Sugar Binding Effects on the Enzymatic Reaction and Conformation Near the Active Site of Pokeweed Antiviral Protein Revealed by Fluorescence Spectroscopy

In various trials for elucidating the physiological function of pokeweed antiviral protein (PAP), studies on the interaction with sugar are essential. The fluorescence titration curves showed that PAP retained the strong affinity against N-acetylglucosamine (NAG) and two sites in one PAP molecule co-operatively participated in the binding. In the complex of PAP with NAG, Trp208 located at the entrance lid site of substrate came closer to Tyr72 about 0.3 Å. Furthermore, the fluorescence anisotropy decay measurement demonstrated that the segmental rotation of Trp208 was enlarged by the binding of PAP with NAG. Such conformational changes around the active site closely correlate with the enzymatic activity of PAP. The N-glycosidase activity of PAP was enhanced more than two times in the presence of NAG. The obtained results consistently suggested the enzymatic activity of PAP would be regulated through the conformation change near the active site induced by the binding with NAG.     

Control of composition and crystallinity in hydroxyapatite films deposited by electron cyclotron resonance plasma sputtering

Hydroxyapatite (HAp) films were deposited by electron cyclotron resonance plasma sputtering under a simultaneous flow of H₂O vapor gas. Crystallization during sputter-deposition at elevated temperatures and solid-phase crystallization of amorphous films were compared in terms of film properties. When HAp films were deposited with Ar sputtering gas at temperatures above 460 °C, CaO byproducts precipitated with HAp crystallites. Using Xe instead of Ar resolved the compositional problem, yielding a single HAp phase. Preferentially c-axis-oriented HAp films were obtained at substrate temperatures between 460 and 500 °C and H₂O pressures higher than 1×10⁻² Pa. The absorption signal of the asymmetric stretching mode of the PO₄³⁻ unit (ν₃) in the Fourier-transform infrared absorption (FT-IR) spectra was the narrowest for films as-crystallized during deposition with Xe, but widest for solid-phase crystallized films. While the symmetric stretching mode of PO₄³⁻ (ν₁) is theoretically IR-inactive, this signal emerged in the FT-IR spectra of solid-phase crystallized films, but was absent for as-crystallized films, indicating superior crystallinity for the latter. The Raman scattering signal corresponding to ν₁ PO₄³⁻ sensitively reflected this crystallinity. The surface hardness of as-crystallized films evaluated by a pencil hardness test was higher than that of solid-phase crystallized films.     

Power extraction using flow-induced vibration of a circular cylinder placed near another fixed cylinder

We conducted an experiment in a towing tank to investigate the performance of an energy extraction system using the flow-induced vibration of a circular cylinder. This experiment tested three different cases involving the following arrangements of cylinder(s) of identical diameter: the upstream fixed–downstream movable arrangement (case F); the upstream movable–downstream fixed arrangement (case R); and a movable isolated cylinder (case I). In cases F and R, the separation distance (ratio of the distance between the centers of the two cylinders to their diameters) is fixed at 1.30. Measurement results show that while cases F and I generate vortex-induced vibration (VIV) resonance responses, case R yields wake-induced vibration (WIV) at reduced velocity over 9.0, which is significantly larger than that of the VIV response, leading to the induction of higher electronic power in a generator. Accordingly, primary energy conversion efficiency is higher in the case involving WIV.     

Suppressed speckle contrast of blue light emission out of white lamp with phosphors excited by blue laser diodes for high-brightness lighting applications

The speckle contrast of blue light emission out of high-brightness white lamps using phosphors excited by InGaN/GaN blue laser diodes is evaluated as a measure of coherence. As a result, speckle contrast of as low as 1.7%, the same level as a blue light emitting diode, is obtained. This implies that the original blue laser light can be converted into incoherent light through lamp structures without any dynamic mechanisms. This unique speckle-free performance is considered to be realized by multiple scattering inside the lamp structure, the multi-longitudinal mode operation of the blue laser diodes, and the use of multiple laser diodes. Such almost-incoherent white lamps can be applied for general lighting without any nuisance of speckle noise and should be categorized as lamps rather than lasers in terms of laser safety regulation.     

Nuclear Moment Studies with Polarized Radioactive Nuclear Beams

Magnetic dipole and electric quadrupole moments of nuclei in the light-mass neutron-rich region have been studied by taking advantage of spin-polarized radioactive nuclear beams that have been obtained from the projectile fragmentation reaction. Analyses of the results reveal a few interesting phenomena characteristic of nuclear structures in this region. In particular, we report in some detail the latest result on the magnetic moment of the ¹⁷C ground state. The distinctly small value of the g-factor obtained, |g(¹⁷C)|=0.5054±0.0025, clearly excludes a I ^π=1/2⁺ candidate for the spin-parity assignment of this marginally bound nucleus, providing a reasonable account of the non-halo nature reported in recent breakup reaction experiments. Finally, future plans at the upcoming radioactive beam facility presently under construction at RIKEN are briefly mentioned. This revised version was published online in September 2006 with corrections to the Cover Date.     

Precise measurement of soil deformation and fluctuation in drawbar pull for steel and rubber-coated rigid wheels

The travelling performance of rigid wheels on sand stratum is measured using two kinds of surface material, i.e. steel and steel coated with rubber. A new method for measuring the displacement of soil beneath the wheel has been developed using small polyester film markers. The trajectories of soil particles beneath the wheels are approximated by an exponential function and the fluctuations in the drawbar pull are represented by a sinusoidal function. The amplitude and basic wavelength of the fluctuation in the drawbar pull are discussed for both types of wheels.     

Ultrafast all-optical signal processing with Symmetric Mach–Zehnder type all-optical switches

We present Symmetric Mach–Zehnder (SMZ) type all-optical switches: an SMZ all-optical switch, a polarization-discriminating SMZ (PD-SMZ) all-optical switch, and a delayed interference signal wavelength converter (DISC). These switches are capable of ultrafast, low control power, and low chirp switching, which is not restricted by slow relaxation of highly efficient nonlinearities. High repetition operation unrestricted by slow relaxation is also possible for these switches. This is because of a push–pull modulation scheme or sometimes called a differential phase modulation scheme. These three devices are similar, but different in some important aspects, thus a comparison is made among the three. Then semiconductor optical amplifiers (SOAs) are discussed as a nonlinear phase shifter for these devices. Then, ultrafast all-optical signal processing using SOA based SMZs is demonstrated. Error-free demultiplexing from 168 to 10.5 Gbit/s is presented, in which a hybrid-integrated SMZ (HI-SMZ) is used as a demultiplexer. In pulse regeneration experiment, the signal pulses at 84 Gbit/s are regenerated by the PD-SMZ and the regenerated pulses are demultiplexed to 10.5 Gbit/s by the HI-SMZ to verify error-free operation. The retiming capability of this scheme is quantitatively demonstrated. Also presented is error-free all-optical wavelength conversion at 168 Gbit/s using the DISC. These results represent the fastest error-free operations reported to date in each category.     

Temperature dependent quantum well state on Cu(1 1 0)(2 × 1) striped surface studied by angle resolved photoelectron spectroscopy

We have investigated the temperature dependence of angle resolved photoelectron spectroscopy for the lateral quantum well states (QWS) on the striped Cu(1 1 0)(2 × 1)O surface. For the striped surface with oxygen coverage of 0.25 ML, we have successfully observed two discrete levels along a perpendicular direction to the stripes in the surface Brillouin zone, which is generated by quantization of the Shockley surface state. We have found that the relative photoelectron intensity of the two discrete levels depends on the temperature. The photoelectron intensity tends to concentrate on the ground level of the QWS with decreasing temperature. Our investigation indicates that the electron population of each quantum well level depends on the temperature.