Theoretical study on the adsorption of aromatic compounds on platinum clusters

B3 LYP hybrid functional with LACVP* pseudopotential was applied for the optimization of geometries of complexes resulting from interaction of benzene, pyridine, naphthalene, and quinoline with Pt_n (n = 4, 7) clusters. For benzene‐containing complexes, the most stable form corresponds to a bridge adsorption, with benzene undergoing considerable geometric distortions, assuming a boat‐like conformation. C? H bonds are bended upward from the plane of the cluster. C? C bonds stretch, especially when they form π‐complexes with low coordinated Pt atoms. Some arrangements for pyridine complexes involving the N atom of the organic moiety undergo further distortions, apparently preserving a formal C? N π bond. Except for that distortion, the behavior of any heteroaromatic complex is similar to that of benzene in the same arrangement. The quinoline–Pt₇ complex can suitably be used for simulation of the cinchonidine (CD) anchorage over Pt. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Polysaccharide differences between planktonic and biofilm-associated EPS from Pseudomonas fluorescens B52

The polysaccharides associated with free (planktonic) and surface-attached (biofilm) cells from cultures of Pseudomonas fluorescens strain B52 were compared. Variations in the attached matrix due to surface material (glass or stainless steel) were also analyzed. Two digestion methods were used to optimize the recoveries of sugars, uronic acids and acidic substituents. The yield of analyzable material after digestion reached 90% for the material associated to the biofilms, though only 20–30% for that bound to planktonic cells. The polysaccharide(s) in the biofilm had glucuronic and guluronic acids as main components, besides rhamnose, glucose and glucosamine. The proportion of glucuronic to guluronic acid was higher in the polysaccharide(s) found in biofilms formed on stainless steel than in those on glass.     

Molecular dynamics simulations of a nucleoside analogue of 1,4-dihydro-4-oxoquinoline-3-carboxylic acid synthesized as a potential antiviral agent: Conformational studies in vacuum and in water

Conformational analysis of nucleosides may have direct applications to the structure–activity relationship (SAR) studies and in the design of new drug candidates. Although conformational analysis may be accessed in many different ways, in this work it was performed using molecular dynamics (MD) simulation in order to study the dynamic behavior of a nucleoside derivative of 1,4-dihydro-4-oxoquinoline-3-carboxylic acid, synthesized by our group as a potential antiviral agent. The MD simulation was carried out during 10 ns in vacuum and in a box of water at two different temperatures (i.e., 300 and 600 K) using the AMBER force field. The in vacuum MD simulation results are in agreement with the crystallographic structure and with the DFT calculations of the nucleoside, revealing the anti conformer as the more stable one. The simulation in water, however, shows that both conformers may exist at 300 K, the temperature of the in vivo and in vitro assays, revealing that both the syn and anti conformers should be considered in a MD simulation study of the inhibitor–enzyme complex. Simulations are also in agreement with the NOE experiment, which shows that the anti conformer is the preferential one in DMSO-d6 solution at 298 K.     

Complexes of divalent nickel and copper with the Schiff base derived from 2-(2-aminophenyl)benzimidazole and benzaldehyde

Summary The reactions of divalent nickel and copper salts with the Schiff base derived from 2-(2-aminophenyl)benzimidazole and benzaldehyde, L, yield complexes of general formulae [CuL₂X₂] (X=Cl, Br, or ClO₄), [CuL(SO₄)], [CuL(SO₄)] · 4H₂O, and NiLX₂ (X=Cl, Br, or NCS).All the complexes have been characterized by elemental analyses, magnetic measurements, e.s.r. electronic and i.r. spectral studies. The results show that the Schiff base acts as bidentate ligand through the pyridine-like imine nitrogen of imidazole ring and the azomethine nitrogen. Tentative structures of the complexes are suggested.     

Direct determination of gallium on polyurethane foam by X-ray fluorescence

Gallium chloride is easily extracted from 6M HCl by comminuted polyether-type polyurethane foam. After the extraction step, the gallium absorbed by the PU foam can be quantitatively determined by X-ray fluorescence. A procedure for the direct determination of gallium absorbed by PU foam by XRFS is thus described. Gallium is determined at levels as low as 60 ng/ml (C(L)), with a calibration sensitivity of 424 cps ml/mug, within a linear range 0.1-2.30 mug/ml. The procedure investigated was successfully applied to determination of gallium in aluminum alloys, bauxite and industrial residue samples.     

Preparative Droplet Counter-Current Chromatography for the Separation of the New Nor-Seco-Triterpene and Pentacyclic Triterpenoids from Qualea Parviflora

The methanolic extract of the bark of the medicinal plant Qualea parviflora (Vochysiaceae) contains new nor-seco-triterpene and pentacyclic triterpenoids. They were separated in a preparative scale using droplet counter-current chromatography. The optimum solvent used was composed of a mixture of CHCl₃/MeOH/H₂O (43:37:20, v/v) in the descending mode and led to a successful separation of the new compound 28-nor-17, 22-seco-2α, 3β, 19, 22, 23-pentahydroxy-Δ¹²-oleanane, besides the known triterpenoids bellericagenin B, bellericaside B and arjunglucoside I . Identification was performed by ESI-MS, ¹H NMR and ¹³C NMR analyses.     

Effect of cerium, holmium and samarium ions on the thermal and structural properties of the HZSM-12 zeolite

The study of the incorporation of rare earth elements as additives in Y zeolites is a very interesting field of research, mainly by its potential application as additives in catalytic cracking process. In this work was studied the thermal and structural properties of cerium, holmium and samarium supported on HZSM-12 zeolite. The obtained materials were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), nitrogen adsorption, thermogravimetry (TG/DTG), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). TG/DSC/DTA analyses showed that the dehydration temperatures of RE/HZSM-12 zeolites (RE=Ce, Ho, Sm) increase in relation to pure HZSM-12. The acid properties were investigated by pyridine thermo desorption via TG. The results showed two events of mass loss attributed to elimination of pyridine adsorbed on the weak+medium acid sites and on the strong acid sites.     

Trace and major elements in serum of patients with chronic myelogenous leukemia

Summary Major and trace elements were determined in serum of patients with chronic myelogenous leukemia (CML) using total reflection X-ray fluorescence induced by synchrotron radiation (SRTXRF). CML affects 1 to 2 people per 100,000 and accounts for 7-20% cases of leukemia. It was possible to determine the concentrations of the following elements: P, S, Cl, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Br and Rb. Using analysis of variance (ANOVA) it was observed that the contents of the P, S, Ca, Cr, Mn, Fe, Cu and Rb elements differed significantly at a = 0.05 between groups of healthy subjects and CML patients and also genders (males and females).     

A two-step conversion of alpha,beta-unsaturated ketones to their alpha-carbalkoxy or alpha-carbamoyl derivatives

Several enones are converted into their alpha-iodo derivatives in excellent yields and carbonylated with palladium catalysis in the presence of alcohol or amines to the alpha-carbonyl enones in satisfactory yields.     

Nickel determination in osteoblast-like cell culture medium by adsorptive cathodic stripping voltammetry with a mercury microelectrode

The purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast-like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square-wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10⁻⁴ mol L⁻¹; ammonium chloride buffer: 0.10 mol L⁻¹ (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10⁻⁹ mol L⁻¹ for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays.