Fluorometric assay of nicotinamide methyltransferase with a new substrate, 4-methylnicotinamide

A fluorometric method for the assay of nicotinamide methyltransferase has been established using rat liver 9000 x g supernatant fluid as a model enzyme preparation. 1,4-Dimethylnicotinamide formed enzymatically from a new substrate, 4-methylnicotinamide, is quantified by means of its fluorescence reaction with 4-methoxybenzaldehyde in aqueous alkali. The lower limit of determination of 1,4-dimethylnicotinamide is 100 pmol in the enzymatic reaction mixture. The apparent Km values for 4-methylnicotinamide and for nicotinamide, which is a known substrate for this enzyme, were 0.19 and 0.13 mM, respectively, whereas the relative activity of 4-methylnicotinamide as a methyl acceptor was about 1.5 times the value of nicotinamide.     

Structure of carbon onions and nanotubes formed by arc in liquids

Since carbon nanotubes and onions were discovered, many methods have been proposed for their production. For applications the main requirements are low capital cost, high purity of the produced material, simplicity of technique, and its potential for scale up. Recently a cathodic arc between two graphitic electrodes immersed in liquids has been demonstrated to be a simple method to produce carbon nanoparticles such as nanotubes and onions. In this paper high-resolution transmission electron microscopy is employed to examine the shape of the nanoparticles and the purity of the final material produced under various conditions. In this study we have used an arc discharge in two different liquids--liquid nitrogen and distilled water--and we have changed the grade of the carbon electrodes. The variety in structure, shape, and size of the produced particles is discussed in line with a model proposed to describe the physical process.     

Fluorometric assay of rat tissue N-methyltransferases with nicotinamide and four isomeric methylnicotinamides.

Nicotinamide (NA) and its four isomeric methyl analogs [2-, 4-, 5- and 6-methylnicotinamides (MNs)] were tested as substrates for nicotinamide N-methyltransferase (NNMT) and amine N-methyltransferase (ANMT) using rat liver, kidney, spleen and brain 9000 x g supernatant fluids as model enzyme preparations. The N-methylated products were determined fluorometrically by their reaction with acetophenone or 4-methoxybenzaldehyde to form fluorescent 2,7-naphthyridine derivatives, and the lower limits of the determination were 8-30 pmol/100 microliters. N-Methyltransferase activities were detected in the liver with NA, 4-MN and 5-MN, and in the brain and spleen with 4-MN. On this basis, 5-MN is considered to be a selective substrate for NNMT in addition to NA, which is a known methyl acceptor for this enzyme. Although 4-MN appears to serve as a methyl acceptor for both ANMT and NNMT, it seems to be essentially a selective substrate for brain ANMT because of the absence of NNMT in brain. The fluorometric methods used here are also very useful because of their simplicity, sensitivity and selectivity.     

Short-lived chemical species of57Fe in57Co-labelled Co/IO3/2 studied by time-resolved emission Mössbauer spectroscopy

Time resolved Mössbauer spectra were measured for⁵⁷Co-labelled Co/IO₃/₂ using a delayed coincidence technique. A life-time for unstable⁵⁷Fe(II)-species formed through EC-decay was estimated to be 43±5 ns at room temperature and the initial distribution of⁵⁷Fe(II)/⁵⁷Fe(III) at 14.4 keV nuclear level to be 0.47±0.13. The results are discussed in terms of electron transfer from the decayed⁵⁷Fe(II) atoms to iodate ions.     

EPR and IR spectra of Ni(ClO4)2)·6H2O between 98 and 298 K

EPR measurements between 98 and 298 K on single crystal of Ni(ClO₄)₂·6H₂O have indicated the appearance of a rhombic component in the axial crystal field at Ni²⁺ sites at T_c = 224 K, confirming a phase transition first reported by Chaudhuri from magnetic susceptibility measurements. Temperature variations of g, D and E parameters were determined. IR spectra at room and liquid nitrogen temperatures are consistent with our EPR results.     

Synthesis of Anisotropic Hydrogels and Their Applications

Owing to their water‐rich structures, which are similar to those of biological tissues, hydrogels have long been regarded as promising scaffolds for artificial tissues and organs. However, in terms of the structural anisotropy, most synthetic hydrogels are substantially different from biological systems. Synthetic hydrogels are usually composed of randomly oriented three‐dimensional polymer networks whereas biological systems adopt anisotropic structures with hierarchically integrated building units. Such anisotropic structures often play essential roles in biological systems to exhibit particular functions. In this context, anisotropic hydrogels provide an entry point for exploring biomimetic applications of hydrogels. Reflecting these aspects, an increasing number of studies on anisotropic hydrogels have been reported recently. This Minireview highlights the use and perspectives of these anisotropic hydrogels, particularly focusing on their preparation, structures, and applications.     

Production of aliphatic aldehydes on peroxidation of various types of lipids.

IN vitro peroxidation by air, or xanthine-xanthine oxidase (xanthine-XOD) was performed to estimate the production of aliphatic aldehydes from free polyunsaturated fatty acids (PUFA), triglycerides, phospholipids and rat liver microsomes and mitochondria. The aldehyde contents in peroxidized lipids were determined by liquid chromatography and fluorescence detection. In both peroxidation, pentanal, (E)-4-hydroxy-2-nonenal (4-HN), and hexanal were produced from omega-6 PUFA rich lipids and propanal was markedly enhanced by increasing the degree of fatty acid unsaturation. The ratios of 4-HN to hexanal production in xanthine-XOD peroxidation of the omega-6 PUFA rich lipids, and rat liver microsomes and mitochondria were much higher than those in air peroxidation. The ratios (4-HN/hexanal) obtained in microsomes and mitochondria by xanthine-XOD were similar to those in rat liver observed in vitamin E deficient studies. The determination of these aldehydes may be useful to estimate the kinds of fatty acids peroxidized and investigate in vivo lipid peroxidation mechanism.