Use of nucleic acids in the mobile phase for the determination of ascorbic acid in foods by high-performance liquid chromatography with electrochemical detection

The sodium salts of amino acids, nucleic acids and organic acids were examined in a new mobile phase for the determination of ascorbic acid (AA) in foods. It was possible to use disodium guanosine-5'-monophosphate (GMP) (20 mM GMP, pH 2.1) in a new mobile phase after comparison of five mobile phases. The proposed method is simple, rapid (analysis time: ca. 6 min), sensitive (detection limit: ca. 0.1 ng per injection (5 microl) at a signal-to-noise ratio of 3), highly selective and reproducible [relative standard deviation: ca. 2.7% (n=7)]. The calibration graph of AA was linear in the range of 0.1 to 50 ng per injection (5 microl). Recovery of AA was over 90% by the standard addition method.     

Assay of cholinesterase in an electrode system with an immobilized substrate

A rapid, simple method for the measurement of cholinesterase based on an immobilized acetylcholine substrate is described. Each assay requires only 3 min and the immobilized substrate can be used for 10 assays with excellent results; the substrate can then be renewed easily and quickly. The precision obtained (2.5 %) is the same as that possible with the soluble substrate system.     

Synthesis and DNA strand breakage activity of some 1,4-diazepines

Reactions of 1,3-propanediamine with alpha-dicarbonyl compounds (1a-e) were examined and various condensed heterocyclic compounds such as 1,4-diazepines (2) and 3-pyrimidine derivatives (3) were obtained. Some of 1,4-diazepines (2) showed DNA strand breakage activity.     

Ganea's Conjecture on Lusternik-Schnirelmann Category

A series of complexes Q_p indexed by all primes p is constructedwith catQ_p=2 and catQ_pxSⁿ=2 for either n2 or n=1 and p=2. Thisdisproves Ganea's conjecture on Lusternik–Schnirelmann(LS) category. 1991 Mathematics Subject Classification 55M30.     

The status of the Super-FRS at FAIR

The Super-FRS will be a large-acceptance two-stage superconducting fragment separator with three exit branches serving different experimental areas. Due to the high primary-beam intensity of up to 10¹² ions/s a challenging design of the target area and the components used in the first dipole Super-FRS is necessary. These efforts include high-power production targets, beam-dumps to catch the remaining primary beam, and radiation resistant magnets. In this contribution we summarize the recent developments on these issues.     

Bacterium organizes hierarchical amorphous structure in microbial cellulose

A pellicle, a gel film of microbial cellulose, is a supermolecular system containing 99% of water by weight, which is closely related to an amorphous structure in it. Using ultra-small-angle neutron scattering, in order to cover over a wide range of length scales from nm to 10 microm, we examined the hierarchical amorphous structure in the microbial cellulose, which is synthesized by a bacterium (Acetobacter xylinum). The microbial cellulose swollen by water shows small-angle scattering that obeys a power law q -behavior according to q -alpha as a function of the magnitude of the scattering vector q . The power law, determined by scattering, is attributed to a mass fractal due to the distribution of the center of mass for the crystallite (microfibril) in amorphous cellulose swollen by water. As q increases, alpha takes the values of 2.5, 1, and 2.35, corresponding, respectively, to a gel network composed of bundles, a bundle composed of cellulose ribbons, and concentration fluctuations in a bundle. From the mass fractal q -behavior and its length scale limits, we evaluated a volume fraction of crystallite in microbial cellulose. It was found that 90% of the cellulose bundle is occupied by amorphous cellulose containing water.     

Subfractionation of the dansylated derivatives of glucosyl galactosyl hydroxylysine by liquid chromatography and its application to a specific alpha-1,2-glucosidase assay

The dansyl derivative of glucosyl galactosyl hydroxylysine (GGH) was separated into two components, as GP-I (monodansyl GGH) and GP-II (didansyl GGH) by paper chromatography. GP-I was further fractionated into four peaks (a, b, c and d) by reversed-phase liquid chromatography. These peaks corresponded to the dansyl derivatives at the alpha-amino (a and b) and epsilon-amino (c and d) groups of their hydroxylysine residues. There is the possibility that the fractions for b and d are diastereoisomers of a and c, respectively, since the monodansyl derivative from human urine consists of a and c. GP-II was fractionated into two peaks, e and f, which may possibly be diastereoisomers of each other. Treatment of the a, b, c and d fractions with crude chicken liver enzyme resulted in the preferential cleavage of a and b and the production of monodansyl galactosyl hydroxylysine. Components c and d were also cleaved slowly, resulting in the production of monodansyl hydroxylysine by the successive action of beta-galactosidase on dansyl galactosyl hydroxylysine. The detected alpha-glucosidase activity was strongly inhibited by free mannosamine. The method developed using the monodansyl GGH fraction a (or b) and high-performance liquid chromatography facilitated the detection of alpha-1,2-glucosidase, which acts specifically toward GGH even in a crude enzyme preparation.     

Loading effects of silver oxides upon generation of reactive oxygen species in semiconductor photocatalysis

Superoxide anion radical (O(2)(-*)) and OH radical generations in suspensions of Ag metal-, Ag(2)O-, or AgO-loaded TiO(2) and BiVO(4) photocatalysts in alkaline conditions (pH 12.0) were examined by means of a luminol chemiluminescence (CL) technique and a spin-trapping fluorescence one in which terephthalic acid reacts with an OH radical to afford the highly fluorescent 2-hydroxyterephthalic acid (TAOH), respectively. The observed luminol CL intensity was remarkably enhanced by the AgO loading on TiO(2) as well as BiVO(4). This can be explained by enhancement of O(2)(-*) production on the AgO-loaded photocatalysts caused by the synergetic effects on the thermocatalytic activity upon the AgO surface and the efficient electron-hole separation at the photocatalyst/AgO interface. On the other hand, loading effects of AgO on the TAOH formation were not so significant compared to those on the CL observation, though the TAOH formation rates for the TiO(2) samples were much larger than those for the BiVO(4) ones by about three orders of magnitude. The properties of O(2)(-*) and OH radical generations on these photocatalysts are discussed on the basis of the luminol CL kinetics and approximate band edge positions of TiO(2), BiVO(4), and silver oxides.     

Charge states of Ca atoms in β-dicalcium silicate

In order to study the crystal structure of β‐Ca₂SiO₄, time-of-flight neutron powder diffraction experiments were carried out at temperatures between room temperature (RT) and 600 °C. Rietveld refinement at RT has shown that β‐Ca₂SiO₄ is monoclinic based on P2₁/n symmetry and two different types of Ca sites, Ca(1) and Ca(2). All interatomic distances within 3 Å were calculated, with the valences of Ca(1) with seven CaO bonds and Ca(2) with eight were estimated to be 1.87+ and 2+ by the Zachariasen-Brown-Altermatt formula (bond valence sum). Applying charge neutrality the two charge states of Ca in β‐Ca₂SiO₄ are [Ca(1)SiO₄]²⁻ and Ca(2)²⁺, respectively. Furthermore, the [Ca(1)SiO₄]²⁻ unit has the shortest Ca-O distance, and its length kept constant at 2.23 Å at all temperatures. In the short-range structure analysis at RT, the shortest Ca-O bond was also observed in a radial distribution function. These results imply that the [Ca(1)SiO₄]²⁻ unit has covalency on the shortest Ca-O in addition to Si-O.