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941.
Polydentate nitrogen heterocycle ligand 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) reacted with M(NO3)x (M = Ag, x = 1; M = Cd, x = 2) to give two new complexes [Ag(2,3-dpp)(NO3)]2 (1) and [Cd(2,3-dpp)(NO3)2]n (2). Both complexes have been characterized by single-crystal X-ray diffraction, elemental analyses, IR and 1H NMR spectroscopy. Single-crystal X-ray analyses showed that complex 1 crystallized in monoclinic, space group P21/n is a dimmer containing penta-coordinated Ag+ ion. While compound 2 has 1D chain-like structure with repeat unit Cd(2,3-dpp)(NO3)2, in which the Cd(II) presents octa-coordinated N4O4 donor set with two four-membered chelating rings and two five-membered chelating rings around Cd(II) ion. Meanwhile, every neutral chain [Cd(2,3-dpp)(NO3)2]n is mutually connected by face-to-face π?π packing interactions to form a two dimensional layer. Furthermore, antibacterial activities of compound 1 and luminescent property of the compound 2 are also investigated. 相似文献
942.
Nadia Hanafy Metwally Magda Ahmed Abdalla Mosselhi Abdel Nabi Mosselhi Ebrahim Adel El-Desoky 《Carbohydrate research》2010,345(9):1135-2837
5-Arylidene-2-thioxo-4-thiazolidinones 3a-f react with each of 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl and α-d-galactopyranosyl bromides 4a,b in acetone in the presence of aqueous potassium hydroxide at room temperature to afford N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl) or N-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl) 2-thioxo-4-thiazolidinone derivatives 5a-f. Similarly, the reaction of 5-cycloalkylidene-2-thioxo-4-thiazolidinones 7a,b with 4a gave the corresponding N-glucosides 8a,b. Also, 5-pyrazolidene rhodanines 10a-e react with 4a to afford the new N-glucosides 11a-e. Treatment of compounds 15 and 16 with 4a in the presence of few drops of triethylamine or in KOH solution accomplished the mono- and bis-nucleosides 17 and 18, respectively. Some selected products were tested for their antimicrobial activities. 相似文献
943.
944.
Soil organic carbon budget and fertility variation of black soils in Northeast China 总被引:5,自引:0,他引:5
Black soils in Northeast China are characteristic of high soil organic carbon (SOC) density and were strongly influenced by
human activities. Therefore, any change in SOC pool of these soils would not only impact the regional and global carbon cycle,
but also affect the release and immobilization of nutrients. In this study, we reviewed the research progress on SOC storage,
budget, variation, and fertility under different scenarios. The results showed that the organic carbon storage of black soils
was 646.2 TgC and the most potential sequestration was 2887.8 g m−2. According to the SOC budget, the net carbon emission of black soils was 1.3 TgC year−1 under present soil management system. The simulation of CENTURY model showed that future climate change and elevated CO2 concentration, especially the increase of precipitation, would increase SOC content. Furthermore, fertilization and cropping
sequence obviously influenced SOC content, composition, and allocation among different soil particles. Long-term input of
organic materials such as manure and straw renewed original SOC, improved soil structure and increased SOC accumulation. Besides,
soil erosion preferred to transport soil particles with low density and fine size, decreased recalcitrant SOC fractions at
erosion sites and increased activities of soil microorganism at deposition sites. After natural grasslands were converted
into croplands, obvious variation of soil chemical nutrients, physical structure, and microbial activities had taken place
in surface and subsurface soils, and represented a degrading trend to a certain degree. Our studies suggested that adopting
optimal management such as conservation tillage in black soil region is an important approach to sequester atmospheric CO2 and to slow greenhouse effects. 相似文献
945.
Pollutant effects on Pacific oyster, Crassostrea gigas (Thunberg), hemocytes: Screening of 23 molecules using flow cytometry 总被引:1,自引:0,他引:1
The shellfish industry is an important economic activity in France, occurring mostly in estuarine zones subject to pollution
due to anthropogenic activities. The harmful effects of pollutants on species inhabiting these estuarine zones are not well
known. Among marine species, bivalve mollusks---particularly Pacific oyster, Crassostrea gigas---may serve a model of interest. The species is sedentary and filter-feeding, which favors bioaccumulation of pollutants
in their tissues. Oysters may be suitable for studies on disturbance by pollutants of physiological activities, among which
defense mechanisms are poorly documented in bivalves. In this study, effects of pollutants on hemocyte functions were monitored
in Pacific oyster, C. gigas. Hemocytes were exposed in vitro to selected pollutants. The strategy for investigating the effects of pollutants on hemocyte functions is based on several
biomarkers, which is more relevant than that of published papers based on single-endpoint experiments. Pollutants belonging
to the most important groups of xenobiotics (PAHs, PCBs, and pesticides) were selected and their effect on hemocyte activities
was analyzed using flow cytometry. Twenty-three pollutants were tested and eight of them showed significant modulation of
hemocyte activities. PAHs and PCB 77 induced a decrease of hemocyte activity after an incubation periods of 4 and 24 h at
200 μmol/L. Three pesticides (2,4D, paraoxon, and chlorothalonil) modulated hemocyte activities. A mixture of eight pesticides
also decreased phagocytotic activity. This study is one of the first to investigate the effects of so many pollutants on hemocyte
functions at the same time and therefore allows a real comparison of different pollutant effects 相似文献
946.
Payabvash S Ghahremani MH Goliaei A Mandegary A Shafaroodi H Amanlou M Dehpour AR 《Free radical biology & medicine》2006,41(12):1817-1828
Nitric oxide is known to modulate intracellular glutathione levels, but the relationship between nitric oxide synthesis and glutathione metabolism during endotoxemia is unknown. The present study was designed to examine the effects of increased nitric oxide formation on hepatic glutathione synthesis and antioxidant defense in endotoxemic mice. Our results demonstrate that hepatic glutathione synthesis is decreased for 24 h following injection of lipopolysaccharide (LPS). Administration of the cysteine precursor, L-2-oxothiazolidine-4-carboxylic acid (OTZ), failed to normalize hepatic glutathione concentration, and suggests that decreased γ-glutamylcysteine ligase activity is primarily responsible for the decrease in hepatic glutathione levels during endotoxemia. Inhibition of nitric oxide synthesis prevented the endotoxin-induced changes in hepatic and plasma glutathione status and up-regulated liver glutathione and cysteine synthesis pathways at the level of gene expression. Furthermore, whereas the activity of glutathione peroxidase and glutathione S-transferase decreased during endotoxemia, both of these changes were prevented by inhibition of nitric oxide synthesis. In conclusion, increased nitric oxide synthesis during endotoxemia causes marked changes in glutathione flux and defenses against oxidative stress in the liver. 相似文献
947.
Comparison of Soil Organic Matter in Created, Restored and Paired Natural Wetlands in North Carolina 总被引:1,自引:0,他引:1
Soil organic matter (SOM) content is a key indicator of soil quality and is correlated to a number of important soil processes
that occur in wetlands such as respiration, denitrification, and phosphorus sorption. To better understand the differences
in the SOM content of created (CW), restored (RW), and paired natural wetlands (NWs), 11 CW/RW-NW pairs were sampled in North
Carolina. The site pairs spanned a range of hydrogeomorphic (HGM) subclasses common in the Coastal Plain. The following null
hypotheses were tested: (1) SOM content of paired CW/RWs and NWs are similar; (2) SOM content of wetlands across different
HGM subclasses is similar; and (3) interactions between wetland status (CW/RW vs. NW) and hydrogeomorphic subclass are similar.
The first null hypothesis was rejected as CW/RWs had significantly lower mean SOM (11.8 ± 3.9%) than their paired NWs (28.98
± 8.0%) on average and at 10 out of the 11 individual sites. The second and third null hypotheses were also rejected as CW/RWs
and NWs in the non-riverine organic soil flat subclass had significantly higher mean SOM content (31.08 ± 14.2%) than the
other three subclasses (8.18 ± 2.5, 11.18 ± 8.2, and 10.38 ± 4.2%). Individual sites within this fourth subclass also had
significantly different SOM content. This indicated that it would be inappropriate to include the organic soil flat subclass
with either the riverine or non-riverine mineral soil flat subclasses when considering restoration guidelines. These results
also suggested that if there is a choice in mitigation options between restoration or creation, wetlands should be restored
rather than created, especially those in the non-riverine organic soil flat subclass. 相似文献
948.
We measured root and stem mass at three sites (Piedmont (P), Coastal Plain (C), and Sandhills (S)) in the southeastern United States. Stand density, soil texture and drainage, genetic makeup and environmental conditions varied with site while differences in tree size at each site were induced with fertilizer additions. Across sites, root mass was about one half of stem mass when estimated on a per hectare basis. Stem mass per hectare explained 91% of the variation in root mass per hectare, while mean tree diameter at breast height (D), site, and site by measurement year were significant variables explaining an additional 6% of the variation in root mass per hectare. At the S site, the root:stem ratio decreased from 0.7 to 0.5 when mean tree D increased from 10 to 22 cm. At the P and C sites, where mean root:stem ratios were 0.40 and 0.47, respectively, no significant slope in the root:stem to mean tree D relationship was found over a more narrow range in mean tree D (12–15 and 12–18 cm, respectively). Roots were observed in the deepest layers measured (190, 190, and 290 cm for the P, C, and S sites, respectively); however, the asymptotically decreasing root mass per layer indicated the bulk of roots were measured. Root growth relative to stem growth would need to change with increased mean tree D to explain the results observed here. While these changes in growth rate among plant components may differ across sites, stem mass alone does a good job of estimating root mass across sites. 相似文献
949.
Effects of long-term mineral fertilization and manuring on the biomass of arbuscular mycorrhizal fungi (AMF) were studied in a field experiment. Mineral fertilization reduced the growth of AMF, as estimated using both measurements of hyphal length and the signature fatty acid 16:1ω5, whereas manuring alone increased the growth of AMF. The results of AMF root colonization followed the same pattern as AMF hyphal length in soil samples, but not AMF spore densities, which increased with increasing mineral and organic fertilization. AMF spore counts and concentration of 16:1ω5 in soil did not correlate positively, suggesting that a significant portion of spores found in soil samples was dead. AMF hyphal length was not correlated with whole cell fatty acid (WCFA) 18:2ω6,9 levels, a biomarker of saprotrophic fungi, indicating that visual measurements of the AMF mycelium were not distorted by erroneous involvement of hyphae of saprotrophs. Our observations indicate that the measurement of WCFAs in soil is a useful research tool for providing information in the characterization of soil microflora. 相似文献
950.
Ikhmyangan EN Vasilenko NL Buneva VN Nevinsky GA 《Journal of molecular recognition : JMR》2006,19(2):91-105
We present evidence showing that a small fraction of electrophoretically homogeneous IgGs from the sera of healthy Wistar rats is bound with several different Me2+ ions and oxidizes 3,3'-diaminobenzidine through a peroxidase activity in the presence of H2O2 and through an oxidoreductase activity in the absence of H2O2. During purification on Protein A-Sepharose and gel filtration, the polyclonal IgGs partially lose the Me2+ ions. Therefore, in the absence of external metal ions, the specific peroxidase activity of IgGs from the sera of different rats varied in the range 1.6-26% and increased up to 13-198% after addition of Fe2+ or Cu2+ ions as compared with horseradish peroxidase (HRP, taken for 100%). The oxidoreductase activity of HRP is 24-fold lower than its peroxidase activity, while oxidoreductase and peroxidase activities of IgGs are comparable. Oxidoreductase activities of different IgGs in the absence of external metal ions varied from 22 to 800%, and in the presence of Fe2+ or Cu2+ ions, from 37 to 1100% in comparison with the HRP oxidoreductase activity (100%). Chromatography of the IgGs on Chelex-100 leads to the adsorption of a small IgG fraction bound with metal ions and to its separation to many different subfractions demonstrating various affinities to the chelating resin and increased levels of the specific oxidoreductase and peroxidase activities. Antioxidant enzymes such as superoxide dismutases, catalases, and glutathione peroxidases are known to represent critical defense mechanisms for preventing oxidative modifications of DNA, proteins, and lipids. Peroxidase and oxidoreductase activity of antibodies may play an important role in the protection of organisms from oxidative stress and toxic compounds. 相似文献