Flow-through micro sensor using immobilized peroxidase with chemiluminometric FIA system for determining hydrogen peroxide.

A micromachined flow cell (overall size; 25 x 25 x 1 mm3) was designed for the fast determination of hydrogen peroxide, based on a luminol-H2O2 chemiluminescence reaction catalyzed by immobilized peroxidase (POD). The flow cell consisted of a sandwich of anisotropically etched silicon and glass chips and contained a spiral channel (20 turns, 50 cm long, 150 microm wide, 20 microm depth, channel volume 1.4 microl) and two holes (1 mm diameter). POD was covalently immobilized with 3-(trimethoxysilyl)propyldietylenetriamine and glutaraldehyde on the inner surface of the channel. The chip was placed in front of a window of a photomultiplier tube and used as a flow cell in a single-line flow-injection analysis system using a luminol solution as a carrier solution. The sample volume for one measurement was 0.2 microl. The maximal sampling rate was 315 h(-1) at a carrier solution flow rate of 10 microl min(-1). A calibration graph for H2O2 was linear for 5 nM - 5 microM; the detection limit (signal-to-noise = 3) was 1 nM (7 fg in 0.2 microl injection). The H2O2 concentration in rainwater was determined using this sensor system.     

Semi-empirical method for estimating the β-strength function

A method of estimating the β-strength function from β-decay data on three neighbouring nuclei is proposed. This method is most effective for the β^? decay ofodd-Z even-N nuclei with the neutron number equal to a magic number plus two, and is applied to the β^? decays of ⁸⁷Br and ¹³⁷I The strength functions estimated by this method represent the general trend of experimental data fairly well except for the regions of the lowest and highest excitation energies, where this method is either inapplicable or subject to large uncertainties. The delayed neutron emission probabilities are estimated for these precursors by use of these strength functions, and the results are in agreement with experiment within a factor of two.     

Lithium insertion behavior of carbon nanowalls by dc plasma CVD and its heat-treatment effect

Lithium insertion behavior of carbon nanowall (CNW), which is a two-dimensional carbon nanostructures, was studied by cyclic voltammetry and charge/discharge measurements. It was found that CNW had reversible capacities of more than 200 mAh/g with stable charge/discharge potential like that of graphite even though the materials were produced at low temperature of 973 K. It was also found that CNW showed good responses of lithium insertion/extraction reaction because of their small and uniform particle size with well oriented graphene in nanometer scale. Heat treatment of CNW was found to purify the CNW from by-product amorphous carbon phase and the effect on their charge/discharge property was also clarified.     

Radiation-induced polymerization at high dose rate. III. Isoprene in bulk

Radiation-induced polymerization of isoprene in bulk state was studied at 25°C in a wide dose rate range. Variations of the rate of polymerization and molecular weight of the products were essentially the same as those observed in the monomers which were capable of both radical and cationic polymerizations. At low dose rate, 7.0-230 rad/sec, radical polymerization took place. At high dose rate, 8.8 × 10³-2.2 × 10⁵ rad/sec, radical and cationic polymerizations took place concurrently. The average molecular weight of the high-dose-rate product was about 850, independent of dose rate. The microstructure of the products at high dose rate consisted mainly of trans- 1,4 units with only about 7% of cis- 1,4 and 10% of 3,4-vinyl units. The residual unsaturation in the high-dose-rate products was 90%. Decreases in cis units and residual unsaturation at high dose rate were accounted for by the change in predominant mechanism of polymerization with dose rate.     

Heat capacity of the spinel superconductors CuRh2S4 and CuRh2Se4

We report low-temperature heat capacity measurements on CuRh₂S₄ and CuRh₂Se₄. These compounds undergo a superconducting transition at $T_c=4.72$ and 3.38 K, respectively, with a fully opened superconducting gap. With increasing magnetic field $H$, the Sommerfeld coefficient $\gamma \left(H\right)$ shows a crossover from linear to sublinear $H$ dependence that is consistent with the predictions of recent theoretical calculations. Compared to CuRh₂Se₄, CuRh₂S₄ exhibits a smaller region of the linear-$H$ dependence in $\gamma \left(H\right)$ and pronounced positive curvature in the temperature dependence of the upper critical field.     

Novel variational principles of chemical reaction

Minimum principles of chemical reaction coordinates are established. IRC (intrinsic reaction coordinate) draws the path of minimum distance from reactant to product. The distance is measured in the rigged configuration Riemannian space whose metric is determined by the distribution of the adiabatic potential energy. Moreover, minimum property of the intrinsic principle of least action is established for the intrinsic dynamism of chemical reaction. Minimum principle of the path connecting intercell boundary with cell is also discussed.     

Modulation of structure and dynamics by disulfide bond formation in unfolded states

During oxidative folding, the formation of disulfide bonds has profound effects on guiding the protein folding pathway. Until now, comparatively little is known about the changes in the conformational dynamics in folding intermediates of proteins that contain only a subset of their native disulfide bonds. In this comprehensive study, we probe the conformational landscape of non-native states of lysozyme containing a single native disulfide bond utilizing nuclear magnetic resonance (NMR) spectroscopy, small-angle X-ray scattering (SAXS), circular dichroism (CD) data, and modeling approaches. The impact on conformational dynamics varies widely depending on the loop size of the single disulfide variants and deviates significantly from random coil predictions for both NMR and SAXS data. From these experiments, we conclude that the introduction of single disulfides spanning a large portion of the polypeptide chain shifts the structure and dynamics of hydrophobic core residues of the protein so that these regions exhibit levels of order comparable to the native state on the nanosecond time scale.