CELL SURFACE DAMAGE IN CULTURED MAMMALIAN CELLS WITH SYNCHROTRON RADIATION AT 160 nm

Cultured mammalian cells (HeLa) were allowed to attach onto a membrane filter and were irradiated with 160 nm synchrotron radiation. The cells then were rinsed with medium, fixed, and stained. Some of the cells became detached from the membrane filter during irradiation before post-irradiation incubation at 37°C. The cells remaining attached to the membrane filter were released by trypsinization, collected and examined for dye-exclusion ability with eosin Y. The number of stained cells was increased when the cells were irradiated at 160 nm, while no such increase was observed in cells irradiated with synchrotron radiation at 220 nm, with a low pressure Hg lamp (predominantly 254 nm), or with gamma-rays of ⁶⁰Co. These results indicated that the cell surface was injured by irradiation with synchrotron radiation at 160 nm.     

An unexpected cyclization path to some pyrazoles

The treatment of ketal hydrazones of arylglyoxals (2) with 75% sulfuric acid leads to 3-aroyl-4-phenyl-1-methylpyrazoles (6) as well as 4-phenyl-1-methylpyrazole (7) and the corresponding benzoic acids. Possible mechanisms are discussed.     

Michael addition of N-isobutylidene-t-butylamine to dimethyl methoxymethylenemalonate and a new synthesis of some fused pyrazole derivatives from the adduct

N-Isobutylidenemethylamine reacted with dimethyl methoxymethylenemalonate to afford the N-alkylation product 3a exclusively. Exchanging the N-substituent of the Schiff's base from methyl to t-butyl altered the course of the reaction, allowing Michael addition to take place predominantly. The Michael adduct 4c on reaction with hydrazinoalkanols 6a,b, 6c,d and 6e gave tetrahydropyrazolo[5,1-b]oxazoles 9a,b , tetrahydro-pyrazolo[5,1-b][1,3]oxazines 9c,d and hexahydropyrazolo[5,1-b][1,3]oxazepine 9e , respectively.     

Mechanism of thermal decomposition of peroxide radicals formed in polytetrafluoroethylene by γ-ray irradiation

Thermal decomposition of polymer peroxide radicals formed in γ-irradiated polytetrafluoroethylene, ～CF₂CF(OO·)CF₂～ (radical I) and ～CF₂CF₂(OO～) (radical II), was studied by mass spectral analysis of the gas evolved in comparison with their photolysis with ultraviolet light. In the thermal decomposition of radicals I and II, CO₂ was the most abundant component, with smaller amount of CO, CF₂O, and gases present. In the photolysis, CO instead of CO₂ was the most abundant in the case of radical I, while in the case of radical II, CO₂ was again the main product. When a labeled polymer peroxide radical, ～CF₂CF(¹⁸O-¹⁸O·)CF₂～, was treated with heat or ultraviolet light, C¹⁸O¹⁶O was detected as a main component. In the treatment with ultraviolet light, a large amount of C¹⁸O comparable to that of C¹⁸O¹⁶O was also obtained. The mechanism of main-chain scission of radicals I and II is discussed.     

Biochemical, molecular genetic, and structural analyses of the staphylococcal nucleoid.

The nucleoid structure of an important human pathogen, Staphylococcus aureus, was dissected by atomic force microscopy (AFM). The nucleoids dispersed on a cover glass consisted of fibrous units with two different widths of 40 and 80 nm, a feature shared with those of Escherichia coli. On the other hand, cells exposed to an oxidative stress exhibited clogged nucleoids. A knock-out of mrgA (metallo regulated genes A) encoding a staphylococcal homolog of the nucleoid compaction factor (E. coli Dps) eliminated the compaction response to the oxidative stress and reduced the susceptibilities to H2O2 and UV irradiation. We also observed that the negative supercoiling of plasmids is increased by the oxidative stress. A possible interrelation between the helical density and the nucleoid compaction is discussed in relation to the oxidative stress response.     

Modification of poly(vinyl chloride). XXXI. Crosslinking of poly(vinyl chloride) with 2-R-4,6-dithiol-s-triazine and metal activators

Crosslinking of poly(vinyl chloride) (PVC) with 2-R-4,6-dithiol-s-triazine (R-DT) and metal activators has been studied to determine crosslinking rate constants, induction periods, and apparent activation energy and the final efficiency of crosslinking agents. The rate constants were about 1.4–7.5 min^?1 and the induction periods were about 6.8–24.3 min for various kinds of R-DT at 180°C. The activation energy was about 16.6–33 kcal/mol over the temperature range 160–195°C. The rate constants were strongly influenced by 2-substituted groups (R) in R-DT and increased in the order R′O-? R′NH-< (R′)₂N, where R′ is an alkyl or aryl group. Further, the rate constants increased in the order of: metal carboxylates < metal carboxylates < metal oxides for the activators and in the order of: Pb < Mg < Ca < Ba < Na for metal atoms. The final efficiency was about 75–80% for the activators such as MgO, MgCO₃, PbO, and SnO. The activators containing Na, Ca, and Ba atoms, however, gave final efficiency of more than 100%.     

Evaluation and application of internal standardization in atomic absorption spectrometry with electrothermal atomization

A new dual-channel system developed for use in atomic absorption spectrometry is used to assess the internal standard technique for electrothermal atomization. Cobalt was found to be a suitable internal standard for iron determinations, and is used for determination of 7—330 ng Fe ml^-1 in water samples. With use of the internal standard technique, fluctuations caused by atomizer variables are reduced and interferences from many cations are also decreased.     

Measurements of the solubilities of derivatized amino acids in supercritical carbon dioxide

The solubilities of phenylalanine and tyrosine in supercritical carbon dioxide (SCCO₂) were measured after derivatization as the N-acetyl amino acid ethyl ester, N-carbobenzoxy amino acid and N-acetyl amino acid. Using an SCCO₂ flow system, a measuring method of the saturated solubilities of the derivatized amino acids was established in which the contact height of the extraction cell, i.e. a packed column, is increased till the concentration of a derivatized amino acid at the exit of the cell reaches a plateau. The solubilities of N-acetyl phenylalanine ethyl ester (APEE) exceeded 0.001 mole fraction, which is higher than those of caffeine produced in industrial SCCO₂ processes. A possible way of separating the amino acid mixtures using polarity differences in different amino acid side chains was demonstrated using the solubility data of the N-acetyl-amino acid ethyl esters in SCCO₂, as the solubilities of APEE are higher than those of N-acetyl tyrosine ethyl ester by two orders of magnitude.     

Selective oxygenation of amphiphilic thiacalix[3]pyridine Rh(I) diene complexes in both water and organic solvents

Thiacalix[3]pyridine (Py3S3) reacted with [Rh(diene)(mu-Cl)]2(diene = 1,5-cyclooctadiene (cod), 2,5-norbornadiene (nbd)) to give amphiphilic trigonal bipyramidal complexes, [Rh(Py3S3)(diene)]Cl. Sulfur bridges of the Py3S3 ligand in these complexes were selectively oxygenated by m-chloroperoxybenzoic acid in dichloromethane to give sulfinylcalix[3]pyridine complexes, [Rh(Py3(SO)3)(diene)]+, in which all three oxygen atoms of the SO groups occupy the equatorial positions. Structures of the complexes were analysed by X-ray crystallography and the oxidation reaction was investigated using 1H NMR spectroscopy and electrospray ionisation mass spectrometry showing that the oxygenation of the sulfur atoms in the ligand proceeded stepwise and further oxygenation of the SO moiety occurred only for the nbd complex having the smaller diene ligand resulting in [Rh(Py3(SO)2(SO2))(nbd)]+. On the other hand, the oxidation of [Rh(Py3S3)(cod)]+ by H2O2 in water did not result in oxygenation of the sulfur bridges but the cod ligand is hydroxygenated to give 1,4,5,6-eta4-2-hydroxycycloocta-4-ene-1,6-di-yl.     

Synthesis of gold nanoparticles from an organometallic compound in supercritical carbon dioxide

This article presents the synthesis of gold nanoparticles in a single-phase supercritical fluid carbon dioxide solvent. The gold nanoparticles were formed by the reduction of triphenylphosphine gold(I) perfluorooctanoate with dimethylamineborane. Transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis spectroscopy reveal the formation of gold nanoparticles of 1 nm in diameter. A high dispersion stability of the gold nanoparticles in supercritical carbon dioxide can be obtained by binding both triphenylphosphine and fluorocarbon ligands on the surface of the gold nanoparticles.