Measurements of Singlet Oxygen‐Quenching Activity of Vitamin E Homologs and Palm Oil and Soybean Extracts in a Micellar Solution

Recently, a new assay method that can quantify the singlet oxygen‐absorption capacity (SOAC) of antioxidants (AO) and food extracts in homogeneous organic solvents has been proposed. In the present study, second‐order rate constants (k_Q) for the reaction of singlet oxygen (¹O₂) with vitamin E homologs (α‐, β‐, γ‐, and δ‐tocopherols [Toc] and α‐, β‐, γ‐, and δ‐tocotrienols [Toc‐3]) were measured in an aqueous Triton X‐100 (5.0 wt%) micellar solution (pH 7.4). Toc‐3 showed k_Q values larger than those of Toc in a micellar solution, although Toc and Toc‐3 showed the same k_Q values in a homogeneous solution. Similar measurements were performed for 5 palm oil extracts 1–5 and one soybean extract 6, which contained different concentrations of Toc, Toc‐3, and carotenoids. It has been clarified that the ¹O₂‐quenching rates (k_Q) (that is, the relative SOAC value) obtained for extracts 3–6 may be explained as the sum of the product of the rate constant () and the concentration ([AO‐i]/100) of AO‐i contained. The UV–vis absorption spectra of Toc and Toc‐3 were measured in a micellar solution and chloroform. The results obtained demonstrated that the k_Q values of AO in homogeneous and heterogeneous solutions vary notably depending on (1) polarity (dielectric constant [ε]) of the reaction field between ¹O₂ and AO, (2) the local concentration of AO, and (3) the mobility of AO in solution. The results suggest that the SOAC method is applicable to the measurement of ¹O₂‐quenching activity of general food extracts in a heterogeneous micellar solution.     

Electrical characteristics of Ge-based metal-insulator-semiconductor devices with Ge3N4 dielectrics formed by plasma nitridation

We have fabricated pure germanium nitrides (Ge3N4) using high-density plasma nitridation and investigated electrical properties of Au/Ge3N4/Ge capacitors. We achieved equivalent oxide thickness (EOT) of 1.4 nm, and dielectric constant of Ge3N4 was estimated to be 9.7. The gate leakage current density of 4.3 A/cm2 in the accumulation condition at V(fb)-1 V, where V(fb) is the flatband voltage, was one order of magnitude lower than that of conventional poly-Si/SiO2/Si stacks. The interface state density (D(it)) of Ge3N4/Ge interfaces evaluated by a low-temperature conductance method exhibited a minimum value of 9.4 x 10(11) cm(-2)eV(-1) at E - E(v) = 0.27 eV. Furthermore, the insulating property and interface quality of Ge3N4/Ge system was found to be thermally stable up to 650 degrees C. These results indicate that Ge3N4 is a promising candidate for either a gate insulator or an interfacial layer under high-k dielectrics for Ge-MIS devices.     

Quantitative measurements of amino acids by terahertz time-domain transmission spectroscopy

The quantitative analysis of amino acids by terahertz (THz) time-domain absorption spectroscopy is demonstrated. The optical densities of the amino acids were found to be linearly proportional to the concentration. The molar absorption coefficients of L-glutamic acid (L-Glu), L-glutamic acid sodium salt (Na-L-Glu), L-glutamic acid hydrochloric salt (HCl-L-Glu), L-cysteine (L-Cys), and L-histidine (L-His) were calculated by averaging the THz spectra of the amino acids at several different concentrations in approximately the 0.2-1.0 mol L(-1) range. The concentrations of L-Glu, L-Cys, and L-His mixed samples were successfully calculated with errors of less than 11% and 20% when their concentrations were higher than 0.45 and 0.22 mol L(-1), respectively, by using the obtained molar absorption coefficient.     

Enantioselective Synthesis of Chiral Homoallyl Alcohols and Homoallylamines by Nucleophilic Addition of an Allylboron Reagent Modified by a Polymer‐Supported Chiral Ligand

Crosslinked polymer‐supported chiral N‐sulfonylamino alcohols 5–8 have been prepared by suspension polymerization of enantiopure N‐sulfonylamino alcohol monomers 1–4 with styrene and divinylbenzene. Polymer‐supported chiral allylboron reagents were prepared from the polymeric chiral ligands. Enantioselective additions of the polymer‐supported allylboron reagents to aldehydes and N‐(trimethylsilyl)imines have been successfully carried out in the heterogeneous system. The corresponding optically active homoallyl alcohols and homoallylamines were obtained in high yields with high enantioselectivities (up to 95% ee) which are almost the same as those obtained from homogeneous analogues. The polymer‐supported chiral ligands used were recovered easily and can be reused without any loss of activity.