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101.
The removal of polycyclic aromatic hydrocarbons by membrane bioreactor (MBR) under aerobic conditions had been studied using naphthalene (NAP) and phenanthrene (PHE) as model compounds. Three MBRs with submerged ultra-filtration hollow fiber membranes were operated applying different operational conditions during 6.5 months. Complete NAP and PHE removal was obtained applying loads of 7 gNAP kgTSS?1 day?1 and 0.5 gPHE kgTSS?1 day?1, while the organic loading rate was adjusted to 0.26 kgCOD kgTSS?1 day?1, with the biomass concentration being 6000 mgTSS L?1, the hydraulic retention time (HRT) 8 h and the solids retention time (SRT) 30 days. Load increases, as well as HRT and SRT reductions, affected the NAP and PHE removals. Biodegradation was found to be the major NAP and PHE removal mechanism. There was no NAP accumulation in the biomass. Low PHE quantities remain sorbed in the biomass and the contribution of the sorption in the removal of this compound was estimated to be less than 0.01 %. The volatilization does not contribute to the PHE removal in MBRs, but the contribution of NAP volatilization can reach up to 0.6 % when HRT of 8 h is applied. 相似文献
102.
Christelle Hély Kelly K. Caylor Peter Dowty Samuel Alleaume Robert J. Swap Hank H. Shugart Christopher O. Justice 《Ecosystems》2007,10(7):1116-1132
Abstract
We present a regional fuel load model (1 km2 spatial resolution) applied in the southern African savanna region. The model is based on a patch-scale production efficiency
model (PEM) scaled up to the regional level using empirical relationships between patch-scale behavior and multi-source remote
sensing data (spatio-temporal variability of vegetation and climatic variables). The model requires the spatial distribution
of woody vegetation cover, which is used to determine separate respiration rates for tree and grass. Net primary production,
grass and tree leaf death, and herbivory are also taken into account in this mechanistic modeling approach. The fuel load
model has been calibrated and validated from independent measurements taken from savanna vegetation in Africa southward from
the equator. A sensitivity analysis on the effect of climate variables (incoming radiation, air temperature, and precipitation)
has been conducted to demonstrate the strong role that water availability has in determining productivity and subsequent fuel
load over the southern African region. The model performance has been tested in four different areas representative of a regional
increasing rainfall gradient—Etosha National Park, Namibia, Mongu and Kasama, Zambia, as well as in Kruger National Park,
South Africa. Within each area, we analyze model output from three different magnitudes of canopy coverage (<5, 30, and 50%).
We find that fuel load ranges predicted by the model are globally in agreement with field measurements for the same year.
High rainfall sustains green herbaceous production late in the dry season and delays tree leaf litter production. Effect of
water on production varies across the rainfall gradient with delayed start of green material production in more arid regions. 相似文献
103.
Francesca Passaretta Domenico Bosco Lucia Centurione Maria Antonietta Centurione Fabio Marongiu Roberta Di Pietro 《Journal of cellular and molecular medicine》2020,24(7):4350-4355
Human Amniotic Epithelial Cells (hAEC) isolated from term placenta are a promising source for regenerative medicine. However, it has long been debated whether the hAEC population consists of heterogeneous or homogeneous cells. In a previous study, we investigated the characteristics of hAEC isolated from four different regions of the amniotic membrane finding significant heterogeneity. The aim of this study was to evaluate the hepatic differentiation capability of hAEC isolated from these four regions. Human term placentae were collected after caesarean section and hAEC were isolated from four regions of the amniotic membrane (R1-R4, according to their relative distance from the umbilical cord) and treated in hepatic differentiation conditions for 14 days. hAEC-derived hepatocyte-like cells showed marked differences in the expression of hepatic markers: R4 showed higher levels of Albumin and Hepatocyte Nuclear Factor (HNF) 4α whereas R1 expressed higher Cytochrome P450 enzymes, both at the gene and protein level. These preliminary results suggest that hAEC isolated from R1 and R4 of the amniotic membrane are more prone to hepatic differentiation. Therefore, the use of hAEC from a specific region of the amniotic membrane should be taken into consideration as it could have an impact on the outcome of therapeutic applications. 相似文献
104.
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106.
Melissa A. Partridge Sumana Gopinath Simon J. Myers Jens R Coorssen 《Journal of chemical biology》2016,9(1):9-18
An initial proteomic analysis of the cuprizone mouse model to characterise the breadth of toxicity by assessing cortex, skeletal muscle, spleen and peripheral blood mononuclear cells. Cuprizone treated vs. control mice for an initial characterisation. Select tissues from each group were pooled, analysed in triplicate using two-dimensional gel electrophoresis (2DE) and deep imaging and altered protein species identified using liquid chromatography tandem mass spectrometry (LC/MS/MS). Forty-three proteins were found to be uniquely detectable or undetectable in the cuprizone treatment group across the tissues analysed. Protein species identified in the cortex may potentially be linked to axonal damage in this model, and those in the spleen and peripheral blood mononuclear cells to the minimal peripheral immune cell infiltration into the central nervous system during cuprizone mediated demyelination. Primary oligodendrocytosis has been observed in type III lesions in multiple sclerosis. However, the underlying mechanisms are poorly understood. Cuprizone treatment results in oligodendrocyte apoptosis and secondary demyelination. This initial analysis identified proteins likely related to axonal damage; these may link primary oligodendrocytosis and secondary axonal damage. Furthermore, this appears to be the first study of the cuprizone model to also identify alterations in the proteomes of skeletal muscle, spleen and peripheral blood mononuclear cells. Notably, protein disulphide isomerase was not detected in the cuprizone cohort; its absence has been linked to reduced major histocompatibility class I assembly and reduced antigen presentation. Overall, the results suggest that, like experimental autoimmune encephalomyelitis, results from the standard cuprizone model should be carefully considered relative to clinical multiple sclerosis. 相似文献
107.
Tapas K. Nandi Hridoy R. Bairagya Bishnu P. Mukhopadhyay K. Sekar Dipankar Sukul Asim K. Bera 《Journal of biosciences》2009,34(1):27-34
The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the
11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W1 and W2 (W220
and W222 in the template 1PPN structure) were observed to form H-bonds with the Ob atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated
structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation
of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at
the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad. 相似文献
108.
Konstantinos Papakostas Maria Botou Stathis Frillingos 《The Journal of biological chemistry》2013,288(52):36827-36840
The evolutionarily broad family nucleobase-cation symporter-2 (NCS2) encompasses transporters that are conserved in binding site architecture but diverse in substrate selectivity. Putative purine transporters of this family fall into one of two homology clusters: COG2233, represented by well studied xanthine and/or uric acid permeases, and COG2252, consisting of transporters for adenine, guanine, and/or hypoxanthine that remain unknown with respect to structure-function relationships. We analyzed the COG2252 genes of Escherichia coli K-12 with homology modeling, functional overexpression, and mutagenesis and showed that they encode high affinity permeases for the uptake of adenine (PurP and YicO) or guanine and hypoxanthine (YjcD and YgfQ). The two pairs of paralogs differ clearly in their substrate and ligand preferences. Of 25 putative inhibitors tested, PurP and YicO recognize with low micromolar affinity N6-benzoyladenine, 2,6-diaminopurine, and purine, whereas YjcD and YgfQ recognize 1-methylguanine, 8-azaguanine, 6-thioguanine, and 6-mercaptopurine and do not recognize any of the PurP ligands. Furthermore, the permeases PurP and YjcD were subjected to site-directed mutagenesis at highly conserved sites of transmembrane segments 1, 3, 8, 9, and 10, which have been studied also in COG2233 homologs. Residues irreplaceable for uptake activity or crucial for substrate selectivity were found at positions occupied by similar role amino acids in the Escherichia coli xanthine- and uric acid-transporting homologs (XanQ and UacT, respectively) and predicted to be at or around the binding site. Our results support the contention that the distantly related transporters of COG2233 and COG2252 use topologically similar side chain determinants to dictate their function and the distinct purine selectivity profiles. 相似文献
109.