Influence of intraperitoneal injection of rare earth compounds on the activities of antioxidant enzymes and the level of lipid peroxidation in mice livers

Following intraperitoneal injection of lanthanum and terbium chloride and their complexes of diethyltriaminopentagacetic acid (DTPA) to adult mice with a dose of 0.28 mmol/kg body weight/day for three days. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the content of lipid end product, malonaldehyde (MDA) in the mice livers have been assayed respectively. The results show that the activity of SOD was increased and the content of MDA was reduced for LaCl3 treated mice and the two targets were not changed for TbCl3, but the activity of GSH-Px was reduced markedly for both LaCl3 and TbCl3 while the above three targets were not changed for La-DTPA and Tb-DTPA complexes.

A NMR investigation on the interaction of lanthanide complexes with phospholipid bilayers

One and two dimentional NMR methods were used to investigate the interactions of lanthanide complexes (Lncit(2) and Ln-DTPA) with phospholipid bilayers, The results showed that in the phospholipid bilayers dispersion containing citrate ligand at pH 7.4, lanthanide ions would initially combine with citrate ligand and form Lncit, complexes which have little effect on the structure of phospholipid bilayers. Ln-DTPA complex does not affect the bilayers structure either. These results provided important experimental data for evaluating scientifically the toxicities of lanthanide ions when they were introduced into the biological body.

Sol-gel synthesis and luminescence of Y4Al2O9:RE3+(RE=Eu, Tb)

Y4Al2O9 (YAM) was prepared by a sol-gel process, using yttrium and aluminum citrate complexes as precursors. The sol-gel process produced single-phase YAM at 900 degrees C, as opposed to the conventional solid-state reaction, which led to the formation of other phases, even if at 1600 degrees C. The emission and excitation spectra of Eu3+ and Tb3+ in YAM showed the existence of two luminescence centers, agreeing with the crystal structure of YAM. The spectral properties of the samples are discussed.

SYNTHESES AND CHARACTERIZATION OF [(MU-CF3CO2)(2)LN(MU-CF3CHO2)ALR(2)CENTER-DOT-2THF](2) AND THEIR CATALYTIC ACTIVITIES FOR POLYMERIZATION OF SOME POLAR MONOMERS

Three new bimetallic complexes were synthesized and crystalized by reactions of (CF3CO2)(3)Ln With R(1) AlR(2)(Ln=Nd and Y, R(1)=H, R=i-C4H9; Ln=Eu, R=R(1)=C2H5) in tetrahydrofuran solution, and their crystal structures were determined using a X-ray diffraction method. The structures and the questions on valence state and noncoplanarity in the structures were confirmed and cracked by means of H-1 NMR and C-13 NMR spectra, especially by C-13-H-1 COSY 2D NMR technique. A general formula of molecules of the three rare earth complexes was defined as follows: [(mu-CF3CO2)(2)Ln(mu-CF3CHO2)AlR(2) . 2THF](2) A mechanism on the formation of the new complexes was also proposed through the following five steps: alkylating, beta-elimination (or hydrogenation), hydrogen transfer, linkage and association. Both Y-Al and Eu-Al complexes function as a catalyst in polymerization of MMA and ECH. The polymer obtained from the first monomer is mainly syndiotactic chain structure and the polymerization of the last monomer shows higher catalytic activity. The Y-Al complex also capable of ring-opening polymerization of THF in case of adding-vary small amount of ECH and a oxonium ion mechanism of THF polymerization was suggested from the analysis of THF polymer terminal.

LANTHANIDE PERCHLORATE COMPLEXES OF 1,4-BIS(PHENYLSULFINYL)BUTANE

Seven trivalent lanthanide perchlorate complexes of the types [Ln(bphab)(4)ClO4] (ClO4)2 (where La = La(III), Pr(III), Nd(III) and Eu(III)) and [Ln(bphab)(3)ClO4] (ClO4)(2) (where Ln = Ho(III), Er(III) and Lu(III), and bphab = 1,4-bis(phenylsulfinyl)butane) have been synthesized by the reaction of bphsb with lanthanide(III) perchlorate in methanol-chloroform mixture. The complexes have been characterized by elemental analyses, molar conductance, electronic and infrared spectral techniques. Several bonding parameters have been calculated from the absorption spectra of the Pr(III), Nd(III), Ho(III) and Er(III) complexes. Infrared spectral data suggest that bphsb acts as bidentate ligand coordinating through the oxygen atoms of the S=O moieties.

C-13 AND H-1 NMR STUDIES OF SOLUTION STRUCTURE OF LANTHANIDE COMPLEX WITH GLYCYL-GLYCINE

C-13 and H-1 NMR technique was used to study the interaction of Gly-Gly with heavy lanthanide cations Dy3+, Ho3+, Er3+, Tm3+ and Yb3+ in aqueous solution. The stability constants for the 1:1 and 1:2 complexes of Gly-Gly with Ho3+ and Yb3+ were determined from the titration curves of chemical shift versus concentration ratio of lanthanide to Gly-Gly. The solution structure of the Ln-Gly-Gly complex was analyzed based upon the C-13 and H-1 lanthanide induced shifts and the results show that in the complex Gly Gly is coordinated to the lanthanide ion through the carboxyl oxygens with the backbone of the ligand in an extended state.

Diversity of pigment-protein complexes of photosynthetic organisms.

PS I, PS II and light-harvesting complexes (LHC) in oxygen evolving photosynthetic organisms were reviewed. These organisms include cyanobacteria, red algae, brown algae, diatoms, chrysophytes, dinophytes, xanthophytes, crypophytes, green algae and green plants. The diversity of pigment-protein complexes that fuel the conversion of radiant energy to chemical bond energy was highlighted, and the evolutionary relationships among the LHC structural polypeptides and the characteristics of the fluorescence emission of PS I at 77 K was discussed.

Ammonia synthesis over Ru/C catalysts with different carbon supports promoted by barium and potassium compounds

Ammonia synthesis over ruthenium catalysts supported on different carbon materials using Ba or K compounds as promoters has been investigated. Ba(NO3)(2), KOH, and KNO3 are used as the promoter or promoter precursor, and activated carbon (AC), activated carbon fiber (ACF). and carbon molecular sieve (CMS) are used as the support. The activity measurement for ammonia synthesis was carried out in a flow micro-reactor under mild conditions: 350-450 degreesC and 3.0 MPa. Results show that KOH promoter was more effective than KNO3. and that Ba(NO3)(2) was the most effective promoter among the three. The roles of promoters can be divided into the electronic modification of ruthenium, the neutralization of surface functional groups on the carbon support and the ruthenium precursor. The catalyst with AC as the support gave the highest ammonia concentration in the effluent among the supports used, while the catalyst with ACF as the support showed the highest turnover-frequency (TOF) value. It seems that the larger particles of Ru on the carbon supports are more active for ammonia synthesis in terms of TOF value. (C) 2001 Elsevier Science B.V. All rights reserved.

Computational Methods for RNA Structure Validation and Improvement.

With increasing recognition of the roles RNA molecules and RNA/protein complexes play in an unexpected variety of biological processes, understanding of RNA structure-function relationships is of high current importance. To make clean biological interpretations from three-dimensional structures, it is imperative to have high-quality, accurate RNA crystal structures available, and the community has thoroughly embraced that goal. However, due to the many degrees of freedom inherent in RNA structure (especially for the backbone), it is a significant challenge to succeed in building accurate experimental models for RNA structures. This chapter describes the tools and techniques our research group and our collaborators have developed over the years to help RNA structural biologists both evaluate and achieve better accuracy. Expert analysis of large, high-resolution, quality-conscious RNA datasets provides the fundamental information that enables automated methods for robust and efficient error diagnosis in validating RNA structures at all resolutions. The even more crucial goal of correcting the diagnosed outliers has steadily developed toward highly effective, computationally based techniques. Automation enables solving complex issues in large RNA structures, but cannot circumvent the need for thoughtful examination of local details, and so we also provide some guidance for interpreting and acting on the results of current structure validation for RNA.

Synthesis of cycloruthenated compounds as potential anticancer agents

A library of 19 cycloruthenated derivatives is constructed by making use of the well-known cyclometalation reaction. Their geometries are modified in a straightforward manner by addition of either mono- or bidentate ligands, such as bipyridine, phenanthroline, 1,2-bis(diphenylphosphanyl)ethane, dimethylphenylphosphane, triphenylphosphane, and 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane (PTA) ligands, to cationic cycloruthenated centers. The antitumor properties of the compounds thus obtained are investigated in order to compare them with recently reported ruthenium complexes and cisplatin. IC50 values against mammalian cells (A-172, HCT-116, and RDM-4) are determined for the library compounds and some of them, such as those derived from orthoruthenated phenylpyridine and a bidentate N,N ligand, display activity of the same order of magnitude as cisplatin.

Structure and solvation in ionic liquids

This Account describes experimental data used to understand the structure of ionic liquids and solute-solvent interactions of both molecular solutes and dissolved metal complexes. In general, the structures of the ionic liquids determined from experimental data show good agreement with both simulated structures and solid-state structures. For all ionic liquids studied, strong charge ordering is found leading to long-range order even in the presence of a solute. For dissolved metal complexes, the ionic liquid is not innocent and a clear dependence on the speciation is observed with variations in both the cation and anion.

Polynuclear metal complexes obtained from the task-specific ionic liquid betainium bistriflimide

The task-specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf2N], was used to dissolve metal oxides and hydroxides. The crystal structures of the resulting metal betaine bistriflimide complexes exhibit a rich structural variety. A trimeric structure was found for the cobalt(II) compound, [Co-3(bet)(8)(Hbet)(2)(H2O)(2)][Tf2N](9)[Hbet], a tetrameric structure for the manganese(II) and zinc(II) compound, [Mn-4(bet)(10)(H2O)(4)][Tf2N](8) and [Zn-4(bet)(10)(H2O)(2)][Tf2N](8), respectively, a pentameric structure for the nickel(II) compound, [Ni-5(bet)(12)(H2O)(6)][Tf2N](10), an oxo-hydroxo-cluster formation for the lead(II) compound, [(Pb4O)Pb(OH)(bet)(8)(Tf2N)3] [Tf2N](4)center dot MeOH, and a polymeric structure for the silver(I) compound, [Ag-2(bet)(2)(Tf2N)Ag-2(bet)(2)][Tf2N](3). The zwitterionic nature of the betaine ligand and the weakly coordinating ability of the bis(trifluoromethylsulfonyl)imide [Tf2N]- anion facilitates the incorporation of metal ions into oligonuclear and polynuclear metal complexes.

A new approach for the detection of ethylene using silica-supported palladium complexes

The coordination of olefins to square-planar Pd(II) and Pt(II) complexes containing 2,9-dimethylphenanthroline (L1) often involves a change of color associated with a change of geometry at the metal center. In order to obtain suitable colorimetric detectors for ethylene gas, a series of new Pd(II) and Pt(II) compounds with a range of 2,9-disubstituted phenanthroline ligands [2,9-di-n-butyl-1,10-phenanthroline (L-2), 2,9-di-s-butyl-1,10-phenanthroline (L3), 2,9-diphenyl-1,10-phenanthroline (L4), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine, L5)] have been prepared and their reactivity toward ethylene investigated both in solution and after depositing the detector compounds on a variety of solid supports. The Pd(II) complex [PdCl2(L2)] supported on silica undergoes a clear color change upon exposure to ethylene, while remaining stable toward air and water, and forms the basis for new simple colorimetric detectors with potential applications in ethylene pipe-leak detection and the monitoring of fruit ripening. Encouragingly, the detector is able to discriminate between fruit at different stages of ripening. The response of the detector to other volatiles was also examined, and specific color changes were also observed upon exposure to aromatic acetylenes. The crystal structures of four new derivatives, including the ethylene-Pt(II) complex [PtCl2(C2H4)(L2)], are also described.

Rare-earth complexes of ferrocene-containing ligands: Visible-light excitable luminescent materials

The ferrocene-derivatives bis(ferrocenyl-ethynyl)-1,10-phenanthroline (Fc(2)phen) and ferrocenoyltrifluoroacetone (Hfta) have been used to synthesize ferrocene-containing rare-earth beta-diketonate complexes. The complexes [Ln(tta)(3)(Fc(2)phen)] and [Ln(fta)(3)(phen)] (where Ln = La, Nd, Eu, Yb) show structural similarities to the tris(2-thenoyltrifluoroacetonate)(1,10-phenanthroline)lanthanide(III) complexes, [Ln(tta)(3)(phen)]. The coordination number of the lanthanide ion is 8, and the coordination sphere can be described as a distorted dodecahedron. However, the presence of the ferrocene moieties shifts the ligand absorption bands of the rare-earth complexes to longer wavelengths so that the complexes can be excited not only by ultraviolet radiation but also by visible light of wavelengths up to 420 nm. Red photoluminescence is observed for the europium(III) complexes and near-infrared photoluminescence for the neodymium(III) and ytterbium(III) complexes. The presence of the ferrocene groups makes the rare-earth complexes hydrophobic and well-soluble in apolar organic solvents.

Long-lived near-infrared luminescent lanthanide complexes of imidodiphosphinate

Near-infrared emitting complexes of Nd(III), Er(III), and Yb(III) based on hexacoordinate lanthanide ions with an aryl functionalized imidodiphosphinate ligand, tpip, have been synthesized and fully characterized. Three tpip ligands form a shell around the lanthanide with the ligand coordinating via the two oxygens leading to neutral complexes, Ln(tpip)(3). In the X-ray crystal structures of Er(III) and Nd(III) complexes there is evidence of CH-pi interactions between the phenyl groups. Photophysical investigations of solution samples of the complexes demonstrate that all complexes exhibit relatively long luminescence lifetimes in nondeuteurated solvents. Luminescence studies of powder samples have also been recorded for examination of the properties of NIR complexes in the solid state for potential material applications. The results underline the effective shielding of the lanthanide by the twelve phenyl groups of the tpip ligands and the reduction of high-energy vibrations in close proximity to the lanthanide, both features important in the design of NIR emitting lanthanide complexes.