Synthesis and Application of Hydride Silica Composites for Rapid and Facile Removal of Aqueous Mercury

The adsorption of ionic mercury(II) from aqueous solution on functionalized hydride silicon materials was investigated. The adsorbents were prepared by modification of mesoporous silica C‐120 with triethoxysilane or by converting alkoxysilane into siloxanes by reaction with acetic acid. Mercury adsorption isotherms at 20 °C are reported, and maximum mercury loadings were determined by Langmuir fitting. Adsorbents exhibited efficient and rapid removal of ionic mercury from aqueous solution, with a maximum mercury loading of approximately 0.22 and 0.43 mmol of Hg g^?1 of silica C‐120 and polyhedral oligomeric silsesquioxane (POSS) xerogel, respectively. Adsorption efficiency remained almost constant from pH 2.7 to 7. These inexpensive adsorbents exhibiting rapid assembly, low pH sensitivity, and high reactivity and capacity, are potential candidates as effective materials for mercury decontamination in natural waters and industrial effluents.     

The Use of Solar Radiation by the Photosynthetic Bacterium,Rhodopseudomonas palustris: Model Simulation of Conditions Found in a Shallow Pond or a Flatbed Reactor

Photosynthetic bacteria are attractive for biotechnology because they produce no oxygen and so H₂‐production is not inhibited by oxygen as occurs in oxygenic photoorganisms. Rhodopseudomonas palustris and Afifella marina containing BChl a can use irradiances from violet near‐UV (VNUV) to orange (350–650 nm) light and near‐infrared (NIR) light (762–870 nm). Blue diode‐based pulse amplitude modulation technology was used to measure their photosynthetic electron transport rate (ETR). ETR vs Irradiance curves fitted the waiting‐in‐line model—ETR = (ETR_max × E/E_opt) × exp (1 ? E/E_opt). The equation was integrated over pond depth to calculate ETR of Afifella and Rhodopseudomonas in a pond up to 30 cm deep (A₃₇₆, 1 cm = 0.1). Afifella saturates at low irradiances and so photoinhibition results in very low photosynthesis in a pond. Rhodopseudomonas saturates at ≈15% sunlight and shows photoinhibition in the surface layers of the pond. Total ETR is ≈335 μmol (e^?) m^?2 s^?1 in NUV + photosynthetically active radiation light (350–700 nm). Daily ETR curves saturate at low irradiances and have a square‐wave shape: ≈11–13 mol (e^?) m^?2 day^?1 (350–700 nm). Up to 20–24% of daily 350–700 nm irradiance can be converted into ETR. NIR is absorbed by water and so competes with the bacterial RC‐2 photosystem for photons.     

The mass spectrometric fragmentation of n-heptane

The electron impact fragmentation of n-heptane has been investigated using ¹³C labelled derivatives. A mechanism is proposed for the loss of alkyl radicals where the cleavage of a C? C bond is coupled with the rearrangement of a hydrogen atom, thus yielding a secondary alkyl ion that eventually fragments further by a subsequent loss of olefin. For alkyl ions with less than six carbon atoms this consecutive pathway is in competition with formation directly from the molecular ion. The consecutive pathway contributes about 15% to the intensity of the alkyl ions with four and five carbon atoms and 80% for smaller ions. The electron energy dependence was studied.     

FORMATION OF 5-HYDROXYMETHYLCYTOSINE-CONTAINING PYRIMIDINE DIMERS IN UV-IRRADIATED BACTERIOPHAGE T4 DNA

Cyclobutyl pyrimidine dimers composed of 5-hydroxymethylcytosine and thymine (5HMC>T dimer for a mutant of T4 ( denV ) that is unable to excise pyrimidine dimers from its DNA. The ability of 5HMC to form dimers suggests that other modified pyrimidines such as 5-methylcytosine can participate in dimer formation, particularly at the UV wavelengths in sunlight likely to be responsible for the induction of skin cancer.     

Synthesis of 2-isopropylidenehydrazinylthiazole and its subsequent annelation to the corresponding thiazolo[2,3-c]-s-triazole

An unequivocal synthesis of a new thiazolo[2,3-c]-s-triazole substituted at the C-5 position by a very useful methyl triphenylphosphonium salt has been achieved starting from the corresponding 2-isopropylidenehydrazinylthiazole and formic acid. Ring closure was found to be very easy without isolation of a formylhydrazino intermediate. The thiazole derivative was prepared from isopropylidenethiosemicarbazide and (3-chloro-2-oxo)propyltriphenylphosphonium chloride in a good yield.     

Electrospray ionization mass spectrometry of ginsenosides

Ginsenosides R(b1), R(b2), R(c), R(d), R(e), R(f), R(g1), R(g2) and F(11) were studied systematically by electrospray ionization mass spectrometry in positive- and negative-ion modes with a mobile-phase additive, ammonium acetate. In general, ion sensitivities for the ginsenosides were greater in the negative-ion mode, but more structural information on the ginsenosides was obtained in the positive-ion mode. [M + H](+), [M + NH(4)](+), [M + Na](+) and [M + K](+) ions were observed for all of the ginsenosides studied, with the exception of R(f) and F(11), for which [M + NH(4)](+) ions were not observed. The signal intensities of [M + H](+), [M + NH(4)](+), [M + Na](+) and [M + K](+) ions varied with the cone voltage. The highest signal intensities for [M + H](+) and [M + NH(4)](+) ions were obtained at low cone voltage (15-30 V), whereas those for [M + Na](+) and [M + K](+) ions were obtained at relatively high cone voltage (70-90 V). Collision-induced dissociation yielded characteristic positively charged fragment ions at m/z 407, 425 and 443 for (20S)-protopanaxadiol, m/z 405, 423 and 441 for (20S)-protopanaxatriol and m/z 421, 439, 457 and 475 for (24R)-pseudoginsenoside F(11). Ginsenoside types were identified by these characteristic ions and the charged saccharide groups. Glycosidic bond cleavage and elimination of H(2)O were the two major fragmentation pathways observed in the product ion mass spectra of [M + H](+) and [M + NH(4)](+). In the product ion mass spectra of [M - H](-), the major fragmentation route observed was glycosidic bond cleavage. Adduct ions [M + 2AcO + Na](-), [M + AcO](-), [M - CH(2)O + AcO](-), [M + 2AcO](2-), [M - H + AcO](2-) and [M - 2H](2-) were observed at low cone voltage (15-30 V) only.     

Synthesis and biological evaluation of novel fused indolo [3, 2-c] [1,8] naphthyridine derivatives as potential antibacterial agents

Nine novel fused indolo [1,8] naphthyridine derivatives were synthesized using the Povarov reaction, in a one-pot system, and were fully characterized by spectroscopic techniques such as FT-IR, NMR, TOF-MS, and elemental analysis. Furthermore, their antibacterial activities against six bacterial strains were assessed. The results of the bioassay demonstrated that compounds 4a, 4c, and 4i showed good inhibitory effect with a MIC value ranging from 0.04687 to 0.09375?µM against Bacillus cereus and Staphylococcus aureus. The toxicity of 4a–i, evaluated through mutagenicity test against Salmonella typhimurium TA 98 and TA100 strains, revealed that there was no significant increase in the number of revertant colonies in comparison with the control, sodium azide.     

Phase separation of micellar solutions at extreme dilution: A study of polystyrene-b-poly(sodium acrylate) micelles in aqueous NaCl solutions

Micellar solutions of polystyrene-b-poly(sodium acrylate) copolymers in aqueous NaCl were studied by static light scattering (SLS). It was found that micellar solutions of the copolymer, at concentrations of NaCl at, or above, 2.0 mol dm⁻³, became turbid on dilution at constant salt concentration and at constant temperature. Turbidity arose from highly dilute solutions (typically at a concentration three orders of magnitude lower than the overlap concentration of the micelle, C*), but at concentrations above the expected critical micellization concentrations (c.m.c.s). The observed turbidity was attributed to the phase separation of the micellar phase. A systematic investigation of the phase separation phenomenon was performed. The effects of various parameters on the solution behavior of the micellar solutions were studied, including the effect of the concentration of NaCl, the effect of temperature, and the effect of the length of the hydrophilic, corona-forming poly(sodium acrylate) block. Phase separation was attributed to the presence of a very large excess of NaCl in the dilute micellar solutions. It was proposed that phase separation arose because of the reduced hydration of the polyion, the decreased electrostatic repulsion between the micelles, and the increase in the amount of ion binding, which occur in highly dilute salt solutions. © 1996 John Wiley & Sons, Inc.     

Fast-atom bombardment mass spectrometry and low energy collision-induced tandem mass spectrometry of tauroconjugated bile acid anions

Fragmentation of negative ions produced by fast-atom bombardment (FAB) from 14 tauroconjugated bile acids and some of their deuterated analogs has been studied by mass spectrometry and by collision-induced dissociation (CED) tandem mass spectrometry at low energy. Low energy collision-induced dissociation of the deprotonated molecules [M - H]^? of these tauroconjugated bile acids leads to both charge-driven and charge-remote fragmentations (CRF). The former yields neutral loss from the side chain with charge migration during the fragmentation process. These fragments dominate the CID spectra, but are absent from the FAB spectra. Their relative abundances are dependent on the number and the positions of the hydroxyl groups in the steroid nucleus and thus permit distinction among some positional isomers. The CRF fragments correspond to cleavages in the side chain up to fragmentations across the steroid rings with charge retention on the sulfonate group. These CRF fragments, which also are useful for structural identification, are less intense in CID than in FAB spectra. It appears that these charge-remote fragments are favored by unsaturation in the steroid rings, either as keto groups or as endocyclic double bonds. Tandem mass spectrometry combined with the use of deuterated analogs demonstrates that the structures of the survivor pseudomolecular ions and of the CRF fragments are not rearranged.