José Parada

Rapid capillary electrophoresis analysis of glutathione and glutathione disulfide in roots and shoots of plants exposed to copper

INTRODUCTION Glutathione and glutathione disulfide can be determined by capillary zone electrophoresis; however, the frequent use of acidic precipitation of protein from samples prior to analysis generates an acidic matrix of strength and pH that may cause changes in the method sensitivity, comigration of species or changes in the equilibria that relate both species in cells or fluids. OBJECTIVE To optimise electrophoretic conditions for glutathione and glutathione disulfide determination, and to improve pre-analytical treatment for better visualization of the signals of both peptides in an acidic matrix. METHODOLOGY The method consisted of direct photometric detection at 185 nm and 300 mm borate at pH 7.6 as background electrolyte. The variables under study were voltage applied, injection time, capillary length and electrolyte pH. Seedlings were hydroponically grown and the peptides were extracted with metaphosphoric acid. RESULTS The resulting acidic matrix was previously treated with the same background electrolyte to prevent comigration and to improve signal resolution. The optimised method showed good reproducibility and linearity, with correlation coefficients above 0.999 and detection limits below 3 microM, and determination of both analytes in less than 3 min. Analyte recovery in the process was in the 88-104% range. The concentration range found in hydroponically grown tomato plants, irrespective of copper level, was 45-100 nmol/g fresh weight for glutathione and below 56 nmol/g fresh weight for glutathione disulfide. CONCLUSION The results obtained here support the applicability of the method to the fast and simultaneous determination of glutathione and glutathione disulfide in tissue of shoots and roots of plants grown under either normal or stressful conditions.

Complexation of amino sugars with cobalt(III)bis(phenanthroline)

Abstract Complexes of Co(III)bis(phenanthroline) with β - d -mannosamine and α - d -galactosamine can be isolated as the triiodide salts. The complex with d -mannosamine has the Δ -configuration at Co(III). Complexation with d -galactoamine gives the Δ - in excess over the Λ - complex, and the Δ -complex can be isolated chromatographically. Complexation involves cis -1-OH and 2-NH 2 groups, eq , ax respectively with β -mannosamine and ax , eq respectively, with α -galactosamine, as with α -glucosamine, based on 1 H NMR spectra. Galactosamine complexes in aqueous solution decompose to the free sugar, but the mannosamine complex is much more stable.

Mixed complexes of cobalt(III) with phenanthroline and galactose or arabinose

Abstract Mixed complexes of bis-phenanthroline cobalt(III) and α- d -galactose or β- d - or l -arabinose are identified in aqueous solution from their 1H NMR and circular dichroism (CD) spectra. Galactose forms only the Δ-complex, but d -arabinose gives preferentially Δ-, and l -arabinose preferentially Λ-complexes, consistent with structural optimization with PM3 (tm) parameters. The Λ-complex is formed initially from β- d -arabinose, but the Δ-complex is preferred thermodynamically. Examination of the absorption and CD spectra gives information on configuration at cobalt(III) and allows assignments of electronic transitions in Co(III) and the phenanthroline residues.

Complexation of sucrose with cobalt(III)bis(phenanthroline)

The delta-[Co(III)bis(phenanthroline)(sucrose)]3+ complex forms with little perturbation of the sucrose conformation, and complexation by HO-2(g) and HO-1(f).

SIMULTANEOUS DETERMINATION OF GLUTATHIONE AND GLUTATHIONE DISULFIDE IN AN ACID EXTRACT OF PLANT SHOOT AND ROOT BY CAPILLARY ELECTROPHORESIS

This study describes the fast and simultaneous determination of glutathione and glutathione disulfide by Capillary Zone Electrophoresis in plant extracts of shoot and root of tomato plants. Frequent use of acidic precipitation of protein generates an acidic matrix of strength and pH that may cause changes in the method sensitivity, comigration of species or changes in the equilibria that relate both species in cells or fluids. In this study, the resulting acidic matrix was previously treated with the same background electrolyte to prevent comigration and to improve signal resolution. Optimization of some parameters of the technique allowed the determination of both analytes in less than three minutes. The optimized method showed good reproducibility and linearity, with correlation coefficients above 0.999 and detection limits below 3 µM for both peptides. Analyte recovery in the process was in the 88-104% range. The concentration found in tomato plants hydroponically grown in the absence of stress factors was in the 51-100 nmol g-1 range, fresh weight for GSH and 5-32 nmol g-1 range, fresh weight for GSSG.

A Cu(II) POLYMERIC COMPLEX SURVEYING TRIETHANOLAMINE AND 1,2-DI(4-PYRIDYL)ETHYLENE AS BRIDGING LIGANDS

We report the synthesis and crystal structure of a copper (II) polymeric complex (I) prepared by reaction of Cu(ClO4)2 ·5H2O with H3tea (triethanolamine,) and dpe (1,2-di(4-pyridyl)ethylene). in ethanol. The compound is made up of two well differentiated substructures, the first one being a cationic 1D polymer balanced by ClO4- counteranions {[Cu2(H2tea)2(dpe)]·(ClO4)2}n and the second one made is up of two dimers of different occupancies and charge content, viz., [Cu2(Htea)2(dpe)] (neutral, 64% occupancy) and [Cu2(H2tea)2(dpe)]2+ (cationic, 36% occupancy), this latter fraction balancing the charge introduced by ClO4- anions with 72% occupancy. Both substructures differ in that the Hmtea anions in the dimers (m = 1,2) do not bridge cations as their homologue H2tea does in the polymer, but chelate instead one single Cu each. As shown in scheme. The structure of (I) is compared with its close relative [Cu2(H2tea)2(dpe)]·(bpe)·(ClO4)2·H2O (II), where the same original constituents assemble in a slightly different way1.

Sucrose bis(1,10-phenanthroline)cobalt (III). Predicted distortion at the octahedral center

Abstract The two 1,10-phenanthroline ligands in the mixed Δ-cobalt(III) complex with sucrose are in different environments relative to the sucrose ligand as shown by differences in their 1H NMR signals and predicted by structural optimization. There is considerable congestion between the glucose moiety and one of the phenanthrolines in the Δ-complex, and the interactions which stabilize it, relative to a Λ-complex, are analyzed. Differences in 1H chemical shifts of the phenanthrolines are related to their mutual interactions and those with the glucose moiety of the sugar, which lead to π-shielding in some of its 1H NMR signals. Absorption and circular dichroism (CD) spectra are analyzed with assignment of the electronic transitions.

SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL ACTIVITY OF COBALT(III) COMPLEX WITH PHENANTHROLINE AND MALTOSE

ABSTRACT The mononuclear cobalt(III) complex derived from 1,10-phenanthroline and maltose ([Co(phen) 2 maltose]Cl 2 ∙3H 2 O) ( 1 ) has been synthesized and characterized in aqueous solution. Its characterization was based on its optical and spectroscopic properties.The antimicrobial activity of this complex was screened in vitro against the microorganisms Escherichia coli DH5a, Salmonella enterica sv Enteritidis ISP/953, Klebsiella pneumoniae RYC492, Pseudomonas aeruginosa PAO1, Enterococcus faecalis ATCC 29212, Bacillus cereus GCA234, Micrococcus sp. Staphylococcus aureus ATCC25923.Complex ( 1 ) showed antibacterial activity with a bacteriostatic effect over Gram positive and negative bacteria. The cytotoxicity of complex (1) was tested in vitro on human embryonic kidney cells. Keywords: Carbohydrate-cobalt(III) complexes; circular dichroism; antibacterial activity. e-mail: jparada@ciq.uchile.cl 1. INTRODUCTION Transition metal complexes are of interest since they display a wide variety of application in fields ranging from materials science and catalysis to biological activity [1].From the biological point of view, several studies have shown that the complexes may have antibacterial, antifungal and antitumor activity [2].The biological activity of metal complexes is highly dependent on the nature of the metal ions and the donor sequence of the ligands because different ligands exhibit different biological properties [3].An interesting group of ligands are the carbohydrates [4], whose complexes have shown significant antimicrobial activity against Gram-positive and Gram-negative bacterial strains as well as a few fungal strains [5]. Poller and Parkin reported the synthesis of organometallic derivatives of sucrose (lead, tin and germanium). In that study organotin was found to exhibit higher biocidal activities than would be expected from the tin content [6].A few sugar-cobalt complexes with antibacterial activity have been reported. An important example is grafted PVA polymer with a derivative of erythro-ascorbic acid (pentulosono-lactone-2,3-enedianisoate) reported by Salih et al. It was evaluated for antimicrobial properties against four pathogenic bacteria (

Enantioselective addition of diethylzinc to benzaldehyde catalyzed by an organometallic Ti(IV) compound and a xylose derivative

A derivative of D-xylose, 1,2-O-isopropylidene-α-D-xylofuranose (1), with Ti(OiPr)4 was used as a chiral catalyst in the asymmetric alkylation of benzaldehyde with diethylzinc (Et2Zn) for the high-yield production (90% conversion) and moderate enantioselectivity (45% ee (S)) of 1-phenyl-1-propanol. Optimum conditions (conversion and enantioselectivity) for the catalytic system formed by 1 and Ti(IV) were 10.0 mol % of 1 and 1 equivalent of Ti(IV) with respect to benzaldehyde in CH2Cl2 as a solvent, at room temperature. In the asymmetric alkylation of benzaldehyde with Et2Zn compound 1 in substoichiometric amount with Ti(OiPr)4 forms a chiral catalyst of the Ti(IV)-sugar type that ensures the good-yield conversion and the enantioselectivity of the reaction.

ENANTIOSELECTIVE ADDITION OF DIETHYL ZINC TO BENZALDEHYDE CATALYZED BY TI(IV) AND GLUCOSE DERIVATIVES

D-Glucose derivatives 1,2:5,6-di-O-isopropyline-a-D-glucofuranose (1) and 1,2-O-isopropyline-a-D-glucofuranose (2) with Ti(IV) are chiral catalysts in the addition of diethylzinc to benzaldehyde. The Ti(IV)-carbohydrate catalytic system is optimal with excess Ti(IV) and substoichiometric carbohydrate and 2 is the more active chiral catalyst probably because this derivative acts as a bidentate ligand in the proposed reaction. The arrangement of OH groups is crucial in determining the configuration of the alcohol product.