Loops, Chains, Sheets, and Networks from Variable Coordination of Cu(hfac)(2) with a Flexibly Hinged Aminoxyl Radical Ligand

One pair of reactants, Cu(hfac)(2) = M and the hinge-flexible radical ligand 5-(3-N-tert-butyl-N-aminoxylphenyl)pyrimidine (3PPN = L), yields a diverse set of five coordination complexes: a cyclic loop M(2)L(1) dimer; a 1:1 cocrystal between an M(2)L(2) loop and an ML(2) fragment; a ID chain of M(2)L(2) loops linked by M; two 2D M(3)L(2) networks of (M-L)(n) chains crosslinked by M with different repeat length pitches; a 3D M(3)L(2) network of M(2)L(2) loops cross-linking (M-L)(n)-type chains with connectivity different from those in the 2D networks. Most of the higher dimensional complexes exhibit reversible, temperature-dependent spin-state conversion of high-temperature paramagnetic states to lower magnetic moment states having antiferromagnetic exchange within Cu-ON bonds upon cooling, with accompanying bond contraction. The 3D complex also exhibited antiferromagnetic exchange between Cu(II) ions linked in chains through pyrimidine rings.

Vanadium complexes with 2-pyridineformamide thiosemicarbazones: In vitro studies of insulin-like activity

Reaction of VOCl(2) with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives in ethanol gave as products [VO(H2Am4DH) Cl(2)] (1), [VO(H2Am4Me) Cl(2)] center dot 1/2HCl (2), [VO(H2Am4Et) Cl(2)] center dot HCl (3) and [VO(2Am4Ph) Cl] (4). Upon the dissolution of 1-4 in water, oxidation immediately occurs with the formation of [VO(2)(2Am4DH)] (5), [VO(2)(2Am4Me)] (6), [VO(2)(2Am4Et)] (7) and [VO(2)(2Am4Ph)] (8). The crystal and molecular structures of 5 and 6 were determined. Complexes 5-8 inhibited glycerol release in a similar way to that observed with insulin but showed a low enhancing effect on glucose uptake by rat adipocytes. (C) 2008 Elsevier B.V. All rights reserved.

Structure and thermal reactivity of Zn(II) salts of isocinchomeronic acid (2,5-pyridinedicarboxylic acid)

The synthesis, an improved refined crystal and molecular structure re-determination, and the thermal decomposition behavior of two Zn(II) derivatives of isocinchomeronic acid (2,5-pyridinedicarboxylic acid or H(2)2,5-pydc) are presented. [Zn(2,5-pydc)(H(2)O)(3)Zn(2,5-pydc)(H(2)O)(2)](2) (1) crystallizes in the triclinic P-1 space group with a = 7.106(2), b = 11.450(2), c = 11.869(1) angstrom, alpha = 107.29(1), beta = 104.08(1), gamma = 90.32(2)degrees, and Z = 2. [Zn(2,5-pydc)(H(2)O)(2)] center dot H(2)O (2) is orthorhombic (P2(1)2(1)2(1) space group), with a = 7.342(1), b = 9.430(1), c = 13.834(2) angstrom, and Z = 4. The structures were refined to agreement R(1)-factors of 0.0315 (1) and 0.0336 (2). Complex (1) is arranged as molecular Zn(4)(2,5-pydc)(4)(H(2)O)(10) tetramers, the cages of which define channels that remain unblocked by anions. Compound (2) is polymeric with Zn(2,5-pydc)(H(2)O)(2) and Zn(2,5-pydc)(H(2)O)(3) units linked through bridging ligands. Both compounds were synthesized under mild conditions in aqueous media, without need to resort to hydrothermal media. Changing the pH from 4.51 to 5.75 suffices to direct the chemical processes toward the orthorhombic compound rather than to the triclinic one.

Singlet oxygen reacts with 2 `,7 `-dichlorodihydrofluorescein and contributes to the formation of 2 `,7 `-dichlorofluorescein

There are controversial reports in the literature concerning the reactivity of singlet oxygen ((1)O(2)) with the redox probe 2`,7`-dichlorodihydrofluorescein (DCFH). By carefully preparing solutions in which (1)O(2) is quantitatively generated in the presence of DCFH, we were able to show that the formation rate of the fluorescent molecule derived from DCFH oxidation, which is 2`,7`-dichlorofluorescein (DCF), increases in D(2)O and decreases in sodium azide, proving the direct role of (1)O(2) in this process. We have also prepared solutions in which either (1)O(2) or dication (MB(center dot 2+)) and semi-reduced (MB(center dot)) radicals of the sensitizer and subsequently super-oxide radical (O(2)(center dot-)) are generated. The absence of any effect of SOD and catalase ruled out the DCFH oxidation by O(2)(center dot-), indicating that both (1)O(2) and MB(center dot 2+) react with DCFH. Although the formation of DCF was 1 order of magnitude larger in the presence of MB(center dot 2+) than in the presence of (1)O(2), considering the rate of spontaneous decays of these species in aqueous solution, we were able to conclude that the reactivity of (1)O(2) with DCFH is actually larger than that of MB(center dot 2+). We conclude that DCFH can continue to be used as a probe to monitor general redox misbalance induced in biologic systems by oxidizing radicals and (1)O(2).

Influence of rhBMP-2 on bone formation and osseointegration in different implant systems after sinus-floor elevation. An in vivo study on sheep

Background Several studies have reported certain bone morphogenic proteins (BMPs) to have positive effects on bone generation Although some investigators have studied the effects of human recombinant BMP (rhBMP-2) in sinus augmentation in sheep, none of these studies looked at the placement of implants at the time of sinus augmentation Furthermore, no literature could be found to report on the impact that different implant systems, as well as the positioning of the implants had on bone formation if rhBMP-2 was utilized in sinus-lift procedures Purpose The aim of this study was to compare sinus augmentation with rhBMP-2 on a poly-D, L-lactic-co-glycolic acid gelatine (PLPG) sponge with sinus augmentation with autologous pelvic cancellous bone in the maxillary sinus during the placement of different dental Implants Materials and methods Nine adult female sheep were submitted to bilateral sinus-floor elevation In one side (test group) the sinus lift was performed with rhBMP-2 on a PLPG-sponge, while the contralateral side served as the control by using cancellous bone from the iliac crest Three different implants (Branemark (R), 31 (R) and Straumann (R)) were inserted either simultaneously with the sinus augmentation or as a two staged procedure 6 weeks later The animals were sacrificed at 6 and 12 weeks for histological and histomorphometrical evaluations during which bone-to-implant contact (BIC) and bone density (BD) were evaluated Results BD and BIC were significantly higher at 12 weeks in the test group if the Implants were placed at the time of the sinus lift (p < 0 05) No difference was observed between the different implant systems or positions Conclusions The use of rhBMP-2 with PLPG-sponge increased BIC as well as BD in the augmented sinuses if compared to autologous bone Different implant systems and positions of the implants had no effect on BIC or BD (C) 2010 European Association for Cranio-Maxillo-Facial Surgery

Interaction with calmodulin is important for the secretion of thimet oligopeptidase following stimulation

Thimet oligopeptidase (EC 3.4.24.15; EP24.15) was originally described as a neuropeptide-metabolizing enzyme, highly expressed in the brain, kidneys and neuroendocrine tissue. EP24.15 lacks a typical signal peptide sequence for entry into the secretory pathway and is secreted by cells via an unconventional and unknown mechanism. In this study, we identified a novel calcium-dependent interaction between EP24.15 and calmodulin, which is important for the stimulated, but not constitutive, secretion of EP24.15. We demonstrated that, in vitro, EP24.15 and calmodulin physically interact only in the presence of Ca(2+), with an estimated K(d) value of 0.52 mu m. Confocal microscopy confirmed that EP24.15 colocalizes with calmodulin in the cytosol of resting HEK293 cells. This colocalization markedly increases when cells are treated with either the calcium ionophore A23187 or the protein kinase A activator forskolin. Overexpression of calmodulin in HEK293 cells is sufficient to greatly increase the A23187-stimulated secretion of EP24.15, which can be inhibited by the calmodulin inhibitor calmidazolium. The specific inhibition of protein kinase A with KT5720 reduces the A23187-stimulated secretion of EP24.15 and inhibits the synergistic effects of forskolin with A23187. Treatment with calmidazolium and KT5720 nearly abolishes the stimulatory effects of A23187 on EP24.15 secretion. Together, these data suggest that the interaction between EP24.15 and calmodulin is regulated within cells and is important for the stimulated secretion of EP24.15 from HEK293 cells.

A scenario for torus T(2) destruction via a global bifurcation

We show a scenario of a two-frequeney torus breakdown, in which a global bifurcation occurs due to the collision of a quasi-periodic torus T(2) with saddle points, creating a heteroclinic saddle connection. We analyze the geometry of this torus-saddle collision by showing the local dynamics and the invariant manifolds (global dynamics) of the saddle points. Moreover, we present detailed evidences of a heteroclinic saddle-focus orbit responsible for the type-if intermittency induced by this global bifurcation. We also characterize this transition to chaos by measuring the Lyapunov exponents and the scaling laws. (C) 2007 Elsevier Ltd. All rights reserved.

Ion dependence of magnetic anisotropy in MFe(2)O(4) (M = Fe, Co, Mn) nanoparticles synthesized by high-temperature reaction

The influence of different M(2+) cations on the effective magnetic anisotropy of systems composed of MFe(2)O(4) (M Fe, Co and Mn) nanoparticles was investigated. Samples were prepared by the high-temperature (538 K) solution phase reaction of Fe (acac) 3, Co (acac) 2 and Mn (acac) 2 with 1,2 octanodiol in the presence of oleic acid and oleylamine. The final particles are coated by an organic layer of oleic acid that prevents agglomeration. Transmission electron microscopy (TEM) images show that particles present near spherical form and a narrow grain size distribution, with mean diameters in the range of 4.5 - 7.6 nm. Powder samples were analyzed by ac susceptibility and Mossbauer measurements, and K(eff) for all samples was evaluated using both techniques, showing a strong dependence on the nature of the divalent cation. (C) 2008 Elsevier B.V. All rights reserved.

Synthesis and Structural Analysis of New Palladium(II) Thiosaccharinates with Triphenylphosphane or Diphosphanes

A series of palladium(II) thiosaccharinates with triphenylphosphane (PPh(3)), bis(diphenylphosphanyl)methane (dppm), and bis(diphenylphosphanyl)ethane (dppe) have been prepared and characterized. From mixtures of thiosaccharin, Htsac, and palladium(II) acetylacetonate, Pd(acac)(2), the palladium(II) thiosaccharinate, Pd(tsac)(2) (tsac: thiosaccharinate anion) (1) was prepared. The reaction of I with PPh(3), dppm, and dppe leads to the mononuclear species Pd(tsac)(2)(PPh(3))(2)center dot MeCN (2), [Pd(tsac)(2)(dppm)] (3), Pd(tsac)(2)(dppm)(2) (4), and [Pd(tsac)(2)(dppe)]center dot MeCN (5). Compounds 2, 4, and 5 have been prepared also by the reaction of Pd(acac)(2) with the corresponding phosphane and Htsac. All the new complexes have been characterized by chemical analysis, UV/Vis, IR, and Raman spectroscopy. Some of them have been also characterized by NMR spectroscopy. The crystalline structures of complexes 3, and 5 have been studied by X-ray diffraction techniques. Complex 3 crystallizes in the monoclinic space group P2(1)/n with a = 16.3537(2), b = 13.3981(3), c = 35.2277(7) angstrom, beta = 91.284(1)degrees, and Z = 8 molecules per unit cell, and complex 5 in P2(1)/n with a = 10.6445(8), b = 26.412(3), c = 15.781(2) angstrom, beta = 107.996(7)degrees, and Z = 4. In compounds 3 and 5, the palladium ions are in a distorted square planar environment. They are closely related, having two sulfur atoms of two thiosaccharinate anions, and two phosphorus atoms of one molecule of dppm or dppe, respectively, bonded to the Pd(II) atom. The molecular structure of complex 3 is the first reported for a mononuclear Pd(II)-dppm-thionate system.

New insights on the Lewis acidity of diorganolead(IV) compounds: Diphenyllead(IV) complexes with N,O,S-chelating ligands

The reactions of PbPh2(OAC)(2) with alkylglyoxylate thiosemicarbazones (HRGTSC, R = Et, Bu) afforded complexes of the type [PbPh2(GTSC)] center dot H2O, [PbPh2(RGTSC)(2)] and [PbPh2Cl(BUGTSC)]. The structures of HRGTSC (R = Me, Et, Bu), [PbPh2(OAc)(RGTSC)](R = Me, Et, Bu), [PbPh2Cl(BuGTSC)] and [PbPh2(GTSC)] center dot H2O have been studied by X-ray diffraction. [PbPh2(OAc)(RGTSC)] and [PbPh2(GTSC)] center dot H2O have [PbC2NO3S] kernels and the coordination sphere of the metal is pentagonal bipyramidal. [PbPh2Cl(BuGTSC)] has a [PbC2NOSCI] kernel and the coordination geometry around lead is pentagonal bipyramidal with one vacant site. Analysis of the bond distances in [PbPh2(GTSC)] center dot H2O suggests a significant affinity between diphenyllead(IV) and carboxylate donor groups, supporting a borderline acidic character for this organometallic cation. H-1 and C-13 NMR spectra in DMSO-d(6) suggest the partial dissociation of the acetate in [PbPh2(OAc)(RGTSC)] solutions and indicate some differences in the coordination mode of the two RGTSC(-) ligands in [PbPh2(RGTSC)(2)] complexes. (C) 2007 Elsevier Ltd. All rights reserved.

New Pd(II) and Pt(II) complexes with N,S-chelated pyrazolonate ligands: Molecular and supramolecular structure and preliminary study of their in vitro antitumoral activity

New Pd(II) and Pt(II) complexes [ML2] (HL = a substituted 2,5-dihydro-5-oxo-1H-pyrazolone-1-carbothioamide) have been synthesized by reacting K2MCl4 (M = Pd, Pt) or Pd(OAc)(2) with beta-ketoester thiosemicarbazones. The structures of seven of these complexes were determined by X-ray diffraction. Although all exhibit a distorted square-planar coordination with trans- or (in one case) cis-[MN2S2] kernels, their supramolecular arrangements vary widely from isolated molecules to 3D-networks. The in vitro antitumoral assays performed with two HL ligands and their metal complexes showed significant cytostatic activity for the latter, with the most active [ML2] derivative (a palladium complex) being about sixteen times more active than cis-DDP against the cis-platinum-resistant cell line A2780cisR. (c) 2007 Elsevier Inc. All rights reserved.

An eigenvalue problem for the biharmonic operator on Z(2)-symmetric regions

In this work we show that the eigenvalues of the Dirichlet problem for the biharmonic operator are generically simple in the set Of Z(2)-symmetric regions of R-n, n >= 2, with a suitable topology. To accomplish this, we combine Baire`s lemma, a generalised version of the transversality theorem, due to Henry [Perturbation of the boundary in boundary value problems of PDEs, London Mathematical Society Lecture Note Series 318 (Cambridge University Press, 2005)], and the method of rapidly oscillating functions developed in [A. L. Pereira and M. C. Pereira, Mat. Contemp. 27 (2004) 225-241].

Effect of SO(2) on the Transport Properties of an Imidazolium Ionic Liquid and Its Lithium Solution

Transport coefficients have been measured as a function of the concentration of sulfur dioxide, SO(2), dissolved in 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)-imide, [BMMI][Tf(2)N], as well as in its lithium salt solution, Li[Tf(2)N]. The SO(2) reduces viscosity and density and increases conductivity and diffusion coefficients in both the neat [BMMI] [Tf(2)N] and the [BMMI][Tf(2)N]-Li[Tf(2)N] solution. The conductivity enhancement is not assigned to a simple viscosity effect; the weakening of ionic interactions upon SO(2) addition also plays a role. Microscopic details of the SO(2) effect were unraveled using Raman spectroscopy and molecular dynamics (MD) simulations. The Raman spectra suggest that the Li(+)-[Tf(2)N] interaction is barely affected by SO(2), and the SO(2)-[Tf(2)N] interaction is weaker than previously observed in an investigation of an ionic liquid containing the bromide anion. Transport coefficients calculated by MD simulations show the same trend as the experimental data with respect to SO(2) content. The MD simulations provide structural information on SO(2) molecules around [Tf(2)N], in particular the interaction of the sulfur atom of SO(2) with oxygen and fluorine atoms of the anion. The SO(2)-[BMMI] interaction is also important because the [BMMI] cations with above-average mobility have a larger number of nearest-neighbor SO(2) molecules.

Detailed analysis of the charge transfer complex N,N-dimethylaniline-SO(2) by Raman spectroscopy and density functional theory calculations

Although the amine sulfur dioxide chemistry was well characterized in the past both experimentally and theoretically, no systematic Raman spectroscopic study describes the interaction between N,N-dimethylaniline (DMA) and sulfur dioxide (SO(2)). The formation of a deep red oil by the reaction of SO(2) with DMA is an evidence of the charge transfer (CT) nature of the DMA-SO(2) interaction. The DMA -SO(2) normal Raman spectrum shows the appearance of two intense bands at 1110 and 1151 cm(-1), which are enhanced when resonance is approached. These bands are assigned to nu(s)(SO(2)) and nu(phi-N) vibrational modes, respectively, confirming the interaction between SO(2) and the amine via the nitrogen atom. The dimethyl group steric effect favors the interaction of SO(2) with the ring pi electrons, which gives rise to a pi-pi* low-energy CT electronic transition, as confirmed by time-dependent density functional theory (TDDFT) calculations. In addition, the calculated Raman DMA-SO(2) spectrum at the B3LYP/6-311++g(3df,3pd) level shows good agreement with the experimental results (vibrational wavenumbers and relative intensities), allowing a complete assignment of the vibrational modes. A better understanding of the intermolecular interactions in this model system can be extremely useful in designing new materials to absorb, detect, or even quantify SO(2). Copyright (C) 2009 John Wiley & Sons, Ltd.

Fast batch injection analysis of H(2)O(2) using an array of Pt-modified gold microelectrodes obtained from split electronic chips

A fast and robust analytical method for amperometric determination of hydrogen peroxide (H(2)O(2)) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H(2)O(2) amperometric determination in the concentration range from 0.8 mu mol L(-1) to 100 mu mol L(-1). The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 mu mol L(-1) (3 sigma). The anodic current peaks obtained after a series of 23 successive injections of 50 mu L of 25 mu mol L(-1) H(2)O(2) showed an RSD < 0.9%. To ensure the good selectivity to detect H(2)O(2), its determination was performed in a differential mode, with selective destruction of the H(2)O(2) with catalase in 10 mmol L(-1) phosphate buffer solution. Practical application of the analytical procedure involved H(2)O(2) determination in rainwater of Sao Paulo City. A comparison of the results obtained by the proposed ampermetric method with another one which combines flow injection analysis (FIA) with spectrophotometric detection showed good agreement. (C) 2011 Elsevier B.V. All rights reserved.