Characterization of an avidin-bonded column for direct injection in reversed-phase high-performance liquid chromatography

An automatic method for the determination of metabolites of Ropivacaine in urine was set up. It utilizes supported liquid membrane extraction for sample clean-up and enrichment, followed by ion-pair chromatography determination using UV detection. The extraction was very selective with no observed interfering compounds from the urine matrix, permitting simple isocratic chromatographic analysis. The detection limits for spiked urine samples were 2–18 nM for the different compounds. The repeatability was 1–3% (RSD) with an internal standard that was also extracted, and about twice without this standard. A throughput of 3.3 samples per hour was achieved and the liquid membrane was stable for more than a week.     

Targeting of mitomycin C to the liver by the use of asialofetuin as a carrier.

Desialylated fetuin (asialofetuin) was adopted as a carrier for introducing drugs in parenchymal liver cells. Mitomycin C, as a model guest-compound, was covalently attached to asialofetuin through a spacer of the succinyl group. The asialofetuin-mitomycin C conjugate contained 4.4 w/w% of mitomycin C and liberated it gradually at physiological conditions (t1/2 = 37 h). The survival time of the conjugate in rat blood circulation was significantly smaller than that of the non-desialylated fetuin conjugate; the elimination half-life was 7.3 min after intravenous injection. At 30 min after injection of the conjugate in rats, 40% of the dose was present in the liver. Parenchymal cells in the liver selectively took up the conjugate, which was highly distributed to the lysosomal fraction in the cell. The greater uptake of the conjugate by hepatocytes reflected the increased excretion in the bile; totally 10.4% of the dose was recovered.     

Direct asymmetric organocatalytic Michael reactions of alpha,alpha-disubstituted aldehydes with beta-nitrostyrenes for the synthesis of quaternary carbon-containing products

[reaction: see text] Direct asymmetric catalytic Michael reactions have been performed using chiral-amine/acid bifunctional catalysts. Performed with 0.3 equiv of (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine and 0.3 equiv of trifluoroacetic acid as the catalyst, the reaction of alpha,alpha-dialkylaldehydes with (E)-beta-nitrostyrene provided the alpha,alpha-dialkyl Michael products in up to 96% yield with up to 91% ee. With respect to enantioselectivity, l-proline was a poor catalyst of this class of Michael reactions.     

Upward temperature shift of the intrinsic phase lag of the magnetization of Bis(phthalocyaninato)terbium by ligand oxidation creating an S = 1/2 spin

An alternating-current (ac) magnetic susceptibility measurement for the [(Pc)(2)Tb(III)](0) complex (Pc = phthalocyaninato) has shown that ligand oxidation of the anionic [(Pc)(2)Tb(III)](-) complex gives rise to a significant upward shift of the temperature range where the magnetization response shows a phase lag behind the time-varying external magnetic field. The peaks of the out-of-phase component of the ac susceptibility of the pi-radical [(Pc)(2)Tb(III)](0) were observed at 50, 43, and 36 K with ac magnetic fields of 10(3), 10(2), and 10 Hz, respectively, which were more than 10 K higher than the corresponding values of the anionic complex with a closed-shell pi-system. The ac susceptibility measurements on the complex with octa(dodecoxy)-substituted Pc ligand, which is readily dilutable in diamagnetic media, proved that the significant rise of the temperatures occurs as an intrinsic single-molecular property of the complex possessing both J = 6 and S = (1)/(2) systems, and is not due to long-range magnetic order or interactions between adjacent unpaired pi-electrons.     

INAA determination of holmium in submilligram samples of cosmochemical and geochemical interest and the second-order activation interference

Second-order neutron activation becomes a serious interference in NAA determinations of REE in submilligram samples of meteoritic and terrestrial materials when neutron fluences reach levels of 10²⁰ n·cm^–2 or more. The Dy-interference to Ho determination and the Eu-interference to Gd determination are quite, large. We discuss the importance of second-order activation interferences in REE determinations, and present an experimental method to correct the Dy-interference to Ho determination by INAA. Ho concentrations in splits of less than 0.2 mg of BCR-1 and SP can be accurately determined by INAA with a neutron fluence of 2·10²⁰ n·cm^–2 in spite of large Dy interferences of up to 200%. It is necessary for NAA determinations of REE with high neutron fluences that each REE standard be separated from its neighboring REE, in order to correct the second-order activation interferences experimentally.     

Conductive characteristics of radical‐bearing polythiophenes using a microcomb‐shaped electrode

The electric conductivity of π‐conjugated and radical‐bearing polymers, i.e., polythiophenes bearing pendant galvinoxyl and phenoxyl radical groups, was measured using a microcomb‐shaped electrode. The electric conductivity was found to be enhanced by the radical content in the polymer. The infrared (IR) and Raman spectroscopies suggested a structural change from an aromatic form to a quinoid one in the polythiophene backbone by the phenoxyl radical generation. The effect of the pendant galvinoxyl radical's unpaired electron on the electric conductivity of the polythiophene was discussed by comparing the conductivity of a radical‐bearing polystyrene and a polythiophene mixed with low‐molecular radical molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

Formation of ice nanotube with hydrophobic guests inside carbon nanotube

A composite ice nanotube inside a carbon nanotube has been explored by molecular-dynamics and grand canonical Monte Carlo simulations. It is made from an octagonal ice nanotube whose hollow space contains hydrophobic guest molecules such as neon, argon, and methane. It is shown that the attractive interaction of the guest molecules stabilizes the ice nanotube. The guest occupancy of the hollow space is calculated by the same method as applied to clathrate hydrates.     

Hydrogen-bonded networks in organic conductors: crystal structures and electronic properties of charge-transfer salts of tetracyanoquinodimethane with 4,4'-biimidazolium having multiprotonated States

[structure: see text] Novel hydrogen-bonded charge-transfer salts of TCNQ with mono- and diprotonated 4,4'-biimidazolium were synthesized in order to demonstrate the high potential of the 4,4'-biimidazole system in a molecular conductor from the viewpoint of crystal engineering and electronic modulation. Crystal structure analyses of neutral 4,4'-biimidazole and TCNQ salts revealed the formation of two types of hydrogen-bonding modes of the 4,4'-biimidazole moiety depending on the protonated states. Neutral 4,4'-biimidazole possessed a linear chain mode of hydrogen-bonding to construct two-dimensional network. In the TCNQ salt of monoprotonated 4,4'-biimidazolium, the 4,4'-biimidazole moiety formed a dimer by a complementary mode of hydrogen-bonding. In contrast, the salt of diprotonated 4,4'-biimidazolium showed a double linear chain mode of hydrogen-bonding to construct a three-dimensional network. The formation of two types of hydrogen-bonding modes made the difference in the stacking patterns of TCNQ columns and in their transport properties. The TCNQ salt of diprotonated 4,4'-biimidazolium exhibited high electrical conductivity (sigma(rt) = 1.1 x 10(-1) S cm(-1)).     

A simple and simultaneous determination of acyclovir and ganciclovir in human plasma by high-performance liquid chromatography

A simple high-performance liquid chromatographic method was developed for the simultaneous determination of the therapeutic levels of acyclovir and ganciclovir in human plasma. After precipitation of plasma proteins with 6% perchloric acid, acyclovir and ganciclovir were simultaneously determined by reversed-phase chromatography with spectophotometric detection at 254 nm. The peak heights for acyclovir and ganciclovir were linearly related to their concentrations ranging from 0.063 to 2.080 micro g/mL. The recovery was 100.48-102.84% for acyclovir and 99.26-103.07% for ganciclovir. The intra- and inter-day relative standard deviation values were in the range 0.186-8.703% for acyclovir and 0.137-6.424% for ganciclovir. The detection limits for both compounds were 0.01 micro g/mL determined as the signal-to-noise ratio of 3. The present method is applicable to therapeutic monitoring during antiviral medication.