Low-density to high-density transition in Ce75Al23Si2 metallic glass

Using in situ high-pressure x-ray diffraction (XRD), we observed a pressure-induced polyamorphic transition from the low-density amorphous (LDA) state to the high-density amorphous (HDA) state in Ce(75)Al(23)Si(2) metallic glass at about 2 GPa and 300 K. The thermal stabilities of both LDA and HDA metallic glasses were further investigated using in situ high-temperature and high-pressure XRD, which revealed different pressure dependences of the onset crystallization temperature (T(x)) between them with a turning point at about 2 GPa. Compared with Ce(75)Al(25) metallic glass, minor Si doping shifts the onset polyamorphic transition pressure from 1.5 to 2 GPa and obviously stabilizes both LDA and HDA metallic glasses with higher T(x) and changes their slopes dT(x)/dP. The results obtained in this work reveal another polyamorphous metallic glass system by minor alloying (e.g. Si), which could modify the transition pressure and also properties of LDA and HDA metallic glasses. The minor alloying effect reported here is valuable for the development of more polyamorphous metallic glasses, even multicomponent bulk metallic glasses with modified properties, which will trigger more investigations in this field and improve our understanding of polyamorphism and metallic glasses.

Amorphouslike diffraction pattern in solid metallic titanium

Amorphouslike diffraction patterns of solid elemental titanium have been detected under high pressure and high temperature using in situ energy-dispersive x-ray diffraction and a multianvil press. The onset pressure and the temperature of formation of amorphous titanium is found to be close to the alpha-beta-omega triple point in the P-T phase diagram. Amorphous Ti has been found to be thermally stable up to 1250 degrees C for at least 3 min at some pressures. By analyzing the conditions for producing amorphous elemental Zr and Ti, we observed a multi-phase-point amorphization phenomenon for preparing single-element bulk amorphous metals. The results reported may open a new way to preparing single-element bulk amorphous metals with a high thermal stability.

Determination of levodopa methyl ester and its metabolites in rat serum by CZE with amperometric detection

A reliable and reproducible method, capillary zone electrophoresis with amperometric detection (CZE-AD), has been developed for separation and quantification of levodopa methyl ester (LDME) and its biotransformation products levodopa (L-DOPA) and dopamine (DA) in rat serum. A carbon-disk electrode was used as working electrode. The optimum conditions for CZE detection were 50 mmol L(-1) phosphate solution at pH 7.0 as running buffer, 17 kV as separation voltage, 1.0 V (vs Ag/AgCl, 3.0 mol L(-1)) as detection potential, and sample injection for 8 s at 17 kV. The linear ranges were from 2.4 x 10(-2) to 2.2 microg mL(-1) for LDME, 2.9 x 10(-1) to 49.5 microg mL(-1) for L-DOPA, and 1.4 x 10(-2) to 1.5 microg mL(-1) for DA with correlation coefficients of 0.9997, 0.9994, and 0.9999, respectively. The detection limits for LDME, L-DOPA, and DA were 14.6, 98.0, and 9.7 ng mL(-1), respectively. Recoveries were 80.3% for LDME, 93.5% for L-DOPA, and 86.5% for DA. This method was applied to serum samples after intravenous injection of LDME and L-DOPA to rats.

Effects of Lu-Duo-Wei capsules on superoxide dismutase activity and contents of malondialdehyde and lipofuscin in the brain of the housefly

The biochemical actions of Lu-Duo-Wei capsules and tea polyphenol in relation to their antioxidant capability have been compared in the male housefly, Musca domestica. It was found that tea polyphenol had the effect of increasing the activity of superoxide dismutase (SOD) in the brain of the housefly only at the 60th day in the experimental period whereas Lu-Duo-Wei showed more obvious effects on SOD than tea polyphenol irrespective of experimental days. Moreover, the contents of malondialdehyde (MDA) and the rate of lipofuscin accumulation were decreased by the effect of Lu-Duo-Wei at the 20th, 40th, 50th and 60th days, while the similar effect of tea polyphenol on the content of MDA and lipofuscin was observed only at the 40th day. These results indicated that the biochemical actions of Lu-Duo-Wei in antiaging was much stronger than those of tea polyphenol, the mechanism of which was probably related to the synergistic effect of its involved antioxidants and others as well as the exclusive promotion of SOD biosynthesis/or a reduction of free radical-induced damage of the enzyme.

Effects of lu-duo-wei capsule on prolonging life span of housefly and Drosophila melanogaster

Lu-Duo-Wei capsule is a product of Chinese medicine having high efficacy in scavenging superoxide and hydroxyl radicals. It contains antioxidants, which may increase longevity, but whether Lu-Duo-Wei capsule has such an effect is unknown. In this study, supplementing the basic diet with Lu-Duo-Wei resulted in prolonging the life span of houseflies and fruit flies. Moreover, the effect of prolonging the life span of houseflies by Lu-Duo-Wei was significantly higher than that of tea polyphenol. The result not only confirms our previous report but also supports the free radical theory of aging.

Effect of lu-duo-wei on scavenging superoxide and hydroxyl radicals in vitro

Irradiation of a riboflavin-containing system by ultraviolet light was used to produce superoxide radical (.O2-). Hydroxyl radical (.OH) was generated by the system of Fe(II)-H2O2. Using electron spin resonance and spin trapping techniques, the effect of Lu-Duo-Wei, a capsule consisting extracts of green tea, Fructus Lycii and Semen Ziziphi Spinosae, on scavenging .O2- and .OH was observed. The results showed that the efficiency of scavenging .O2- and .OH by Lu-Duo-Wei was much higher than that by tea polyphenol alone. It is suggested that the synergistic action of tea polyphenol and other components are responsible for the scavenging effect of Lu-Duo-Wei on .O2- and .OH.

Purification and properties of acetylcholinesterase from human brain

Acetylcholinesterase from human caudate nucleus and partial thalamus was purified by using Con A-Sepharose, short-arm and long-arm ligand Sepharose affinity chromatographies. SDS-PAGE of the purified AChE under the reduced condition showed one main band, corresponding to a molecular weight of 66 kD. The purified AChE with a specific activity of 3384 U/mg protein represented 20% activity of the homogenate supernatant. Analysis of purified AChE by gradient slab PAGE and DISC-PAGE with activity staining revealed the existence of monomer, dimer, tetramer, hexamer and octomer of the enzyme. The isoelectric point of AChE ranged between pH 5.6 and 6.0. Con A-Sepharose affinity chromatography retained most of the applied AChE activity implying that the enzyme is a kind of glycoprotein. The isolated human brain AChE had no cross-immunoreactivity with 3F3 and weak cross-immunoreactivity with 2G8 and 1H11 anti-Torpedo AChE antibodies. Balb/c mice were immunized with human cerebellum AChE purified with Con A and short-arm ligand affinity chromatographies. The antiserum produced showed strong cross-immunoreactivity with Torpedo AChE but weak cross-immunoreactivity with human RBC membrane AChE. The purified human brain striatum AChE was reduced and alkylated, and then hydrolyzed by immobilized TPCK-treated trypsin. Trypsin peptides in the hydrolysate was separated by RP-HPLC. Several large peptide peaks and numbers of small peaks were observed. The large peaks showed obvious immunoreactivity with the mouse anti human cerebellum AChE antiserum.

Oxidative modification of bovine erythrocyte superoxide dismutase by hydrogen peroxide and ascorbate -Fe(III)

Exposure of superoxide dismutase to hydrogen peroxide or ascorbate -Fe(III) gives rise to the modification of the enzyme structure and the changes of its function as well as of its immunological property. The structure alterations are especially shown as the loss of the enzyme-bound copper, the production of peptide fragments, the formation of carbonyl groups in the amino acid side chains, the increase in the contents of aspartic acid, glutamic acid and glycine and a decrease in the number of histidine, proline, arginine, lysine, serine and threonine. Accompanying the structure changes, the enzyme lost its catalytic activity. Hydrogen peroxide and ascorbate -Fe(III) exhibited different effects on the structural and functional changes of the enzyme. Furthermore, the bovine superoxide dismutase exposed to hydrogen peroxide or ascorbate -Fe(III) with different kinds of antisera such as antibovine, anticanine, antiporcine and antihuman superoxide dismutase antisera all showed greatly increases in the reactivities. It is proposed that reactive oxygen species may play a role in the building up of circulating immune complexes in autoimmune diseases.

Determination of sub-ng ml levels of mercury in water by electrolytic deposition and electrothermal atomic-absorption spectrophotometry

The determination of trace mercury in water samples by electrolytic deposition and electrothermal atomic-absorption spectrophotometry is described. Traces of mercury in water are preconcentrated by electrolytic reduction and deposition on a platinum wire cathode, which is then put into a graphite cup for direct atomization and measurement. The method is sensitive and simple, with a detection limit of 0.04 ng/ml. Almost all the metal ions commonly found in water samples can be tolerated, because of the selective deposition at controlled potential.