Effect of metal ions on the stability of metallothionein in the degradation by cellular fractions in vitro

Metallothioneins (MT), small molecular weight metal binding proteins are known to play an important protective role against heavy metal toxicity, either as antioxidants or pre-oxidants. However, the mode of metabolic fate of MTs in various metal complexes is not clearly understood. This study was carried out to better understand the mode of selective turnover rate of various form of MT in complexes with different metals. The degradation of in vitro translated mouse 35S-cysteine-MT was examined in lysosomal or cytosolic fractions from mouse liver by gel electrophoresis and autoradiography. Overnight incubations of MT showed extensive proteolysis in the lysosomal fraction but not in cytosolic fractions. However, Cu2+-MT was found to be stable under the same experimental condition. In contrast, Zn did not interfere with MT degradation. These results suggest that lysosomes are chiefly responsible for MT removal and appears to be selective on the metals involved in the MT complex. In vitro, translated, radiolabeled MT provides a suitable substrate for investigating the characteristics of MT degradation.     

Determination of antiferromagnetic exchange coupling in the tetrahedral thiolate-bridged diferrous complex [Fe2(SEt)6]2-

Protein-bound iron-sulfur clusters and their synthetic analogues are characterized by tetrahedral metal sites, multiple oxidation levels, and exchange coupling. The recent attainment of several all-ferrous protein clusters and the presence of sulfide- and thiolate-bridged sites in the all-ferrous state of the nitrogenase P-cluster provides an imperative for determination of exchange coupling between tetrahedral Fe(II) sites with sulfur bridges. The cluster in the previously reported compound (Et(4)N)(2)[Fe(2)(SEt)(6)] is centrosymmetric with distorted tetrahedral coordination and a planar Fe(2)(mu-SEt)(2) bridge unit. The compound is diamagnetic at 4.2 K, indicating antiferromagnetic coupling. The lower limit J > 80 cm(-)(1) (H = JS(1).S(2)) is obtained by M?ssbauer spectroscopy. Analysis of magnetic susceptibility data affords J = 165 +/- 15 cm(-)(1). It is noteworthy that the J value of the diferrous pair obtained here is comparable to the J values reported for the mixed-valence state of plant-type Fe(2)S(2) ferredoxins. The near temperature independence of the quadrupole splitting (DeltaE(Q) = 3.25 mm/s at 4.2 K and 3.20 mm/s at 180 K) indicates that no excited orbital states are appreciably populated at temperatures less than 300 K. The paramagnetism arises solely from thermal population of the S = 1 state of the spin ladder. This work provides the only measure of antiferromagnetic coupling by Fe(II) pairs in a tetrahedral sulfur environment.     

Emission pattern of high-energy pions: A new probe for the early phase of heavy-Ion collisions

Recent results from CLEO on B-->Kpi indicate that the phase gamma may be substantially different from that obtained from other fit to the KM matrix elements in the standard model. We show that gamma extracted using B-->Kpi,pipi is sensitive to new physics occurring at loop level. It provides a powerful method to probe new physics in electroweak penguin interactions. Using effects due to anomalous gauge couplings as an example, we show that within the allowed ranges for these couplings information about gamma obtained from B-->Kpi,pipi can be very different from the standard model prediction.     

Efficient synthesis of a configurationally stable l-serinal derivative

An efficient synthesis of a configurationally stable l-serinal derivative 8 was achieved using an N-hydroxymethyl group in about 50% overall yield in four steps from l-serine. Not more than 1% racemization was observed during the preparation of 8. Its enantiomeric integrity was maintained for at least 15 days at room temperature, and it was stable on silica gel. The orthogonal protective groups of 8 would make it a useful chiral synthon.     

Bis-1,4-(p-diarylaminostryl)-2,5-dicyanobenzene derivatives with large two-photon absorption cross-sections

Synthesis and physical properties of novel multibranched two-photon materials are reported. The compound with three units of 4-(p-diphenylaminostyryl)-2,5-dicyanostyryl moieties attached to the central triphenylamine core exhibits a very large two-photon absorption cross-section.     

Large Oscillations of a Thin Cantilever Beam: Physical Experiments and Simulation Using the Absolute Nodal Coordinate Formulation

Many papers have studied computer-aided simulations of elastic bodies undergoing large deflections and large deformations. But there have not been many attempts to check the validity of the numerical formulations used in these studies. The main aim of this paper is to demonstrate the validity of one such numerical formulation, the absolute nodal coordinate formulation (ANCF), by comparing the results it generates with the results of real experiments. Large oscillations of a thin cantilever beam are studied in this paper to numerically model the beam, which also accounts for the effects of an attached end-point weight and damping forces. The experiments were carried out using a high-speed camera and a data acquisition system.     

Comparison between the magnetic specific heat of NdBa2Cu3O x and DyBa2Cu3O x

Low temperature heat-capacity measurements have been performed to study the magnetic ordering in NdBa₂Cu₃O _x and DyBa₂Cu₃O _x . In order to investigate the type of ordering, magnetic fields up to 6 T and hydrostatic pressures up to 4.5 kbar were applied. While for NdBa₂Cu₃O _x and DyBa₂Cu₃O _x both the fully oxidized and the fully oxygen reduced samples display long rang antiferromagnetic ordering, only magnetic short range interaction could be found for samples in an intermediate range of oxygen concentration. For NdBa₂Cu₃O _x , where superexchange is believed to be the dominant magnetic interaction,T _N is three times higher in the sample withx=6.26 compared to the one withx=6.98. In contrast,T _N of DyBa₂Cu₃O _x is almost oxygen independent as expected for this mainly dipolar interacting system.     

Precise nonselective chemically assisted ion-beam etching of AlGaAs/GaAs Bragg reflectors byin situ laser reflectometry

Precision etch-depth control is realized by a chemically assisted ion-beam etching system incorporated within situ laser reflectometry. By counting the number of interference fringes, etch-depth control better than a quarter-wave thickness is easily obtained. Optimized etching conditions for highly anisotropic etching of bulk GaAs and AlGaAs/GaAs distributed Bragg reflectors are obtained. With the ability to etch-stop just below the active region by thein situ monitoring, InGaAs vertical-cavity surface-emitting lasers with CW threshold current density as low as 380 A cm^-2 with output power >11 mW are fabricated. Spatial uniformity is 5% over a 1-cm² sample, which corresponds to one pair over 20 pairs of quarter-wave stacks of AlGaAs/GaAs distributed Bragg reflectors.     

Rapid updating of optical arbitrary waveforms via time-domain multiplexing

We demonstrate high-fidelity optical arbitrary waveform generation with 5 GHz waveform switching via time-domain multiplexing. Compact, integrated waveform shapers based on silica arrayed-waveguide grating pairs with 10 GHz channel spacing are used to shape (line-by-line) two different waveforms from the output of a 10-mode x 10 GHz optical frequency comb generator. Characterization of the time multiplexer's complex transfer function (amplitude and phase) by frequency-resolved optical gating permits compensation of its impact on the switched waveforms and matching of the measured and target waveforms to better than G'=5%.     

Preparation and heat transfer properties of nanoparticle-in-transformer oil dispersions as advanced energy-efficient coolants

Three kinds of nanofluids are prepared by dispersing Al₂O₃ and AlN nanoparticles-in-transformer oil. The thermal conductivity of the nanoparticle–oil mixtures increases with particle volume fraction and thermal conductivity of the solid particle itself. The AlN nanoparticles at a volume fraction of 0.5% can increase the thermal conductivity of the transformer oil by 8% and the overall heat transfer coefficient by 20%. From the natural convection test using a prototype transformer, the cooling effect of Al₂O₃/AlN-oil nanofluids on the heating element and oil itself is confirmed. However, the excess quantity of surfactant has a harmful effect on viscosity, thermal property, chemical stability, and thus it is strongly recommended to control the addition of the surfactant with great care.