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11.
Thermogravimetric analysis of plant water content in relation with heavy metal stress 总被引:1,自引:0,他引:1
We have used simultaneous thermogravimetry & differential scanning calorimetry (TG/DSC) to estimate water content of wheat plants exposed to toxic concentration of copper and cadmium. Our study revealed that water content tends to decrease along with the increase of the exogenous heavy metal supply. These data suggested a different status of water: on the one hand, form an organ to another, and on the other hand, in stressed plants compared with control plants. The observed differences could be correlated with reshaping processes induced by heavy metal stress, especially at cell wall level. Accumulation of fibrous constituents having important properties like ion binding and water-holding capacity, may affect water distribution and interactions. TG/DSC appears as a promising technique for revealing certain aspects of stress biochemistry and physiology in plants. 相似文献
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Matthias Golecki Jochen Lach Alexander Jeremies Frank Lungwitz Dr. Michael Fronk Prof. Dr. Georgeta Salvan Prof. Dr. Dietrich R. T. Zahn Jaena Park Dr. Yulia Krupskaya Dr. Vladislav Kataev Prof. Dr. Rüdiger Klingeler Prof. Dr. Bernd Büchner Benjamin Mahns Prof. Dr. Martin Knupfer Dr. Pablo F. Siles Dr. Daniel Grimm Prof. Dr. Oliver G. Schmidt Andreas Reis Prof. Dr. Werner R. Thiel Daniel Breite Prof. Dr. Bernd Abel Prof. Dr. Berthold Kersting 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7787-7801
A new strategy for the fixation of redox‐active dinickel(II) complexes with high‐spin ground states to gold surfaces was developed. The dinickel(II) complex [Ni2L(Cl)]ClO4 ( 1 ClO4), in which L2? represents a 24‐membered macrocyclic hexaaza‐dithiophenolate ligand, reacts with ambidentate 4‐(diphenylphosphino)benzoate (dppba) to form the carboxylato‐bridged complex [Ni2L(dppba)]+, which can be isolated as an air‐stable perchlorate [Ni2L(dppba)]ClO4 ( 2 ClO4) or tetraphenylborate [Ni2L(dppba)]BPh4 ( 2 BPh4) salt. The auration of 2 ClO4 was probed on a molecular level, by reaction with AuCl, which leads to the monoaurated NiII2AuI complex [NiII2L(dppba)AuICl]ClO4 ( 3 ClO4). Metathesis of 3 ClO4 with NaBPh4 produces [NiII2L(dppba)AuIPh]BPh4 ( 4 BPh4), in which the Cl? is replaced by a Ph? group. The complexes were fully characterized by ESI mass spectrometry, IR and UV/Vis spectroscopy, X‐ray crystallography ( 2 BPh4 and 4 BPh4), cyclic voltammetry, SQUID magnetometry and HF‐ESR spectroscopy. Temperature‐dependent magnetic susceptibility measurements reveal a ferromagnetic coupling J=+15.9 and +17.9 cm?1 between the two NiII ions in 2 ClO4 and 4 BPh4 (H=?2 JS1S2). HF‐ESR measurements yield a negative axial magnetic anisotropy (D<0), which implies a bistable (easy axis) magnetic ground state. The binding of the [Ni2L(dppba)]ClO4 complex to gold was ascertained by four complementary surface analytical methods: contact angle measurements, atomic‐force microscopy, X‐ray photoelectron spectroscopy, and spectroscopic ellipsometry. The results indicate that the complexes are attached to the Au surface through coordinative Au? P bonds in a monolayer. 相似文献
13.
Venkata R. Kethineedi Georgeta Crivat Matthew A. Tarr Zeev Rosenzweig 《Analytical and bioanalytical chemistry》2013,405(30):9729-9737
In this paper we describe the fabrication and characterization of new liposome encapsulated quantum dot–fluorescence resonance energy transfer (FRET)-based probes for monitoring the enzymatic activity of phospholipase A2. To fabricate the probes, luminescent CdSe/ZnS quantum dots capped with trioctylphosphine oxide (TOPO) ligands were incorporated into the lipid bilayer of unilamellar liposomes with an average diameter of approximately 100 nm. Incorporating TOPO capped quantum dots in liposomes enabled their use in aqueous solution while maintaining their hydrophobicity and excellent photophysical properties. The phospholipid bilayer was labeled with the fluorophore NBD C6-HPC (2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexa decanoyl-sn-glycero-3-phosphocholine). The luminescent quantum dots acted as FRET donors and the NBD dye molecules acted as FRET acceptors. The probe response was based on FRET interactions between the quantum dots and the NBD dye molecules. The NBD dye molecules were cleaved and released to the solution in the presence of the enzyme phospholipase A2. This led to an increase of the luminescence of the quantum dots and to a corresponding decrease in the fluorescence of the NBD molecules, because of a decrease in FRET efficiency between the quantum dots and the NBD dye molecules. Because the quantum dots were not attached covalently to the phospholipids, they did not hinder the enzyme activity as a result of steric effects. The probes were able to detect amounts of phospholipase A2 as low as 0.0075 U mL?1 and to monitor enzyme activity in real time. The probes were also used to screen phospholipase A2 inhibitors. For example, we found that the inhibition efficiency of MJ33 (1-hexadecyl-3-(trifluoroethyl)-sn-glycero-2-phosphomethanol) was higher than that of OBAA (3-(4-octadecyl)benzoylacrylic acid). 相似文献
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15.
Using static oxygen-bomb calorimetry, the standard enthalpies of combustion of the 2,4-and 2,6-isomers of dinitrophenol have been determined as ?2697.22 and ?2723.08 ± 3.18 kJ mole?1, respectively. Standard enthalpies of formation have been calculated as ?235.50 and ?209.64 ± 3.27 kJ mole?1, respectively. 相似文献
16.
Aniela Pop Florica Manea Ciprian Radovan Plamen Malchev Adriana Bebeselea Cristina Proca Georgeta Burtica Stephen Picken Joop Schoonman 《Electroanalysis》2008,20(22):2460-2466
The assessment of an expanded graphite‐Ag‐zeolite‐epoxy composite (EG‐Z‐Ag‐Epoxy) electrode for the determination of 4‐chlorophenol (4‐CP) is described and compared to the corresponding expanded graphite‐epoxy composite (EG‐Epoxy) electrode. Cyclic voltammetry was used to characterize the electrochemical behavior and determination of 4‐CP at both electrodes in 0.1 M Na2SO4 and 0.1 M NaOH supporting electrolytes. A substantial enhancement of sensitivity for the determination of 4‐CP at the EG‐Z‐Ag‐Epoxy electrode was reached by applying a chemical preconcentration step prior to voltammetric quantification. Also, under these last conditions the lowest limit of detection of 1 μM illustrates the analytical versatility of this electrode in a concentration range where aquatic 4‐chlorophenol pollution is known to occur. 相似文献
17.
Popescu G Barauskas J Nylander T Tiberg F 《Langmuir : the ACS journal of surfaces and colloids》2007,23(2):496-503
The aqueous phase behavior of mixtures of 1-glycerol monooleate (GMO) and its ether analogue, 1-glyceryl monooleyl ether (GME) has been investigated by a combination of polarized microscopy, X-ray diffraction, and NMR techniques. Three phase diagrams of the ternary GMO/GME/water system have been constructed at 25, 40, and 55 degrees C. The results demonstrate that the increasing amount of GME favors the formation of the reversed phases, evidenced by the transformation of the lamellar and bicontinuous cubic liquid crystalline phases of the binary GMO/water system into reversed micellar or reversed hexagonal phases. For a particular liquid crystalline phase, increasing the GME content has no effect on the structural characteristics and hydration properties, thus suggesting ideal mixing with GMO. Investigations of dispersed nanoparticle samples using shear and a polymeric stabilizer, Pluronic F127, show the possibility of forming two different kinds of bicontinuous cubic phase nanoparticles by simply changing the GMO/GME ratio. Also NMR self-diffusion measurements confirm that the block copolymer, Pluronic F127, used to facilitate dispersion formation, is associated with nanoparticles and provides steric stabilization. 相似文献
18.
Wang Z Masson G Peiris FC Ozin GA Manners I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(33):9372-9383
Facile synthetic routes have been developed that provide access to cationic and anionic water-soluble polyferrocenylsilane (PFS) polyelectrolytes with controlled molecular weight and narrow polydispersity. Living photolytic ring-opening polymerization of amino-functionalized [1]ferrocenophane (fc) monomers [fcSiMe{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)}] (3), [fcSi{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)}(2)] (10), [fcSiMe(C[triple chemical bond]CCH(2)NMe(2))] (14), and [fcSiMe(p-C(6)H(4)CH(2)NMe(2))] (20) yielded the corresponding polyferrocenylsilanes [(fcSiMe{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)})(n)](5), [(fcSi{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)}(2))(n)] (11), [{fcSiMe(C[triple chemical bond]CCH(2)NMe(2))}(n)] (15), and [{fcSiMe(p-C(6)H(4)CH(2)NMe(2))}(n)] (21) with controlled architectures. Further derivatization of 5, 15, and 21 generated water-soluble polyelectrolytes [(fcSiMe{C[triple chemical bond]CCH(2)N(CH(2)CH(2)CH(2)SO(3)Na)(2)})(n)] (6), [{fcSiMe(C[triple chemical bond]CCH(2)NMe(3)OSO(3)Me)}(n)] (7), and [{fcSiMe(p-C(6)H(4)CH(2)NMe(3)OSO(3)Me)}(n)] (22), respectively. The polyelectrolytes were readily soluble in water and NaCl aqueous solutions, with 6 and 22 exhibiting long-term stability in aqueous media. The PFS materials 6 and 22, have been utilized in the layer-by-layer (LbL) self-assembly of electrostatic superlattices. Our preliminary studies have indicated that films made from controlled low molecular-weight PFSs possess a considerably thinner bilayer thickness and higher refractive index than those made from PFSs that have an uncontrolled high molecular-weight. These results suggest that the structure and optical properties of LbL ultra-thin films can be tuned by varying polyelectrolyte chain length. The water-soluble low molecular weight PFSs are also useful materials for a range of applications including LbL self-assembly in highly confined spaces. 相似文献
19.
Travis P. Sharkey-Toppen Georgeta MihaiAndrei Maiseyeu Tam TranBradley D. Clymer Orlando P. SimonettiSubha V. Raman 《Magnetic resonance imaging》2013
T2? quantification has been shown to noninvasively and accurately estimate tissue iron content in the liver and heart; applying this to thin-walled carotid arteries introduces a new challenge to the estimation process. With most imaging voxels in a vessel being along its boundaries, errors in parameter estimation may result from partial volume mixing and misregistration due to motion in addition to noise and other common error sources. To minimize these errors, we propose a novel technique to reliably estimate T2? in thin regions of vessel wall. The technique weights data points to reduce the influence of expected error sources. It uses neighborhoods of data to increase the number of points for fitting and to assess lack of fit for automated outlier detection and deletion. The performance of this method was observed in simulations, phantom and in vivo patient studies and compared to results obtained using a pixelwise linear least squares estimation of T2?. The new proposed method showed a closer match to the expected results, and a 4.2-fold decrease in interobserver variability for in vivo studies. This increased confidence in estimation should improve the ability to reliably quantify iron noninvasively in the arterial wall. 相似文献
20.
Ana Ferreira Miguel Ramalho Rafael O.P. de Campos Vasco Heredia Andreia Roque Georgeta Vaidean Richard C. Semelka 《Magnetic resonance imaging》2013