Amperometric determination of 6-mercaptopurine on functionalized multi-wall carbon nanotubes modified electrode by liquid chromatography coupled with microdialysis and its application to pharmacokinetics in rabbit

In this paper, multi-wall carbon nanotubes fuctionalized with carboxylic groups modified electrode (MWNT-COOH CME) was fabricated. This chemically modified electrode (CME) can be used as the working electrode in the liquid chromatography for the determination of 6-mercaptopurine (6-MP). The results indicate that the CME exhibits efficiently electrocatalytic oxidation for 6-MP with relatively high sensitivity, stability and long-life. The peak currents of 6-MP are linear to its concentrations ranging from 4.0×10⁻⁷ to 1.0×10⁻⁴ mol l⁻¹ with the calculated detection limit (S/N=3) of 2.0×10⁻⁷ mol l⁻¹. Coupled with microdialysis, the method has been successfully applied to the pharmacokinetic study of 6-MP in rabbit blood. This method provides a fast, sensible and simple technique for the pharmacokinetic study of 6-MP in vivo.     

Generation of NH-azomethine imine intermediates through the 1,2-hydrogen shift of hydrazones and their intermolecular cycloaddition reaction with olefinic dipolarophiles

The thermal 1,2-hydrogen shift of the hydrazone generates the NH-azomethine imine intermediate in the 4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carbaldehyde system under mild conditions. Therein, the resulting NH-azomethine imine should be stabilized by forming an internal hydrogen bond with the carbonyl oxygen at the 4-position. Its smooth stereoselective intermolecular cycloaddition reaction with olefinic dipolarophiles giving pyrazolidine derivatives is discussed.     

Synthesis of novel phenylazomethine dendrimers having a cyclam core and their zinc complex

[structure: see text] Novel phenylazomethine dendrimers having a cyclam core were synthesized by the convergent method. The dendrimers showed selective coordination with zinc chloride on the cyclam ring and with tin chloride on the imine groups. The metal cyclam exhibits a metal-assembling function to provide a multinuclear hetero metal complex.     

Convergent synthesis of the A-F ring segment of yessotoxin and adriatoxin

A convergent synthesis of the A-F ring segment of yessotoxin and adriatoxin was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis.     

Characterization of saccharide moiety in the electroplax sodium channel.

Carbohydrate chains on the large peptide of the voltage-sensitive sodium channel from Electrophorus electricus electroplax have been partially characterized by the lectin-blotting technique combined with digestion using three glucosidases: neuraminidase, endo-beta-N-acetylglucosaminidase H, and peptide: N-glycosidase F. The results show that both N-linked oligosaccharides and O-linked (mucin-type) oligosaccharides are present. In N-linked oligosaccharides, the results suggest the presence of complex- and hybrid-type oligosaccharides which contain bisecting N-acetylglucosamine(s), as well as the complex-type oligosaccharides with the alpha-Fuc-GlcNAc-(Asn) residue(s). In O-linked oligosaccharides, they must carry Gal beta1----3GalNAc- moieties which contain NeuNAc residues in the terminal.     

Characterization of cationic acid phosphatase isozyme from rat liver mitochondria.

Acid phosphatase isozyme was highly purified from rat liver mitochondrial fraction. The enzyme showed an isoelectric point value of above 9.5 on isoelectric focusing, and the apparent molecular weight was estimated to be 32000 by Sephadex G-100 gel filtration or 16000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme catalyzed the hydrolysis of adenosine 5'-triphosphate, adenosine 5'-diphosphate, thiamine pyrophosphate, inorganic pyrophosphate, and phosphoprotein such as casein and phosvitin, but not of several phosphomonoesters, except for p-nitrophenyl phosphate and o-phosphotyrosine. The enzyme was not inhibited by L-(+)-tartrate, and was significantly activated by Fe2+ and reducing agents such as ascorbic acid, L-cysteine,and dithiothreitol. The enzyme was found to be distributed in various rat tissues including liver, spleen, kidney, small intestine, lung, stomach, brain and heart, but not in skeletal muscle.     

Kinetic study of ion exchange reaction between lysozyme and carboxymethyl Sephadex C-25

The ion-exchange reaction of lysozyme with carboxymethyl Sephadex C-25 was followed by conductivity change as a function of time just after the rapid mixing of the protein solution with the Sephadex suspension. A single relaxation process was observed; the conductivity increased exponentially with time in the 100 s scale. In this process, protons were released from the Sephadex C-25 in the same time scale. The relaxation process slowed down with an increase in the lysozyme concentration, but it quickened upon the addition of HCl. On the other hand, the potential on the Sephadex C-25 surface changed from a negative value to a positive one with an increase in the amount of lysozyme adsorbed on the surface. On the basis of these data, the relaxation process was attributed to the ion-exchange reaction of lysozyme with several protons of carboxymethyl groups of the Sephadex.     

Immunoactivity of polymer microspheres with their hydrophilic/hydrophobic heterogeneous surface sensitized with an antibody

Styrene/2-hydroxyethyl methacrylate polymer microspheres consisting of various polymer compositions were produced by emulsifier-free seeded emulsion polymerization technique. Using these microspheres, which should have hydrophilic/hydrophobic heterogeneous surface, the effects of surface hydrophilicity on the main, fundamental requirements for an immunomicrosphere — high colloidal stability, sensitive immunologic agglutinability and insensitive non-specific agglutinability — were studied in detail. There was a region of the surface hydrophilicity that satisfied the three requirements simultaneously.Part CII of the series Studies on Suspension and Emulsion.     

High-performance liquid chromatographic analysis of serum short-chain fatty acids by direct derivatization

The application of direct derivatization in conjunction with high-performance liquid chromatography is described for the analysis of short-chain fatty acids in serum. The method is based on the reaction of these acids with acidic 2-nitrophenylhydrazine hydrochloride, without complicated isolation steps, which produces their non-volatile hydrazine derivatives. The hydrazides of fourteen saturated and unsaturated, straight and branched, short-chain fatty acids were separated from other acid hydrazides and interfering components by a simple solvent extraction, and were eluted isocratically on a reversed-phase C8 column within 24 min. UV detection demonstrated that the detection limits for the acids were 200-400 fmol per injection with linearity over the range from 400 fmol to 5 nmol per injection. Analytical recoveries ranged from 96.8% to 103.1% and coefficients of variation ranged from 0.9% to 3.8%. The present method is simple, accurate and adequate for the analysis of short-chain fatty acids in biological fluids and tissues of patients suffering from organic acidemias.