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161.
The strategy to identify cadmium deactivation mechanism in Arabidopsis thaliana has been developed using selective and sensitive hyphenated techniques. Cadmium concentrations, in main parts of the plant, were determined by ICP-MS and total amount was found as 0.43-0.44 μg g−1 in leaves and 3.3-3.4 μg g−1 in roots. Speciation of the metal complexes in cells was investigated by SEC-ICP-MS in order to estimate the accumulation process. Phytochelatins, desglycyl-phytochelatins and phytochelatins homologues lacking the N-terminal γ-linked glutamic acid were extracted from plant and were identified by RPLC-ESI-MS. Two-dimensional chromatography allowed to link the metal complexes separated by SEC with isoforms of phytochelatins analyzed by high resolution RPLC and confirm their significant responsibility for metal accumulation. The potential of the cadmium complexes speciation indicates that obtained results could be reliable source of knowledge to confirm the information coming from the well-known genomic sequence of Arabidopsis and to estimate the role of γ-glutamyl transpeptidase in metabolism of glutathione. 相似文献
162.
W. Bocian J. Jaźwiński O. Staszewska J. W. Wiench L. Stefaniak G. A. Webb 《Chemistry of Heterocyclic Compounds》1996,32(11-12):1358-1366
Multinuclear1H,13C,14N,15N, and17O NMR data are presented for some sydnones, isosydnones and isothiosydnones. The type of valence tautomerism shown in (Fig. 1) is not observed for the compounds studied. At high pH compounds2 and12 are found to undergo transformations. The more suitable NMR parameters are reported for establishing the structures of mesoionic compounds containing three heteroatoms in the five-membered conjugated ring. Someab initio GIAO calculations on a model structure of sydnones and related compounds have been performed. 相似文献
163.
Andrzej Czerwiński Iwona Kiersztyn Michał Grdeń 《Journal of Solid State Electrochemistry》2003,7(6):321-326
The effect of temperature on hydrogen and deuterium electrosorption into a palladium LVE (limited-volume electrode) has been
investigated. A decrease in hydrogen capacity (H/Pd ratio) with increasing temperature has been observed. Temperature strongly
influences the plots of measured H(D)/Pd values vs. potential scan rate. In addition, hydrogen absorption was found to be
dependent on the composition of the surrounding electrolyte solution. These results have confirmed the hypothesis that two
different mechanisms of hydrogen desorption from the palladium electrode take place, namely electrochemical oxidation and
non-electrochemical recombination. Further, the ratio between the rate constants for these two processes has been found to
change with temperature.
Electronic Publication 相似文献
164.
Marek Trojanowicz Joanna Szpunar-Łobińska Zdzislaw Michalski 《Mikrochimica acta》1991,103(3-4):159-169
An original computer-controlled solid-state photometer has been developed and its potential for simultaneous multicomponent flow-injection analysis of binary and ternary mixtures is demonstrated. The device is simple in construction. Its principle of operation is based on rapid sequential measurements of the absorbance of the complexes formed by the analytes with chromogenic reagents at the wavelengths corresponding to the emission maxima of three light emitting diodes (563, 580 and 638 nm). 相似文献
165.
Zusammenfassung Bei der Pyrolyse phosphor-organischer Verbindungen in Sauerstoffatmosphäre bilden sich P-Oxide, die die C,H-Bestimmung stören. Deren Verhalten im Verbrennungsrohr und ihre Absorption an geeigneten Kontakten wurden untersucht. Durch den Einsatz32P- markierter Ausgangsverbindungen und Aktivitätsmessung des32P sowohl durch die Wandung des Verbrennungsrohres als auch im zerkleinerten Füllungsmaterial war die laufende Bestimmung der durch die Kontaktschicht absorbierten Phosphormenge möglich. 30 verschiedene Absorptionsmittel wurden geprüft. Der Einfluß der Strömungsgeschwindigkeit des Trägergases, der Temperatur der Kontaktschicht, der Art der Verbrennung sowie der Anordnung des Verbrennungsrohres wurde untersucht. Die Absorptionsleistung der Kontakte ist stark von der Gasgeschwindigkeit abhängig.
Investigation of absorption of the phosphorus oxides arising in the combustion of organophosphorus compounds by means of32P-labelled substances
Summary In the pyrolysis of organophosphorus compounds in an oxygen atmosphere P oxides are formed which interfere with determination of carbon and hydrogen. Their behaviour in the combustion tube and their absorption on suitable contacts were investigated. By the use of32P-labelled starting compounds and measuring the activity of32P both through the wall of the combustion tube and in the comminuted filling material, continuous determination of the amount of phosphorus absorbed through the contact layer was possible. Thirty different absorption media were tested. The influence of the flow rate of the carrier gas, the temperature of the contact layer, the nature of combustion as well as the arrangement of the combustion tube was examined. The absorption efficiency of the contacts is highly dependent on the speed of the gas.相似文献
166.
Prof. Dr. Stefan Smoliński Janusz Jamrozik Maria Jamrozik 《Monatshefte für Chemie / Chemical Monthly》1977,108(5):1145-1151
We have obtained four new bispirane systems in which both spiroatoms are vicinal atoms in cyclopropane or cyclobutane rings and in which the heterocyclic component has the basic structure of 1,4-dioxep-2-ene. We have shown that from two possibilities (bispiran, propellan) the general reaction leads only to a bispiran system. To the bispiran2 exhibiting the highest hyperchromism we ascribed the bispirocoplanar conformation (Fig. 1).
Mit 3 Abbildungen 相似文献
Mit 3 Abbildungen 相似文献
167.
J. Kaleciński 《Journal of Radioanalytical and Nuclear Chemistry》1998,232(1-2):87-90
The radiation-chemical processes in aqueous solutions of dichromates, isopolymolybdates and isopolytungstates have been studied.
The radiation reduction of Cr(VI) to Cr(III), Mo(VI) to Mo(V) and W(VI) to W(V) takes place. Molybdenum and tungsten blues
are the products of the last two processes in acid solutions. The yields of reduction decrease significantly with the increase
of pH. The mechanisms of the processes have been discussed. The photochemical reduction of Mo(VI) and W(VI) for the production
of corresponding 5-valent states have been used to the study of their electron scavenging efficiencies. It has been shown
that these efficiencies decrease in the order: Mo(V)>W(V)>Cr(VI)>Mo(VI)>W(VI). 相似文献
168.
The nucleophilic dimethoxycarbene (DMC; 2 ) generated by thermal decomposition of 2,5‐dihydro‐1,3,4‐oxadiazole derivative 1 in boiling toluene reacts smoothly with N‐(9H‐fluoren‐9‐ylidene)‐4‐methylbenzenesulfonamide ( 7b ) to yield carbonimidoate derivative 10 . A multi‐step reaction pathway, initiated by the attack of DMC onto the C?N bond and followed by the migration of the sulfonyl group (or via a sulfinate anion) is proposed to explain the formation of the final product. In contrast to the formal ketimine 7b , N‐benzylidene‐4‐methylbenzenesulfonamide ( 7a ), a formal aldimine, does not react with DMC under comparable conditions. 相似文献
169.
Distribution coefficients of Pt, Ir, Pd and Rh in the systems Dowex 1 [Br?]?HBr plus 0.0035M bromine and Dowex 1 [Br?]?HBr plus 2% N2H4·HCl, were determined with the aid of radioactive tracers by batch equilibration for the resins of nominal cross-linking 2, 4 and 8, respectively. Column experiments showed that Dowex 1X4 should be used for separations because of the favourable dynamics of the column process. Elution conditions for the quantitative separation of both trace and milligram amounts of Ir?Pt, Rh?Pt, Pd?Pt and Ir?Pd?Pt mixtures are given. Some data on the effect of temperature upon the quality of separation are also presented. 相似文献
170.
A solution of a Zn-complex of recombinant mouse MT-1 isoform (Zn(7)-MT-1) was prepared and titrated with Cd(2+) ions. A method based on the coupling of capillary zone electrophoresis (CZE) with electrospray MS detection was developed for the analysis of the stoichiometry of the species formed during the titration. The method offered the possibility of the on-line removal of up to 100 mM Tris or phosphate buffer solutions that would otherwise suppress the electrospray signal. By allowing the determination of the metal stoichiometry of the complex species present in solution the method was shown to be complementary to circular dichroism and UV-VIS spectrophotometry conventionally used for similar studies. The titration of the Zn(7)-MT complex with Cd(II) showed the sequential displacement of the Zn by Cd. The unusually high stability of the Cd(6)Zn(1)-MT species was observed which suggests a structural role of the remaining Zn(II) ion. 相似文献