L-Malate-sensing electrode based on malate dehydrogenase and NADH oxidase

An L-malate-sensing electrode was constructed from an oxygen electrode and a layer containing immobilized malate dehydrogenase (MDH) and NADH oxidase. MDH catalyses the dehydrogenation of L-malate by NAD⁺ and NADH oxidase catalyses the regeneration of NAD⁺ with the use of oxygen. The regeneration enables the L-malate oxidation to proceed efficiently even in a medium of neutral pH. At pH 8.0, L-malate in the concentration range 5 μM–1.5 mM can be measured. The relative standard deviation for the measurement is 1.2% (L-malate concentration, 0.2 mM; n=10). The present L-malate-sensing electrode is stable for 8 weeks. A two-electrode sensor system consisting of the L-malate-sensing electrode and an L-lactate-sensing electrode based on lactate oxidase was prepared and applied to the simultaneous determination of the two components in wines.     

Electron wave functions at the nuclear surface

Finite size corrections of Bhalla and Rose are examined in the midway to the point-nucleus limit. A possible reason of poor convergence of their positron wave functions is suggested.     

57Fe Mössbauer study YBa2Cu3−xFexO7−y

Mössbauer measurement is made on the system YBa₂Cu_3?xFe_xO_7?y (0.03≤x≤1.0) at various temperatures. It is found that the sites occupied by Fe ions can be classified into major two and minor one groups. The isomer shifts for the major two groups are nearly zero relative to metallic iron, and their quadrupole splittings are large (about 1.9 and 1.1 mm/s). By comparison of the spectra measured before and after a heat-treatment in vacuum, it is concluded that the Fe ions with the largest quadrupole splitting occupy the pyramidal sites, and the other the planer sites. Two different hyperfine magnetic fields (240 and 442 k0e) are observed at 1.7 K for the specimen with x=0.2. It is proposed that the valence states of Fe ions of the major two groups are pentavalent.     

Mössbauer and magnetization studies on the ferromagnet Fe3−x Ru x Si

⁹⁹Ru and⁵⁷Fe Mössbauer spectroscopic studies were carried out on ternary intermetallic compounds containing ruthenium, Fe_3–x Ru _x Si, within the concentration range 0.1x1.5. Magnetization of the samples was also measured in the temperature range between 4 K and room temperature.⁹⁹Ru Mössbauer spectra ofx=0.5 and 1.0 were fitted satisfactorily with a broad component ofH _hf, the peak positions of which were 340 and 270 kOe, respectively.     

Decay of the new isotope127Pr

A new isotope,¹²⁷Pr, has been identified and its decay has been studied using on-line isotope separation of⁹⁴Mo (³⁶Ar,p2n) reaction products. The half-life of the isotope was determined to be 7.7(6) s, and a /X-ray spectrum has been obtained. A partial level scheme is proposed for¹²⁷Ce on the basis of-singles,-gated and-coincidence data.The authors would like to thank the TIARA cyclotron crew for their cooperation in generating an intense³⁶Ar beam as well as in operating the cyclotron. This work was partly supported by the JAERI-University Collaborative Research Project.     

OH rotational quantum state distributions and relaxation efficiencies for the reaction system O(1D) + H2O → 2OH

The OH rotational distribution from O(¹D) + H₂O → 2OH is presented. The v' = 0 distribution corresponds to two Boltzmann distributions. ≈500 K (k = 1–6) and ≈2500 K (k ? 6). Rotational relaxation efficiencies for N₂, He, O₂ were ?0.1, ?0.1, ?0.4. More limited data are presented for the v' = 1 and 2 levels.     

A new method for partition of interaction energy. Relation between stabilization energy and orbital mixing

A new method for partition of interaction energy is proposed. The scheme given here easily connects the calculated stabilization energy with the orbital mixing in analyzing orbital interactions of molecules. The method can reveal the relation between the change of electron distribution and stabilization energy. As an example, orbital interaction energies are estimated for diazocompounds, diazomethane and diazirine.     

Theoretical rate constants of super-exchange hole transfer and thermally induced hopping in DNA

Recently, the electronic properties of DNA have been extensively studied, because its conductivity is important not only to the study of fundamental biological problems, but also in the development of molecular-sized electronics and biosensors. We have studied theoretically the reorganization energies, the activation energies, the electronic coupling matrix elements, and the rate constants of hole transfer in B-form double-helix DNA in water. To accommodate the effects of DNA nuclear motions, a subset of reaction coordinates for hole transfer was extracted from classical molecular dynamics (MD) trajectories of DNA in water and then used for ab initio quantum chemical calculations of electron coupling constants based on the generalized Mulliken-Hush model. A molecular mechanics (MM) method was used to determine the nuclear Franck-Condon factor. The rate constants for two types of mechanisms of hole transfer-the thermally induced hopping (TIH) and the super-exchange mechanisms-were determined based on Marcus theory. We found that the calculated matrix elements are strongly dependent on the conformations of the nucleobase pairs of hole-transferable DNA and extend over a wide range of values for the "rise" base-step parameter but cluster around a particular value for the "twist" parameter. The calculated activation energies are in good agreement with experimental results. Whereas the rate constant for the TIH mechanism is not dependent on the number of A-T nucleobase pairs that act as a bridge, the rate constant for the super-exchange process rapidly decreases when the length of the bridge increases. These characteristic trends in the calculated rate constants effectively reproduce those in the experimental data of Giese et al. [Nature 2001, 412, 318]. The calculated rate constants were also compared with the experimental results of Lewis et al. [Nature 2000, 406, 51].