High pressure Raman studies of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and CuTCNQ

The high-pressure Raman studies of 7,7,8,8-tetracyanoquinodimethane (TCNQ) single crystals and polycrystalline CuTCNQ are presented in this paper. TCNQ shows a phase transition at 22 kbar, a pressure higher than reported earlier. CuTCNQ undergoes a first order phase transition at 30 kbar, which is characterized by the abrupt disappearance of all the Raman bands.     

Determination of tripolyphosphate in frozen cod and scallop adductor by ion chromatography

We introduce a method for the determination of tripolyphosphate in frozen cod and scallop adductor by using ion chromatography. The tripolyphosphate was extracted from minced cod and scallop adductor with deionized water by ultrasonic leaching, and then the proteins soluble in water were precipitated with trichloroacetic acid and removed by filtering. An ion chromatograph with an ionpac AS11-HC anion-exchange column, an ASRS (Anion Self Regenerating Suppression), a conductivity detector and a gradient pump (sodium hydroxide gradient) was used. The detection limit was below 5 mg tripolyphosphate/kg cod or scallop adductor. This method is applicable to the determination of polyphosphates in aquatic products and the procedures are easy to implement.     

<Emphasis Type="Italic">Ab initio</Emphasis> study of small coinage metal telluride clusters Au<Subscript>n</Subscript>Te<Subscript>m</Subscript> (<Emphasis Type="Italic">n,m</Emphasis> = 1, 2)

The geometries of the most stable isomers of gold telluride systems AuTe, Au₂Te, and AuTe₂ are determined using the MP2 method. The aspect of gold—telluride interaction, the electron correlation, and relativistic effects on geometry and stability are investigated at the MP2 and CCSD(T) theoretical levels. The results show that the electron correlation and relativistic effects are responsible not only for gold—gold attraction but also for additional gold—telluride interaction. The gold—telluride interaction is strong enough to modify the known pattern of bare gold clusters. Both effects are essential for determining the geometry and relative stability of this type of systems.     

Analysis of Zoledronic Acid and Its Related Substances by Ion-Pair RP-LC

A simple high-performance liquid chromatographic method – ion-pair reversed- phase high performance liquid chromatography (RPIC) has been developed and employed for the analysis of zoledronic acid and its related substances in bulk material and commercial dosage forms. The mobile phase was a mixture of methanol (20%) and 5 mmol L^–1 phosphate buffer (80%) containing 6 mmol L^–1 tetrabutylammonium bromide, adjusted to pH 7.0 with sodium hydroxide. C₈ column was used as the stationary phase. The chromatographic conditions were optimized. The active ingredient – zoledronic acid was successfully separated from its related substances, including remained imidazol-1-yiacetic acid in the synthesis of zoledronic acid and other possible impurities of oxidation and decomposition. The excipients did not interfere with the determination of zoledronic acid in commercial dosage formulations. The method was rapid, simple, accurate and reproducible. It was not only successfully employed for the assay of zoledronic acid in bulk material and pharmaceutical dosage forms but also for the determination of its related substances.     

Heterometallic lead-titanium oxyalkoxide precursors to lead titanate thin films

Two lead titanium oxyalkoxides with composition Pb₂Ti₄O₂(O₂CCH₃)₂(OC₂H₅)₁₄ and Pb₂Ti₂O₂(O₂CCH₃)₂(OCH(CH₃)₂)₈ have been isolated and characterised by elemental analysis, IR, ²⁰⁷Pb NMR and molecular weight measurements. X-ray structural analysis of the 1:2 complex confirmed the presence of two Pb₂Ti₂O units which are linked by a common Pb···Pb edge and are held together by alkoxide and acetate bridges. The acetate groups have migrated from the Pb to the Ti centres during the reaction. Hydrolysis of the 1:1 Pb/Ti complex produced clear gels providing the H₂O/complex ratio was less than 4. Heat treatment of the gel results in loss of residual organics below 400°C. The XRD pattern indicates the presence of the pyrochlore and perovskite phases after heating at 500°C but the sample is poorly crystalline. Complete conversion to the perovskite phase of lead titanate occurs on heating to 600°C for 1 hour. Thin films of lead titanate were deposited by dip-coating a solution of this complex in isopropanol. Analyses of the films, carried out using electron microprobe, Scanning Auger Spectroscopy and Rutherford Backscattering, indicated that they were of excellent quality, crystalline after heating at 600°C and with relatively sharp substrate-coating interface.     

Interfacial properties of self-organized TiO<Subscript>2</Subscript> nanotubes studied by impedance spectroscopy

The semiconductor properties of the interface TiO₂/electrolyte in high organized porous oxide structures were analyzed by means of impedance spectroscopy near the flat band potential. The impedance and capacitance studies performed on the as-anodized and thermally treated samples (anatase) indicate the presence of a duplex structure formed by (1) the oxide at the bottom of the pores and (2) the walls of pores with different donor densities and surface state concentrations.     

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.     

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.