Determination of sodium azide in beverages by ion chromatography

A convenient method for determination of sodium azide in beverages using ion chromatography is described. This method combines the specificity for azide with a simple sample preparation using a bubble and trap apparatus that removes any interferences. Sodium azide in a sample was acidified, and the azide was converted to the volatile hydrazoic acid, which was trapped in 2.5 mM sodium hydroxide solution. Determination was performed by isocratic ion chromatography using suppressed conductivity detection. Calibration curves were linear for 0.5 to 20 microg/mL sodium azide and the detection limit was 0.05 microg/mL. Recoveries of sodium azide from spiked samples (10.0 microg/g) were more than 82.6%. The method was then used to analyze various beverages.     

Design and synthesis of highly sensitive and selective fluorescein-derived magnesium fluorescent probes and application to intracellular 3D Mg2+ imaging

The role of intracellular magnesium ions is of high interest in the fields of pharmacology and cellular biology. To accomplish the dynamic and three-dimensional imaging of intracellular Mg2+, there is a strong desire for the development of optimized Mg2+ fluorescent probes. In this paper we describe the design, synthesis, and cellular application of the three novel Mg2+ fluorescent probes KMG-101, -103, and -104. The compounds of this series feature a charged beta-diketone as a binding site specific for Mg2+ and a fluorescein residue as the fluorophore that can be excited with an Ar+ laser such as is widely used in confocal scanning microscopy. This molecular design leads to an intensive off-on-type fluorescent response toward Mg2+ ions. The two fluorescent probes KMG-103 and -104 showed suitable dissociation constants (Kd,Mg2+ = 2 mM) and nearly a 10-fold fluorescence enhancement over the intracellular magnesium ion concentration range (0.1-6 mM), allowing high-contrast, sensitive, and selective Mg2+ measurements. For intracellular applications, the membrane-permeable probe KMG-104AM was synthesized and successfully incorporated into PC12 cells. Upon application of the mitochondria uncoupler FCCP to the probe-incorporated cells, the resulting increase in the free magnesium ion concentration could be followed over time. By using a confocal microscope, the intracellular 3D magnesium ion concentration distributions were satisfactorily observed.     

Tandem base-promoted ring-opening/Brook rearrangement/allylic alkylation of O-silyl cyanohydrins of beta-silyl-alpha,beta-epoxyaldehyde: scope and mechanism

Metalated O-silyl cyanohydrins of beta-silyl-alpha,beta-epoxyaldehyde have been found to serve as functionalized homoenolate equivalents by a tandem sequence involving base-promoted ring opening of the epoxide, Brook rearrangement, and alkylation of the resulting allylic anion. On the basis of mechanistic studies involving competitive experiments using the diastereomeric cyanohydrins, we propose a reaction pathway involving a silicate intermediate 36 formed by a concerted process via an anti-opening of the epoxide followed by the formation of an O-Si bond.     

Studies of the polymerization of diallyl compounds. XXVI. Enhanced polymerizability by the hydroxyl group in the polymerization of diallyl hydroxydicarboxylates

In order to elucidate the effect of the hydroxyl group on the polymerization of diallyl hydroxydicarboxylates, we investigated in detail the radical polymerizations of diallyl succinate (DASu), diallyl malate (DAMa), and diallyl tartrate (DATa), each of which have similar structure differing only in the number of hydroxyl groups present. The rate of polymerization (R_p) was quite enhanced in the order DASu < DAMa < DATa, in accord with the increase in the number of hydroxyl groups within a monomer unit. The enhanced ability of the allylic monomer radical to reinitiate chain growth was also in the same order, as was clear from the dependence of R_p on the initiator concentration. The dependence of the residual unsaturation of the polymer on the monomer concentration in the polymerizations of DAMa and DATa was abnormal in terms of cyclopolymerization. These results are discussed in connection with the formation of the intermolecular hydrogen bond through the hydroxyl groups.     

Fluorimetric assay for measuring Dns-His-Lys-Arg-His-Lys cleaving enzyme using high-performance liquid chromatography

A rapid and sensitive assay for the determination of Dns-His-Lys-Arg-His-Lys cleaving enzyme activity is reported. This assay is based on fluorimetric detection of a dansylated dipeptide, 5-dimethylaminonaphthalene-1-sulfonyl-His-Lys, enzymatically formed from the substrate 5-dimethylaminonaphthalene-1-sulfonyl-His-Lys-Arg-His-d-Lys, after separation by high-performance liquid chromatography (HPLC) using a C-18 reversed-phase column by isocratic elution. This assay is sensitive enough to measure 5-dimethylaminonaphthalene-1-sulfonyl-His-Lys at concentrations as low as 7 pmol, and yields highly reproducible results and requires less than 9.0 min per sample for separation and quantitation. The optimum pH for Dns-His-Lys-Arg-His-Lys cleaving enzyme activity was 7.5-8.0. The Michaelis constant (K_m) and the maximum velocity (V_max) values were 33.3 μM and 47.07 pmol/(μg h), respectively with the use of enzyme extract obtained from bovine pituitary. By using this assay, axonal transport of this enzyme activity was observed 48 h after double ligations of rat sciatic nerves. The high sensitivity and selectivity of this assay would be useful for clarification of the physiological role of this enzyme.     

Novel long-chain anteiso-alkanes and anteiso-alkanoic acids in Antarctic rocks colonized by living and fossil cryptoendolithic microorganisms

Saponified extracts of rock samples colonized by cryptoendolithic microbial communities from the McMurdo Dry Valleys of Southern Victoria Land, Antarctica, were separated into hydrocarbon and fatty acid fractions by silica gel column chromatography. Hydrocarbons and methyl esters of fatty acids were analyzed by capillary gas chromatography-mass spectrometry. Unusually, a suite of long-chain anteiso-alkanes (a-C20 to a-C30) and anteiso-alkanoic acids (a-C20 to a-C30) were detected in many samples, together with straight-chain, branched and/or cyclic and acyclic isoprenoid compounds. These novel compounds are probably derived from unidentified heterotrophic bacteria or symbiotic processes in a unique microbial community in the Antarctic cold desert and suggest the occurrence of a special biosynthetic pathway. Long-chain anteiso-alkanes are probably formed through microbial decarboxylation of corresponding anteiso-alkanoic acids. They may serve as new biomarkers in environmental and geochemical studies.     

Synthesis and polymerization of 4-o-vinylbenzyl-2,2,6,6-tetramethylpiperidine

Some hindered amine polymers containing 2,2,6,6-tetramethylpiperidine structure were synthesized. A new monomer, 4-O-vinylbenzyl-2,2,6,6-tetramethylpiperidine, was homopolymerized and copolymerized with some vinyl monomers in the presence of AIBN as an initiator. The obtained amine polymers were oxidized with hydrogen peroxide to obtain the polymers having nitroxyl radical moiety.     

Development of rectangular column structured titanium oxide photocatalysts anchored on silica sheets by a wet process

Commercially available powdered photocatalysts such as P-25 are known to show high photocatalytic performance. However, in practical use, their anchoring onto a substrate without any binders is still very difficult. The purpose of this study is to design and develop high-performance photocatalysts that can be anchored onto a substrate, and to this end we have prepared a titanium oxide photocatalyst using a wet process. The results of this study led to the successful development of rectangular column structured titanium oxide crystals which could be anchored onto silica sheets. The rectangular columnar crystal was 100- 500 nm wide and 1000- 5000 nm long. Moreover, investigations on the complete oxidation reaction of acetaldehyde into CO₂ and H₂O showed a high performance equivalent to that of the most efficient marketed powdered photocatalysts.     

Rapid and high-resolution analysis of geometric polyprenol homologues by connected octadecylsilylated monolithic silica columns in high-performance liquid chromatography

A Chromolith Performance octadecylsilyl (ODS) monolithic silica column (Merck) was compared with a conventional microparticulate ODS-bonded silica column in the high-performance liquid chromatography separation of natural polyprenols. A system comprising two connected monolithic columns afforded an equivalent separation at half the analysis time of the conventional method. Furthermore, ten connected columns achieved a tremendously high-resolution separation, in which the complicated series of homologous polyprenols with geometric isomerism were fully separated.     

Analysis to obtain precise density fluctuation of supercritical fluids by small-angle X-ray scattering

A procedure of analysis for small-angle X-ray scattering (SAXS) data has been established to obtain density fluctuation of supercritical fluids near the critical point. It is indispensable for the certain analysis to utilize both of high-quality SAXS data measured under stable thermodynamic condition and accurate P–ρ–T data in supercritical region. As a standard example, SAXS measurements have been performed for supercritical CO₂, which is a suitable sample satisfying the condition for both experiment and analysis. The measurements were carried out along four isothermal conditions at reduced temperature of T_r = T/T_c = 1.020, 1.022, 1.043 and 1.064. Comparing the experimental density fluctuation with calculated one from the most reliable equation of state, the differences are within 8% at most.