Influence of Cyclodextrins on the Kinetics of Oxidation of Amino Acids and BSA by Hydrazyl Radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin.     

The microscopic investigation of structures of moving flux lines by neutron and muon techniques

We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux lines in low T _c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Self-assembly of flowerlike AlOOH boehmite 3D nanoarchitectures

In this work, a hydrothermal route using an ethanol-water solution to progressively synthesize a sequence of flowerlike three-dimensional gamma-AlOOH boehmite nanostructures without employing templates or matrixes for self-assembly is presented. The flowerlike boehmite nanoarchitectures exhibit three hierarchies of self-organization, i.e., single-crystalline nanorods, nanostrips, and bundles, which are characterized by scanning and transmission electron microscopy. The sequence of products obtained after different processing times indicates a self-assembly mechanism. The hydrogen bonding on the surface of nanorods or nanostrips possibly plays a key role, as identified by FTIR spectra of the products after they had been heated to 1000 degrees C. The specific surface area and pore-size distribution of the obtained product as determined by gas-sorption measurements show that the boehmite nanoarchitectures exhibit high BET surface area and porosity properties.     

High-aspect-ratio aluminum borate nanowire bundles supported by sucrose

High-aspect-ratio and single-crystal aluminum borate (Al(18)B(4)O(33)) nanowire bundles with an ordered orientation were synthesized by using an innovative sucrose-assisted growth process. The process involves the dehydration and polycondensation of aluminum borate-sucrose solution to form a highly viscous precursor. The sucrose plays a crucial role in the growth of the nanowire bundles by supporting as a polymeric substrate and a type of adhesive template. Electron microscopy was used to characterize the high-aspect-ratio nanowire bundles. A possible growth mechanism for the nanowire bundles is proposed.