EARLY EFFECTS OF NEAR-ULTRAVIOLET RADIATION ON YEAST CELLS: CHANGES IN CELL SIZE

Exponentially growing yeast cells showed a drastic shrinkage when irradiated in water suspension (but not in buffer) with broad-band near-UV radiation. This was clearly seen soon after irradiation in size-distribution curves measured by a Coulter counter. This early shrinkage was observed at a near-UV fluence where the survival enters a region of exponential decline after a large shoulder. We further observed the formation of a distinct band in a density-gradient-centrifugation profile, presumably corresponding to the near-UV-affected cells. A survival test showed that the cells making up this band were dead.     

High performance liquid chromatography with UV detection for the simultaneous determination of sympathomimetic amines using 4-(4,5-diphenyl-1H-imidazole-2-yl)benzoyl chloride as a label

A high performance liquid chromatographic method has been developed for the simultaneous determination of (+/-) fenfluramine (Fen) and phentermine (Phen) in addition to three other sympathomimetic amines-ephedrine (E), norephedrine (NE) and 2-phenylethylamine (2-PEA), using cyclohexylamine (CX) as an internal standard in plasma. The compounds were derivatized with 4-(4,5-diphenyl-1H-imidazole-2-yl)benzoyl chloride (DIB-Cl) to give the DIB-derivatives. The derivatives were then separated using an isocratic HPLC system with UV detection. The limits of detection for Fen, Phen, E, NE and 2-PEA in plasma ranged from 0.32 to 22.9 pmol on column at a signal-to-noise ratio of 3. The recoveries following alkaline extraction from plasma samples of known concentrations were found to be more than 94% for the studied compounds. This method might be useful for the screening of the studied sympathomimetic amines in human plasma samples in forensic as well as toxicological studies. Furthermore, the developed method was modified for the simultaneous determination of Fen and Phen in human and rat plasma using fluoxetine as an internal standard. The methods are reproducible and precise. Finally, the two drugs were administered intraperitoneally to rats in combination, and their plasma levels over the investigated time course were successfully determined.     

Stereoselective synthesis of multisubstituted butadienes through directed Mizoroki-Heck reaction and homocoupling reaction of vinyl(2-pyridyl)silane

[reaction: see text] We have developed the homocoupling reaction of alkenyl(2-pyridyl)silanes mediated by CuI and CsF, in which the strong directing effect of the 2-pyridyl group was observed. The homocoupling reaction was successfully integrated with the Mizoroki-Heck reaction of vinyl(2-pyridyl)silane with aryl halides, enabling a rapid and stereoselective synthesis of multisubstituted butadienes. From a relatively small compound library, it was possible to detect a number of fluorescent butadienes with a wide range of fluorescence color variations (blue to reddish-orange).     

Synthesis of a soluble ureido-naphthyridine oligomer that self-associates via eight contiguous hydrogen bonds

[structure; see text] An iterative synthetic route to organic-soluble ureido-naphthyridine oligomers has been developed. Use of this protocol allowed synthesis of a short ureido-naphthyridine oligomer, which presents a self-complementary DDAADDAA hydrogen bonding array (D = hydrogen bond donor, A = hydrogen bond acceptor). Strong self-association via eight hydrogen bonds was observed in organic solution.     

Stereoselective pyrroline-ring formation through the cyclization of conjugated azomethine ylides at the periphery of pyrido[1,2-a]pyrimidine system

The thermal reaction of N-benzyl-N-[3-(N-substituted imino)methyl-4-oxo-4H-pyrido[1,2-a]pyrimidin-2-yl]amino acid esters, generated from aldehyde esters and primary amines, provides 2,3-dihydropyrido[1,2-a]pyrrolo[2,3-d]pyrimidin-4(1H)-one derivatives effectively and stereoselectively. Therein, the stereoselective generation of conjugated azomethine ylides from the imine esters and their cyclization is essential for the pyrroline-ring formation.     

Molecular bilayer-based superstructures of a fullerene-carrying ammonium amphiphile: structure and electrochemistry

The synthesis of a water-soluble C60-carrying single-chain ammonium amphiphile, 10- (N-methyl-2-fulleropyrrolidyl)decyltrimethylammonium bromide (1) as well as the characterization of aqueous solutions and cast films of 1 are described. X-ray diffraction study suggests that cast films of 1 form a multilayer structure based on biomembrane-like molecular bilayers. Electron microscopy has revealed that 1 produces both fibrous and disk-like aggregates with 10-12 nm of thickness through self-organization of 1 in aqueous solution. Differential scanning calorimetry, dynamic light scattering, FTIR, and UV-visible absorption studies were also carried out to characterize aqueous solutions and cast films of 1. Electrochemistry for an aqueous solution and for cast films of just 1 and 1 incorporated in lipid films on electrodes was conducted. It was found that films of just 1 and of 1/lipid cast on electrodes showed electron transfer reactions leading to the generation of the fullerene dianion or trianion. In contrast, electrochemistry of aqueous solution of 1 at a bare electrode gives a cathodic current near -0.5 to -0.6 V against SCE; however, an anodic current for the solution did not appear.     

Intramolecular charge-transfer fluorescence from 9,9′-bianthryl absorbed on porous glass

9,9′-bianthryl (BA) absorbed on porous glass exhibits both intramolecular charge-transfer (CT) and anthracene-like fluorescence. The CT fluorescence exhibits no temperature dependence, suggesting that orientational relaxation on the time scale of fluorescence decay is absent. Complex fluorescence decay characteristics from BA and 9,10-diphenyl anthracene (DA) absorbed on the glass are interpreted in terms of absorption on a variety of sites.     

Disposition of triazolam in the rat by brain microdialysis and semi-micro column high-performance liquid chromatography with UV absorbance detection

A semi-micro column high-performance liquid chromatography with ultraviolet detection for the determination of triazolam is described. The method was applied to determine plasma and brain microdialysate concentrations of triazolam after single intravenous bolus of 2.5 mg/kg to rat. The separation was achieved on a 250 x 1.5 mm i.d. C(18) column and the column effluent was monitored at 222 nm. The detection limits at a signal-to-noise ratio of 3 obtained using spiked plasma and artificial cerebrospinal fluid were 2.1 and 0.7 ng/mL, respectively. The intra- and inter-day reproducibility of the present method were satisfactory with the highest relative standard deviation of 9.1 (n > or = 5). The present method was successfully applied to study the disposition of triazolam in rat (n = 5) by analyzing plasma and brain microdialysate samples.     

Production and characterization of thermally-annealed large clusters by high-pressure laser-vaporization technique

We have developed a high-pressure laser-vaporization cluster source, which enables us to produce large, annealed clusters. Large carbon clusters up to C ₂₀₀₀ ⁺ , annealed sodium fluoride clusters of Na⁺(NaF)_n, and ammonium iodide clusters of NH ₄ ⁺ (NH₄I)_n have been produced by this technique. Annealed ammonium iodide clusters show a transition from hydrogen bonded complexes to ionic crystals as the cluster size increases. The characterization of the present technique and the production processes of the large, annealed clusters are discussed.     

Measurement of reaction rate distributions in a plastic phantom irradiated by 40- and 65-MEV quasi-monoenergetic neutrons

Reaction rate distributions in a plastic phantom were measured with solid state nuclear track detectors and a fission counter for 40- and 65-MeV quasi-monoenergetic neutrons generated by the 7Li(p,n) reactions with 43- and 68-MeV protons at AVF cyclotron of Japan Atomic Energy Research Institute. Measured distributions were compared with calculated ones.