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61.
Fine root biomass and tree species effects on potential N mineralization in afforested sodic soils 总被引:1,自引:0,他引:1
The study was carried out under three types of plantation forest of 40 years, growing on infertile sodic soils, poor in organic matter and N content, of Indogangetic alluvium at Lucknow (26°45 N; 80°53 E). Fine root biomass estimated under three forests did not differ much with season, or with species (106–113 g m-2) but varied with soil depth to 0.45 m. The proportion of very fine roots (<0.5 mm) increased with soil depth. Available N in soil was greatest under mixed forest followed by Eucalyptus camaldulensis and Acacia nilotica planted soils. N was maximum in summer season and decreased with soil depth. Nitrogen mineralization during anerobic incubation of 14 days could not be differentiated by tree species, but the monsoon season favoured the process and winter season retarded it. Mineralization decreased with soil depth corresponding to fine roots. There was a reduction in bulk density of soil, pH and EC in forested soil compared to a similar but non forested soil, whereas, organic C and total N increased in forested soils. N mineralization was found to be affected significantly with the fine root biomass and available N content in the soils, whereas negative relations of mineralized N with pH and EC were noticed, though these were not significantly different in this study. 相似文献
62.
Wireless networks experience a high level of errors and losses. These physical layer characteristics have an impact on the
performance of the higher layers. In addition, the performance of each protocol layer is contingent on the behavior of the
other layers. Vertical dependency is a term which describes this inter-dependence between layers. In the wireless and mobile
environment, the effects of vertical dependence are particularly pronounced due to the dynamic nature of the environment and
due to the fact that traditional assumptions about protocol layer interactions do not always hold. In this paper, we consider
the vertical dependencies between various layers in the protocol stack, studying the performance of the Network File System
under various error models and improvement techniques. Our experimental results demonstrate the dependency of the application
performance on the details of the error characteristics and other protocol layers. After studying the vertical dependencies,
we improve NFS performance by implementing changes to the application level reliability mechanisms. Understanding of the vertical
dependencies enables development of effective methods for performance enhancement and efficient reaction to errors and changes
on the wireless media.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
63.
Saccharomyces cerevisiae HOP1, which encodes a component of synaptonemal complex, plays an important role in crossing over between homologues. Hop1p contains a zinc finger motif, and substitution of a conserved Cys371 by Ser rendered the hop1 mutant allele defective in sporulation and meiosis. However, the molecular mechanism underlying the function of Hop1 zinc finger motif (ZnF) remains obscure. Here we show that wild-type Hop1 ZnF binds significantly better to the Holliday junction compared with other recombination intermediates. Consequently, the salt titration midpoint for dissociation of the Holliday junction-ZnF complex was higher than the complexes containing flush-ended linear or tailed duplex DNA. Although DNase I footprinting showed that Hop1 ZnF binds to each of the four arms of the junction, KMnO4 probing and 2-aminopurine fluorescence emission data disclosed that it distorts the DNA structure along a pair of symmetrical arms. Molecular modeling studies show that Hop1 ZnF forms a unique zinc-binding fold, reminiscent of the basic helix-loop-helix motif. In the presence of Zn2+, docking studies show that alpha helix 1, which is replete with basic amino acid residues, makes stabilizing contacts with the sugar-phosphate backbone. Structural comparison revealed a striking similarity between RecG wedge domain and Hop1 ZnF motif. We propose that Hop1 ZnF motif plays a key role in the physical monitoring of recombination intermediates and branch migration of the Holliday junction. 相似文献
64.
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66.
The cystic fibrosis transmembrane regulator (CFTR) is a cyclic-AMP dependent chloride channel expressed at the apical surface of epithelial cells lining various organs such as the respiratory tract. Defective processing and functioning of this protein caused by mutations in the CFTR gene results in loss of ionic balance, defective mucus clearance, increased proliferation of biofilms and inflammation of human airways observed in cystic fibrosis (CF) patients. The process by which CFTR folds and matures under the influence of various chaperones in the secretory pathway remains incompletely understood. Recently, calumenin, a secretory protein, belonging to the CREC family of low affinity calcium binding proteins has been identified as a putative CFTR chaperone whose biophysical properties and functions remain uncharacterized. We compared hydropathy, instability, charge, unfoldability, disorder and aggregation propensity of calumenin and other CREC family members with CFTR associated chaperones and calcium binding proteins, wild-type and mutant CFTR proteins and intrinsically disordered proteins (IDPs). We observed that calumenin, along with other CREC proteins, was significantly more charged and less folded compared to CFTR associated chaperones. Moreover like IDPs, calumenin and other CREC proteins were found to be less hydrophobic and aggregation prone. Phylogenetic analysis revealed a close link between calumenin and other CREC proteins indicating how evolution might have shaped their similar biophysical properties. Experimentally, calumenin was observed to significantly reduce F508del-CFTR aggregation in a manner similar to AavLEA1, a well-characterized IDP. Fluorescence microscopy based imaging analysis also revealed altered trafficking of calumenin in bronchial cells expressing F508del-CFTR, indicating its direct role in the pathophysiology of CF. In conclusion, calumenin is characterized as a charged protein exhibiting close similarity with IDPs and is hypothesized to regulate F508del-CFTR folding by electrostatic effects. This work provides useful insights for designing optimized synthetic structural correctors of CFTR mutant proteins in the future. 相似文献
67.
Inflammatory cytokines and oxidized low density lipoproteins increase endothelial cell expression of membrane type 1-matrix metalloproteinase 总被引:9,自引:0,他引:9
Rajavashisth TB Liao JK Galis ZS Tripathi S Laufs U Tripathi J Chai NN Xu XP Jovinge S Shah PK Libby P 《The Journal of biological chemistry》1999,274(17):11924-11929
68.
Moon DK Tripathi A Sullivan D Siegler MA Parkin S Posner GH 《Bioorganic & medicinal chemistry letters》2011,21(9):2773-2775
Four 5-carbon-linked trioxane dimer orthoesters (6a-6d) have been prepared in 4 or 5 chemical steps from the natural trioxane artemisinin (1). When administered orally to malaria-infected mice using a single dose of only 6 mg/kg body weight along with 18 mg/kg of mefloquine hydrochloride, trioxane dimer orthoester sulfone 6d completely and safely cured the mice; after 30 days, the cured mice showed no detectable parasitemia, gained at least as much weight as the control mice (no infection), and behaved normally. 相似文献
69.
Tripathi AK Tripathi R Ganguli A Bazzicalupo M 《Canadian journal of microbiology》1998,44(11):1110-1113
The characterization of a DNA fragment with a Tn5 insertion in a regulatory nif gene of Azospirillum brasilense is reported. Restriction endonuclease mapping, Southern hybridization with a Tn5 probe, and nucleotide sequencing revealed that IS50 had duplicated in Tn5. The duplication of an IS50 element suggests the occurrence of a replicative mechanism of transposition. A strategy, based on the bacterial ability of homologous recombination that was used to precisely eliminate Tn5 along with the duplicated IS50 element, is presented. 相似文献
70.
Lakshmi Pathak Vineeta Singh Ram Niwas Khwaja Osama Saif Khan Shafiul Haque C. K. M. Tripathi B. N. Mishra 《PloS one》2015,10(9)
Cholesterol oxidase (COD) is a bi-functional FAD-containing oxidoreductase which catalyzes the oxidation of cholesterol into 4-cholesten-3-one. The wider biological functions and clinical applications of COD have urged the screening, isolation and characterization of newer microbes from diverse habitats as a source of COD and optimization and over-production of COD for various uses. The practicability of statistical/ artificial intelligence techniques, such as response surface methodology (RSM), artificial neural network (ANN) and genetic algorithm (GA) have been tested to optimize the medium composition for the production of COD from novel strain Streptomyces sp. NCIM 5500. All experiments were performed according to the five factor central composite design (CCD) and the generated data was analysed using RSM and ANN. GA was employed to optimize the models generated by RSM and ANN. Based upon the predicted COD concentration, the model developed with ANN was found to be superior to the model developed with RSM. The RSM-GA approach predicted maximum of 6.283 U/mL COD production, whereas the ANN-GA approach predicted a maximum of 9.93 U/mL COD concentration. The optimum concentrations of the medium variables predicted through ANN-GA approach were: 1.431 g/50 mL soybean, 1.389 g/50 mL maltose, 0.029 g/50 mL MgSO4, 0.45 g/50 mL NaCl and 2.235 ml/50 mL glycerol. The experimental COD concentration was concurrent with the GA predicted yield and led to 9.75 U/mL COD production, which was nearly two times higher than the yield (4.2 U/mL) obtained with the un-optimized medium. This is the very first time we are reporting the statistical versus artificial intelligence based modeling and optimization of COD production by Streptomyces sp. NCIM 5500. 相似文献