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ISBN: (纸本)9787030631558

关键词： Toxicity   Biomarker   Nano-silver   Liver   Pollution   Silver nitrate  

摘要： The present study aimed to evaluate the effects of different waterborne sublethal concentrations of Ag-NPs LC50 (96h) on common carp Cyprinus carpio using a multi-biomarker approach. Fish (9.22 +/- 0.12 g) were stocked in fiberglass tanks and exposed to concentrations of 0 (control), 12.5%, 25% and 50% of Ag-NPs LC50 (96h) or Ag-NO3 LC50 (96h), as the source of Ag+ ion, for a period of 21 days. At the end of study, tissue Ag contents were significantly (P < 0.05) higher and different in fish exposed to concentrations of 25% and 50% compared to the control. The numbers of RBCs, hematocrit, and MCHC values at these concentrations differed significantly in respect to the control. No significant effects were observed for hemoglobin, MCH, and MCV values. The number of WBCs was significantly higher at concentrations of 12.5% and 25% compared to the control, Meanwhile, the percentage of neutrophils significantly elevated at concentrations of 25% and 50%. Serum total protein at concentration of 50% detected significantly lower than that of 12.5% or the control. The serum albumin and globulin levels significantly declined in Ag-NPs-exposed groups versus the control. The serum ACH50 and total immunoglobulins showed significantly lower values in the treatments of 25% and 50% compared to the control. The serum glucose, cortisol, ALT, and ALP values significantly escalated upon Ag-NPs exposure. The serum SOD and CAT showed enhanced activity in the treatment of 12.5% vice versa significantly diminished at concentrations of 25% and 50% compared to the control. The exposure to the concentrations of 25% and 50% significantly dwindled the lysozyme activity and total immunoglobulin levels in skin mucus. In conclusion, sublethal concentrations of Ag-NPs LC50 (96h) impaired fish health status at higher concentrations and 12.5% of Ag-NPs LC50 (96h) was presumably safe for common carp aquaculture.

关键词： Holliday junction   RuvC   Pseudomonas aeruginosa   Biochemical characterization   Crystal structure  

摘要： The Holliday junction, a four-way DNA structure, is an important intermediate of homologous recombination. Proper Holliday junction resolution is critical to complete the recombination process. In most bacterial cells, the Holliday junction cleavage is mainly performed by a specific endonuclease RuvC. Here, we describe the biochemical properties and the crystal structure of RuvC from an opportunistic pathogen, Pseudomonas aeruginosa (PaRuvC). PaRuvC specifically binds to the Holliday junction DNA and preferentially cleaves it at the consensus 5'-TTC-3'. PaRuvC uses Mg2+ as the preferred divalent metal cofactor for Holliday junction cleavage and its optimum pH is 8.0-9.0. Elevated temperatures (37-60 degrees C) boost the catalytic activity, but temperatures higher than 53 degrees C reduce the protein stability. The crystal structure of PaRuvC determined at 2.4 angstrom and mutagenesis analysis reveal key residues involved in the dimer formation, substrate binding and catalysis. Our results are expected to provide useful information to combat antibiotic resistance of Pseudomonas aeruginosa by targeting its homologous recombination system. (C) 2020 Elsevier Inc. All rights reserved.

关键词： Theobroma cacao   Oxidative stress   Copper   Gene expression   Detoxification   ROS  

摘要： Copper (Cu), besides being an essential micronutrient for plants, is a component of fungicides used in cacao farming. The objective of this study was to evaluate Cu toxicity in leaves of young plants of cocoa genotype CCN 51, applied via the leaf as cuprous oxide fungicide at different concentrations (0, 1.5, 3, 4.5 and 6 g Cu L-1) by means of physiological, biochemical, molecular and nutritional changes at leaf level. Cu concentrations (4.5 and 6 g Cu L-1) applied via leaf severely affected leaf gas exchange, promoted changes in the activity of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) enzymes, free proline concentration, lipid peroxidation and expression of the genes psbA, psbO, Mt2b, sod cyt, sod chl and per-1, as well as changes in concentration of mineral macro and micronutrients in leaf. It was concluded, therefore, that the application of different concentrations of Cu via cuprous oxide fungicide to leaf induced an imbalance in the leaf metabolism of the young plants of CCN 51, through modifications in leaf gas exchange, in the activity of the enzymatic and non-enzymatic antioxidative metabolism, in the expression of genes related to oxidative stress, photosynthesis and mechanisms of cellular detoxification. In addition, a dose-dependent type response pattern was verified, indicating that there was a synergism in the cellular detoxification pathways in eliminating excess reactive oxygen species (ROS).

关键词： Catalase   Chemical composition   Drought   Proline   Peroxidase   Relative water content  

摘要： In this study, we measured the morphological, biochemical, and chemical responses to soil drying in nine tea clones [Camellia sinensis (L.) O. Kuntze] grown in a field. Thirteen-year-old tea plants at Shahid Eftekhari Fashalam Experimental Station, Tea Research Center of Iran, were subject to drought stress by withholding water for 40 days. The control group of the clones was regularly watered. The soil moisture content of the non-irrigated and irrigated plants was monitored throughout the experiment. The effects of drought stress were measured by studying physiological (Relative Water Content), biochemical (Proline and Total Sugar Content), and antioxidant activities (Catalase and Peroxidase) after 20 days and 40 days of drought imposition. Green leaf yield and chemical parameters included total polyphenol, caffeine, water extract, and total ash were measured after 40 days of drought stress. Drought stress resulted in a decrease in total polyphenol, water extract, and total ash and an increase in proline, total sugar concentration and, in CAT and POD activities, as a consequence of reduced RWC of the leaves. Thus, drought stress caused a range of biochemical, physiological, and chemical variations, resulting in membrane damage and loss in the functions of the cell and finally a decrease in the tea growth as one of the most important economic crops. The results of grouping the clones under irrigation and drought stress conditions and comparing them with the results of mean comparison of the traits showed that in all cases, clones 276, 100, 285, and 277 were in the group that can be identified as the drought-tolerant group. Also, the results showed that in most cases, clones 278 and 74 were placed in a group that had low values for all the traits and could be considered as a group that is susceptible to drought stress. Overall, these findings provide new insight into the mechanisms of tolerance to drought in tea plants.

关键词： Peptides and proteins   Carbohydrates   Monomers   Crystal structure   Biosynthesis  

摘要： Karrosainiire (3-amino-3-deoxy-D-glucose) is a characteristic sugar unit found in;kanamycins, a group of aminoglycoside antibiotics. The kanosamine moiety originates from ID-glucose in kanarny'cin biosynthesis. However, the timing of the replacement of the 3-OH group of the D-glucose-derived biosynthetic intermediate with the amino group is elusive. Comparison of biosynthetic gene clusters for related aminoglycoside antibiotics suggests that the nicotinamide adenine dinucleotide (NAD+)-dependent dehydrogenase KanD2 and the pyridoxal 5'-phosphate (PLP)-dependent aminotransferase KanS2 are responsible for the introduction of the amino group at the C3 position of kanosamine. In this study, we demonstrated that KanD2 and IKanS2 convert kanarrrycin A, B, and C to the corresponding 3"-cleantino-3"-hydroxykanamycins (3"-hks) in the presence of PLP, 2-oxogltrtarate, and NADH via a reverse reaction in the pathway- Furthermore, we observed that all of the 3"-hks are oxidized by I(ailD2 with MAD, but ID-glucose, UDP-D-glucose, sD-glucose 6-phosphate, and D-glucose 1-phosphate are not. Crystal structure analysis of KanD2 complexed with 3"-hkB and NADH illustrated the selective recognition of pseudotrisaccharides, especially the D-glucose moiety with 2-deolcystreptarnine, by a combination of hydrogen bonds and CH a- interactions. Overall, it was clarified that the karrosamine moiety of kairaittycins is constructed after the glitcosylation of the pseudodisaccharide biosynthetic intermediates in kanarriycin biosynthesis.

关键词： pyruvate kinase   crystal structure   enzyme kinetics   allosteric regulation   glycolysis   amino acids   asparagine   aspartate   pyruvate kinase muscle isoform 2 (PKM2)   valine   valine   fluorescence binding   cancer metabolism   oligomerization  

摘要： Pyruvate kinase muscle isoform 2 (PKM2) is a key glycolytic enzyme involved in ATP generation and critical for cancer metabolism. PKM2 is expressed in many human cancers and is regulated by complex mechanisms that promote tumor growth and proliferation. Therefore, it is considered an attractive therapeutic target for modulating tumor metabolism. Various stimuli allosterically regulate PKM2 by cycling it between highly active and less active states. Several small molecules activate PKM2 by binding to its intersubunit interface. Serine and cysteine serve as an activator and inhibitor of PKM2, respectively, by binding to its amino acid (AA)-binding pocket, which therefore represents a potential druggable site. Despite binding similarly to PKM2, how cysteine and serine differentially regulate this enzyme remains elusive. Using kinetic analyses, fluorescence binding, X-ray crystallography, and gel filtration experiments with asparagine, aspartate, and valine as PKM2 ligands, we examined whether the differences in the side-chain polarity of these AAs trigger distinct allosteric responses in PKM2. We found that Asn (polar) and Asp (charged) activate PKM2 and that Val (hydrophobic) inhibits it. The results also indicate that both Asn and Asp can restore the activity of Val-inhibited PKM2. AA-bound crystal structures of PKM2 displayed distinctive interactions within the binding pocket, causing unique allosteric effects in the enzyme. These structure-function analyses of AA-mediated PKM2 regulation shed light on the chemical requirements in the development of mechanism-based small-molecule modulators targeting the AA-binding pocket of PKM2 and provide broader insights into the regulatory mechanisms of complex allosteric enzymes.

关键词： Circulating fluidized beds   Liquid-solid fluidization   Gas-liquid-solid fluidization   Potential applications   Proteins recovery   Wastewater treatment  

摘要： Circulating fluidized beds (CFBs) possess many significant advantages over conventional fluidized beds, including enhanced interfacial contact efficiency and reduced back-mixing. Building on the many successful industrial applications of gas-solid CFBs, liquid-solid circulating fluidized beds (LSCFBs) and gas-liquid-solid circulating fluidized beds (GLSCFBs) have recently also received increasing interests due to their massive potential in chemical-biochemical, environmental and pharmaceutical processes. This review summarizes the progress in the past several decades concerning LSCFBs and GLSCFBs, with more emphasis placed on the reported applications, after a general description of the unique features of the two types of CFBs. Most of the examples given in this review are still in laboratory-scale, but useful guidance can be provided to researchers or companies for further study and/or commercial exploration.

关键词： Hexosaminidase   L.corrianus   Lysosomal enzyme  

摘要： Two thermostable isoforms of a hexosaminidase were purified to homogeneity from the soluble extract of fresh water mussel Lamellidens corrianus, employing a variety of chromatographic techniques. Hexosaminidase A (HexA) is a heterodimer with subunit masses of similar to 80 and 55 kDa. Hexosaminidase B (HexB) is a homodimer with a subunit mass of 55-60 kDa. Circular dichroism spectroscopic studies indicated that both HexA and HexB contain beta-sheet as the major secondary structural component with considerably lower content of alpha-helix. The temperature and pH optima of both the isoforms were found to be 60 degrees C and 4.0, respectively. The IC50 values for HexA with N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, D-galactosamine, D-glucosamine, methyl alpha-D-mannopyranoside and D-mannose are 3.7, 72.8, 307, 216, 244 and 128 mM, respectively, whereas the corresponding IC50 values for HexB were estimated as 5.1, 61, 68, 190, 92 and 133 mM. respectively. Kinetic parameters K-M and V-max. for HexA and B with p-nitrophenyl N-acetyl-beta-D-glucosaminide are 4 mM, 023 mu ***(-1) .mL(-1) and 2.86 mM, 0.29 mu mol-min(-1).mL(-1), respectively, and with p-nitrophenyl N-acetyl-beta-D-galactosaminide are 4.5 mM, 0.054 mu ***(-l) .mL(-1 )and 1.4 mM, 0.14 mu ***(-1). mL(-)(1), respectively. GalNAc inhibited both isolorms in a non-competitive manner, whereas a mixed mode of inhibition was observed with GIcNAc with both forms. (C) 2020 Published by Elsevier B.V.