Structure Determination of an AgI‐Mediated Cytosine–Cytosine Base Pair within DNA Duplex in Solution with 1H/15N/109Ag NMR Spectroscopy

The structure of an Ag^I‐mediated cytosine–cytosine base pair, C–Ag^I–C, was determined with NMR spectroscopy in solution. The observation of 1‐bond ¹⁵N‐¹⁰⁹Ag J‐coupling (¹J(¹⁵N,¹⁰⁹Ag): 83 and 84 Hz) recorded within the C–Ag^I–C base pair evidenced the N3–Ag^I–N3 linkage in C–Ag^I–C. The triplet resonances of the N4 atoms in C–Ag^I–C demonstrated that each exocyclic N4 atom exists as an amino group (?NH₂), and any isomerization and/or N4–Ag^I bonding can be excluded. The 3D structure of Ag^I–DNA complex determined with NOEs was classified as a B‐form conformation with a notable propeller twist of C–Ag^I–C (?18.3±3.0°). The ¹⁰⁹Ag NMR chemical shift of C‐Ag^I‐C was recorded for cytidine/Ag^I complex (δ(¹⁰⁹Ag): 442 ppm) to completed full NMR characterization of the metal linkage. The structural interpretation of NMR data with quantum mechanical calculations corroborated the structure of the C–Ag^I–C base pair.     

Electrospun nanofiber membranes from polysulfones with chiral selector aimed for optical resolution

Polysulfones with three types of alanyl residue, such as N-α-acetylalanine (Ac-Ala-OH), N-α-benzoylalanine (Bzo-Ala-OH), and N-α-benzyloxycarbonylalanine (Z-Ala-OH), as chiral selectors were prepared by polymer reaction. The resulting modified polysulfones showed chiroptical properties, indicating that the chiral selector residues were successfully introduced into the polysulfone. Nanofiber membranes prepared from the polymeric materials showed adsorption selectivity toward mixtures of racemic Glu, which were adopted as model racemates. Flux values for the nanofiber membranes were enhanced two to three orders of magnitude in comparison with the corresponding typical membranes, but without reduction in permselectivity. In the present study, it is shown that nanofiber is a suitable membrane form not only for molecularly imprinted membranes, but it exhibits enhanced throughput in comparison with typical dense membranes without concurrent reduction in permselectivity.     

Neuronal mechanism of epileptogenesis in EL mouse

The convulsions of the EL mouse (EL) were described by Imaizumi et al. in 1954 and were established as epilepsy by Suzuki in 1976. The EL mouse has been kept as an inbred strain and is considered one of the best animal models originated in Japan. The mode of inheritance is autosomal dominant, and environmental risk factors for seizure occurrence are hypothesised to contribute to the polygenic background. Paroxysmal activities in the EL brain arise from the parietal cortex (PCX) and are augmented in the hippocampus, demonstrated by electrophysiology and autoradiography using 2-deoxy glucose when clinical symptoms of seizures appeared. The neurons in the EL PCX, where GABA activity is lower than that of DDY PCX demonstrate increased excitability to proprioceptive sensory input. After repetitive seizure-provoking stimuli, seizures are more easily induced, eventually occurring spontaneously. This phenomenon of “abnormal plasticity” is also observed in the EEG, decreasing GABA activity, expression of the immediately early gene, and various biochemical and molecular processes. This phenomenon is similar to the learning or progressive process of certain neurological diseases.     

Mechanism of mode selection in Rayleigh—Bénard convection with free—rigid boundaries

Higher harmonic resonances with wavenumber ratio of 1:2, 1:2:3 and so on are shown to take place in Rayleigh—Bénard convection under free—rigid boundary condition. Bifurcation diagrams for two-dimensional motion are obtained for the Prandtl number P = 7. The subharmonic instability is explained by a couple of amplitude equations obtained from weakly nonlinear stability theory. A straightforward extension of the coupled amplitude equations leads to a model which consists of n amplitude equations. The mechanism of mode selection is illustrated by numerical simulations of the model equations.     

The theta-temperature depression caused by topological effect in ring polymers studied by Monte Carlo simulation

We studied equilibrium conformations of linear and ring polymers in dilute solutions over the wide range of segment number N of up to 2048 with Monte Carlo simulation, and evaluated N dependence of the radii of gyration, R(g), of chains. The polymer molecules treated in this study are assumed to be composed of beads and bonds, and they are put in a three-dimensional face-centered cubic (FCC) lattice. The values of Flory's critical exponent, ν, for linear and ring polymers were estimated from the N dependence of R(g), and the temperatures at which ν reach 1/2 were obtained. Here we define those as Θ-temperatures in this report. The simulation result shows that the Θ-temperature for ring polymers is evidently lower than that of the linear polymers, and the origin of the Θ-temperature depression is discussed. Since R(g) of a ring polymer is smaller than that for a linear polymer at the same N and temperature, the segment density for a ring polymer is increased by the topological effect and the repulsive force between segments of a ring polymer at the Θ-temperature for a linear polymer is stronger. Thus, the origin of the Θ-temperature depression for ring polymers is the repulsive force emphasized by the topological effect of rings.     

Mannich Reaction Under High Pressee. Dimethylaminomethylation of Ketones with bis(Diyethylamino)methane under Mild Conditions

Dimethylaminomethylation of ketones with bis(dimethyl-amino)methane takes place cleanly in methanol at room temperature in the kiro bar region.     

Complexation of Terbium Ion with the Copolymer of Acrylic Acid and Acrylamide Grafted onto Polyethylene

Acrylic acid (AA) and acrylamide (AAm) were graft copolymerized onto polyethylene powder by the preirradiation method. The PE powder grafted with both AA and AAm (PE-g-(AA-co-AAm)) rapidly adsorbed Tb ion with an efficiency higher than did PE powder grafted with AA (PE-g-AA). The complex formation constant of Tb ion with PE-g-(AA-co-AAm) was larger than that with PE-g-AA because the introduction of the acrylamide part decreased the steric hindrance for complexation between Tb and the carboxyl group of the graft chains. Tb ion was efficiently separated from transition metal ions, such as Co, upon passage of a solution through a column packed with PE-g-(AA-co-AAm).     

Oblique detonation waves stabilized in rectangular-cross-section bent tubes

Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through rectangular-cross-section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The oblique detonation waves were stabilized under the conditions of high initial pressure and a large curvature radius of the inside wall of the rectangular-cross-section bent tube. The geometrical shapes of the stabilized oblique detonation waves were calculated, and the results of the calculation were in good agreement with those of our experiment. Moreover, it was experimentally shown that the critical condition under which steady-state oblique detonation waves can stably propagate through the rectangular-cross-section bent tubes was the curvature radius of the inside wall of the rectangular-cross-section bent tube equivalent to 14–40 times the cell width.