Reaction of poly(vinyl alcohol) with tetravalent ceric ion

Poly(vinyl alcohol) (PVAI) was oxidized by ceric ion, Ce(IV), in aqueous HNO₃ medium at different temperatures and found to be degraded as a result of selective cleavage of the 1,2-glycol unit existing in PVAl. The rate of oxidation increased with increasing temperature. The aldehyde groups formed at the ends of the degraded polymer upon oxidation were relatively stable at 0°C. With rise of temperature, the aldehyde groups reacted either with excess of Ce(IV) to carboxylic acids or with hydroxyl groups of PVAl molecules to give acetal linkage. When the acetalization predominated over the oxidation to carboxyl group, gelation of the reaction mixture was observed. Based on these results, a plausible mechanism of oxidation of PVAl with Ce(IV) and the subsequent reactions is discussed.     

Synthesis of potent beta-secretase inhibitors containing a hydroxyethylamine dipeptide isostere and their structure-activity relationship studies

Several beta-secretase inhibitors were designed based on hydroxyethylamine dipeptide isostere (HDI) structures and were synthesized by a methodology using the aza-Payne rearragement and O,N-acyl transfer reactions to study their structure-activity relationships. Among these pseudopeptides, effective compounds were developed as the first beta-secretase inhibitors containing the HDI transition state mimic with potent enzyme inhibitory activity (IC50 < 100 nM).     

Determination and purification of sesamin and sesamolin in sesame seed oil unsaponified matter using reversed‐phase liquid chromatography coupled with photodiode array and tandem mass spectrometry and high‐speed countercurrent chromatography

In Asian countries, sesame seed oil unsaponified matter is used as a natural food additive due to its associated antioxidant effects. We determined and purified the primary lignans sesamin and sesamolin in sesame seed oil unsaponified matter using reversed‐phase liquid chromatography coupled with photodiode array and tandem mass spectrometry and high‐speed countercurrent chromatography. Calibration curves showed good correlation coefficients (r² > 0.999, range 0.08 and/or 0.15 to 5 μg/mL) with a limit of detection (at 290 nm) of 0.02 μg/mL for sesamin and 0.04 μg/mL for sesamolin. Sesame seed oil unsaponified matter contained 2.82% sesamin and 2.54% sesamolin, respectively. Direct qualitative analysis of sesamin and sesamolin was achieved using quadrupole mass spectrometry with positive‐mode electrospray ionization. Pure (>99%) sesamin and sesamolin standards were obtained using high‐speed countercurrent chromatographic purification (hexane/ethyl acetate/methanol/water; 7:3:7:3). An effective method for determining and purifying sesamin and sesamolin from sesame seed oil unsaponified matter was developed by combining these separation techniques for standardized food additives.     

Sensitivity analysis incorporating fuzzy evaluation for scaling constants of multiattribute utility functions

A multiattribute utility function can be represented by a function of single-attribute utility functions if the decision maker’s preference satisfies additive independence or mutually utility independence. Additive independence is a preference condition stronger than mutually utility independence, and the multiattribute utility function is in the additive form if the former condition is satisfied, otherwise it is in the multiplicative form. In this paper, we propose a method for sensitivity analysis of multiattribute utility functions in multiplicative form, taking into account the imprecision of the decision maker’s judgment in the procedures for determining scaling constants (attribute weights).     

Utilization of microgravity to improve the crystal quality of biologically important proteins: chaperonin-60, GrpE, B-subunit of V-type ATPase, and MIF

Protein crystallization experiments under microgravity were performed by using commercial vapor diffusion apparatus (CVDA) hardware on the STS-84 shuttle mission. Chaperonin-60, GrpE, the B subunit of V-type ATPase, and the selenomethionine substituted proteins of macrophage migration inhibitory factor (MIF) were selected as target proteins. The results indicate that microgravity positively affected their crystal growth, supporting the practical utilization of microgravity for the protein structure determination.     

Low-temperature STM/STS studies on boron-doped (1 1 1) diamond films

We have performed scanning tunneling microscopy/spectroscopy (STM/STS) experiments on (1 1 1)-oriented epitaxial films of heavily boron-doped diamond (T_c∼5.4 K). We present that tunneling conductance spectra show temperature-dependent spatial variations. In the low-temperature region (T=0.47 K), the tunneling spectra do not show strong spatial dependence and a superconducting energy gap is observed independent of the surface morphology. In the high-temperature region (T=4.2 K), on the other hand, the tunneling conductance spectra show significant spatial dependence, indicating the inhomogeneous distribution of the superconducting property due to the distribution of boron atoms.