Use of an amino acid in the mobile phase for the determination of ascorbic acid in food by high-performance liquid chromatography with electrochemical detection

The possibility of using monosodium L-glutamate (MSG) (20 mM MSG, pH 2.1) in the mobile phase for the determination of ascorbic acid (AA) in foods by high-performance liquid chromatography (HPLC) with electrochemical detection was examined. The hydrodynamic voltammogram of AA and the background current were also examined. The applied potential was set at 400 mV versus an Ag/AgCl reference electrode. It was demonstrated that MSG was a useful mobile phase for the determination of AA in foods. This paper also examines the stability of AA under various conditions in order to optimize HPLC conditions and the pre-run sample stabilization. The proposed method is simple, rapid (analysis time: approximately 6 min), sensitive (detection limit: approximately 0.1 ng per injection (5 microl) at a signal-to-noise ratio of 3), highly selective and reproducible (relative standard deviation: approximately 2.5%, n=7). The calibration graph of AA was linear in the range 0.1-50 ng per injection (5 microl). Recovery of AA was over 90% by the standard addition method.     

Photoalkylation of phenanthro[9,10-d] oxazole

The photochemical reaction of phenanthro[9,10-d]oxazole with ethanol, 1-propanol, 2-propanol, or diethyl ether resulted in the substitution of the 1-and/or 2-hydroxyalkyl and/or alkyl groups at the position 2.     

Studies on the constituents of Luffa acutangula Roxb. I. Structures of acutosides A--G, oleanane-type triterpene saponins isolated from the herb.

From the herb of Luffa acutangula ROXB. (Cucurbitaceae), seven oleanane-type triterpene saponins, acutosides A--G, were isolated and their structures were determined. Acutoside A is oleanolic acid 3-O-beta-D-glucopyranosyl-(1----2)-beta-D-glucopyranoside. Acutosides B, D, E, F and G have a common prosapogenin structure, acutoside A, and only differ in the structures of the ester-linked sugar moieties. Acutoside B is a 28-O-[O-beta-D-xylopyranosyl-(1----4)-O-alpha-L-rhamnopyranosyl-(1----2) -alpha-L-arabinopyranosyl] ester, D is a 28-O-[O-beta-D-xylopyranosyl-(1----3)-O-beta-D-xylopyranosyl-(1----4)-O- alpha-L-rhamnopyranosyl-(1----2)-alpha-L-arabinopyranosyl] ester, E is a 28-O-[O-alpha-L-arabinopyranosyl-(1----3)-O-beta-D-xylopyranosyl-( 1----4)-O-alpha-L-rhamnopyranosyl-(1----2)-alpha-L-arabinopyranosyl] ester, F is a 28-O-[O-beta-D-xylopyranosyl-(1----3)-[O-beta-D-xylopyranosyl-(1----4)-O -alpha-L-rhamnopyranosyl-(1----2)-alpha-L-arabinopyranosyl] ester, and G is a 28-O-beta-D-xylopyranosyl-(1----3)-[O-alpha-L-arabinopyranosyl-(1- ---3)-O-beta-D-xylopyranosyl-(1----4)]-O-alpha-L- rhamnopyranosyl-(1----2)-alpha-L-arabinopyranosyl] ester. Acutoside C is a machaelinic acid (=21 beta-hydroxyoleanolic acid) saponin having the same sugar moiety as that of acutoside B.     

Carboxylic acids as promoters for internucleotide-bond formation via condensation of a nucleoside phosphoramidite and a nucleoside: relationship between the acidity and the activity of the promoter

The relationship between the activity and the acidity of a carboxylic acid as a promoter for condensation of a nucleoside phosphoramidite and a nucleoside was investigated. The investigation revealed that the acid, the pKa value of which in acetonitrile is less than 18, is capable of promoting the condensation reaction, and acid with a pKa value outside of this range does not serve as a promoter. In carboxylic acids serving as promoters, the ones with higher acidity generally show greater activity. In particular, acids with a pKa value less than ca. 16 (measured by a potentiometric method), such as trichloroacetic acid (pKa=10.6), trifluoroacetic acid (pKa=12.7), dichloroacetic acid (pKa=13.2 or 15.8), and 2,4-dinitrobenzoic acid (pKa=16.1), show high levels of activity higher than that of conventionally used 1H-tetrazole. These carboxylic acids generally serve as excellent promoters for both the liquid-phase and the solid-phase synthesis of oligonucleotides via phosphoramidite method.     

Synthesis and nonlinear properties of poly[1,4‐bis(4‐alkylpyridinium)butadiyne triflate]

1,4‐Bis(4‐alkylpyridinium)butadiyne triflate ( 2a and 2b ) that was prepared by the reaction of 1,4‐bis(4‐pyridyl)butadiyne ( 1 ) with alkyl trifluoro‐methanesulfonate, was found to grow into a large crystal as a result of the quaternized structure. The thermal treatment of 2a and 2b gave rise to 1,4‐addition polymerization to yield the polydiacetylene. The third‐order nonlinear optical susceptibility [χ⁽³⁾] of the polymer was determined by the femto‐second Z‐scan method to exhibit the remarkable high value of 1.1 × 10^?11 esu at 650 nm. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3686–3691, 2001     

Lusternik-Schnirelmann category of

First we give an upper bound of , the L-S category of a principal -bundle for a connected compact group with a characteristic map . Assume that there is a cone-decomposition of in the sense of Ganea that is compatible with multiplication. Then we have for , if is compressible into with trivial higher Hopf invariant . Second, we introduce a new computable lower bound, for . The two new estimates imply , where is a category weight due to Rudyak and Strom.

     

PHITS—a particle and heavy ion transport code system

The paper presents a summary of the recent development of the multi-purpose Monte Carlo Particle and Heavy Ion Transport code System, PHITS. In particular, we discuss in detail the development of two new models, JAM and JQMD, for high energy particle interactions, incorporated in PHITS, and show comparisons between model calculations and experiments for the validations of these models. The paper presents three applications of the code including spallation neutron source, heavy ion therapy and space radiation. The results and examples shown indicate PHITS has great ability of carrying out the radiation transport analysis of almost all particles including heavy ions within a wide energy range.     

(EZ)-Cyclobilirubin formation from bilirubin in complex with serum albumin derived from various species

We determined the specificity of photochemical changes of bilirubin in complex with serum albumin from various species. There were no general trends in the configurational photoisomerizations of (ZE)-bilirubin/(ZZ)-bilirubin and (EZ)-bilirubin/(ZZ)-bilirubin associated with the albumins from various species as compared to those associated with human serum albumin. The absorbance spectra of bilirubin in complex with albumins from various species differed, indicating that the three-dimensional structures of (ZZ)-bilirubin bound to the various serum albumins, which are substrates of (ZE)- and (EZ)-bilirubin, differ among species. The rates of conversion of the (EZ)-bilirubin isomer into the structural cyclobilirubin isomer were similar for the albumins of chicken, rat, rabbit, dog, bovine, and pig, and were significantly slower than the rate for human serum albumin. This suggests that the three-domain human albumin has evolved to allow ready conversion of (EZ)-bilirubin to (EZ)-cyclobilirubin. Cyclobilirubin formation in a bilirubin-alpha-fetoprotein solution was much lower than that in a bilirubin–human serum albumin solution. It is believed that the ability of human serum albumin to facilitate the photochemical change of bilirubin was evolutionarily selected in response to neonatal jaundice in humans.