排序方式: 共有69条查询结果,搜索用时 69 毫秒
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Baumann MJ Eklöf JM Michel G Kallas AM Teeri TT Czjzek M Brumer H 《The Plant cell》2007,19(6):1947-1963
High-resolution, three-dimensional structures of the archetypal glycoside hydrolase family 16 (GH16) endo-xyloglucanases Tm-NXG1 and Tm-NXG2 from nasturtium (Tropaeolum majus) have been solved by x-ray crystallography. Key structural features that modulate the relative rates of substrate hydrolysis to transglycosylation in the GH16 xyloglucan-active enzymes were identified by structure-function studies of the recombinantly expressed enzymes in comparison with data for the strict xyloglucan endo-transglycosylase Ptt-XET16-34 from hybrid aspen (Populus tremula x Populus tremuloides). Production of the loop deletion variant Tm-NXG1-DeltaYNIIG yielded an enzyme that was structurally similar to Ptt-XET16-34 and had a greatly increased transglycosylation:hydrolysis ratio. Comprehensive bioinformatic analyses of XTH gene products, together with detailed kinetic data, strongly suggest that xyloglucanase activity has evolved as a gain of function in an ancestral GH16 XET to meet specific biological requirements during seed germination, fruit ripening, and rapid wall expansion. 相似文献
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Abstract High voltage electroporation has been investigated as a method for rapid recovery of plasmid and chromosomal DNA from the cyanobacteria Nostoc PCC 7121, Synechococcus PCC 7002, and Anabaena PCC 7120. Pulses of 18 kV/cm and higher applied to concentrated Nostoc cells carrying a shuttle plasmid (pRL25) resulted in copious release of nucleic acids and phycobiliproteins into the suspending medium. Small portions of these supernatants, when electroporated with Escherichia coli , gave rise to hundreds of E. coli transformants which contained pRL25. Electroporation of Synechococcus carrying plasmid pAQE19 did not cause detectable release of macromolecules but did reveal a low-level, voltage independent 'leakage' of pAQE19 into the medium. Electroextraction of Nostoc or Anabaena followed by addition of E. coli and delivery of a second high-voltage pulse permitted direct, one-cuvette transfer of shuttle plasmids from these cyanobacteria into E. coli . Electroextraction of single cyanobacterial colonies, as shown for Nostoc , also released sufficient chromosomal DNA for amplification of specific sequences by the polymerase chain reaction. 相似文献
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Hlastala Michael P.; Chornuk Myron A.; Self David A.; Kallas Harry J.; Burns John W.; Bernard Susan; Polissar Nayak L.; Glenny Robb W. 《Journal of applied physiology》1998,84(4):1278-1288
This study was undertaken to assess theinfluence of gravity on the distribution of pulmonary blood flow (PBF)using increased inertial force as a perturbation. PBF was studied inunanesthetized swine exposed toGx (dorsal-to-ventraldirection, prone position), where G is the magnitude of the force ofgravity at the surface of the Earth, on the Armstrong LaboratoryCentrifuge at Brooks Air Force Base. PBF was measured using 15-µmfluorescent microspheres, a method with markedly enhanced spatialresolution. Each animal was exposed randomly to 1, 2, and3 Gx. Pulmonary vascularpressures, cardiac output, heart rate, arterial blood gases, and PBFdistribution were measured at each G level. Heterogeneity of PBFdistribution as measured by the coefficient of variation of PBFdistribution increased from 0.38 ± 0.05 to 0.55 ± 0.11 to0.72 ± 0.16 at 1, 2, and 3Gx, respectively. At 1Gx, PBF was greatest in theventral and cranial and lowest in the dorsal and caudal regions of thelung. With increased Gx,this gradient was augmented in both directions. Extrapolation of thesevalues to 0 G predicts a slight dorsal (nondependent) region dominanceof PBF and a coefficient of variation of 0.22 in microgravity. Analysisof variance revealed that a fixed component (vascular structure)accounted for 81% and nonstructure components (including gravity)accounted for the remaining 19% of the PBF variance across the entireexperiment (all 3 gravitational levels). The results are inconsistentwith the predictions of the zone model. 相似文献
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Leandro F. Tarosso Mariana M. Sauer Sabri Sanabani Maria Teresa Giret Helena I. Tomiyama John Sidney Shari M. Piaskowski Ricardo S. Diaz Ester C. Sabino Alessandro Sette Jorge Kalil-Filho David I. Watkins Esper G. Kallas 《PloS one》2010,5(7)
Background
HIV-1-infected individuals who spontaneously control viral replication represent an example of successful containment of the AIDS virus. Understanding the anti-viral immune responses in these individuals may help in vaccine design. However, immune responses against HIV-1 are normally analyzed using HIV-1 consensus B 15-mers that overlap by 11 amino acids. Unfortunately, this method may underestimate the real breadth of the cellular immune responses against the autologous sequence of the infecting virus.Methodology and Principal Findings
Here we compared cellular immune responses against nef and vif-encoded consensus B 15-mer peptides to responses against HLA class I-predicted minimal optimal epitopes from consensus B and autologous sequences in six patients who have controlled HIV-1 replication. Interestingly, our analysis revealed that three of our patients had broader cellular immune responses against HLA class I-predicted minimal optimal epitopes from either autologous viruses or from the HIV-1 consensus B sequence, when compared to responses against the 15-mer HIV-1 type B consensus peptides.Conclusion and Significance
This suggests that the cellular immune responses against HIV-1 in controller patients may be broader than we had previously anticipated. 相似文献26.
Gubernator B Króliczewski J Kallas T Szczepaniak A 《Biochimica et biophysica acta》2006,1764(4):735-742
The Rieske 2Fe-2S protein is a central component of the photosynthetic electron transport cytochrome b6f complex in chloroplast and cyanobacterial thylakoid membranes. We have constructed plasmids for expression in Escherichia coli of full-length and truncated Spinacia oleracea Rieske (PetC) proteins fused to the MalE, maltose binding protein. The expressed Rieske fusion proteins were found predominantly in soluble form in the E. coli cytoplasm. These proteins could be readily purified for further experimentation. In vitro reconstitution of the characteristic, "Rieske-type" 2Fe-2S cluster into these fused proteins was accomplished by a chemical method employing reduced iron and sulfide. Cluster incorporation was monitored by electron paramagnetic resonance and optical circular dichroism (CD) spectroscopy. CD spectral analysis in the ultraviolet region suggests that the spinach Rieske apoprotein must be in a partially folded conformation to incorporate an appropriate iron-sulfur cluster. These data further suggest that upon cluster integration, further folding occurs, allowing the Rieske protein to attain a final, native structure. The data presented here are the first to demonstrate successful chemical reconstitution of the 2Fe-2S cluster into a Rieske apoprotein from higher plant chloroplasts. 相似文献
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Mariana D. Batista Camilla Tincati Jeffrey M. Milush Emily L. Ho Lishomwa C. Ndhlovu Vanessa A. York Esper G. Kallas Jorge Kalil Sheila M. Keating Philip J. Norris David Chang Patrick Unemori Kieron S. Leslie Toby Maurer Wilson Liao Douglas F. Nixon 《PloS one》2013,8(2)
Background
The immunopathogenic mechanisms leading to psoriasis remain unresolved. CD57 is a marker of replicative inability and immunosenescence on CD8+ T cells and the proportion of CD57 expressing CD8+ T cells is increased in a number of inflammatory conditions.Methodology
We examined the expression of CD57 on T cells in the skin of patients affected with psoriasis, comparing lesional and unaffected skin. We also assessed functionality of the T cells by evaluating the secretion of several inflammatory cytokines (IL-17A, IFN-gamma, IL-2, IL-33, TNF-alpha, IL-21, IL-22, and IL-27), from cell-sorted purified CD4+ and CD8+ T cells isolated from lesional and unaffected skin biopsies of psoriasis patients.Principal Findings
We observed that the frequency of CD57+CD4+ and CD57+CD8+ T cells was significantly higher in unaffected skin of psoriasis patients compared to lesional skin. Sorted CD4+ T cells from psoriatic lesional skin produced higher levels of IL-17A, IL-22, and IFN-gamma compared to unaffected skin, while sorted CD8+ T cells from lesional skin produced higher levels of IL-17, IL-22, IFN-gamma, TNF-alpha, and IL-2 compared to unaffected skin.Conclusions/Significance
These findings suggest that T cells in unaffected skin from psoriasis patients exhibit a phenotype compatible with replicative inability. As they have a lower replicative capacity, CD57+ T cells are less frequent in lesional tissue due to the high cellular turnover. 相似文献28.
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Sabri Saeed Sanabani ��velyn Regina de Souza Pastena Antonio Charlys da Costa Vanessa Pouza Martinez Walter Kleine-Neto Ana Carolina Soares de Oliveira Mariana Melillo Sauer Katia Cristina Bassichetto Solange Maria Santos Oliveira Helena Tomoko Iwashita Tomiyama Ester Cerdeira Sabino Esper Georges Kallas 《PloS one》2011,6(10)