Reversible formation of F+-centers over platinum promoted sulfated zirconia upon hydrogen treatment

Reversible formation of F⁺-centers was observed over platinum promoted sulfated zirconia in the presence and absence of hydrogen. The intensity of ESR signal of F⁺-centers was increased by treatment in He stream and it was decreased rapidly by supply of hydrogen in gas phase. This behavior seems to be related to proton spillover.     

Radiation sterilization of enzyme hybrids with biodegradable polymers

Ionizing radiations, which have already been utilized for the sterilization of medical supplies as well as gas fumigation, should be the final candidate to decontaminate “hybrid” biomaterials containing bio-active materials including enzymes because irradiation induces neither heat nor substances affecting the quality of the materials and our health. In order to check the feasibility of ⁶⁰Co-gamma rays on these materials, we selected commercial proteases including papain and bromelain hybridized with commercial activated chitosan beads and demonstrated that these enzyme-hybrids suspended in water showed the significant radiation durability of more than twice as much as free enzyme solution at 25-kGy irradiation. Enhanced thermal and storage stability of the enzyme hybrids were not affected by the same dose level of irradiation, either, indicating that commercial irradiation sterilization method is applicable to enzyme hybrids without modification.     

Chiral β-dimethylaminoalkylphosphines. Highly efficient ligands for a nickel complex catalyzed asymmetric grignard cross-coupling reaction

Chiral β-dimethylaminoalkylphosphines were prepared starting with amino acids, (S)-alanine, (S)-phenylalanine, (R)-phenylglycine, (S)-valine, and (R)-tert-leucine. The chiral phosphines were found to be highly efficient ligands for a nickel catalyzed asymmetric Grignard cross-coupling reaction (38～94% optical yield).     

Determination of molecular weight distribution of nylon 12 by gel permeation chromatography

Molecular weight distribution of Nylon 12 was determined with hexafluoroisopropanol/toluene mixture as eluent by gel permeation chromatography. Calibration curve for Nylon 12 was easily obtained from that of polystyrene because the method of universal calibration was applicable among these polymers. The molecular weight distributions of Nylon 12 were always broader than expected by the theory of polymerization, i.e., most probable distribution. This result was not caused by broadening effect in gel permeation chromatography, but by polymerization itself.     

Stereoselective adduct formation of α-acylcamphorato-copper(II) chelates with some chiral Lewis bases

The formation constants of the mono-adducts of α-acylcamphorato-copper(II) chelates such as (+)-Cu(facam)₂, (?)-Cu(facam)₂, (+)-Cu(hfbc)₂ and (?)-Cu(hfbc)₂ with some chiral Lewis bases were determined spectrophotometrically in benzene. In order to compare the adduct formation constants obtained with the (+)- and (?)-forms, some pairs of chiral Lewis bases such as 1-amino-2-propanol [(R)(?), (S)(+)], 1-(α-naphthyl)ethylamine [(R)(+), (S)(?)], α-phenyl ethylamine [(R)(+), (S)(?)] and also quinine and quinidine were examined as neutral ligands. Although not very pronounced, the effects of combinations obtained for (+)- or (?)-Cu(II) chelates and (+)- or (?)-ligands indicate that formation constants obtained by the formation of adducts with the ligands having different directions of the optical rotation seems to be superior to those with the same direction.     

The characteristic fragment ions and visualization of cationic starches on pulp fiber using ToF‐SIMS

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to investigate the distribution of cationic starch on pulp fiber. To identify the characteristic fragment ions of the cationic starches, deuterium‐labeled cationic starches were prepared and analyzed using ToF‐SIMS. The starch 2‐hydroxypropyltrimethylammonium chloride derivative generated characteristic fragments at m/z 58 and 59, which were identified as [H₂C?N(CH₃)₂]⁺ and [N(CH₃)₃]^+·, respectively. The fragmentation patterns were also suggested. From the imaging analysis, the adsorption of the cationic starch on fibers was uneven on individual fibers, as well as between fibers. This may have been on account of fiber morphology and structure. On examining scanning electron microscope (SEM) images, the quaternary ammonium starch derivative (QS) did not penetrate the fiber. No migration of cationic starch was observed under various drying conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

Changes of plasma L-arginine levels in spontaneously hypertensive rats under induced hypotension

Nicardipine, a dihydropyridine type calcium channel blocker, was infused at two flow-rates into spontaneously hypertensive (SH) and control normotensive Wistar-Kyoto (WKY) rats (young, 6-week-old and adult, 23-week-old, n = 5) under pentobarbital anesthesia, to cause hypotension. Mean arterial blood pressure and the concentrations of plasma amino acids and norepinephrine (NE) were measured before infusion and at each step of the infusion. The reduction in blood pressure caused by nicardipine induced a decrease in plasma L-arginine concentration in both young and adult SH rats, this effect being larger in adult rats. There was no significant change in plasma levels of L-arginine in age-matched WKY rats. The concentration of other amino acids did not change in both rat strains. On the contrary, there was an increase in plasma NE concentration in both SH and WKY rats after infusion with nicardipine. Plasma L-arginine concentration showed a good inverse correlation with the logarithm of plasma NE concentration in SH and WKY rats and the correlation was expressed as Y = -alpha log(X) + m (Y, plasma L-arginine concentration (nmol/mL); X, plasma NE concentration (pmol/mL); alpha, a slope; and m, an intercept). alpha, 43.0 and 4.35 for 23-week-old SH and WKY rats, respectively, and 17.0 and 4.0 for 6-week-old SH and WKY rats, respectively. The present data together with previous data suggest a direct noradrenergic stimulation of the synthesis of nitric oxide (NO) from L-arginine. The findings also indicate an impairment of the L-arginine metabolism or pools in SH rats compared with WKY rats. The deficiency of L-arginine increases with the age of SH rats and could be related to the development and maintenance of hypertension due to inefficient production of NO.     

Crystal structure of hexagonal SrAl2O4 at 1073 K

The crystal structure of SrAl₂O₄ at 1073 K was determined from conventional X-ray powder diffraction data using direct methods, and it was further refined by the Rietveld method. The structure was hexagonal (space group P6₃, Z=6) with a=0.89260(3) nm, c=0.84985(2) nm and V=0.58639(3) nm³. Final reliability indices were R_wp=7.87%, R_p=5.87% and R_B=4.19%. The [AlO₄] tetrahedra are linked to form trigonally distorted rings and they are joined in layers. These layers are stacked with a two-layer repeat and connected by the tetrahedral apices. All of the Sr atoms occupy the centers of the rings when viewed along the c-axis. The structure is described as a stuffed derivative of tridymite.     

A fluorimetric, column-switching HPLC and its application to an elimination study of LLU-alpha enantiomers in rat plasma

A method for the enantiomeric determination of 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (LLU-alpha, gamma-CEHC) in rat plasma was developed using high-performance liquid chromatography (HPLC) with a fluorimetric derivatization with 4-N, N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) followed by O-acetylation with acetyl chloride. The proposed HPLC system used two non-chiral columns (phenyl and octadecylsilica) and a chiral column (a modified cellulose type), which were connected via two column-switching valves. A derivatized sample prepared from rat plasma was first separated on the phenyl column, and the fraction including LLU-alpha derivative was introduced to the octadecylsilica column to quantify the concentration of the mixture of S- and R-LLU-alpha. Finally, the LLU-alpha derivative was directly injected into the chiral column to obtain the ratio of the enantiomers. The proposed HPLC system was applied to the enantiomeric determination of LLU-alpha in plasma after intravenous administration of racemic LLU-alpha. S-LLU-alpha was eliminated faster than R-LLU-alpha, and its concentration in plasma decreased to one-third at 2 min after dosing.     

Autorecycling oxidation of alcohol catalyzed by 1,3,7,9,11,12,14-heptazapentacene-2,4,8,10 (14H,3H,9H,12H)-tetraones (mixed flavins)

1,3,7,9,11,12,14-Heptazapentacene-2,4,8,10 (14$\text{H}$,3$\text{H}$,9$\text{H}$,12$\text{H}$)-tetraones (mixed flavins) were prepared by the cyclization of 1,5-dihydro-8-[N-alkyl-N-(5-nitrouracil-6-yl)-amino-5-deazaflavins with Vilsmeier reagent. The mixed flavins oxidized alcohol under neutral condition in sunlight and a remarkable autorecycling was observed.