Zirconia-based column high-performance liquid chromatography/atmospheric pressure photoionization tandem mass spectrometric analyses of drug molecules in rat plasma

A method using zirconia-based column high-performance liquid chromatography (HPLC) interfaced with an atmospheric pressure photoionization (APPI) source and a tandem mass spectrometer (MS/MS) was developed for the quantitative determination of new chemical entities in rat plasma in support of pharmacokinetics studies. The ionization suppression resulting from endogenous components of the biological matrices on the quantitative zirconia-based column HPLC/APPI-MS/MS method was investigated using the post-column infusion technique. The analytical results for 'rapid rat pharmacokinetics' for 12 drug discovery compounds, obtained by both silica-based phase (S-phase) and zirconia-based phase (Z-phase) chromatographic separation, are in good agreement in terms of accuracy. The application of a Z-phase column for high-temperature fast HPLC/MS/MS methods was explored to reduce the analysis time from 3 min to 30 s for column temperatures of 25-110 degrees C, respectively. The chromatographic retention times and peak responses of all analytes were found to be reproducible under high-temperature conditions following 100 continuous injections, with %CV less than 0.4 and 5, respectively.     

Structures and Properties of Spherical 90‐Vertex Fullerene‐Like Nanoballs

By applying the proper stoichiometry of 1:2 to [Cp^RFe(η⁵‐P₅)] and CuX (X=Cl, Br) and dilution conditions in mixtures of CH₃CN and solvents like CH₂Cl₂, 1,2‐Cl₂C₆H₄, toluene, and THF, nine spherical giant molecules having the simplified general formula [Cp^RFe(η⁵‐P₅)]@[{Cp^RFe(η⁵‐P₅)}₁₂{CuX}₂₅(CH₃CN)₁₀] (Cp^R=η⁵‐C₅Me₅ (Cp*); η⁵‐C₅Me₄Et (Cp^Et); X=Cl, Br) have been synthesized and structurally characterized. The products consist of 90‐vertex frameworks consisting of non‐carbon atoms and forming fullerene‐like structural motifs. Besides the mostly neutral products, some charged derivatives have been isolated. These spherical giant molecules show an outer diameter of 2.24 (X=Cl) to 2.26 nm (X=Br) and have inner cavities of 1.28 (X=Cl) and 1.20 nm (X=Br) in size. In most instances the inner voids of these nanoballs encapsulate one molecule of [Cp*Fe(η⁵‐P₅)], which reveals preferred orientations of π–π stacking between the cyclo‐P₅ rings of the guest and those of the host molecules. Moreover, π–π and σ–π interactions are also found in the packing motifs of the balls in the crystal lattice. Electrochemical investigations of these soluble molecules reveal one irreversible multi‐electron oxidation at E_p=0.615 V and two reduction steps (?1.10 and ?2.0 V), the first of which corresponds to about 12 electrons. Density functional calculations reveal that during oxidation and reduction the electrons are withdrawn or added to the surface of the spherical nanomolecules, and no Cu²⁺ species are involved.     

Current transport along grain boundaries in d-wave superconductors

The use of a classic phase retrieval algorithm has been previously used to determine the local critical current J_c(x) along the length of grain boundary Josephson junctions that can be characterized using a standard s-wave model. The phase retrieval approach has been modified for use with d-wave dominated superconductors to allow for negative local currents along the boundary. In general solutions to the 1-D phase problem are not unique, however in the present work special constraints are employed experimentally to ensure uniqueness. The various current distribution solutions and their possible uniqueness are explored. The solutions are consistent with most existing d-wave Josephson junction boundary models and can be used to understand the basic current distribution along 45° YaBa₂Cu₃O_7−x grain boundary junctions as well as providing a means for mapping the location of self-generated flux cores.     

Completion of Countably Seminormed Spaces

Let E be a vector space with a topology generated by countably many increasing seminorms p1 p2 ...and let _{p i} be the completion of E/ker (pi) with respect to pi. If pi are norms compatible in a certain sense, it is known that E is a complete space if and only if E=_{i=1 p i} . In this paper we give a similar characterization of complete spaces in a general case when pi are seminorms, without any additional assumptions. Our characterization coincides with the known one if pi are compatible norms.     

Static and Dynamic Quenching of Tryptophan Fluorescence in Various Proteins by a Chromium (III) Complex

The interaction of a chromium (III) complex, (R,R)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diaminochromium (III), with human serum albumin, bovine serum albumin, lysozyme, and free tryptophan was studied using steady-state fluorescence spectroscopy. Dynamic and static quenching constants were calculated using Stern-Volmer kinetics. The complex bound more tightly to the serum albumins than to lysozyme or free tryptophan, but only one binding site was determined in all systems. The interaction was also determined to be thermodynamically favorable, and the binding constants were on the order of 10³–10⁶. The fluorescence quenching was static in nature with Forster distances in the 1.8–2.0 nm range.     

Flexible,phase-matched,linear receive arrays for high-field MRI in monkeys

High signal-to-noise ratios (SNR) are essential for high-resolution anatomical and functional MRI. Phased arrays are advantageous for this but have the drawback that they often have inflexible and bulky configurations. Particularly in experiments where functional MRI is combined with simultaneous electrophysiology, space constraints can be prohibitive. To this end we developed a highly flexible multiple receive element phased array for use on anesthetized monkeys. The elements are interchangeable and different sizes and combinations of coil elements can be used, for instance, combinations of single and overlapped elements. The preamplifiers including control electronics are detachable and can serve a variety of prefabricated and phase matched arrays of different configurations, allowing the elements to always be placed in close proximity to the area of interest. Optimizing performance of the individual elements ensured high SNR at the cortical surface as well as in deeper laying structures. Performance of a variety of arrangements of gapped linear arrays was evaluated at 4.7 and 7T in high-resolution anatomical and functional MRI.