication in Raji/DC-SIGN+ cells and in monocyte-derived DC (MDDC).Methodology/Principal Findings
A dose-dependent anti-DENV activity of the CBAs Hippeastrum hybrid (HHA), Galanthus nivalis (GNA) and Urtica dioica (UDA), but not actinohivin (AH) was observed against all four DENV serotypes as analyzed by flow cytometry making use of anti-DENV antibodies. Remarkably, the potency of the CBAs against DENV in MDDC cultures was significantly higher (up to 100-fold) than in Raji/DC-SIGN+ cells. Pradimicin-S (PRM-S), a small-size non-peptidic CBA, exerted antiviral activity in MDDC but not in Raji/DC-SIGN+ cells. The CBAs act at an early step of DENV infection as they bind to the viral envelope of DENV and subsequently prevent virus attachment. Only weak antiviral activity of the CBAs was detected when administered after the virus attachment step. The CBAs were also able to completely prevent the cellular activation and differentiation process of MDDC induced upon DENV infection.Conclusions/Significance
The CBAs exerted broad spectrum antiviral activity against the four DENV serotypes, laboratory-adapted viruses and low passage clinical isolates, evaluated in Raji/DC-SIGN+ cells and in primary MDDC. 相似文献123.
Shweta Malik Mariya I. Petrova Ingmar J. J. Claes Tine L. A. Verhoeven Pieter Busschaert Mario Vaneechoutte Bart Lievens Ivo Lambrichts Roland J. Siezen Jan Balzarini Jos Vanderleyden Sarah Lebeer 《Applied and environmental microbiology》2013,79(15):4576-4585
Lactobacilli are important for the maintenance of a healthy ecosystem in the human vagina. Various mechanisms are postulated but so far are poorly substantiated by molecular studies, such as mutant analysis. Bacterial autoaggregation is an interesting phenomenon that can promote adhesion to host cells and displacement of pathogens. In this study, we report on the identification of a human vaginal isolate, Lactobacillus plantarum strain CMPG5300, which shows high autoaggregative and adhesive capacity. To investigate the importance of sortase-dependent proteins (SDPs) in these phenotypes, a gene deletion mutant was constructed for srtA, the gene encoding the housekeeping sortase that covalently anchors these SDPs to the cell surface. This mutant lost the capacity to autoaggregate, showed a decrease in adhesion to vaginal epithelial cells, and lost biofilm-forming capacity under the conditions tested. These results indicate that the housekeeping sortase SrtA of CMPG5300 is a key determinant of the peculiar surface properties of this vaginal Lactobacillus strain. 相似文献
124.
Objectives
To compare the impact of scheduling caesarean section prior to versus after 39 completed weeks of gestation on the occurrence of unscheduled caesarean section and rescheduling of the procedure.Methods
Secondary analysis from a multicentre randomised open-label trial including singleton pregnant women with a healthy foetus and a reliable due date. Women were allocated by computerized telephone randomisation to planned caesarean section at 38 weeks and three days or 39 weeks and three days. The outcomes were unscheduled deliveries with provided reasons, such as spontaneous labour onset or supervening complications, and any changes in the scheduled delivery date. Statistical analyses were according to intention-to-treat using Fisher’s exact test.Results
From March 2009 to June 2011 1,274 women were included. Median difference in gestational age at delivery was six days. Compared to the 38 weeks group, the women in the 39 weeks group were more likely to have an unscheduled caesarean section (15.2% vs. 9.3%; RR 1.64, 95% CI 1.21; 2.22), to deliver between 6 pm and 8 am (10 % vs. 6%; RR 1.68, 95% CI 1.14; 2.47), or to have the procedure rescheduled (36.7% vs. 23%; RR 1.6, 95% CI 1.34;1.90).Conclusions
Scheduling caesarean section after 39 weeks leads to a 60% increase in unscheduled caesarean sections and a 70% increase in delivery outside regular work hours as compared to scheduling of the procedure prior to 39 weeks.Trial Registration
www.clinicaltrials.gov NCT00835003 http://www.clinicaltrials.gov/ct2/show/NCT00835003?term=NCT00835003&rank=1 相似文献125.
Anna Pereira-Fernandes Heidi Demaegdt Karine Vandermeiren Tine L. M. Hectors Philippe G. Jorens Ronny Blust Caroline Vanparys 《PloS one》2013,8(10)
Recently the environmental obesogen hypothesis has been formulated, proposing a role for endocrine disrupting compounds (EDCs) in the development of obesity. To evaluate this hypothesis, a screening system for obesogenic compounds is urgently needed. In this study, we suggest a standardised protocol for obesogen screening based on the 3T3-L1 cell line, a well-characterised adipogenesis model, and direct fluorescent measurement using Nile red lipid staining technique. In a first phase, we characterised the assay using the acknowledged obesogens rosiglitazone and tributyltin. Based on the obtained dose-response curves for these model compounds, a lipid accumulation threshold value was calculated to ensure the biological relevance and reliability of statistically significant effects. This threshold based method was combined with the well described strictly standardized mean difference (SSMD) method for classification of non-, weak- or strong obesogenic compounds. In the next step, a range of EDCs, used in personal and household care products (parabens, musks, phthalates and alkylphenol compounds), were tested to further evaluate the obesogenicity screening assay for its discriminative power and sensitivity. Additionally, the peroxisome proliferator activated receptor γ (PPARγ) dependency of the positive compounds was evaluated using PPARγ activation and antagonist experiments. Our results showed the adipogenic potential of all tested parabens, several musks and phthalate compounds and bisphenol A (BPA). PPARγ activation was associated with adipogenesis for parabens, phthalates and BPA, however not required for obesogenic effects induced by Tonalide, indicating the role of other obesogenic mechanisms for this compound. 相似文献
126.
Benucci GM Raggi L Albertini E Grebenc T Bencivenga M Falcinelli M Di Massimo G 《FEMS microbiology ecology》2011,76(1):170-184
Truffles (Tuber spp.) and other ectomycorrhizal species form species-rich assemblages in the wild as well as in cultivated ecosystems. We aimed to investigate the ectomycorrhizal communities of hazels and hornbeams that are growing in a 24-year-old Tuber aestivum orchard. We demonstrated that the ectomycorrhizal communities included numerous species and were phylogenetically diverse. Twenty-nine ectomycorrhizal taxa were identified. Tuber aestivum ectomycorrhizae were abundant (9.3%), only those of Tricholoma scalpturatum were more so (21.4%), and were detected in both plant symbionts with a variation in distribution and abundance between the two different hosts. The Thelephoraceae family was the most diverse, being represented by 12 taxa. The overall observed diversity represented 85% of the potential one as determined by a jackknife estimation of richness and was significantly higher in hazel than in hornbeam. The ectomycorrhizal communities of hornbeam trees were closely related phylogenetically, whereas no clear distribution pattern was observed for the communities in hazel. Uniform site characteristics indicated that ectomycorrhizal relationships were host mediated, but not host specific. Despite the fact that different plant species hosted diverse ectomycorrhizal communities and that the abundance of T. aestivum differed among sites, no difference was detected in the production of fruiting bodies. 相似文献
127.
Thomassen LV Vigsnæs LK Licht TR Mikkelsen JD Meyer AS 《Applied microbiology and biotechnology》2011,90(3):873-884
Potato pulp is a poorly utilized, high-volume co-processing product resulting from industrial potato starch manufacturing.
Potato pulp mainly consists of the tuber plant cell wall material and is particularly rich in pectin, notably galactan branched
rhamnogalacturonan I type pectin which has previously been shown to exhibit promising properties as dietary fiber. The objective
of this study was to solubilize dietary fibers from potato pulp by a one-step minimal treatment procedure and evaluate the
prebiotic potential of the fibers. Statistically designed experiments were conducted to investigate the influence of enzyme
type, dosage, substrate level, incubation time, and temperature on the enzyme catalyzed solubilization to define the optimal
minimal enzyme treatment for maximal fiber solubilization. The result was a method that within 1 min released 75% [weight/weight
(w/w)] dry matter from 1% (w/w) potato pulp treated with 1.0% (w/w) [enzyme/substrate (E/S)] pectin lyase from Aspergillus nidulans and 1.0% (w/w) E/S polygalacturonase from Aspergillus aculeatus at pH 6.0 and 60 °C. Molecular size fractionation of the solubilized fibers revealed two major fractions: one fraction rich
in galacturonic acid of 10–100 kDa indicating mainly homogalacturonan, and a fraction >100 kDa rich in galactose, presumably
mainly made up of β-1,4-galactan chains of rhamnogalacturonan I. When fermented in vitro by microbial communities derived from fecal samples from three healthy human volunteers, both of the solubilized fiber fractions
were more bifidogenic than fructo-oligosaccharides (FOS). Notably the fibers having molecular masses of >100 kDa selectively
increased the densities of Bifidobacterium spp. and Lactobacillus spp. 2–3 times more than FOS. 相似文献
128.
Lantto J Haahr Hansen M Rasmussen SK Steinaa L Poulsen TR Duggan J Dennis M Naylor I Easterbrook L Bregenholt S Haurum J Jensen A 《Journal of virology》2011,85(4):1820-1833
The eradication of smallpox (variola) and the subsequent cessation of routine vaccination have left modern society vulnerable to bioterrorism employing this devastating contagious disease. The existing, licensed vaccines based on live vaccinia virus (VACV) are contraindicated for a substantial number of people, and prophylactic vaccination of large populations is not reasonable when there is little risk of exposure. Consequently, there is an emerging need to develop efficient and safe therapeutics to be used shortly before or after exposure, either alone or in combination with vaccination. We have characterized the human antibody response to smallpox vaccine (VACV Lister) in immunized volunteers and isolated a large number of VACV-specific antibodies that recognize a variety of different VACV antigens. Using this broad antibody panel, we have generated a fully human, recombinant analogue to plasma-derived vaccinia immunoglobulin (VIG), which mirrors the diversity and specificity of the human antibody immune response and offers the advantage of unlimited supply and reproducible specificity and activity. The recombinant VIG was found to display a high specific binding activity toward VACV antigens, potent in vitro VACV neutralizing activity, and a highly protective efficacy against VACV challenge in the mouse tail lesion model when given either prophylactically or therapeutically. Altogether, the results suggest that this compound has the potential to be used as an effective postexposure prophylaxis or treatment of disease caused by orthopoxviruses. 相似文献
129.
The bifunctional protein U5-52K is associated with the spliceosomal 20 S U5 snRNP, and it also plays a role in immune response as CD2 receptor binding protein 2 (CD2BP2). U5-52K binds to the CD2 receptor via its GYF-domain specifically recognizing a proline-rich motif on the cytoplasmic surface of the receptor. The GYF-domain is also mediating the interaction of the proteins U5-52K and U5-15K within the spliceosomal U5 snRNP. Here we report the crystal structure of the complex of GYF-domain and U5-15K protein revealing the structural basis for the bifunctionality of the U5-52K protein. The complex structure unveils novel interaction sites on both proteins, as neither the polyproline-binding site of the GYF-domain nor the common ligand-binding cleft of thioredoxin-like proteins, to which U5-15K belongs, are involved in the interaction of U5-15K and U5-52K. 相似文献
130.