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.     

Experimental Setup for Observation the Bose–Einstein Condensation of Magnons in Solid Antiferromagnets CsMnF3 and MnCO3

The Bose–Einstein condensation of magnons was observed in 1984 in superfluid ³He–B. The same phenomena should exist in solid magnetic systems. We describe here a partly digital experimental setup for studying solid antiferromagnets CsMnF₃ and MnCO₃ by pulse and continuous wave nuclear magnetic resonance. With this equipment, the Bose–Einstein condensation of magnons was observed for the first time in these single crystals.     

Electron paramagnetic resonance of Gd3+ ions in powders of LaF3:Gd3+ nanocrystals

The observation of electron paramagnetic resonance of Gd³⁺ ions in nanosized powders of rare-earth fluorides LaF₃:Gd³⁺ has been reported. The measurements have been performed on a single crystal and micro- and nanosized powders at room temperature. Electron paramagnetic resonance spectra and spin-Hamiltonian parameters of Gd³⁺ ions have been obtained. A qualitative difference of spectra in nano- and micropowders due to the increase in the spread of the crystal field parameters with the decrease in the particle size has been found. The relationship between the single-crystal domain size and the hydrothermal treatment time has been established.     

Size effect in the (PrF3 nanoparticles-3He) system

Spin kinetics of adsorbed and liquid ³He in contact with crystalline nanopowders of the Van Vleck paramagnet PrF₃ at a temperature of 1.5 K has been studied by nuclear magnetic resonance. The correlation between the parameters of the nuclear magnetic relaxation of ³He and the sizes of the sample particles has been found. A qualitative model of the magnetic relaxation of ³He describing the experimental results has been proposed.     

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.     

Photoinduced toxicity of PrF<Subscript>3</Subscript> and LaF<Subscript>3</Subscript> nanoparticles

PrF₃ and LaF₃ nanoparticles were synthesized by the hydrothermal method. The size distribution of these nanoparticles in the colloidal solution produced was studied by photon correlation spectroscopy. The mean diameter of the nanoparticles was 42 ± 1 nm. During the study of the toxicity of the nanoparticles, the mixture of a colloidal solution of the nanoparticles with cells to be studied was irradiated by 30-mW continuous lasers at wavelengths of 532 and 473 nm. The concentration of salmonella cells in normal saline was 10⁶ cell/mL, while that of nanoparticles was 0.1 g/L. The cell survival percentage was 39, 34, and 20% for the irradiation times of 5, 10, and 15 min, respectively, at an optimal laser radiation power density of 0.4 W/cm at a wavelength of 532 nm. It was ascertained that LaF₃ nanoparticles do not possess the property of photoinduced toxicity and the apoptosing effect. Moreover, the property of photoinduced toxicity is not shared by microparticles, in contrast to nanoparticles.     

Experimental proof of the existence of water clusters in fullerene-like PrF<Subscript>3</Subscript> nanoparticles

Synthesized fullerene-like nanoparticles of the Van Vleck paramagnet PrF₃ have been studied by nuclear magnetic resonance cryoporometry. Water clusters have been discovered in the internal cavities of the nanoparticles. The analysis of the experimental data indicates that the cluster radius is 1–2.3 nm. The obtained data agree well with the high-resolution transmission electron microscopy data.