Communication: Synthetic Studies on Sialoglycoconjugates 110: Efficient Assembly of α-Linked Tetrameric Sialoglycosides Coupled with Galactose and Lactose

Polysialoglycoconjugates, such as polysialylated ganglio-series gangliosides and N-CAM (neural cell adhesion molecule), are of interest because of their important physiological functions in association with neural cell development, differentiation, neuron network formation, and so on.^2-4 Chemical synthesis of these glycoconjugates provides an effective method to elucidate their biological significance in nature at the molecular level, providing not only genuine original glycoconjugates but also their derivatives and analogs designed for biological investigation. We have established⁵ an efficient method to construct dimeric and trimeric sialoglycosides by using the lactonated sialic acid derivatives as building blocks, and succeeded in the systematic synthesis of various polysialogangliosides such as GD3, GQ1b, GQlbα and, very recently, GT3.⁶ In this paper, as a part of our continuous synthetic approach directed toward the polysialoglycoconjugates, we report the first synthesis of α-linked tetrameric sialoglycosides coupled with a galactose and lactose residue.     

Towards slow μ− production via muon catalyzed fusion

Slow ^– production via dd-CF using a two-layer arrangement is investigated. To determine its feasibility, experimental measurements are now in progress using the muonic X-ray detection method. The following experimental steps are being considered: (1) measurement of the number of ^– stopped inside a solid H₂/D₂ layer by detecting p K X-rays, (2) hot d emission detection by placing a secondary target at a distance of 10–30 mm from the layer and by detecting specific delayed X-rays, (3) measurement of the disappearance of d emission as the added D₂ layer is increased, (4) dd-CF measurement by detecting fusion protons, and (5) slow ^– emission detection. Results of the initial test experiment are presented.     

Thawing of frozen vegetables observed by a small dedicated MRI for food research

The thawing process for boiled and frozen edible vegetables was traced by a dedicated MRI for food research. The MRI system is small, with a 1.0-T static magnetic field, and can be placed in an ordinary research room with a light air conditioner. Images of green soybeans, broad beans, okra, asparagus and taro were measured by the spin-echo method (echo time=7 ms) with 0.1 or 0.2 s and 1 s repetition times. The images appeared along with the thawing time, and signals uniformly covered the sliced plane of the samples in the thawed condition. Information about the thawing process and tissue structures of the materials was obtained during transit thawing conditions. The thawing kinetics were examined with increased signal intensity, which were divided into two types. The signal increased linearly and saturated for okra and asparagus but exhibited convex curves for soybeans, broad beans and taro. The small MRI was stable, its handling was simple, and the internal structures of food materials could be accurately identified, although the grey-scale of the images was insufficient for determining precise textural fluctuations of tissue organization. We conclude that the devised MRI is useful for examining the quality of frozen foods and for developmental research into frozen foods.     

Precise measurement of positronium hyperfine splitting using the Zeeman effect

Positronium is an ideal system for the research of the quantum electrodynamics (QED) in bound state. The hyperfine splitting (HFS) of positronium, Δ_HFS, gives a good test of the bound state calculations and probes new physics beyond the Standard Model. A new method of QED calculations has revealed the discrepancy by 15 ppm (3.9σ) of Δ_HFS between the QED prediction and the experimental average. There would be possibility of new physics or common systematic uncertainties in the previous all experiments. We describe a new experiment to reduce possible systematic uncertainties and will provide an independent check of the discrepancy. We are now taking data and the current result of Δ_HFS?=?203.395 1 ±0.002 4 (stat., 12 ppm) ±0.001 9 (sys., 9.5 ppm) GHz has been obtained so far. A measurement with a precision of O(ppm) is expected within a year.     

The mechanism for negative photochromism of spiropyran in silica

The mechanism for negative photochromism of spiropyran in silica was investigated. Prior to our study, the chemical origin of the high thermal stability of the photomerocyanine form (PMC‐form) dispersed in perhydropolysilazane (PHPS), which is converted to silica at ambient temperature, had been investigated. The high thermal stability of the PMC‐form is attributed to the protonated PMC‐form (H???PMC‐form), which is produced by intermolecular hydrogen bonding between oxide anions generated by the cleavage of the C ? O bonds and the partially uncondensed Si ? OH and O ? H bonds of silica. Furthermore, the H???PMC‐form could be thermally isomerized from the SP‐form without UV light irradiation. This specific phenomenon is caused by the so‐called negative photochromism. In this study, we proposed a mechanism for negative photochromism according to the relationship of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The relationship between the HOMOs was determined using cyclic voltammetry (CV) and ultraviolet photoelectron spectroscopy (UPS). On the other hand, the relationship between the LUMOs was determined from the respective optical bandgap. As a result, the HOMO level of H???PMC‐form was ?6.1 eV and that of SP‐form was ?5.3 eV. Accordingly, the thermodynamic stabilization of H???PMC‐form was attributed to the thermal isomerization through negative photochromism from the SP‐form. Copyright © 2011 John Wiley & Sons, Ltd.     

Subject Index to Volume 33

This paper reports the investigation of microdroplet sample preparation for phosphate, strontium and rubidium using X-ray fluorescence. Sample filter papers were prepared by drying under several different conditions and the front and the back sides of the filter papers were measured using X-ray fluorescence (XRF), scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron-probe microanalysis (EPMA).

It was reported by Murata and Murokado that the elemental distribution difference between the front and the back sides after drying the filter paper led to erratic data.¹ It has been found that the intensity difference between the front and the back sides was due to the condensation of the material of interest on the surface of the filter papers and the amount of the condensed material on the filter paper was related to the temperature at which the filter paper was dried.

Optimum temperature at which a filter paper is dried and an appropriate internal standard are essential to reproducible measurements.     

New approaches inμ + SR studies on critical phenomena in Ni

The critical phenomena in Ni are probed by pulsedSR method under longitudinal- and zero external magnetic fields. The sample magnetization around the critical temperature is confirmed simultaneously by bulk magnetization measurement in situ, disappearance of transverseSR signal and recovery of asymmetry under longitudinal field. At the same time, the ratio of the ⁺ hyperfine field to the bulk magnetization in the ferromagnetic phase below the critical temperature is determined from the observables obtained only in the present experiment. The zero- and low-field longitudinal relaxation rate of muon does not diverge in approaching toT _c in the paramagnetic region, but seems to reach a saturation value.This work is supported by the Grand-in-Aid of the Japanese Ministry of Education, Culture and Science.     

Electronic structures of Laves phase compounds

The electronic structures of Laves phase compounds AB₂ (A = Y, Zr, Nb; B = Cr, Mn, Co, Ni) were investigated systematically by the LMTO method within the framework of the LSD approximation. Comparing the calculated total energy for hypothetical para-, ferro-, and antiferromagnetic state with the C14 and the C15 structure, the theoretical predictions are in good agreement with the experiments concerning the stability of the crystal structure and the magnetism. The magnetic stability critically depends upon the change of the lattice spacing, which leads to the colorful behaviors of the magnetism in Fe Laves phase compounds and the anomalous volume change in the antiferromagnetic state of YMn₂.     

Well-posedness of the cauchy problem in gevrey classes for some weakly hyperbolic equations of higher order

This article is devoted to the study of the Cauchy problem in Gevrey classes for some higher order weakly hyperbolic equations with time-dependent coefficients and without lower order terms.     

Photon-echo profile in the ultrashort time region for pentacene molecules in crystals

Photon-echo behavior in the ultrashort time region is studied for pentacene molecules in p-terphenyl crystals at 1.7 K by means of the accumulated three-pulse echo. We show highly resolved echo spectra with a parameter of time separation and also time behavior of echo intensity as a function of pulse separation measured at various frequencies near the peak position of the absorption line of the S₀–S₁ transition. We demonstrate various features of echo profile in both time and frequency domains, which are dependent on the time region of observation.