Cadmium speciation in Arabidopsis thaliana as a strategy to study metal accumulation system in plants

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.     

Additional of functional vinylzinc reagents to nitrones: synthesis of (E)-N-allylhydroxylamines and their rearrangement into (E)-O-allylhydroxylamines

The vinylzinc reagents derived from hydrozirconation of alkynes and transmetallation add readily to nitrones to yield pure (E)-N-allylhydroxylamines; some of these rearrange into O-allylhydroxylamines.     

Effects of structural factors on the pi-dimerization and/or disproportionation of the cation radical of extended TTF containing thiophene-based pi-conjugated spacers

The electrochemical and chemical oxidation of extended TTF 4 and 5 are analysed by cyclic voltammetry, Visible/NIR and ESR spectroscopies, and the X-ray structures of the new salts 5 x BF(4)(CH(2)Cl(2)) and 4 x ClO(4)(THF)(1/2) are presented. The effects of structural factors on the pi-dimerization or the disproportionation reaction of the cation radical are shown. The oxidation of compound 4 presents the successive formation of stable cation radical and dication species both in dichloromethane (DCM) and in a CH(3)CN/THF mixture. In contrast, for compound 5, the stability of the oxidation states strongly depends on the nature of the solvent. In DCM, the oxidation of 5 proceeds by two close one-electron transfers while in CH(3)CN/THF the dication is directly formed via a two-electron process. The X-ray structures of the two salts reveal the formation of pi-dimers of cation radical. While the dimer (5(2))(2+) is due mainly to pi-pi interactions between the conjugating spacer, the multiplication of the sulfur atoms in compound 4 contributes to stabilize the dimer by the combined effects of S-S and pi-pi interactions. Visible/NIR and ESR experiments confirm the higher tendency of 4(+)(.) to dimerize with the occurrence of dimer and monomer in solution, while for 5(+)(.) only the monomer is detected in DCM. On the other hand, by dissolution of 5 x BF(4)(CH(2)Cl(2)) in CH(3)CN, only the neutral and the dicationic states of compounds 5 are observed owing to the disproportionation reaction.     

Template-Reaktion von Bis(acetylacetonato)-dioxo-molybdän(VI) mit Benzoylhydrazin

Template Reaction of Bis(acetylacetonato)-dioxo-molybdenum(VI) with Benzoylhydrazone By reaction of bis(acetylacetonato)-dioxo-molybdenum(VI) with benzoylhydrazine benzoylhydrazido(2?)-acetylacetonebenzoylhydrazonato(2?)-oxo-molybdenum(VI) was formed beside another species. The compound was characterized by mass spectrometry and X-ray structural analysis. Crystallographic data see ?Inhaltsübersicht”?.     

低温燐光的研究及应用

本文综述了44篇文献,介绍低温燐光的发展概况及其应用。     

Monitoring of the metal displacement from the recombinant mouse liver metallothionein Zn(7)-complex by capillary zone electrophoresis with electrospray MS detection

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.     

Selective functionalizations of 2-phenylpyridine: lactones upon organic versus organometallic activations

2-Phenylpyridine activated by chromium tricarbonyl reacts with bis(TMS) ketene acetals to give pyridine-substituted bicyclic γ-lactones. On the other hand, its reaction with the same acetals leads, upon activation with methylchloroformate, to dihydropyridines which can be oxidized to highly substituted, lactone-containing piperidines.     

A spectroscopic study of cobalt(III) furyldioximates

Summary The electronic properties of a series of cobalt(III)trans-furyldioximato-complexes of the type [CoB(FH)₂X] (B=NH₃, X=Cl, Br, I or NO₂; B=pyridine (py) or thiocarbamide (thio), X=Cl or Br; B=imidazole (imid), X=Br), [Co(FH₂)(FH)Cl₂] and [Co(thio)₂(FH)₂]NO₃ were studied by i.r., u.v. and¹H and¹³C n.m.r. spectra The results were compared with those from the corresponding dimethylglyoximato-complexes. It was concluded that -conjugation over the equatorial plane in the furyldioximates is greater than in the dimethylglyoximates. There is some evidence of thetrans-influence of the anionic ligands in the ammines which are in the order NO ₂ ^– >Br^–>Cl^–.     

Countercurrent chromatographic isolation of lolitrem B from endophyte-infected ryegrass (Lolium perenne L.) seed

This paper describes a new method of purification of the Lolitrem B, a tremorgenic mycotoxin produced in planta by the endophytic fungus Neotyphodium lolii. The method is based on the large-scale isolation of the toxin by countercurrent chromatography (CCC). The lolitrem B content in endophyted ryegrass seed, 11 microg/g or 11 ppm, is extracted by stirring finely ground seeds with ethanol for 3 h at room temperature. The concentrated crude extract contains about 0.6 mg/g or 600 ppm of lolitrem B. It is then submitted to CCC purification with a biphasic four-solvent liquid system. A 160-fold enrichment was obtained in one step producing a raffinate containing 10% or 100 mg/g of the toxin. Further purifications were then performed by thin layer and low pressure liquid chromatography. Twenty-eight micrograms of lolitrem B with a 96% purity grade were obtained from 8 kg of seeds (yield 32%).     

Metallophthalocyanines with rod-shaped substituents

4-(4′-Dioctylaminocarbonylbiphenyloxy) phthalonitrile was synthesized from 4-(4′-carboxybiphenyloxy)phthalonitrile and dioctylamine in the presence of Et₃N. Metallophthalocyanines (Zn, Co and Cu) substituted with four dioctylaminocarbonyl biphenyloxy groups on the peripheral positions were prepared from 4-(4′-dioctylaminocarbonylbiphenyloxy)phthalonitrile and the corresponding divalent metal salts (Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The new phthalocyanines are soluble in common organic solvents. These compounds were characterised by ¹H-NMR, ¹³C-NMR, FT-IR, UV-Vis and mass spectroscopies.