PHOTOSENSITIZATION BY ANTIMALARIAL DRUGS

Abstract The antimalarial drugs, chloroquine, hydroxychloroquine, quinine, quinacrine, amodiaquine and primaquine and the local anaesthetic, dibucaine, were tested for in vitro photosensitizing capability by irradiation with 365 nm UV light in aqueous solutions. The ability of these compounds to photosensitize the oxidation of 2,5-dimethylfuran, histidine, tryptophan or xanthine, and to initiate the free radical polymerization of acrylamide was examined in the pH range 2-12. Chloroquine and hydroxychloroquine show maximal photooxidative behaviour when in the monocation form at pH 9, in contrast to quinine which is extremely efficient as the dication below pH 4. This pattern appears to relate to the fluorescence yield as a function of pH. Chloroquine in the monocation or neutral form was found to undergo dechlorination upon irradiation, and this correlates directly with its ability to initiate photo-polymerization of acrylamide. Quinine also gives rise to small polymerization rates, attributed to photo-ionization in the quinoline ring, yielding a cation radical. Amodiaquine, primaquine and quinacrine do not have significant photochemical activity in aqueous solution. Dibucaine exhibits a strong photosensitizing capability at low pH, similar to quinine.     

HEU measurements of holdup and recovered residue in the deactivation and decommission activities of the 321-M Reactor Fuel Fabrication Facility at the Savannah River Site

Summary This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of the Reactor Fuel Fabrication Facility at the Savannah River Site (SRS). The facility was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During this time thousands of uranium-aluminum alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems for this equipment (e.g., chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, Freon?cart, riser crusher, …, etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount of HEU on all components removed from the facility prior to placing in solid waste containers. The ²³⁵U holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus, the holdup measurements were used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of ²³⁵U did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage vaults. Since HEU is an accountable nuclear material, the holdupassays and assays of recovered residue were also important for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality safety controls were not exceeded. This paper discusses theg-ray assay measurements conducted and the modeling of the acquired data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development work required to model new acquisition configurations and to adapt available instrumentation to perform the assays.     

Microwave promoted amination of 3-bromoisoxazoles

This Letter describes the amination of 3-bromoisoxazoles by a nucleophilic aromatic substitution reaction. We have found 3-bromoisoxazoles to be inert to substitution under thermal conditions, however, the employment of phosphazene bases under microwave irradiation facilitates the amination process and allows the corresponding 3-aminoisoxazoles to be isolated in moderate yield.     

Biosynthesis of 4-methylproline in cyanobacteria: cloning of nosE and nosF genes and biochemical characterization of the encoded dehydrogenase and reductase activities

The biosynthesis of the unusual amino acid 4-methylproline in the Nostoc genus of cyanobacteria was investigated on the genetic and enzymatic level. Two genes involved in the biosynthesis were cloned and the corresponding enzymes, a zinc-dependent long-chain dehydrogenase and a Delta(1)-pyrroline-5-carboxylic acid (P5C) reductase homologue, were overexpressed in Escherichia coli and biochemically characterized. Putative substrates were synthesized to test enzyme substrate specificities, and deuterium labeling studies were carried out to reveal the stereospecificities of the enzymatic reactions with respect to the substrates as well as to the coenzymes.     

Thermal effects of contamination,adsorbed water and annealing on the DTA of powdered quartz

During the grinding of quartz, water is adsorbed from the atmosphere, but this water gave no detectable thermal effect on DTA because it was evolved uniformly up to 1000°. However, in conjunction with an iron contaminant, the adsorbed water was involved in an oxidation reaction causing noticeable thermal effects for quartz powdered in a vibration mill constructed of steel parts. When powdered so finely that the - inversion peak at 573° had disappeared, annealing caused a partial redevelopment of the peak but recrystallization of disrupted quartz was too small an effect to give any detectable exothermic peak on DTA.

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Zusammenfassung Während des Vermahlens von Quartz wird Wasser aus der Atmosphäre adsorbiert, jedoch ergab dieses Wasser keinen nachweisbaren thermischen Effekt in der DTA, da es bis zu 1000° gleichmässig freigesetzt wird. Im Zusammenhang mit einer Eisen-Verunreinigung wurde jedoch das adsorbierte Wasser in eine Oxidationsreaktion einbezogen, welche beim in einer aus Stahlteilen gefertigten Vibrationsmühle zerpulvertem Quartz nachweisbare thermische Effekte verursachten. Wenn so fein pulverisiert wurde, daß der --Inversions-Peak bei 573° verschwunden war, verursachte eine Wärmebehandlung eine teilweise Wiederentwicklung des Peaks, jedoch war die Rekristallisation des zerstörten Quartzes zu geringfügig um einen nachweisbaren exothermen Peak in der DTA-Kurve zu ergeben.

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Résumé Lors du broyage du quartz, il se produit une adsorption de l'eau atmosphérique mais cette eau ne donne pas d'effet thermique décelable par ATD car elle se dégage régulièrement jusqu'à 1000°. Cependant, en présence de fer comme contaminant, l'eau adsorbée intervient dans une réaction d'oxydation qui donne des effets thermiques perceptibles dans le cas de quartz pulvérisé dans un vibrobroyeur en acier. Si le quartz est en poudre assez fine pour que le pic d'inversion - à 573° disparaisse, le recuit provoque la réapparition partielle du pic. La recristallisation du quartz est cependant trop faible pour donner un effet exothermique décelable par ATD.

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, , 1000°. , , . - 573° , , , - .

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We are grateful to the Science Research Council for supporting this work.     

Pyridine-containing m-phenylene ethynylene oligomers having tunable basicities

Incorporation of a pyridine monomer into the backbone of a m-phenylene ethynylene oligomer allows functionalization of the interior binding cavity of the folded oligomer. The basicity of the inwardly directed pyridine moiety was modulated by changing the substituents on the pyridine ring and through oligomer folding, granting access to a pK(a) range of 5-14 in acetonitrile. [reaction: see text]     

Formation of Bi-Sb, Bi-Sn, and Bi-Sb-Sn Nanoclusters in Silica Xerogel Matrices from Mixed-Metal Oxide Precursors

Homogeneous mixed-metal oxides of the general formula (Bi/E/Si)O _x , where E represents a dopant element (E=Sb, Sn, or Sb/Sn), can be prepared using typical sol-gel processing techniques. Reduction of the in-situ Bi(III) and E ions by hydrogen affords nanocomposites of Bi-Sb, Bi-Sn, or Bi-Sb-Sn widely dispersed throughout the silica xerogel matrix. The materials prepared have high Bi-E metal loading of 52–60 wt. % containing Bi-E alloy nanoclusters of 12–15 nm average diameter. These results demonstrate a convenient method for the production of practical quantities of nanostructured bismuth alloy ceramic composites at high metal content.     

Instrumental neutron activation analysis of tree rings for dendrochemical studies

Instrumental neutron activation analysis (INAA) was employed to determine zinc, cadmium and potassium concentrations in the growth rings of ponderosa pine (Pinus ponderosa Dougl.) trees growing along the shores of Lake Roosevelt in Washington State, U.S.A. where mineral processing activities have resulted in high burdens of zinc and cadmium in the lake sediments. The tree growing along the contaminated waterway display elevated concentrations of zinc in its growth rings relative to a tree growing along an uncontaminated tributary of Lake Roosevelt. Cadmium concentrations in the growth rings from both sites are similar from 1988 to 1993. Water quality data indicate an increased concentration of cadmium in the lake from 1984 to 1988. The increased concentrations of cadmium in the lake water were reflected in apparent increases in concentrations of cadmium in individual rings of the tree sampled at the contaminated site. This suggests that translocation of cadmium in the sapwood of heartwood-forming species does not occur in the short term, and thus may not be a limiting factor in using trees as environmental monitors for cadmium. In addition, five-year tree ring segments were analyzed and subsequently reanalyzed as individual single-year ring segments. The analytical data obtained for the pooled individual rings are essentially the same as for the five-year segments, demonstrating the utility of NAA for dendrochemical studies.