共查询到20条相似文献,搜索用时 31 毫秒
1.
Rebecca Bullard-Dillard Kim E. Creek Walter A. Scrivens James M. Tour 《Bioorganic chemistry》1996,24(4):376-385
This paper describes thein vivobehavior and potential metabolism of C60and a more water-soluble quaternary ammonium salt-derivatized C60. In both cases, a14C-labeled fullerene core was utilized for the target molecules that were intravenously injected into female Sprague–Dawley rats. The14C-labeled C60(*C60) was rapidly (within 1 min) cleared from the circulation and the majority of the *C60accumulated in the liver (90–95%). *C60was not eliminated from the liver over the 120-h period of this study. Our results also suggest that C60is not metabolized by the typical oxidative patterns characteristic of other polycyclic aromatics. Therefore, although not acutely toxic, use of C60, or its derivatives that could be cleaved back to the parent C60in vivo, would likely lead to long-term fullerene accumulation in the liver. The uptake of *C60and14C-labeled ammonium salt-derivatized C60(1)by human keratinocytesin vitroshowed that while both *C60and1are readily taken up by cells,1accumulates more slowly. Additionally, while C60, at rather high concentrations (2.0 μM) and over extended periods of time (8 days), is able to inhibit the growth of human keratinocytes by about 50%, this effect showed little, if any, photoinducability. 相似文献
2.
In the present report, the metabolism of dehydroepiandrosterone, 5-androstene-3β, 17β-diol and androstenedione has been studied in two different Shionogi tumors, one is androgendependent (“androgen sensitive”) and grows in intact male mice and the other is apparently androgen-independent (“androgen insensitive”) since the cells continue to grow in castrated antiandrogen (Flutamide) treated male animals. Our data clearly show that both the sensitive and insensitive tumors contain 3β-hydroxysteroid Δ5-Δ4 isomerase which causes the transformation of C19 steroids into potent androgenic steroids. However, the androgen sensitive tumor is able to convert 5-androstene-3β, l7β-diol into 2-hydroxyestrogens while the rate of conversion is extremely low in the insensitive tumor. Most interestingly, the production of 5α-reduced steroids observed in both tissues was clearly higher in insensitive tumor homogenates. 相似文献
3.
Paulette Schmitt Acharan S. Narula Pierre Benveniste Alain Rahier 《Phytochemistry》1981,20(2):197-201
The addition of 25-azacycloartanol to the medium of suspension cultures of bramble cells resulted, after 6 weeks of growth, in a large decrease in the percentage of C10 side-chain sterols, sitosterol and isofucosterol (83 % of the total in the control, 9 % in the treated cells), and in a spectacular increase in the percentage of C8 side-chain sterols, cycloartenol, desmosterol and cholesterol (less than 1 % in the control, 53 % in the treated cells). In addition the relative percentage of C9 side-chain sterols, mainly 24-methylene cholesterol increased significantly (from 16 to 37 %). A secondary effect of 25-azacycloartanol consisted in an increase of the percentage of Δ24 sterols and in a decrease of the percentage of sterols with a saturated side chain. These results are in agreement with an inhibition by 25-azacycloartanol of the C-24 and C-28 methyltransferases and of the Δ24 reductase. 相似文献
4.
Jen-Hsien Weng 《Acta Physiologiae Plantarum》2009,31(3):639-647
Two C3 dicotyledonous crops and five C4 monocotyledons treated with three levels of nitrogen were used to evaluate quantitatively the relationship between the allocation
of absorbed light energy in PSII and photosynthetic rates (P
N) in a warm condition (25–26°C) at four to five levels [200, 400, 800, 1,200 (both C3 and C4) and 2,000 (C4 only) μmol m−2 s−1] of photosynthetic photon flux density (PPFD). For plants of the same type (C3 or C4), there was a linear positive correlation between the fraction of absorbed light energy that was utilized in PSII photochemistry
(P) and P
N, regardless of the broad range of their photosynthetic rates due to species-specific effect and/or nitrogen application;
meanwhile, the fraction of absorbed light energy that was dissipated through non-photochemical quenching (D) showed a negative linear regression with P
N for each level of PPFD. The intercept of regression lines between P and P
N of C3 and C4 plants decreased, and that between D and P
N increased with increasing PPFD. With P and D as the main components of energy dissipation and complementary to each other, the fraction of excess absorbed light energy
(E) was unchanged by P
N under the same level of PPFD. At the same level of P
N, C4 plants had lower P and higher D than C3 plants, due to the fact that C4 plants with little or no photorespiration is considered a limited energy sink for electrons. Nevertheless there was a significant
negative linear correlation between D and P when data from both C3 and C4 plants at varied PPFD levels was merged. The slope of regression lines between P and D was 0.85, indicating that in plants of both types, most of the unnecessary absorbed energy (ca. 85%) could dissipate through
non-photochemical quenching, when P was inhibited by low P
N due to species-specific effect and nitrogen limitation at all levels of illumination used in the experiment. 相似文献
5.
C3 photosynthesis is an inefficient process, because the enzyme that lies at the heart of the Benson–Calvin cycle, ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) is itself a very inefficient enzyme. The oxygenase activity of Rubisco is an unavoidable side reaction that is a consequence of its reaction mechanism. The product of oxygenation, glycollate 2-P, has to be retrieved by photorespiration, a process which results in the loss of a quarter of the carbon that was originally present in glycollate 2-P. Photorespiration therefore reduces carbon gain. Purely in terms of carbon economy, there is, therefore, a strong selection pressure on plants to reduce the rate of photorespiration so as to increase carbon gain, but it also improves water- and nitrogen-use efficiency. Possibilities for the manipulation of plants to decrease the amount of photorespiration include the introduction of improved Rubisco from other species, reconfiguring photorespiration, or introducing carbon-concentrating mechanisms, such as inorganic carbon transporters, carboxysomes or pyrenoids, or engineering a full C4 Kranz pathway using the existing evolutionary progression in C3–C4 intermediates as a blueprint. Possible routes and progress to suppressing photorespiration by introducing C4 photosynthesis in C3 crop plants will be discussed, including whether single cell C4 photosynthesis is feasible, how the evolution of C3–C4 intermediates can be used as a blueprint for engineering C4 photosynthesis, which pathway for the C4 cycle might be introduced and the extent to which processes and structures in C3 plant might require optimisation. 相似文献
6.
A novel organic-inorganic hybrid pentaborate [Ni(C4H10N2)(C2H8N2)2][B5O6(OH)4]2 has been synthesized by hydrothermal reaction and characterized by FT-IR, Raman spectroscopy, elemental analyses and DTA-TGA. Its crystal structure was determined from single crystal X-ray diffraction. The structure consists of isolated polyborate anion [B5O6(OH)4]− and nickel complex cation of [Ni(C4H10N2)(C2H8N2)2]2+, in which the two kinds of ligands come from the decomposition of triethylenetriamine material. The [B5O6(OH)4]− units are connected to one another through hydrogen bonds, forming a three-dimensional framework with large channel along the a and c axes, in which the templating [Ni(C4H10N2)(C2H8N2)2]2+ cations are located. The assignments of the record FT-IR absorption frequencies and Raman shifts were given. 相似文献
7.
铕标记抗癌胚抗原单克隆抗体C17的研究和应用 总被引:1,自引:0,他引:1
用合成的N′-(对-异硫氰基苄基)-二乙三胺-N1,N2,N3,N3-四乙酸铕钠为螫合剂.用Sephadex G-50凝胶柱层析分离标记C17和过量试剂.分部收集的层析物的光密度图和荧光强度图完全一致.蛋白峰处两管标记C17的比活性分别为5.2和8.9Eu3+离子每C17分子,而且C17的标记回收率为64%.标记C17至少在6个月内是稳定的.用铕标记物得到的时间分辨免疫荧光分析的标准曲线具有良好线性和斜率,表明标记物免疫活性良好,而且已用于血清CEA分析. 相似文献
8.
Bruno Therrien Ludovic Vieille-Petit Georg Süss-Fink 《Inorganica chimica acta》2004,357(11):3289-3294
The trinuclear arene-ruthenium cluster cation [H3Ru3(C6H6)(C6Me6)2(O)]+, containing a μ3-oxo cap and three arene ligands that span a hydrophobic pocket above the metal skeleton, has been crystallised as tetrafluoroborate salt in the presence of various guest molecules. The host-guest complexes have been characterised by single-crystal X-ray structure analysis. With chloroform as the guest molecule, a CHCl3 molecule sits perfectly in the hydrophobic pocket, the hydrogen atom being encapsulated inside the cavity. When dioxane is added during the crystallisation process, the cluster forms infinite chains which are connected by a complex network of hydrogen bonds involving the μ3-oxo ligand, water and dioxane molecules. Interestingly, in the presence of phenol, a water molecule is hydrogen-bonded between the μ3-oxo ligand and the phenol molecule, forming a one-dimensional μ3-O ? H2O ? HO hydrogen-bonded chain. Finally, with benzoic acid, a head-to-tail host-guest chain is obtained, the phenyl ring being incorporated in the hydrophobic pocket, while the acid group is hydrogen-bonded to the μ3-oxo ligand. 相似文献
9.
Lourdes Cabrera 《Inorganica chimica acta》2006,359(9):3066-3071
Trityl borate salts [4-RPyCPh3][B(C6F5)4] (R = H 1, tBu 2, Et 3, NMe24) and [R3PCPh3][B(C6F5)4] (R = Me 5, nBu 6, Ph[1] 7, p-MeC6H48) are readily prepared via equimolar reaction of the appropriate pyridine or phosphine and trityl borate [CPh3][B(C6F5)4]. The analogous reactions of PiPr3 affords the product [(p-iPr3P-C6H4)Ph2CH][B(C6F5)4] (9) while the corresponding reactions of Cy3P and tBu3P gave the cyclohexadienyl derivatives [(p-R3PC6H5)CPh2][B(C6F5)4] (R = Cy 10, tBu 11). X-ray structures of 5 and 9 are reported. 相似文献
10.
Vineet Sharma Rakesh Bohra John E. Drake Mark E. Light 《Inorganica chimica acta》2007,360(6):2009-2015
New oxovanadium(V) complexes with internally functionalized oximes of the type VO{OPri}3−n{ONC(CH3)(Ar)}n] (where Ar = C4H3O-2, C4H3S-2 and C5H4N-2 and n = 1-3) have been prepared in quantitative yields by the reaction of VO(OPri)3 with the corresponding oximes in various stoichiometric ratios in refluxing anhydrous benzene. The products have been characterized by elemental analyses and spectroscopic (FT IR, 1H, 13C{1H} and 51V NMR) studies. FAB mass spectral analysis of [VO{OPri}{ONC(CH3)C4H3S}2] indicates the monomeric nature of the complex. 51V NMR values for these complexes suggest the formation of tetra-coordinate species in solution. However, the single crystal X-ray diffraction studies of [VO{ONC(CH3)(C4H3O-2)}3] and [VO{ONC(CH3)(C4H3S-2)}3] · 0.5C6H6 exhibit the presence of vanadium(V) atoms in a unique hepta-coordination state with distorted pentagonal bipyramidal geometry in the solid state. The oxo- atom occupies the axial position while the oximato ligands are bonded in a dihapto (η2-N,O) manner with the formation of three membered rings. 相似文献
11.
A new aluminoborate, [C5H6N][AlB12O14(OH)12], has been hydrothermally synthesized at 200 °C. The single-crystal diffraction study reveals that it crystallizes in space group C2/c. It consists of aluminoborate clusters [AlB12O14(OH)12]− and counterions [C5H6N]+. The aluminoborate cluster contains an Al(OH)6 octahedron as a core that is capped by two raft-like polyborate units [B6O7(OH)6]. These clusters are further interlinked by extensive hydrogen bonding to form a three-dimensional (3D) network, containing large channels along the b-axis, in which the [C5H6N]+ cations are located. 相似文献
12.
Marrigje M. Conradie 《Inorganica chimica acta》2009,362(2):519-9294
A NMR study of the reaction mixture of the square planar [Rh((C4H3S)COCHCOR)(CO)(PPh3)] complex and CH3I, where R = CF3, C6H5 or C4H3S, revealed that two types of alkyl and one (R = CF3) or two (R = C6H5 or C4H3S) types of acyl species exist in the system. Two isomers of each species with an unsymmetrical β-diketonato ligand were observed. 1H-1H NOESY NMR unambiguously showed that the PPh3 group is in the apical position in the more stable RhIII-alkyl product. Theoretical computations of the equilibrium geometry of the possible reaction products, consistent with experimental observations, revealed that the first alkyl product results from trans addition to RhI and that the second thermodynamic alkyl product adopts an octahedral geometry with the PPh3 group and the iodide above and below the square planar plane. Theoretical computations also revealed that the thermodynamic acyl product adopts a square-pyramidal geometry with the COCH3 group in the apical position. 相似文献
13.
Luís Cunha-Silva Filipe A. Almeida Paz Michaele J. Hardie Tito Trindade 《Inorganica chimica acta》2009,362(1):263-270
The crystalline compounds (Hbipy)2[Ge(C2O4)3] (1) and (Hphen)2[Ge(C2O4)3] · 2(H2O) (2) [Hbipy+ is the 2,2′-bipyridinium cation (C10H9N2), and Hphen+ is the 1,10′-phenathrolinium cation (C12H9N2)] were isolated from mild hydrothermal syntheses and their structures were elucidated from single-crystal X-ray diffraction. The two compounds were further characterised by vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetric analysis (TGA) and CHN elemental composition. Compounds 1 and 2 comprise the tris(oxalato-O,O′)germanate dianion complex, [Ge(C2O4)3]2−, which co-crystallises with Hbipy+ (in 1), or Hphen+ and water molecules (in 2). In 1, the germanium oxalate anionic complex, [Ge(C2O4)3]2−, and the Hbipy+ organic residues interact mutually via N-H?O hydrogen bonding interactions, leading to supramolecular discrete hydrogen-bonded units which are further interconnected via π-π stacking. Compound 2, on the other hand, exhibits a more complex hydrogen bonding network due to the presence of the water molecules of crystallisation which, along with π-π stacking between neighbouring Hphen+ residues, mediate the crystal packing. 相似文献
14.
The Mrs of glycollate oxidase (EC 1.1.3.1) (GAO) determined soon after extraction from the leaves of several C3 and C4 plants are reported. The enzyme isolated from the C3 plants wheat, barley, spinach, pea and tobacco has Mr in the range 160–180 000 and is probably a homotetramer. GAO purified from pea was previously reported as a dimer and as an octamer from spinach leaves. Therefore the quaternary structure of these GAOs soon after extraction differs from that of the purified proteins. The enzymes from the C4 plants maize and sugar cane have Mrs ca twice this value in the range 290–310 000, whilst that of the C4 grass Panicum maximum has an Mr of 162 000. An improved spectrophotometric assay for GAO, using a non-carcinogenic dye, is described. 相似文献
15.
Axel Raisig Gerhard Sandmann 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2001,1533(2):164-170
The desaturation reactions of C30 carotenoids from diapophytoene to diaponeurosporene was investigated in vitro and by complementation in Escherichia coli. The expressed diapophytoene desaturase from Staphylococcus aureus inserts three double bonds in an FAD-dependent reaction. The enzyme is inhibited by diphenylamine. In the complementation experiment diapophytoene desaturase was able to convert C40 phytoene to some extend but exhibited a high affinity to ζ-carotene. Comparison to the reaction of a phytoene desaturase from Rhodobacter capsulatus catalyzing a parallel three-step desaturation sequence with the corresponding C40 carotenes revealed that this desaturase can also convert C30 diapophytoene. Other homologous bacterial C40 carotene desaturases could also utilize C30 substrates, including one type of ζ-carotene desaturase which converted diaponeurosporene to diapolycopene. Further complementation experiments including the diapophytoene synthase gene from S. aureus revealed that the C30 carotenogenic pathway is determined by this initial enzyme which is highly homologous to C40 phytoene synthases. 相似文献
16.
The reaction of lead(II) nitrate with trisodium citrate Na3(C6H5O7) in a 1:22.5 ratio at pH 4.8 provides crystals of {Na(H2O)3}[Pb5(H2O)3(C6H5O7)3(C6H6O7)]·9.5H2O (1). The structure of 1 is two-dimensional and exhibits five distinct Pb(II) sites and four different modes of citrate bonding. The five lead sites all display hemidirected coordination geometries, that is, irregular distribution of neighboring oxygen atoms resulting in obvious gaps in the coordination spheres. Consequently, the lead coordination geometries exhibit proximal bonding to a number of oxygen donors, as well as distal interactions with nearest neighbors. The coordination numbers vary from 8 to 10, with ‘5+3’, ‘5+4’, ‘6+4’ and ‘7+3’ coordination modes where the first number refers to the proximal ligands and the second to the distal set. The four crystallographically distinct citrate groups include three with deprotonated carboxylate groups (C6H5O7)3− and one with a single protonated carboxyl group (C6H6O7)2. The citrate ligands bridge 3, 5, 7 and 7 lead sites. Three of the citrate groups exhibit tridentate chelation coordination to a lead site through two carboxylate oxygen donors and the hydroxyl groups. One citrate group projects an uncoordinated -OH group and a pendant protonated carboxyl group into the interlamellar domain. This latter carboxyl group coordinates to a sodium cation, which exhibits five coordinate geometry defined by three aqua ligands and the carbonyl oxygen of the -CO2H groups in the basal plane and a citrate -OH donor in the apical position. 相似文献
17.
The analgesic effect elicited by intracerebroventricular (icv) administration of either morphine or d-ala2-methionine-enkephalin (d-ala2-met-enk) was studied during the onset and offset of morphine tolerance in DBA/2J (DBA) and C57 BL/6J (C57) strains of mice. DBA mice become tolerant to the analgesic effect of morphine icv injected after receiving 8 subcutaneous (sc) injections (2 injections daily × 4 days) of the ED50 of morphine for analgesia. In c57 mice tolerance to morphine icv-administered is evident after only a single sc injection of morphine ED50. On the contrary the development of cross-tolerance to the analgesic effect of d-ala2-met-enk is similar in both strains of mice. With respect to the offset period, the recovery of the analgesic effect of morphine and d-ala2-met-enk is slower in C57 than in DBA mice; in C57 mice tolerance to both morphine and d-ala2-met-enk is still present 10 days after morphine withdrawal. These results suggest the existence of a strain dependent rate in the onset of tolerance to the analgesic effect of morphine. C57 mice represent an interesting tool to investigate tolerance to opiates and opioid peptides. 相似文献
18.
Fabien Charbonneau 《Inorganica chimica acta》2010,363(8):1779-53
The mechanism for the preparation of Me2Si(C5Me4)2Cr, 1, from CrCl2(THF)x and Me2Si(C5Me4)2Li2 was investigated and - in contrast to earlier claims - no evidence was found for the participation of an auxiliary ligand. The formation and stability of 1 is attributed to the combination of correct reaction conditions and a highly substituted ligand framework. Reactions with other ligands under identical conditions did not lead to the formation of ansa-chromocenes. Reaction with H4C2Ind2Li2 afforded the η3-Ind bridged dimer {H4C2(η5-Ind)(μ-,η3-Ind)Cr}2, 9. Complex 1 does not coordinate PPh3 or carbenes, but from reaction with two equivalents of xylyl isocyanide the CH-activated complex Me2Si(C5Me4)(η3-C5Me3(H)(CH2)Cr(CNC6MeH3)2, 7, was obtained. Complexes 7 and 9 were characterised by X-ray crystallography. 相似文献
19.
Yi-Shan Song 《Inorganica chimica acta》2005,358(1):191-195
A novel chain-like luminescent samarium coordination polymer {Sm3(C8H4O4)4(C12N2H8)2(NO3)}n (C8H4O4 = phthalate, C12N2H8 = 1,10-phenanthroline) has been assembled by hydrothermal process. The title complex crystallizes in the monoclinic system, space group P2(1)/c, with lattice parameters a = 22.56(3) Å, b = 11.155(15) Å, c = 20.32(3) Å, β = 96.70(2)°, V = 5078(12) Å3, F(000) = 2964, GOF = 0.857, R1 = 0.0358, wR2 = 0.0597, Z = 4. Samarium ions exhibit different coordination modes from each other and lead to the unexpected high asymmetrical structure. To our knowledge, it is the first example of lanthanide coordination polymers comprising the three asymmetrical central Sm3+ fragments. The photophysical properties have been studied with excitation and emission spectra. 相似文献
20.
Temperature and vapor pressure deficit (VPD) effects on turfgrass growth are almost always confounded in experiments because VPD commonly is substantially increased in elevated-temperature treatments. The objective of this study as to examine specifically the influence of VPD on transpiration response of four ‘warm-season’ (C4) and four ‘cool-season’ (C3) turfgrasses to increasing VPD at a stable temperature (29.3 ± 1.5 °C). Although transpiration rates were noticeably lower in C4 grasses, transpiration rates increased linearly in response to increasing VPD across the range of 0.8–3.0 kPa. In contrast, transpiration rates of C3 increased sharply with increasing VPD across the range of low VPDs, but became constrained at higher VPDs (>1.35 kPa). Restricted transpiration rate at elevated VPD was most evident in Agrostis palustris and Lolium perenne. Assuming restricted transpiration rates reflect a limitation on leaf CO2 uptake, these results indicate that the commonly observed decline in growth of C3 (and success of C4) grasses at elevated temperature may include a sensitivity to elevated VPD. 相似文献