共查询到20条相似文献,搜索用时 31 毫秒
1.
Z.-D. Feng L.X. Wang Y.H. Ji L.L. Guo X.Q. Lee S.I. Dworkin 《Palaeogeography, Palaeoclimatology, Palaeoecology》2008,257(3):335-343
We explored the relationships between surface-soil (1–20 cm) organic carbon isotopic signatures and associated climatic factors in central-east Asia in an attempt to develop transfer functions that can be used to retrieve the paleoclimatic information stored in the thick eolian–paleosol sequences within the area. Our analysis shows that the negative correlation between the surface-soil organic δ13C values and the mean annual precipitation is robust (R2 = 0.453; n = 196; p < 0.05) and the negative correlation with the growing-season (April–September) precipitation is more significant (R2 = 0.4966; n = 196; p < 0.05). Our study further shows that the positive correlation between the surface-soil organic δ13C values and mean growing-season aridity is most significant (R2 = 0.5805; n = 196; p < 0.05). We have smoothed both the organic δ13C values and the mean growing-season aridity values using a 3-point moving-window average-filter method in an attempt to remove some of random errors and found that the positive correlation between the two is further increased (R2 = 0.7784; n = 192; p < 0.05). These robust linear relationships demonstrate their value in reconstructing paleoclimate changes in the study area. The documented climatic dependency of the surface-soil carbon isotopic composition in the study area might have resulted both from the humidity-related isotopic enrichment processes of the dominant C3 plants (stomatal conductance and photosynthetic discrimination) and from the aridity-related abundance of C4 plants (mainly Chenopodiaceae species) along the S–N bioclimatic gradient. 相似文献
2.
Nikhil Reddy Madadi Narsimha Reddy Penthala Lisa K. Brents Benjamin M. Ford Paul L. Prather Peter A. Crooks 《Bioorganic & medicinal chemistry letters》2013,23(7):2019-2021
A small library of N-benzyl indolequinuclidinone (IQD) analogs has been identified as a novel class of cannabinoid ligands. The affinity and selectivity of these IQDs for the two established cannabinoid receptor subtypes, CB1 and CB2, was evaluated. Compounds 8 (R = R2 = H, R1 = F) and 13 (R = COOCH3, R1 = R2 = H) exhibited high affinity for CB2 receptors with Ki values of 1.33 and 2.50 nM, respectively, and had lower affinities for the CB1 receptor (Ki values of 9.23 and 85.7 nM, respectively). Compound 13 had the highest selectivity of all the compounds examined, and represents a potent cannabinoid ligand with 34-times greater selectivity for CB2R over CB1R. These findings are significant for future drug development, given recent reports demonstrating beneficial use of cannabinoid ligands in a wide variety of human disease states including drug abuse, depression, schizophrenia, inflammation, chronic pain, obesity, osteoporosis and cancer. 相似文献
3.
《Inorganica chimica acta》2006,359(11):3549-3556
A series of cationic trispyrazolylmethane complexes of the general form [TmRM(CH3CN)3]2+ (Tm = tris(pyrazolyl)methane, 1, R = 3,5-Me2, M = Fe(II); 2, R = 3-Ph, M = Fe(II); 3, R = 3,5-Me2, M = Co(II); 4, R = 3-Ph, M = Co(II)) with ‘piano-stool’ structures was prepared by the reaction of the N3tripodal ligands (TmR)with [(CH3CN)6M](BF4)2 in a 1:1 stoichiometric ratio. Magnetic susceptibility measurements indicate that all four complexes with BF4− counter anions are paramagnetic, high-spin systems in the solid state with μeff at high temperatures of 5.2 (1, S = 2), 5.4 (2, S = 2), 4.9 (3, S = 3/2) and 4.6 (4, S = 3/2) BM, respectively. Comparisons of bond lengths from the metal centre to the TmR nitrogen donors, and from the metal centre to the acetonitrile nitrogen donors indicate that the neutral tripodal ligands appear to be more weakly coordinated to the metal centre than are the acetonitrile ligands. Reactions of these tripodal complexes with bidentate phosphine ligands, such as 1,2-diphosphinoethane or 1,2-bis(diallylphosphino)ethane leads to displacement of the tripodal ligand, or to the formation of more thermally stable bis-ligand complexes M(TmR)2 (R = 3,5-dimethyl). 相似文献
4.
《Inorganica chimica acta》2006,359(6):1855-1869
A series of discrete, mononuclear palladium(II)–methyl complexes, together with several palladium(II)–chloro analogues, of pyridine-functionalised bis-NHC ligands have been prepared via ligand transmetallation from the silver(I)-NHC complexes. The reported complexes comprise examples with both the methylene-bridged 2,6-bis[(3-R-imidazolin-2-yliden-1-yl)methyl]pyridine (RC∧N∧C; R = Mes, dipp, tBu) and planar 2,6-bis(3-R-imidazolin-2-yliden-1-yl)pyridine (RCNC; R = Mes, dipp) ligands and, when combined with the previously reported MeC∧N∧C/MeCNC examples, cover a broad spectrum of ligand substituent steric and electronic properties, including the bulky Mes and dipp groups frequently used in catalytic applications. The palladium(II) complexes have been characterised by a variety of methods, including single crystal X-ray crystallography, with the shielding of the Pd–Me groups in the proton NMR spectra of some of the N-aryl substituted examples correlated with the proximity of the aryl rings to the methyl group in the solid state structures. The [PdMe(RC∧N∧C/RCNC)]+ complexes undergo thermal degradation via reductive methyl-NHC coupling to give 2-methyl-3-R-imidazolium-1-yl species with relative stabilities in the order of [PdMe(MesC∧N∧C)]BF4 > [PdMe(MeC∧N∧C)]BF4 ≈ [PdMe(MesCNC)]BF4 > [PdMe(MeCNC)]BF4 > [PdMe(tBuC∧N∧C)]BF4 ≫ [PdMe(tBuCNC)]BF4 (not isolable). A comparison of the activity of the complexes as precatalysts in a model Heck coupling reaction shows greatest activity in those species bearing bulkier N-substituents, with complexes bearing RC∧N∧C ligands generally more efficient precatalysts than those bearing RCNC ligands. 相似文献
5.
《Biochemical Engineering Journal》2007,33(3):226-232
In the present work experiments were carried out to study the effect of free gossypol on the growth of Candida tropicalis ZAU-1, evaluate its ability in biodegrading free gossypol, analyze the time course of solid-state fermentation, and model the microbial growth by determining the kinetics of dry matter weight loss, total carbohydrate concentration and the free gossypol content during solid-state fermentation. Results showed that the biomass in inorganic salts glucose medium were unaffected by free gossypol at 500 and 1000 mg/l levels, compared with the control group (p > 0.05); degradation of free gossypol reached 95.12% and 94.12%, respectively. A logistic equation (R2 = 0.9922), describing the growth model of C. tropicalis ZAU-1 was obtained, with the maximum values of um and Xm at 0.0970 h−1 and 21.8631% of dry matter weight loss, respectively. A good-fit curvilinear regression model was achieved to describe the change pattern of total carbohydrate concentration (R2 = 0.9910), and the biodegradation pattern of free gossypol (R2 = 0.9825). These models could be used to predict the fermentation course by C. tropicalis ZAU-1 under solid-state fermentation. 相似文献
6.
Synthesis of (R,S)-[4-11C]baclofen via Michael addition of nitromethane labeled with short-lived 11C
Koichi Kato Ming-Rong Zhang Kazutoshi Suzuki 《Bioorganic & medicinal chemistry letters》2009,19(21):6222-6224
The synthesis of (R,S)-[4-11C]baclofen, the first 11C-labeled GABAB agonist, was demonstrated via Michael addition of nitro[11C]methane as a key step. A tetrabutylammonium fluoride promoted Michael addition of nitro[11C]methane to methyl p-chlorocinnamate, followed by the nitro-group reduction in the presence of NiCl2 and NaBH4 in aqueous MeOH and alkaline hydrolysis yielded (R,S)-[4-11C]baclofen in 36.4 ± 1.8% radiochemical conversion in three steps within 20 min. 相似文献
7.
Xia Wang Yan Li Winnie Deuther-Conrad Fang Xie Xin Chen Meng-Chao Cui Xiao-Jun Zhang Jin-Ming Zhang Jörg Steinbach Peter Brust Bo-Li Liu Hong-Mei Jia 《Bioorganic & medicinal chemistry》2013,21(1):215-222
We report the synthesis and evaluation of a series of fluoro-oligo-ethoxylated 4-benzylpiperazine derivatives as potential σ1 receptor ligands. In vitro competition binding assays showed that 1-(1,3-benzodioxol-5-ylmethyl)-4-(4-(2-fluoroethoxy)benzyl)piperazine (6) exhibits low nanomolar affinity for σ1 receptors (Ki = 1.85 ± 1.59 nM) and high subtype selectivity (σ2 receptor: Ki = 291 ± 111 nM; Kiσ2/Kiσ1 = 157). [18F]6 was prepared in 30–50% isolated radiochemical yield, with radiochemical purity of >99% by HPLC analysis after purification, via nucleophilic 18F? substitution of the corresponding tosylate precursor. The log DpH 7.4 value of [18F]6 was found to be 2.57 ± 0.10, which is within the range expected to give high brain uptake. Biodistribution studies in mice demonstrated relatively high concentration of radiotracers in organs known to contain σ1 receptors, including the brain, lungs, kidneys, heart, and spleen. Administration of haloperidol 5 min prior to injection of [18F]6 significantly reduced the concentration of radiotracers in the above-mentioned organs. The accumulation of radiotracers in the bone was quite low suggesting that [18F]6 is relatively stable to in vivo defluorination. The ex vivo autoradiography in rat brain showed high accumulation of radiotracers in the brain areas known to possess high expression of σ1 receptors. These findings suggest that [18F]6 is a suitable radiotracer for imaging σ1 receptors with PET in vivo. 相似文献
8.
There is a world-wide trend for deteriorating water quality and light levels in the coastal zone, and this has been linked to declines in seagrass abundance. Localized management of seagrass meadow health requires that water quality guidelines for meeting seagrass growth requirements are available. Tropical seagrass meadows are diverse and can be highly dynamic and we have used this dynamism to identify light thresholds in multi-specific meadows dominated by Halodule uninervis in the northern Great Barrier Reef, Australia. Seagrass cover was measured at ∼3 month intervals from 2008 to 2011 at three sites: Magnetic Island (MI) Dunk Island (DI) and Green Island (GI). Photosynthetically active radiation was continuously measured within the seagrass canopy, and three light metrics were derived. Complete seagrass loss occurred at MI and DI and at these sites changes in seagrass cover were correlated with the three light metrics. Mean daily irradiance (Id) above 5 and 8.4 mol m−2 d−1 was associated with gains in seagrass at MI and DI, however a significant correlation (R = 0.649, p < 0.05) only occurred at MI. The second metric, percent of days below 3 mol m−2 d−1, correlated the most strongly (MI, R = −0.714, p < 0.01 and DI, R = −0.859, p = <0.001) with change in seagrass cover with 16–18% of days below 3 mol m−2 d−1 being associated with more than 50% seagrass loss. The third metric, the number of hours of light saturated irradiance (Hsat) was calculated using literature-derived data on saturating irradiance (Ek). Hsat correlated well (R = 0.686, p < 0.01; and DI, R = 0.704, p < 0.05) with change in seagrass abundance, and was very consistent between the two sites as 4 Hsat was associated with increases in seagrass abundance at both sites, and less than 4 Hsat with more than 50% loss. At the third site (GI), small seasonal losses of seagrass quickly recovered during the growth season and the light metrics did not correlate (p > 0.05) with change in percent cover, except for Id which was always high, but correlated with change in seagrass cover. Although distinct light thresholds were observed, the departure from threshold values was also important. For example, light levels that are well below the thresholds resulted in more severe loss of seagrass than those just below the threshold. Environmental managers aiming to achieve optimal seagrass growth conditions can use these threshold light metrics as guidelines; however, other environmental conditions, including seasonally varying temperature and nutrient availability, will influence seagrass responses above and below these thresholds. 相似文献
9.
Vanessa Dutra Silva Jeferson Schneider Carletto Eduardo Carasek Boris Ugarte Stambuk Maria da Graça Nascimento 《Process Biochemistry》2013,48(8):1159-1165
The α,β-unsaturated carbonyl compound (4S)-(+)-carvone was selectively reduced to (1R,2R,4S)-iso-dihydrocarveol using baker's yeasts. The conversion of the bioreduction reaction was monitored using a green hollow-fiber liquid–liquid–liquid microextraction (HF-LLLME) technique. Several parameters which may affect the bioreduction of (4S)-(+)-carvone, such as temperature, time, substrate/enzyme ratio, pH and buffer concentration, were evaluated. The effect of some additives, such as trehalose, DMSO and the ionic liquid [BMIm][PF6], was also studied. The (1R,2R,4S)-iso-dihydrocarveol was recovered with 52.7% conversion and diastereoisomeric excess >99% after 48 h of reaction at 40 °C in an aqueous monophasic system, with 0.1 mol L?1 buffer concentration (pH 7.5) and a substrate/yeast cell mass ratio of 8.0 mg g?1. The HF-LLLME microextraction technique allowed the optimization of the reaction with a reduction of over 99.5% in relation to the use of organic solvents. 相似文献
10.
《Inorganica chimica acta》2005,358(14):4394-4402
Combining dimethylphosphinylethanols HO(R1R2)CCH2PMe2 (1: R1 = R2 = C6H5; 2: R1 = R2 = 4-OMe–C6H4; 5: R1 = R2 = 4-NMe2–C6H4) with methyl(methoxo)(trimethylphosphine)nickel gave mononuclear methyl(trimethylphosphine)nickel(chelate) compounds 7–9. Ligand 6 (R1 = Me, R2 = 4-OMe–C6H5) afforded a dinuclear methylnickel compound 14. By reacting (TMEDA)lithium-dimethylphosphinylmethanide with ketones OC(R1R2), the dimethylphosphinylethanols HO(R1R2)CCH2PMe2 (3: R1R2 = 9-fluorenyl; 4: R1 = H, R2 = C6H5) were synthesized as prechelate ligands. Under otherwise similar conditions, the fluorenyl substituted anion in 3 gave rise to a mononuclear complex 10 which was found to act as a source of trimethylphosphine forming dinuclear 11 and at the same time to act as an acceptor of trimethylphosphine forming pentacoordinate 10 · PMe3. Ni(COD)(PMe3)2 was used as a scavenger of PMe3 in converting 8 or 9 to the dinuclear methylnickel compounds 12 and 13, respectively. Modifying the P,O chelating unit of a methyl nickel compound by introducing 2-phosphinylethanolato ligands leads to novel single-component catalysts for ethene oligomerization showing moderate reactivity and thermal stability. 相似文献
11.
Maria Galuppo Renato Iori Gina Rosalinda De Nicola Placido Bramanti Emanuela Mazzon 《Bioorganic & medicinal chemistry》2013,21(17):5532-5547
This study was focused on the possible neuroprotective role of (RS)-glucoraphanin, bioactivated with myrosinase enzyme (bioactive RS-GRA), in an experimental mouse model of Parkinson’s disease (PD). RS-GRA is one of the most important glucosinolates, a thiosaccharidic compound found in Brassicaceae, notably in Tuscan black kale seeds.RS-GRA was extracted by one-step anion exchange chromatography, further purified by gel-filtration and analyzed by HPLC. Following, pure RS-GRA was characterized by 1H and 13C NMR spectrometry and the purity was assayed by HPLC analysis of the desulfo-derivative according to the ISO 9167-1 method. The obtained purity has been of 99%.To evaluate the possible pharmacological efficacy of bioactive RS-GRA (administrated at the dose of 10 mg/kg, ip +5 μl/mouse myrosinase enzyme), C57BL/6 mice were used in two different sets of experiment (in order to evaluate the neuroprotective effects in different phases of the disease), according to an acute (2 injections · 40 mg/kg MPTP) and a sub-acute (5 injections · 20 mg/kg MPTP) model of PD.Behavioural test, body weight changes measures and immunohistochemical localization of the main PD markers were performed and post-hoc analysis has shown as bioactive RS-GRA is able to reduce dopamine transporter degradation, tyrosine hydroxylase expression, IL-1β release, as well as the triggering of neuronal apoptotic death pathway (data about Bax/Bcl-2 balance and dendrite spines loss) and the generation of radicalic species by oxidative stress (results focused on nitrotyrosine, Nrf2 and GFAP immunolocalization). These effects have been correlated with the release of neurotrophic factors, such as GAP-43, NGF and BDNF, that, probably, play a supporting role in the neuroprotective action of bioactive RS-GRA. Moreover, after PD-induction mice treated with bioactive RS-GRA are appeared more in health than animals that did not received the treatment both for phenotypic behaviour and for general condition (movement coordination, presence of tremors, nutrition).Overall, our results suggest that bioactive RS-GRA can protect neurons against the neurotoxicity involved in PD via an anti-apoptotic/anti-inflammatory action. 相似文献
12.
According to the green wave hypothesis, herbivores follow the flush of spring growth of forage plants during their spring migration to northern breeding grounds. In this study we compared two green wave indices for predicting the timing of the spring migration of avian herbivores: the satellite-derived green wave index (GWI), and an index of the rate of acceleration in temperature (GDDjerk). The GWI was calculated from MODIS normalized difference vegetation index (NDVI) satellite imagery and GDDjerk from gridded temperature data using products from the global land data assimilation system (GLDAS). To predict the timing of arrival at stopover and breeding sites, we used four years (2008–2011) of tracking data from 12 GPS-tagged barnacle geese, a long-distance herbivorous migrant, wintering in the Netherlands, breeding in the Russian Arctic. The stopover and breeding sites for these birds were identified and the relations between date of arrival with the date of 50% GWI and date of peak GDDjerk at each site were analyzed using mixed effect linear regression. A cross-validation method was used to compare the predictive accuracy of the GWI and GDDjerk indices. Significant relationships were found between the arrival dates at the stopover and breeding sites for the dates of 50% GWI as well as the peak GDDjerk (p < 0.01). The goose arrival dates at both stopover and breeding sites were predicted more accurately using GWI (R2cv = 0.68, RMSDcv = 5.9 and R2cv= 0.71, RMSDcv = 3.9 for stopover and breeding sites, respectively) than GDDjerk. The GDDjerk returned a lower accuracy for prediction of goose arrival dates at stopover ( R2cv = 0.45, RMSDcv = 7.79) and breeding sites (R2cv = 0.55, RMSDcv = 4.93). The positive correlation between the absolute residual values of the GDDjerk model and distance to the breeding sites showed that this index is highly sensitive to latitude. This study demonstrates that the satellite-derived green wave index (GWI) can accurately predict the timing of goose migration, irrespective of latitude and therefore is suggested as a reliable green wave index for predicting the timing of avian herbivores spring migration. 相似文献
13.
《Aquatic Botany》2005,81(4):326-342
The effects of NH4+ or NO3− on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g−1 d−1), whereas the growth rate of Glyceria was 16% higher in NH4+-N cultures than in NO3−-N cultures (mean = 66.7 and 57.4 mg g−1 d−1 of NH4+ and NO3− treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH4+ cultures than in NO3− cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH4+ treated plants by 16%. The tissue NH4+ concentration (mean = 1.6 μmol g fresh wt−1) was not affected by N treatment, whereas NO3− contents were higher in NO3− (mean = 1.5 μmol g fresh wt−1) than in NH4+ (mean = 0.4 μmol g fresh wt−1) treated plants. In Phragmites, NH4+ (mean = 1.6 μmol g fresh wt−1) and NO3− (mean = 0.2 μmol g fresh wt−1) contents were not affected by the N regime. Species did not differ in NH4+ (mean = 56.5 μmol g−1 root dry wt h−1) and NO3− (mean = 34.5 μmol g−1 root dry wt h−1) maximum uptake rates (Vmax), and Vmax for NH4+ uptake was not affected by N treatment. The uptake rate of NO3− was low in NH4+ treated plants, and an induction phase for NO3− was observed in NH4+ treated Phragmites but not in Glyceria. Phragmites had low Km (mean = 4.5 μM) and high affinity (10.3 l g−1 root dry wt h−1) for both ions compared to Glyceria (Km = 6.3 μM, affinity = 8.0 l g−1 root dry wt h−1). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH4+-N source may participates in the observed success of Glyceria at NH4+ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites. 相似文献
14.
Kun-Eek Kil Zhaoda Zhang Kimmo Jokivarsi Chunyu Gong Ji-Kyung Choi Sreekanth Kura Anna-Liisa Brownell 《Bioorganic & medicinal chemistry》2013,21(19):5955-5962
N-(Chloro-3-methoxyphenyl)-2-picolinamide (3, ML128, VU0361737) is an mGlu4 positive allosteric modulator (PAM), which is potent and centrally penetrating. 3 is also the first mGlu4 PAM to show efficacy in a preclinical Parkinson disease model upon systemic dosing. As a noninvasive medical imaging technique and a powerful tool in neurological research, positron emission tomography (PET) offers a possibility to investigate mGlu4 expression in vivo under physiologic and pathological conditions. We synthesized a carbon-11 labeled ML128 ([11C]3) as a PET radiotracer for mGlu4, and characterized its biological properties in Sprague Dawley rats. [11C]3 was synthesized from N-(4-chloro-3-hydroxyphenyl)-2-picolinamide (2) using [11C]CH3I. Total synthesis time was 38 ± 2.2 min (n = 7) from the end of bombardment to the formulation. The radioligand [11C]3 was obtained in 27.7 ± 5.3% (n = 5) decay corrected radiochemical yield based on the radioactivity of [11C]CO2. The radiochemical purity of [11C]3 was >99%. Specific activity was 188.7 ± 88.8 GBq/mol (n = 4) at the end of synthesis (EOS).PET images were conducted in 20 normal male Sprague Dawley rats including 11 control studies, 6 studies blocking with an mGlu4 modulator (4) to investigate specificity and 3 studies blocking with an mGlu5 modulator (MTEP) to investigate selectivity. These studies showed fast accumulation of [11C]3 (peak activity between 1–3 min) in several brain areas including striatum, thalamus, hippocampus, cerebellum, and olfactory bulb following with fast washout. Blocking studies with the mGlu4 modulator 4 showed 22–28% decrease of [11C]3 accumulation while studies of selectivity showed only minor decrease supporting good selectivity over mGlu5. Biodistribution studies and blood analyses support fast metabolism. Altogether this is the first PET imaging ligand for mGlu4, in which the labeled ML128 was used for imaging its in vivo distribution and pharmacokinetics in brain. 相似文献
15.
《Bioorganic & medicinal chemistry letters》2014,24(23):5418-5422
We present the synthesis and biological evaluation of a collection of s-triazine derivatives as a novel scaffold of compounds with the capability to inhibit the PGE2 production in LPS-induced RAW 264.7 macrophage cells. A total of 12 derivatives were synthesized and assayed for PGE2 reduction at 10 μM concentration. Two compounds (7b and 7i) exhibiting >90% inhibition of PGE2 production were found to have IC50 values of 5.76 and 5.52 μM, respectively. They were counter screened for inhibition on COX-2 activity in a cell free assay. Specifically, compound 7i (R1 = 4-Bn-Ph, R2 = Cl, R3 = Ph, R5 = CO2Me) was highly active in cells while maintaining little COX-2 inhibition (∼0% at 10 μM). Molecular docking study provides the possibility that compound 7i could inhibit PGE2 production by blocking the PGH2 binding site of mPGES-1 instead of COX-2 enzyme. Based on this result, our synthetic efforts will focus on intensive structure–activity relationship (SAR) study of s-triazine scaffold to discovery a potential PGE2 synthesis inhibitor. 相似文献
16.
《Process Biochemistry》2007,42(3):363-373
Methane (CH4) and nitrous oxide (N2O) are important greenhouse gases, because of their contribution to the global greenhouse effect. The present study assessed emissions of N2O and CH4 from constructed wetland microcosms, planted with Phragmites australis and Zizania latifolia, when treating wastewater under different biological oxygen demand (BOD) concentration conditions. The removal rate was 95% for BOD and more than 80% for COD in all three pollutant concentrations, both plants’ removal rates of pollutants were at almost the same level, and both were found to resist BOD concentrations as high as 200 mg L−1. When BOD concentrations fell below 200 mg L−1, the soil plant units reached an average of 80–92% T-N and T-P removal rates; however, as the concentrations increased to 200 mg mg L−1 or when during the initial phases of winter, the removal rates for T-N and T-P decreased to less than 70%. With NH3-N removal, the influences of BOD concentrations and air temperature were more obvious. When BOD concentrations increased to 100 mg L−1 after October, an obvious decrease in NH3-N removal was detected; almost no nitrification occurred beginning in December at BOD concentrations of 200 mg mg L−1. N2O and CH4 emissions showed obvious seasonal changes; higher emissions were observed with higher BOD concentrations, especially among Z. latifolia units. The enumeration of methane-oxidizing bacteria and methane-producing bacteria was also conducted to investigate their roles in impacting methane emissions and their relationships with plant species. The pollutant purification potentials of P. australis and Z. latifolia plant units during wastewater treatment of different pollutant concentrations occurred at almost the same levels. The nutrient outflow and methane flux were consistently higher with Z. latifolia units and higher concentrations of BOD. The more reductive status and higher biomass of methanogens may be the reason for the lower nitrification and higher CH4 emissions observed with Z. latifolia units and higher concentration systems. The Z. latifolia root system is shallow, and the activity of methanotrophs is primarily confined to the upper portion of the soil. However, the root system of P. australis is deeper and can oxidize methane to a greater depth. This latter structure is more favorable as it is better for reducing methane emissions from P. australis soil plant systems. 相似文献
17.
Vattoly J. Majo Matthew S. Milak Jaya Prabhakaran Pratap Mali Lyudmila Savenkova Norman R. Simpson J. John Mann Ramin V. Parsey J. S. Dileep Kumar 《Bioorganic & medicinal chemistry》2013,21(17):5598-5604
The 5-HT1AR partial agonist PET radiotracer, [11C]CUMI-101, has advantages over an antagonist radiotracer as it binds preferentially to the high affinity state of the receptor and thereby provides more functionally meaningful information. The major drawback of C-11 tracers is the lack of cyclotron facility in many health care centers thereby limiting widespread clinical or research use. We identified the fluoroethyl derivative, 2-(4-(4-(2-(2-fluoroethoxy)phenyl)piperazin-1-yl)butyl)-4-methyl-1,2,4-triazine-3,5(2H,4H)dione (FECUMI-101) (Ki = 0.1 nM; Emax = 77%; EC50 = 0.65 nM) as a partial agonist 5-HT1AR ligand of the parent ligand CUMI-101. FECUMI-101 is radiolabeled with F-18 by O-fluoroethylation of the corresponding desmethyl analogue (1) with [18F]fluoroethyltosylate in DMSO in the presence of 1.6 equiv of K2CO3 in 45 ± 5% yield (EOS). PET shows [18F]FECUMI-101 binds specifically to 5-HT1AR enriched brain regions of baboon. The specificity of [18F]FECUMI-101 binding to 5-HT1AR was confirmed by challenge studies with the known 5-HT1AR ligand WAY100635. These findings indicate that [18F]FECUMI-101 can be a viable agonist ligand for the in vivo quantification of high affinity 5-HT1AR with PET. 相似文献
18.
《Bioorganic & medicinal chemistry》2014,22(24):6893-6898
The 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced edema model in mice determined the anti-inflammatory activities in vivo of argentatins A, B and D, the main cycloartenol-type triterpenes present in Parthenium argentatum. Our results showed that argentatin B (ED50 = 1.5 × 10−4 mmol/ear) and argentatin A (ED50 = 2.8 × 10−4 mmol/ear) were more potent anti-inflammatory agents than indomethacin (ED50 = 4.5 × 10−4 mmol/ear), the reference drug. Based on these findings, we decided to evaluate 13 derivatives of argentatins A and B. All the derivatives showed anti-inflammatory activity in the TPA-induced edema model in mice. The most active compound was 25-nor-cycloart-3, 16-dione-17-en-24-oic acid, obtained from argentatin A (ED50 = 1.4 × 10−4 mmol/ear). Argentatin B was assayed as inhibitor of COX-2 activity one of the key enzymes involved in the TPA assay. The results showed that argentatin B at 15 μM doses inhibited 77% COX-2 activity. Docking studies suggest that argentatin B interacts with Arg 120, a key residue for COX-2 activity. 相似文献
19.
Wenmin Chen Peng Zhan Erik De Clercq Christophe Pannecouque Jan Balzarini Xin Jiang Xinyong Liu 《Bioorganic & medicinal chemistry》2013,21(22):7091-7100
A series of N2,N4-disubstituted-1,1,3-trioxo-2H,4H-pyrrolo[1,2-b][1,2,4,6]thiatriazine derivatives (PTTDs) was designed and synthesized by a facile route. The biological assay results showed that five most potent compounds displayed inhibitory activity against HIV-1 at low micromolar concentrations (EC50 = 5.1–8.9 μM). Structure–activity relationship analysis indicated that N2-(3-halogenated-benzyl) analogues were more potent than N2-(unsubstituted-benzyl) analogues. The N4-substitutions contributed to the antiviral activity in the following order: 2-/3-cyano substituted benzyl > 2-/3-halogenated benzyl > non-substituted benzyl > 4-halogenated benzyl. Docking studies of the representative compound revealed the binding conformation of these compounds and provided critical insights for the further development of PTTD analogues. 相似文献
20.
Joel N. Schrauben Dong Guo John L. McCracken James K. McCusker 《Inorganica chimica acta》2008,361(12-13):3539-3547
The bimetallic [M1M2(tren)2(CAn?)]m+ series, where M = GaIII or CrIII and CA is the chloranilate ligand which can take on diamagnetic (CAcat,cat)4? or paramagnetic (CAsq,cat)3? forms, comprises an electronically diverse series of compounds ranging from the closed-shell [Ga2(tren)2(CAcat,cat)]2+ to the S = 5/2 ground state of [Cr2(tren)2(CAsq,cat)]3+. This report deals with the interpretation of the EPR and ENDOR spectra of [Ga2(tren)2(CAsq,cat)](BPh4)2(BF4) (2) and the related derivative [Ga2(tren)2(DHBQ)](BPh4)2(BF4) (2a) (where DHBQ is the fully deprotonated trianionic form of 2,5-dihydroxy-1,4-benzoquinone) in an effort to further characterize the electronic structure of this radical species. The X-band (~9.5 GHz) EPR spectrum of complex 2 acquired in a butyronitrile/propionitrile glass at 4 K reveals a rhombic g-tensor with gxx = 2.0100, gyy = 2.0097, and gzz = 2.0060 with hyperfine interactions due to spin delocalization onto the two Ga nuclei (axx = 4.902 G, ayy = 4.124 G, azz = 3.167 G); the origin of the hyperfine coupling was confirmed by analysis of the room temperature spectra of complexes 2 and 2a. The low-temperature spectrum of complex 2 also indicates the presence of a triplet electronic state characterized by a g-value of 2.009 and axial zero-field splitting of D = 150 G (0.012 cm?1) as determined from measurements carried out at both X- and W-band (~95 GHz) frequencies. This triplet state is believed to arise due to a weak intermolecular Heisenberg exchange interaction between two aggregating complexes. ENDOR measurements on complex 2a at 20 K allowed for a determination of the magnitude of hyperfine coupling to the protons associated with the radical bridge as well as providing a rare example of an ENDOR signal arising from coupling to a gallium nucleus. Finally, these results were combined with literature data on the free semiquinone form of the bridging ligand in order to assess the extent to which density functional theory can predict unpaired spin density distribution in a complex molecule of this type. Although differences between theory and experiment were noted, DFT was able to provide a reasonably accurate picture of the electronic structure of this system as well as provide insight into the spin polarization mechanism(s) responsible for the observed hyperfine interactions. 相似文献