共查询到20条相似文献,搜索用时 15 毫秒
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Khodayar Gholivand Mohammad Abdollahi Fresia Mojahed Ahlam Madani Alizadehgan Gholamreza Dehghan 《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):566-576
Eight newly synthesized carbacylamidophosphates with the general formula RC(O)NHP(O)Cl2 with R = pCl–C6H4 1a, pBr–C6H4 2a, C6H5 3a, and pMe–C6H4 4a and RC(O)NHP(O)(NC4H8O)2 R = pCl–C6H4 1b, pBr–C6H4 2b, C6H5 3b, pMe–C6H4 4b, were selected to compare the inhibition kinetic parameters, IC50, Ki, kp and KD, on human erythrocyte acetylcholinesterase (hAChE) and bovine serum butyrylcholinesterase (BuChE), Also, the in vivo inhibition potency of compound 2a, 2b and 3a, were studied. The data demonstrates that compound 2a and compound 2b are the potent sensitive as AChE and BuChE inhibitors respectively, and the inhibition of hAChE is about 10-fold greater than that of BuChE. 相似文献
3.
Type 1 pili, anchored to the outer membrane protein FimD, enable uropathogenic Escherichia coli to attach to host cells. During pilus biogenesis, the N-terminal periplasmic domain of FimD (FimD(N)) binds complexes between the chaperone FimC and pilus subunits via its partly disordered N-terminal segment, as recently shown for the FimC-FimH(P)-FimD(N) ternary complex. We report the structure of a new ternary complex (FimC-FimF(t)-FimD(N)) with the subunit FimF(t) instead of FimH(p). FimD(N) recognizes FimC-FimF(t) and FimC-FimH(P) very similarly, predominantly through hydrophobic interactions. The conserved binding mode at a "hot spot" on the chaperone surface could guide the design of pilus assembly inhibitors. 相似文献
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Human non-pancreatic secretory phospholipase A2 (hnpsPLA2) is a group IIA phospholipase A2 which plays an important role in the innate immune response. This enzyme was found to exhibit bactericidal activity toward Gram-positive bacteria, but not Gram-negative ones. Though native hnpsPLA2 is active over a broad pH range, it is only highly active at alkaline conditions with the optimum activity pH of about 8.5. In order to make it highly active at neutral pH, we have obtained two hnpsPLA2 mutants, Glu89Lys and Arg100Glu that work better at neutral pH in a previous study. In the present study, we tested the bactericidal effects of the native hnpsPLA2 and the two mutants. Both native hnpsPLA2 and the two mutants exhibit bactericidal activity toward Gram-positive bacteria. Furthermore, they can also kill Escherichia coli, a Gram-negative bacterium. The two mutants showed better bactericidal activity for E. coli at neutral pH than the native enzyme, which is consistent with the enzyme activities. As hnpsPLA2 is highly stable and biocompatible, it may provide a promising therapy for bacteria infection treatment or other bactericidal applications. 相似文献
5.
Luth Robin P Germain P Lecomte M Landrain B Li Y Cluzeau D 《Bioresource technology》2011,102(4):3679-3686
Treatment of liquid manure can result in the production of ammonia, nitrous oxide and methane. Earthworms mix and transform nitrogen and carbon without consuming additional energy. The objective of this paper is to analyse whether earthworms modify the emissions of NH3, N2O, CH4 and CO2 during vermifiltration of pig slurry.The experiment used mesocosms of around 50 L, made from a vermifilter treating the diluted manure of a swine house. Three levels of slurry were added to the mesocosms, with or without earthworms, during one month, in triplicate. Earthworm abundance and gas emissions were measured three and five times, respectively.There was a decrease in emissions of ammonia and nitrous oxide and a sink of methane in treatments with earthworms. We suggest that earthworm abundance can be used as a bioindicator of low energy input, and low greenhouse gas and ammonia output in systems using fresh slurry with water recycling. 相似文献
6.
利用ADP和放射性磷直接合成ATP的方法,研究了无机磷(Pi)和叠氮钠对猪心线粒体ATP合成酶(F1FO-ATPase)ATP合成活性的影响.结果发现无机磷除作为合成ATP的底物参与F1FO-ATPase的合成反应外,还对F1FO-ATPase的合成活性呈现抑制作用,在1 mmol/L ADP存在时,随着Pi浓度由0.01~10 mmol/L增加,抑制合成作用越来越强.与叠氮钠在低浓度时(小于1 mmol/L)只抑制ATP水解,不影响ATP合成的观点不同.实验结果显示0.1 mmol/L叠氮钠表观激活F1FO-ATPase的ATP合成活性,且激活程度与反应体系中所加Pi的浓度呈负相关.当固定Pi浓度(0.1 mmol/L)后,随着叠氮钠浓度的增加表观激活程度也在变化,叠氮钠与磷浓度相等时表观激活程度最大,直至叠氮钠浓度接近0.5 mmol/L时,开始呈现表观抑制现象,叠氮钠浓度高于1 mmol/L之后,就出现解偶联现象. 相似文献
7.
Frasch WD 《Journal of bioenergetics and biomembranes》2000,32(5):539-546
The Mg2+ dependent asymmetry of the F1-ATPase catalytic sites leads to the differences in affinity for nucleotides and is an essential component of the binding-change mechanism. Changes in metal ligands during the catalytic cycle responsible for this asymmetry were characterized by vanadyl (V
IV + O)2+, a functional surrogate for Mg2+. The 51V-hyperfine parameters derived from EPR spectra of VO2+ bound to specific sites on F1 provide a direct probe of the metal ligands. Site-directed mutations of metal ligand residues cause measurable changes in the 51V-hyperfine parameters of the bound VO2+, thereby providing a means to identification. Initial binding of the metal–nucleotide to the low-affinity catalytic site conformation results in metal coordination by hydroxyl groups from the P-loop threonine and catch-loop threonine. Upon conversion to the high-affinity conformation, carboxyl groups from the Walker homology B aspartate and MF1E197 become ligands in lieu of the hydroxyl groups. 相似文献
8.
Assessing the Impact of Advected African Dust on Air Quality and Health in the Eastern United States
Joseph M. Prospero 《人类与生态风险评估》1999,5(3):471-479
Large quantities of African dust are carried into the southeastern United States each summer with concentrations typically in the range of 10 to 100?µg m?3. Because approximately one-third to one-half of the dust mass is in the size range under 2.5?µm diameter, the advection of African dust has implications for the EPA's newly implemented standard for PM2.5 particulate matter and for the assessment of human health effects. It will be difficult to assess the impact of African dust events on air quality because they occur during the summer (maximum in July) when photochemical pollution events are frequent and intense in the eastern United States. Indeed, the presence of dust could affect the evolution of photochemical dust events. In order to assess the role of African dust in air quality in the United States, it will be necessary to develop a set of diagnostic indicators; it appears that dust mineralogy and elemental composition might be useful for this purpose. Various satellite products can be used to characterize the spatial coverage of dust events and, when coupled with meteorological tools, to predict impact regions. 相似文献
9.
Brian D. Cain 《Journal of bioenergetics and biomembranes》2000,32(4):365-371
The a and b subunits constitute the stator elements in the F0 sector of F1F0-ATP synthase.Both subunits have been difficult to study by physical means, so most of the information onstructure and function relationships in the a and b subunits has been obtained using mutagenesisin combination with biochemical methods. These approaches were used to demonstrate thatthe a subunit in association with the ring of c subunits houses the proton channel throughF1F0-ATP synthase. The map of the amino acids contributing to the proton channel is probablycomplete. The two b subunits dimerize, forming an extended flexible unit in the peripheralstalk linking the F1 and F0 sectors. The unique characteristics of specific amino acid substitutionsaffecting the a and b subunits suggested differential effects on rotation during F1F0-ATPaseactivity. 相似文献
10.
Leaf carbon isotope ratios of plants from a subtropical monsoon forest 总被引:12,自引:0,他引:12
Summary Carbon isotope ratios were used to survey the distribution of photosynthetic pathways among taxa, the relationship between photosynthetic pathway and habitat light levels, and the relationship between intercellular CO2 levels of C3 plants and habitat light levels within a subtropical monsoon forest in southern China. Of 128 species, most (94) possessed the C3 photosynthetic pathway; 33 species possessed the C4 pathway and all of these were restricted to high light locations. There was one epiphytic CAM species. The C3 species were classified as occurring in open, intermediate, and closed canopy sites. Among C3 species, carbon isotope ratios tended to become more negative with decreasing light availability in the habitat.C.I.W.D.P.B. Pub no 931 相似文献
11.
Large-conductance calcium and voltage-dependent potassium (BKCa) channel is an important determinant of vascular tone. It is activated by hydrogen peroxide (H2O2) which occurs in various physiological and pathological processes. However, the regulation mechanism is not fully understood. In the present study, the mSlo in the presence or absence of hβ1 were cotransfected with the PTENwt, PTENC124S, PTENG129E in HEK 293 cells. Typical BKCa channel currents could be recorded in cell-attached configurations. We found that PTENwt reduced the H2O2-induced BKCa channel activation during the initial 10 min treatment. In contrast, coexpression with catalytically inactive PTENC124S/PTENG129E mutants that lack lipid phosphatase activity produced no regulation on the H2O2-induced BKCa channel activation. These results demonstrated that PTEN regulated the H2O2-induced BKCa channel activation through phosphatidylinositol 3-phosphatse. However, the inhibitory effect of PTEN on the H2O2-induced BKCa channel activation was attenuated when cells were treated with H2O2 at concentrations higher than 100 μM or at 100 μM for long-term treatment. In addition, the p-AKT expression level in PTENwt overexpressing cells was lower than that in control cells, and the increase of cytoplasmic free calcium concentration ([Ca2+]i) induced by H2O2 was also inhibited. These findings may elucidate a new mechanism for H2O2-induced BKCa channel activation and provide some evidences for the role of PTEN on vasodilation induced by H2O2. 相似文献
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The capability to reassimilate CO2 originating from intracellular decarboxylating processes connected with the photorespiratory glycolate pathway and-or decarboxylation of C4 acids during C4 photosynthesis has been investigated with four species of the genus Flaveria (Asteraceae). The C3-C4 intermediate species F. pubescens and F. anomala reassimilated CO2 much more efficiently than the C3 species F. cronquistii and, with respect to this feature, behaved similarly to the C4 species F. trinervia. Therefore, under atmospheric conditions the intermediate species photorespired with rates only between 10–20% of that measured with F. cronquistii. At low oxygen concentrations (1,5%) the reassimilation potential of F. anomala approached that of F. trinervia and was distinct from that found with F. pubescens. The data are discussed with respect to a possible sequence of events during evolution of C4 photosynthesis. If compared with related data for C3-C4 intermediate species from other genera they support the hypothesis that, during evolution of C4 photosynthesis, an efficient capacity for CO2 reassimilation evolved prior to a CO2-concentrating mechanism.Abbreviations C3, C4
assimilated CO2 initially found in 3-phosphoglycerate (C3) or malate and aspartate (C4)
-
D
reassimilation coefficient
-
R
n
, R
t
net, total CO2 evolution as measured with 0.03 and 3% CO2, respectively
- RuBP
ribulose-1,5-bisphosphate
- TPS
true photosynthesis 相似文献
13.
Schäfer I Rössle M Biuković G Müller V Grüber G 《Journal of bioenergetics and biomembranes》2006,38(2):83-92
The first low-resolution shape of subunit F of the A1AO ATP synthase from the archaeon Methanosarcina mazei Gö1 in solution was determined by small angle X-ray scattering. Independent to the concentration used, the protein is monomeric and has an elongated shape, divided in a main globular part with a length of about 4.5 nm, and a hook-like domain of about 3.0 nm in length. The subunit-subunit interaction of subunit F inside the A1AO ATP synthase in the presence of 1-ethyl-3-(dimethylaminopropyl)-carbodiimide EDC was studied as a function of nucleotide binding, demonstrating movements of subunits F relative to the nucleotide-binding subunit B. Furthermore, in the intact A1AO complex, crosslinking of subunits D-E, A-H and A-B-D was obtained and the peptides, involved, were analyzed by MALDI-TOF mass spectrometry. Based on these data the surface of contact of B-F could be mapped in the high-resolution structure of subunit B of the A1AO ATP synthase. 相似文献
14.
Hydrogen peroxide (H2O2)-induced aggregation of calf platelets and its modification by agents with specific properties were characterized employing
a spectrophotometric assay. An Arrhenius activation energy of 20 ± 1 kcal/mol was found in the temperature range of 25‡-36‡C.
Rate inhibition occurred on either side of this temperature range, and under anaerobic conditions. Exogenous Ca2+ ions were not required but Ca2+ ions, at 1 mM-concentration, optimally increased rates and extent of aggregation at suboptimal H2O2 concentrations but only extent of aggregation at optimal H2O2 concentrations. Ba2+, Sr2+, Cd2+, Mn2+ and Ni2+ ions (1 mM) and Zn2+, Pb2+ and Hg2+ ions (10 mM) were inhibitory. The cyclo-oxygenase inhibitor, indomethacin (10-30 mM) exerted only mild inhibition by a competitive
mechanism. Another cyclo-oxygenase inhibitor, aspirin, functioned to increase aggregation. Ligands acting directly at the
prostaglandin H2/thromboxane A, receptor (5Z. 9, 11, 13E, 15(S) 15-hydroxy 9(11) epoxy methano prosta 5, 13-dien-1-oic acid, pinane thromboxane
A2, arachidonic acid, eicosapentaenoic acid, and N-ethylmaleimide) functioned as competitive inhibitors. Another platelet-activating
sulphydryl reagent, thimerosal, also inhibited competitively while the protein kinase C inhibitor, sphingosine, and the protein
kinase C modulator, Zn2+ ions, inhibited by different mechanisms. The results indicate direct action of H2O2 at the prostaglandin H2/thromboxane A2 receptor, possibly its sulphydryls, to activate the protein kinase C pathway, independently of cyclo-oxygenase products.
The results underscored the power of the kinetic approach for investigating mechanisms of platelet activation. 相似文献
15.
Bennett T. Farmer II Luciano Müller Edward P. Nikonowicz Arthur Pardi 《Journal of biomolecular NMR》1994,4(1):129-133
Summary A set of three 3D (1H, 13C, 15N) triple-resonance correlation experiments has been designed to provide H1-H8 intraresidue sugar-to-base correlations in purines in an unambiguous and efficient manner. Together, the HsCsNb, HsCs(N)bCb, and HbNbCb experiments correlate the H1 sugar proton to the H8 proton of the attached base by means of the {H1, C1, N9, C8, H8} heteronuclear scalar coupling network. The assignment strategy presented here allows for unambiguous H1-H8 intraresidue correlations, provided that no two purines have both the same H1 and C1 chemical shifts and the same C8 and N9 chemical shifts. These experiments have yielded H1-H8 intraresidue sugar-to-base correlations for all five guanosines in the [13C, 15N] isotopically labeled RNA duplex r(GGCGCUUGCGUC)2. 相似文献
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八肽胆囊收缩素对大鼠大脑皮质细胞钙调素活性的影响 总被引:2,自引:0,他引:2
为了探讨胆囊收缩素(CCK)受体在中枢神经系统中的信号传递机制,观察了CCK8和CCKA受体拮抗剂L-364,718、CCKB受体拮抗剂L-365,260对大鼠大脑皮质钙调素(CaM)活性的影响.结果表明:a.CCK8对CaM活性的影响具有时间依赖性,15 min达到最高点后逐渐下降;b.CCK8在10-12~10-7 mol/L范围内可刺激CaM活性的增加,超过10-7 mol/L后,逐渐趋于饱和.c.CCKA受体拮抗剂L-364,718、CCKB受体拮抗剂L-365,260均可抑制10-7 mol/L CCK8引起的CaM活性的增加,但两者IC50相差40倍,L-365,260在较低浓度时即能明显拮抗CCK8引起的CaM活性变化.研究结果提示CCK8可能通过CCKB受体引起CaM活性变化,而CaM可能是CCKB受体的重要信号传递机制之一. 相似文献
18.
Yasemin Ispirli Doğaç Mürvet Çinar Mustafa Teke 《Preparative biochemistry & biotechnology》2013,43(2):144-157
The aim of this study was enhancing of stability properties of catalase enzyme by encapsulation in alginate/nanomagnetic beads. Amounts of carrier (10–100 mg) and enzyme concentrations (0.25–1.5 mg/mL) were analyzed to optimize immobilization conditions. Also, the optimum temperature (25–50°C), optimum pH (3.0–8.0), kinetic parameters, thermal stability (20–70°C), pH stability (4.0–9.0) operational stability (0–390 min), and reusability were investigated for characterization of the immobilized catalase system. The optimum pH levels of both free and immobilized catalase were 7.0. At the thermal stability studies, the magnetic catalase beads protected 90% activity, while free catalase maintained only 10% activity at 70°C. The thermal profile of magnetic catalase beads was spread over a large area. Similarly, this system indicated the improving of the pH stability. The reusability, which is especially important for industrial applications, was also determined. Thus, the activity analysis was done 50 times in succession. Catalase encapsulated magnetic alginate beads protected 83% activity after 50 cycles. 相似文献
19.
Photosystem I is a large macromolecular complex located in the thylakoid membranes of chloroplasts and in cyanobacteria that catalyses the light driven reduction of ferredoxin and oxidation of plastocyanin. Due to the very negative redox potential of the primary electron transfer cofactors accepting electrons, direct estimation by redox titration of the energetics of the system is hampered. However, the rates of electron transfer reactions are related to the thermodynamic properties of the system. Hence, several spectroscopic and biochemical techniques have been employed, in combination with the classical Marcus theory for electron transfer tunnelling, in order to access these parameters. Nevertheless, the values which have been presented are very variable. In particular, for the case of the tightly bound phylloquinone molecule A1, the values of the redox potentials reported in the literature vary over a range of about 350 mV. Previous models of Photosystem I have assumed a unidirectional electron transfer model. In the present study, experimental evidence obtained by means of time resolved absorption, photovoltage, and electron paramagnetic resonance measurements are reviewed and analysed in terms of a bi-directional kinetic model for electron transfer reactions. This model takes into consideration the thermodynamic equilibrium between the iron-sulfur centre FX and the phylloquinone bound to either the PsaA (A1A) or the PsaB (A1B) subunit of the reaction centre and the equilibrium between the iron-sulfur centres FA and FB. The experimentally determined decay lifetimes in the range of sub-picosecond to the microsecond time domains can be satisfactorily simulated, taking into consideration the edge-to-edge distances between redox cofactors and driving forces reported in the literature. The only exception to this general behaviour is the case of phylloquinone (A1) reoxidation. In order to describe the reported rates of the biphasic decay, of about 20 and 200 ns, associated with this electron transfer step, the redox potentials of the quinones are estimated to be almost isoenergetic with that of the iron sulfur centre FX. A driving force in the range of 5 to 15 meV is estimated for these reactions, being slightly exergonic in the case of the A1B quinone and slightly endergonic, in the case of the A1A quinone. The simulation presented in this analysis not only describes the kinetic data obtained for the wild type samples at room temperature and is consistent with estimates of activation energy by the analysis of temperature dependence, but can also explain the effect of the mutations around the PsaB quinone binding pocket. A model of the overall energetics of the system is derived, which suggests that the only substantially irreversible electron transfer reactions are the reoxidation of A0 on both electron transfer branches and the reduction of FA by FX. 相似文献
20.
Comparison of effects of salt and alkali stresses on the growth and photosynthesis of wheat 总被引:10,自引:0,他引:10
The seedlings of wheat were treated by salt-stress (SS, molar ratio of NaCl: Na2SO4 = 1: 1) and alkali-stress (AS, molar ratio of NaHCO3: Na2CO3 = 1: 1). Relative growth rate (RGR), leaf area, and water content decreased with increasing salinity, and the extents of
the reduction under AS were greater than those under SS. The contents of photosynthetic pigments did not decrease under SS,
but increased at low salinity. On the contrary, the contents of photosynthetic pigments decreased sharply under AS with increasing
salinity. Under SS, the changes of net photosynthetic rate (P
N), stomatal conductance (g
s), and transpiration rate (E) were similar and all varied in a single-peak curve with increasing salinity, and they were lower than those of control only
at salinity over 150 mM. Under AS, P
N, g
s, and E decreased sharply with rising salinity. The decrease of g
s might cause the obvious decreases of E and intercellular CO2 concentration, and the increase of water use efficiency under both stresses. The Na+ content and Na+/K+ ratio in shoot increased and the K+ content in shoot decreased under both stresses, and the changing extents under AS were greater than those under SS. Thus
SS and AS are two distinctive stresses with different characters; the destructive effects of AS on the growth and photosynthesis
of wheat are more severe than those under SS. High pH is the key feature of the AS that is different from SS. The buffer capacity
is essentially the measure of high pH action on plant. The deposition of mineral elements and the intracellular unbalance
of Na+ and K+ caused by the high pH at AS might be the reason of the decrease of P
N and g
s and of the destruction of photosynthetic pigments. 相似文献