Excess molar enthalpies of binary mixtures for (tributyl phosphate+methanol/ethanol) at 298.15 K

Excess molar enthalpies of binary mixtures for tributyl phosphate (TBP)+methanol/ethanol were measured with a TAM air Isothermal calorimeter at 298.15 K and ambient. The results for xTBP+(1–x)CH₃OH are negative in the whole range of composition, while the values for xTBP+(1–x)C₂H₅OH change from positive values at low x to small negative values at high x. The experimental results have been correlated with the Redlich–Kister polynomial. IR spectra of the mixtures were measured to investigate the effect of hydrogen bonding in the mixture.     

Synthesis and lysozyme adsorption of rod-like large-pore periodic mesoporous organosilica

Highly ordered rod-like large-pore periodic mesoporous organosilica (PMO) was successfully synthesized at low acid concentration with the assistance of inorganic salt using triblock copolymer P123 as a template. The roles of inorganic salt and acidity in the production of highly ordered mesostructure and the morphology control of PMOs were investigated. It was found that the inorganic salt can significantly widen the range of the synthesis parameters to produce highly ordered 2D hexagonal pore structure of p6mm symmetry. However, the uniform rod-like PMOs can only be synthesized in a narrow range of acid and salt concentrations, which were sensitive to induction time. The adsorption of lysozyme on PMO was studied at different pH values in comparison with adsorption on pure silica material under controlled morphology and pore structure. It was found that the adsorption capacity of lysozyme on the PMO was lower than that on pure SBA-15 silica material and the adsorption amounts are larger at pH 9.6 than at 7.0 for both materials. The results show that the electrostatic interaction between lysozyme and PMO/SBA-15 surface is more dominant than the hydrophobic forces and the interaction of neighboring lysozyme molecules also plays an important role.     

Multidimensional high performance liquid chromatography--capillary electrophoresis separation of a protein digest: an update

The trypsin digest of a mixture of two proteins, namely cytochrome c and myoglobin, was first separated in the first dimension by high-performance liquid chromatography (HPLC). Fractions from the HPLC were collected every 30s with the aid of a fraction collector into a 96-well microtiter plate. After concentration, all the collected fractions were analyzed simultaneaosly in the second dimension by a 96-array capillary electrophoresis system. The labeled peptides were detected by laser-induced fluorescence. An internal standard, allura red, was added to all the fractions, prior to capillary electrophoretic analysis. The internal standard serves two functions, migration time correction and signal intensity correction. The data are presented in two different formats, as an electropherogram of all the fractions and in a two-dimensional (2-D) format. The 2-D plot of the data shows the density of each spot, which corresponds to the concentration of the migrating peptides. The total experimental time for the HPLC and capillary electrophoretic analyses ist less than 1 h, which ist much faster than using 2-D slab-gel electrophoresis or single-capillary capillary electrophoresis.     

A new production method for carrier-free201Tl using IEN'S cyclotron in Rio De Janeiro

A new and simplified method was developed for the separation of thallium 201 which will allow the shipment of a “one shot generator” to distant places and easy elution at the destination. Thallium is produced as usually, through the reaction $${}^{nat}Tl/p,xn/^{201} pb\xrightarrow{{\beta ^ + }}{}^{201}Tl$$ with 24-MeV protons from IEN'S CV-28 cyclotron. The separation is based on the properties of a chelating carboxylic acid cation exchange resin column which at pH 4.5 retains lead while thallim is easily eluted. This column can also be used as a regular generator to produced greater quantities of²⁰¹Tl but at the expense of more elutions.     

Preparation of a piezoelectric immunosensor for the detection of Salmonella paratyphi A by immobilization of antibodies on electropolymerized films

 To obtain new coatings for the preparation of piezoelectric immunosensors, the anodic polymerization of o-aminophenol (oAP), o-phenylenediamine (oPD) and m-phenylenediamine (mPD) onto a gold-plated crystal has been studied. The possibility of immobilizing an antibody (anti-S. paratyphi A) onto the crystal via the electropolymerized films was investigated. The poly-mPD film gave the best results for immobilizing the antibody. With antibodies crosslinked on the poly-mPD film, a piezoelectric immuno-assay for the detection of S. paratyphi A was proposed. The shift (ΔF=F_20s−F_400s, Hz) between the frequency at 20 s after the addition of sample (F_20s), and that of 400 s (F_400s) was used to construct a calibration graph, and shortening of the assay time was achieved. The S. paratyphi A concentration in the range of 10^5–10⁹ cells/ml can be measured by this method. Received: 9 May 1996/Revised: 6 September 1996/Accepted: 19 September 1996     

Synthesis, structure and physical properties of Ru ferrites: BaMRu5O11 (M=Li and Cu) and BaM′2Ru4O11 (M′=Mn, Fe and Co)

The synthesis, structure, and physical properties of five R-type Ru ferrites with chemical formula BaMRu₅O₁₁ (M=Li and Cu) and BaM′₂Ru₄O₁₁ (M′=Mn, Fe and Co) are reported. All the ferrites crystallize in space group P6₃/mmc and consist of layers of edge sharing octahedra interconnected by pairs of face sharing octahedra and isolated trigonal bipyramids. For M=Li and Cu, the ferrites are paramagnetic metals with the M atoms found on the trigonal bipyramid sites exclusively. For M′=Mn, Fe and Co, the ferrites are soft ferromagnetic metals. For M′=Mn, the Mn atoms are mixed randomly with Ru atoms on different sites. The magnetic structure for BaMn₂Ru₄O₁₁ is reported.     

Reactivity of DNA guanyl radicals with phenolate anions

Guanine bases are the most easily oxidized sites in DNA. Electron-deficient guanine species are major intermediates produced in DNA by the direct effect of ionizing radiation (ionization of the DNA itself) because of preferential hole migration within DNA to guanine bases. By using thiocyanate ions to modify the indirect effect (ionization of the solvent), we are able to produce these single-electron-oxidized guanine radical species in dilute aqueous solutions of plasmid DNA where the direct effect is negligible. The guanyl radical species produce stable modified guanine products. They can be detected in the plasmid by converting them to strand breaks after incubation with a DNA repair enzyme. If a phenol is present during irradiation, the yield of modified guanines is decreased. The mechanism is reduction of the guanine radical species by the phenol. It is possible to derive a rate constant for the reaction of the phenol with the guanyl radical. The pH dependence shows that phenolate anions are more reactive than their conjugate acids, although the difference for guanyl radicals is smaller than with other single-electron-oxidizing agents. At physiological pH values, the reduction of a guanyl radical entails the transfer of a proton in addition to the electron. The relatively small dependence of the rate constant on the driving force implies that the electron cannot be transferred before the proton. These results emphasize the potential importance of acidic tyrosine residues and the intimate involvement of protons in DNA repair.     

Quantitation of SU1 1248, an oral multi-target tyrosine kinase inhibitor, and its metabolite in monkey tissues by liquid chromatograph with tandem mass spectrometry following semi-automated liquid-liquid extraction

SU11248 is a potent inhibitor of PDGFR, VEGFR, KIT, and Flt3, and is currently under Phase I clinical evaluation as an anticancer drug. A sensitive and specific analytical method for the quantitation of SU11248 and its metabolite in several monkey tissues (liver, kidney, brain and white fat) using LC-MS-MS following semi-automated liquid-liquid extraction (LLE) was developed and validated. Amounts of 50 mg of tissue were homogenized using an ultrasonic processor. After addition of the stable labelled internal standard (IS) and ammonium hydroxide (0.3%), samples were extracted with 2.5 ml of tert-butyl methyl ether. Following centrifugation, aliquots of 1.8 ml of the organic phase were transferred into a 96-well plate. The Packard Multiprobe II robotic liquid handler was used to perform all steps mentioned above. The organic phase was dried and the residue was reconstituted with 800 microl of 15 mM ammonium formate buffer solution (pH 3.25) using a Tomtec Quadra 96 workstation. Aliquots of 10 microl of the resulting solution were injected into the LC-MS-MS system. A Symmetry Shield C8 column (50 mm x 2.1 mm, 3.5 microm) was used to perform the chromatographic analysis. The mobile phase was 15 mM ammonium formate buffer solution (pH 3.25)-acetonitrile (74:26 (v/v)) with a flow-rate of 0.35 ml/min. Retention times of the metabolite and SU11248 were about 2.5 and 3.5 min, respectively. Total cycle time was 5 min. MS detection used the Applied Biosystems-MDS Sciex API 3000 with TurbolonSpray interface and multiple reaction monitoring (MRM) operated in positive ion mode. The method was validated for both compounds over the calibration range of about 2 and 2000 ng/g. The suitability and robustness of the method for in vivo samples were confirmed by analysis of monkey tissues from animals dosed with SU11248.     

A fibrous hypercrosslinked sorbent prepared on PP-ST-DVB matrix via post-crosslinking reaction

A fibrous sorbent possessing abundant micropore structure was firstly prepared via post-crosslinking reaction on the PP-ST-DVB original fiber. Its micromorphology and sorptive properties were investigated, and the results demonstrated that the novel fibrous hypererosslinked sorbent has narrow pore-size distribution, small average porous radius （1.90 nm）, high specific surface area （362.31 m^2/g）, and fine sorptive properties for small organic molecules.     

Combinatorial synthesis of a small-molecule library based on the vinyl sulfone scaffold

[reaction: see text] A 30-member library of small molecules based on the vinyl sulfone scaffold was prepared on rink amide resin, using solid phase-based reactions such as oxidation and Horner-Wadsworth-Emmons reaction. The library was designed such that three points of diversity were readily introduced in the library to accommodate the S(1)', S(1), and S(2) binding pockets of different cysteine proteases, making the strategy suitable for high-throughput generation of potential cysteine protease inhibitors.